afedulov commented on a change in pull request #211:
URL: https://github.com/apache/flink-statefun/pull/211#discussion_r595074016
##########
File path: docs/content/docs/sdk/java.md
##########
@@ -29,451 +29,395 @@ under the License.
Stateful functions are the building blocks of applications; they are atomic
units of isolation, distribution, and persistence.
As objects, they encapsulate the state of a single entity (e.g., a specific
user, device, or session) and encode its behavior.
Stateful functions can interact with each other, and external systems, through
message passing.
-The Java SDK is supported as an [embedded module]({{< ref
"docs/sdk/overview#embedded-module" >}}).
To get started, add the Java SDK as a dependency to your application.
-{{< artifact statefun-sdk >}}
+{{< artifact statefun-sdk-java >}}
## Defining A Stateful Function
-A stateful function is any class that implements the ``StatefulFunction``
interface.
-The following is an example of a simple hello world function.
+A stateful function is any class that implements the `StatefulFunction`
interface.
+In the following example, a `StatefulFunction` maintains a count for every user
+of an application, emitting a customized greeting.
```java
-package org.apache.flink.statefun.docs;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-public class FnHelloWorld implements StatefulFunction {
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
- @Override
- public void invoke(Context context, Object input) {
- System.out.println("Hello " + input.toString());
- }
-}
-```
+public class GreeterFn implements StatefulFunction {
-Functions process each incoming message through their ``invoke`` method.
-Input's are untyped and passed through the system as a ``java.lang.Object`` so
one function can potentially process multiple types of messages.
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
-The ``Context`` provides metadata about the current message and function, and
is how you can call other functions or external systems.
-Functions are invoked based on a function type and unique identifier.
+ static final TypeName INBOX =
TypeName.forNameFromString("com.example.fns/inbox");
Review comment:
forNameFromString => typeNameFromString
##########
File path: docs/content/docs/sdk/java.md
##########
@@ -29,451 +29,395 @@ under the License.
Stateful functions are the building blocks of applications; they are atomic
units of isolation, distribution, and persistence.
As objects, they encapsulate the state of a single entity (e.g., a specific
user, device, or session) and encode its behavior.
Stateful functions can interact with each other, and external systems, through
message passing.
-The Java SDK is supported as an [embedded module]({{< ref
"docs/sdk/overview#embedded-module" >}}).
To get started, add the Java SDK as a dependency to your application.
-{{< artifact statefun-sdk >}}
+{{< artifact statefun-sdk-java >}}
## Defining A Stateful Function
-A stateful function is any class that implements the ``StatefulFunction``
interface.
-The following is an example of a simple hello world function.
+A stateful function is any class that implements the `StatefulFunction`
interface.
+In the following example, a `StatefulFunction` maintains a count for every user
+of an application, emitting a customized greeting.
```java
-package org.apache.flink.statefun.docs;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-public class FnHelloWorld implements StatefulFunction {
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
- @Override
- public void invoke(Context context, Object input) {
- System.out.println("Hello " + input.toString());
- }
-}
-```
+public class GreeterFn implements StatefulFunction {
-Functions process each incoming message through their ``invoke`` method.
-Input's are untyped and passed through the system as a ``java.lang.Object`` so
one function can potentially process multiple types of messages.
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
-The ``Context`` provides metadata about the current message and function, and
is how you can call other functions or external systems.
-Functions are invoked based on a function type and unique identifier.
+ static final TypeName INBOX =
TypeName.forNameFromString("com.example.fns/inbox");
-### Stateful Match Function
+ static final ValueSpec<Integer> SEEN =
ValueSpec.named("seen").withIntType();
-Stateful functions provide a powerful abstraction for working with events and
state, allowing developers to build components that can react to any kind of
message.
-Commonly, functions only need to handle a known set of message types, and the
``StatefulMatchFunction`` interface provides an opinionated solution to that
problem.
+ @Override
+ CompletableFuture<Void> apply(Context context, Message message) {
+ if (!message.is(User.TYPE)) {
+ throw new IllegalStateException("Unknown type");
+ }
-#### Simple Match Function
+ User user = message.as(User.TYPE);
+ String name = user.getName();
-Stateful match functions are an opinionated variant of stateful functions for
precisely this pattern.
-Developers outline expected types, optional predicates, and well-typed
business logic and let the system dispatch each input to the correct action.
-Variants are bound inside a ``configure`` method that is executed once the
first time an instance is loaded.
+ var storage = context.storage();
+ var seen = storage.get(SEEN).orElse(0);
+ storage.set(SEEN, seen + 1);
-```java
-package org.apache.flink.statefun.docs.match;
+ context.send(
+ MessageBuilder.forAddress(INBOX, name)
+ .withValue("Hello " + name + " for the " + seen + "th time!")
+ .build());
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.match.MatchBinder;
-import org.apache.flink.statefun.sdk.match.StatefulMatchFunction;
+ return context.done();
+ }
+}
+```
-public class FnMatchGreeter extends StatefulMatchFunction {
+This code declares a greeter function that will be
[registered](#exposing-functions) under the logical type name
`com.example.fns/greeter`. Type names must take the form `<namesapce>/<name>`.
+It contains a single `ValueSpec`, which is implicitly scoped to the current
address and stores an integer.
- @Override
- public void configure(MatchBinder binder) {
- binder
- .predicate(Customer.class, this::greetCustomer)
- .predicate(Employee.class, Employee::isManager,
this::greetManager)
- .predicate(Employee.class, this::greetEmployee);
- }
+Every time a message is sent a greeter, it first validates the message
containing a `User` and extracts its name. Both messages and state are strongly
typed - either one of the default [built-in types]({{< ref
"docs/sdk/appendix#types" >}}) - or a [custom type](#types) as in this case.
- private void greetCustomer(Context context, Customer message) {
- System.out.println("Hello customer " + message.getName());
- }
+The function finally builds a custom greeting for the user.
+The number of times that particular user has been seen so far is queried from
the state store and updated
+and the greeting is sent to the users' inbox (another function type).
- private void greetEmployee(Context context, Employee message) {
- System.out.println("Hello employee " + message.getEmployeeId());
- }
+## Types
- private void greetManager(Context context, Employee message) {
- System.out.println("Hello manager " + message.getEmployeeId());
- }
-}
-```
+Stateful Functions strongly types ll messages and state values.
+Because they run in a distributed manner and state values are persisted to
stable storage, Stateful Functions aims to provide efficient and easy to user
serializers.
-#### Making Your Function Complete
+Out of the box, all SDKs offer a set of highly optimized serializers for
common primitive types; boolean, numerics, and strings.
+Additionally, users are encouraged to plug-in custom types to model more
complex data structures.
-Similar to the first example, match functions are partial by default and will
throw an ``IllegalStateException`` on any input that does not match any branch.
-They can be made complete by providing an ``otherwise`` clause that serves as
a catch-all for unmatched input, think of it as a default clause in a Java
switch statement.
-The ``otherwise`` action takes its message as an untyped ``java.lang.Object``,
allowing you to handle any unexpected messages.
+In the [example above](#defining-a-stateful-function), the greeter function
consumes `User` messages, a POJO type containing several fields.
+By defining a custom type, this object can be passed transparently between
functions and stored in state.
+And because the type is tied to a logical typename, instead of the physical
Java class, it can be passed to functions written in other langauge SDKs.
```java
-package org.apache.flink.statefun.docs.match;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.match.MatchBinder;
-import org.apache.flink.statefun.sdk.match.StatefulMatchFunction;
-
-public class FnMatchGreeterWithCatchAll extends StatefulMatchFunction {
-
- @Override
- public void configure(MatchBinder binder) {
- binder
- .predicate(Customer.class, this::greetCustomer)
- .predicate(Employee.class, Employee::isManager,
this::greetManager)
- .predicate(Employee.class, this::greetEmployee)
- .otherwise(this::catchAll);
- }
-
- private void greetCustomer(Context context, Customer message) {
- System.out.println("Hello customer " + message.getName());
- }
-
- private void greetEmployee(Context context, Employee message) {
- System.out.println("Hello employee " + message.getEmployeeId());
- }
-
- private void greetManager(Context context, Employee message) {
- System.out.println("Hello manager " + message.getEmployeeId());
- }
-
- private void catchAll(Context context, Object message) {
- System.out.println("Hello unexpected message");
- }
-}
-```
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.types.SimpleType;
+import org.apache.flink.statefun.sdk.java.types.Type;
+import java.util.Objects;
-#### Action Resolution Order
+public class User {
-Match functions will always match actions from most to least specific using
the following resolution rules.
+ private static final ObjectMapper mapper = new ObjectMapper();
-First, find an action that matches the type and predicate. If two predicates
will return true for a particular input, the one registered in the binder first
wins.
-Next, search for an action that matches the type but does not have an
associated predicate.
-Finally, if a catch-all exists, it will be executed or an
``IllegalStateException`` will be thrown.
+ public static final Type<User> TYPE = SimpleType.simpleImmutableTypeFrom(
+ TypeName.typeNameFromString("com.example/User"),
+ mapper:writeValueAsBytes,
+ bytes -> mapper.readValue(byes, User.class));
-## Function Types and Messaging
+ private final String name;
-In Java, function types are defined as logical pointers composed of a
namespace and name.
-The type is bound to the implementing class in the [module]({{< ref
"docs/sdk/overview#embedded-module" >}}) definition.
-Below is an example function type for the hello world function.
+ private final String favoriteColor;
-```java
-package org.apache.flink.statefun.docs;
+ @JsonCreator
+ public User(
+ @JsonProperty("name") String name,
+ @JsonProperty("favorite_color" String favoriteColor)) {
-import org.apache.flink.statefun.sdk.FunctionType;
+ this.name = Objects.requireNonNull(name);
+ this.favoriteColor = Objects.requireNonNull(favoriteColor);
+ }
-/** A function type that will be bound to {@link FnHelloWorld}. */
-public class Identifiers {
+ public String getName() {
+ return name;
+ }
- public static final FunctionType HELLO_TYPE = new
FunctionType("apache/flink", "hello");
-}
+ public String getFavoriteColor() {
+ return favoriteColor;
+ }
+
+ @Override
+ public String toString() {
+ return "User{name=" name + ",favoriteColor=" favoriteColor + "}"
+ }
```
-This type can then be referenced from other functions to create an address and
message a particular instance.
+## State
-```java
-package org.apache.flink.statefun.docs;
+Stateful Functions treats state as a first class citizen and so all functions
can easily define state that is automatically made fault tolerant by the
runtime.
+State declaration is as simple as defining one or more `ValueSpec`'s
describing your state values.
+Value specifications are defined with a unique (to the function) name and
[type](#types).
+At runtime, functions can `get`, `set`, and `remove` state values scoped to
the address of the current message.
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-/** A simple stateful function that sends a message to the user with id
"user1" */
-public class FnCaller implements StatefulFunction {
+{{< hint info >}}
+All value specificiations must be earerly registered in the
`StatefulFuctionSpec` when composing
+the applications [RequestReplyHandler](#exposing-functions).
+{{< /hint >}}
- @Override
- public void invoke(Context context, Object input) {
- context.send(Identifiers.HELLO_TYPE, "user1", new MyUserMessage());
- }
-}
+```java
+// Value specification for a state named `seen`
+// with the primitive integer type
+ValueSpec
+ .named("seen")
+ .withIntType();
+
+// Value specification with a custom type
+ValueSpec
+ .name("user")
+ .withCustomType(User.TYPE);
```
-## Sending Delayed Messages
+### State Expiration
-Functions are able to send messages on a delay so that they will arrive after
some duration.
-Functions may even send themselves delayed messages that can serve as a
callback.
-The delayed message is non-blocking so functions will continue to process
records between the time a delayed message is sent and received.
+By default, state values are persisted until manually `remove`d by the user.
+Optionally, they may be configured to expire and be automatically deleted
after a specified duration.
```java
-package org.apache.flink.statefun.docs.delay;
-
-import java.time.Duration;
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-public class FnDelayedMessage implements StatefulFunction {
-
- @Override
- public void invoke(Context context, Object input) {
- if (input instanceof Message) {
- System.out.println("Hello");
- context.sendAfter(Duration.ofMinutes(1),
context.self(), new DelayedMessage());
- }
-
- if (input instanceof DelayedMessage) {
- System.out.println("Welcome to the future!");
- }
- }
-}
+// Value specification that will automatically
+// delete the value if the function instance goes
+// more than 30 minutes without being called
+ValueSpec
+ .named("seen")
+ .thatExpiresAfterCall(Duration.ofDays(1))
+ .withIntType();
+
+// Value specification that will automatically
+// delete the value if it goes more than 1 day
+// without being written
+ValueSpec
+ .named("seen")
+ .thatExpireAfterWrite(Duration.ofDays(1))
+ .withIntType();
```
-## Completing Async Requests
-
-When interacting with external systems, such as a database or API, one needs
to take care that communication delay with the external system does not
dominate the application’s total work.
-Stateful Functions allows registering a Java ``CompletableFuture`` that will
resolve to a value at some point in the future.
-Future's are registered along with a metadata object that provides additional
context about the caller.
+## Sending Delayed Messages
-When the future completes, either successfully or exceptionally, the caller
function type and id will be invoked with a ``AsyncOperationResult``.
-An asynchronous result can complete in one of three states:
+Functions can send messages on a delay so that they will arrive after some
duration.
+They may even send themselves delayed messages that can serve as a callback.
+The delayed message is non-blocking, so functions will continue to process
records between when a delayed message is sent and received.
+Additionally, they are fault-tolerant and never lost, even when recovering
from failure.
-### Success
+This example sends a response back to the calling function after a 30 minute
delay.
-The asynchronous operation has succeeded, and the produced result can be
obtained via ``AsyncOperationResult#value``.
+```java
+import java.util.concurrent.CompletableFuture;
+import java.time.Duration;
-### Failure
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.message.Message;
-The asynchronous operation has failed, and the cause can be obtained via
``AsyncOperationResult#throwable``.
+public class DelayedFn implements StatefulFunction {
-### Unknown
+ private static final Logger LOG = LoggerFactory.getLogger(DelayedFn.class);
-The stateful function was restarted, possibly on a different machine, before
the ``CompletableFuture`` was completed, therefore it is unknown what is the
status of the asynchronous operation.
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/delayed");
Review comment:
forNameFromString => typeNameFromString
##########
File path: docs/content/docs/sdk/java.md
##########
@@ -29,451 +29,395 @@ under the License.
Stateful functions are the building blocks of applications; they are atomic
units of isolation, distribution, and persistence.
As objects, they encapsulate the state of a single entity (e.g., a specific
user, device, or session) and encode its behavior.
Stateful functions can interact with each other, and external systems, through
message passing.
-The Java SDK is supported as an [embedded module]({{< ref
"docs/sdk/overview#embedded-module" >}}).
To get started, add the Java SDK as a dependency to your application.
-{{< artifact statefun-sdk >}}
+{{< artifact statefun-sdk-java >}}
## Defining A Stateful Function
-A stateful function is any class that implements the ``StatefulFunction``
interface.
-The following is an example of a simple hello world function.
+A stateful function is any class that implements the `StatefulFunction`
interface.
+In the following example, a `StatefulFunction` maintains a count for every user
+of an application, emitting a customized greeting.
```java
-package org.apache.flink.statefun.docs;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-public class FnHelloWorld implements StatefulFunction {
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
- @Override
- public void invoke(Context context, Object input) {
- System.out.println("Hello " + input.toString());
- }
-}
-```
+public class GreeterFn implements StatefulFunction {
-Functions process each incoming message through their ``invoke`` method.
-Input's are untyped and passed through the system as a ``java.lang.Object`` so
one function can potentially process multiple types of messages.
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
-The ``Context`` provides metadata about the current message and function, and
is how you can call other functions or external systems.
-Functions are invoked based on a function type and unique identifier.
+ static final TypeName INBOX =
TypeName.forNameFromString("com.example.fns/inbox");
-### Stateful Match Function
+ static final ValueSpec<Integer> SEEN =
ValueSpec.named("seen").withIntType();
-Stateful functions provide a powerful abstraction for working with events and
state, allowing developers to build components that can react to any kind of
message.
-Commonly, functions only need to handle a known set of message types, and the
``StatefulMatchFunction`` interface provides an opinionated solution to that
problem.
+ @Override
+ CompletableFuture<Void> apply(Context context, Message message) {
+ if (!message.is(User.TYPE)) {
+ throw new IllegalStateException("Unknown type");
+ }
-#### Simple Match Function
+ User user = message.as(User.TYPE);
+ String name = user.getName();
-Stateful match functions are an opinionated variant of stateful functions for
precisely this pattern.
-Developers outline expected types, optional predicates, and well-typed
business logic and let the system dispatch each input to the correct action.
-Variants are bound inside a ``configure`` method that is executed once the
first time an instance is loaded.
+ var storage = context.storage();
+ var seen = storage.get(SEEN).orElse(0);
+ storage.set(SEEN, seen + 1);
-```java
-package org.apache.flink.statefun.docs.match;
+ context.send(
+ MessageBuilder.forAddress(INBOX, name)
+ .withValue("Hello " + name + " for the " + seen + "th time!")
+ .build());
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.match.MatchBinder;
-import org.apache.flink.statefun.sdk.match.StatefulMatchFunction;
+ return context.done();
+ }
+}
+```
-public class FnMatchGreeter extends StatefulMatchFunction {
+This code declares a greeter function that will be
[registered](#exposing-functions) under the logical type name
`com.example.fns/greeter`. Type names must take the form `<namesapce>/<name>`.
+It contains a single `ValueSpec`, which is implicitly scoped to the current
address and stores an integer.
- @Override
- public void configure(MatchBinder binder) {
- binder
- .predicate(Customer.class, this::greetCustomer)
- .predicate(Employee.class, Employee::isManager,
this::greetManager)
- .predicate(Employee.class, this::greetEmployee);
- }
+Every time a message is sent a greeter, it first validates the message
containing a `User` and extracts its name. Both messages and state are strongly
typed - either one of the default [built-in types]({{< ref
"docs/sdk/appendix#types" >}}) - or a [custom type](#types) as in this case.
- private void greetCustomer(Context context, Customer message) {
- System.out.println("Hello customer " + message.getName());
- }
+The function finally builds a custom greeting for the user.
+The number of times that particular user has been seen so far is queried from
the state store and updated
+and the greeting is sent to the users' inbox (another function type).
- private void greetEmployee(Context context, Employee message) {
- System.out.println("Hello employee " + message.getEmployeeId());
- }
+## Types
- private void greetManager(Context context, Employee message) {
- System.out.println("Hello manager " + message.getEmployeeId());
- }
-}
-```
+Stateful Functions strongly types ll messages and state values.
+Because they run in a distributed manner and state values are persisted to
stable storage, Stateful Functions aims to provide efficient and easy to user
serializers.
-#### Making Your Function Complete
+Out of the box, all SDKs offer a set of highly optimized serializers for
common primitive types; boolean, numerics, and strings.
+Additionally, users are encouraged to plug-in custom types to model more
complex data structures.
-Similar to the first example, match functions are partial by default and will
throw an ``IllegalStateException`` on any input that does not match any branch.
-They can be made complete by providing an ``otherwise`` clause that serves as
a catch-all for unmatched input, think of it as a default clause in a Java
switch statement.
-The ``otherwise`` action takes its message as an untyped ``java.lang.Object``,
allowing you to handle any unexpected messages.
+In the [example above](#defining-a-stateful-function), the greeter function
consumes `User` messages, a POJO type containing several fields.
+By defining a custom type, this object can be passed transparently between
functions and stored in state.
+And because the type is tied to a logical typename, instead of the physical
Java class, it can be passed to functions written in other langauge SDKs.
```java
-package org.apache.flink.statefun.docs.match;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.match.MatchBinder;
-import org.apache.flink.statefun.sdk.match.StatefulMatchFunction;
-
-public class FnMatchGreeterWithCatchAll extends StatefulMatchFunction {
-
- @Override
- public void configure(MatchBinder binder) {
- binder
- .predicate(Customer.class, this::greetCustomer)
- .predicate(Employee.class, Employee::isManager,
this::greetManager)
- .predicate(Employee.class, this::greetEmployee)
- .otherwise(this::catchAll);
- }
-
- private void greetCustomer(Context context, Customer message) {
- System.out.println("Hello customer " + message.getName());
- }
-
- private void greetEmployee(Context context, Employee message) {
- System.out.println("Hello employee " + message.getEmployeeId());
- }
-
- private void greetManager(Context context, Employee message) {
- System.out.println("Hello manager " + message.getEmployeeId());
- }
-
- private void catchAll(Context context, Object message) {
- System.out.println("Hello unexpected message");
- }
-}
-```
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.types.SimpleType;
+import org.apache.flink.statefun.sdk.java.types.Type;
+import java.util.Objects;
-#### Action Resolution Order
+public class User {
-Match functions will always match actions from most to least specific using
the following resolution rules.
+ private static final ObjectMapper mapper = new ObjectMapper();
-First, find an action that matches the type and predicate. If two predicates
will return true for a particular input, the one registered in the binder first
wins.
-Next, search for an action that matches the type but does not have an
associated predicate.
-Finally, if a catch-all exists, it will be executed or an
``IllegalStateException`` will be thrown.
+ public static final Type<User> TYPE = SimpleType.simpleImmutableTypeFrom(
+ TypeName.typeNameFromString("com.example/User"),
+ mapper:writeValueAsBytes,
+ bytes -> mapper.readValue(byes, User.class));
-## Function Types and Messaging
+ private final String name;
-In Java, function types are defined as logical pointers composed of a
namespace and name.
-The type is bound to the implementing class in the [module]({{< ref
"docs/sdk/overview#embedded-module" >}}) definition.
-Below is an example function type for the hello world function.
+ private final String favoriteColor;
-```java
-package org.apache.flink.statefun.docs;
+ @JsonCreator
+ public User(
+ @JsonProperty("name") String name,
+ @JsonProperty("favorite_color" String favoriteColor)) {
-import org.apache.flink.statefun.sdk.FunctionType;
+ this.name = Objects.requireNonNull(name);
+ this.favoriteColor = Objects.requireNonNull(favoriteColor);
+ }
-/** A function type that will be bound to {@link FnHelloWorld}. */
-public class Identifiers {
+ public String getName() {
+ return name;
+ }
- public static final FunctionType HELLO_TYPE = new
FunctionType("apache/flink", "hello");
-}
+ public String getFavoriteColor() {
+ return favoriteColor;
+ }
+
+ @Override
+ public String toString() {
+ return "User{name=" name + ",favoriteColor=" favoriteColor + "}"
+ }
```
-This type can then be referenced from other functions to create an address and
message a particular instance.
+## State
-```java
-package org.apache.flink.statefun.docs;
+Stateful Functions treats state as a first class citizen and so all functions
can easily define state that is automatically made fault tolerant by the
runtime.
+State declaration is as simple as defining one or more `ValueSpec`'s
describing your state values.
+Value specifications are defined with a unique (to the function) name and
[type](#types).
+At runtime, functions can `get`, `set`, and `remove` state values scoped to
the address of the current message.
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-/** A simple stateful function that sends a message to the user with id
"user1" */
-public class FnCaller implements StatefulFunction {
+{{< hint info >}}
+All value specificiations must be earerly registered in the
`StatefulFuctionSpec` when composing
+the applications [RequestReplyHandler](#exposing-functions).
+{{< /hint >}}
- @Override
- public void invoke(Context context, Object input) {
- context.send(Identifiers.HELLO_TYPE, "user1", new MyUserMessage());
- }
-}
+```java
+// Value specification for a state named `seen`
+// with the primitive integer type
+ValueSpec
+ .named("seen")
+ .withIntType();
+
+// Value specification with a custom type
+ValueSpec
+ .name("user")
+ .withCustomType(User.TYPE);
```
-## Sending Delayed Messages
+### State Expiration
-Functions are able to send messages on a delay so that they will arrive after
some duration.
-Functions may even send themselves delayed messages that can serve as a
callback.
-The delayed message is non-blocking so functions will continue to process
records between the time a delayed message is sent and received.
+By default, state values are persisted until manually `remove`d by the user.
+Optionally, they may be configured to expire and be automatically deleted
after a specified duration.
```java
-package org.apache.flink.statefun.docs.delay;
-
-import java.time.Duration;
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-public class FnDelayedMessage implements StatefulFunction {
-
- @Override
- public void invoke(Context context, Object input) {
- if (input instanceof Message) {
- System.out.println("Hello");
- context.sendAfter(Duration.ofMinutes(1),
context.self(), new DelayedMessage());
- }
-
- if (input instanceof DelayedMessage) {
- System.out.println("Welcome to the future!");
- }
- }
-}
+// Value specification that will automatically
+// delete the value if the function instance goes
+// more than 30 minutes without being called
+ValueSpec
+ .named("seen")
+ .thatExpiresAfterCall(Duration.ofDays(1))
+ .withIntType();
+
+// Value specification that will automatically
+// delete the value if it goes more than 1 day
+// without being written
+ValueSpec
+ .named("seen")
+ .thatExpireAfterWrite(Duration.ofDays(1))
+ .withIntType();
```
-## Completing Async Requests
-
-When interacting with external systems, such as a database or API, one needs
to take care that communication delay with the external system does not
dominate the application’s total work.
-Stateful Functions allows registering a Java ``CompletableFuture`` that will
resolve to a value at some point in the future.
-Future's are registered along with a metadata object that provides additional
context about the caller.
+## Sending Delayed Messages
-When the future completes, either successfully or exceptionally, the caller
function type and id will be invoked with a ``AsyncOperationResult``.
-An asynchronous result can complete in one of three states:
+Functions can send messages on a delay so that they will arrive after some
duration.
+They may even send themselves delayed messages that can serve as a callback.
+The delayed message is non-blocking, so functions will continue to process
records between when a delayed message is sent and received.
+Additionally, they are fault-tolerant and never lost, even when recovering
from failure.
-### Success
+This example sends a response back to the calling function after a 30 minute
delay.
-The asynchronous operation has succeeded, and the produced result can be
obtained via ``AsyncOperationResult#value``.
+```java
+import java.util.concurrent.CompletableFuture;
+import java.time.Duration;
-### Failure
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.message.Message;
-The asynchronous operation has failed, and the cause can be obtained via
``AsyncOperationResult#throwable``.
+public class DelayedFn implements StatefulFunction {
-### Unknown
+ private static final Logger LOG = LoggerFactory.getLogger(DelayedFn.class);
-The stateful function was restarted, possibly on a different machine, before
the ``CompletableFuture`` was completed, therefore it is unknown what is the
status of the asynchronous operation.
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/delayed");
-```java
-package org.apache.flink.statefun.docs.async;
+ @Override
+ CompletableFuture<Void> apply(Context context, Message message) {
+ if (!context.caller().isPresent()) {
+ LOG.debug("Message has no known caller meaning it was sent
directly from an ingress");
+ return;
+ }
-import java.util.concurrent.CompletableFuture;
-import org.apache.flink.statefun.sdk.AsyncOperationResult;
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-@SuppressWarnings("unchecked")
-public class EnrichmentFunction implements StatefulFunction {
-
- private final QueryService client;
-
- public EnrichmentFunction(QueryService client) {
- this.client = client;
- }
-
- @Override
- public void invoke(Context context, Object input) {
- if (input instanceof User) {
- onUser(context, (User) input);
- } else if (input instanceof AsyncOperationResult) {
- onAsyncResult((AsyncOperationResult) input);
- }
- }
-
- private void onUser(Context context, User user) {
- CompletableFuture<UserEnrichment> future =
client.getDataAsync(user.getUserId());
- context.registerAsyncOperation(user, future);
- }
-
- private void onAsyncResult(AsyncOperationResult<User, UserEnrichment>
result) {
- if (result.successful()) {
- User metadata = result.metadata();
- UserEnrichment value = result.value();
- System.out.println(
- String.format("Successfully completed future:
%s %s", metadata, value));
- } else if (result.failure()) {
- System.out.println(
- String.format("Something has gone terribly
wrong %s", result.throwable()));
- } else {
- System.out.println("Not sure what happened, maybe
retry");
- }
- }
+ var caller = context.caller().get();
+ context.sendAfter(Duration.ofMinutes(30), MessageBuilder
+ .forAddress(caller)
+ .withValue("Hello from the future!"));
+ }
}
```
-## Persistence
-
-Stateful Functions treats state as a first class citizen and so all stateful
functions can easily define state that is automatically made fault tolerant by
the runtime.
-All stateful functions may contain state by merely defining one or more
persisted fields.
+## Egress
-The simplest way to get started is with a ``PersistedValue``, which is defined
by its name and the class of the type that it stores.
-The data is always scoped to a specific function type and identifier.
-Below is a stateful function that greets users based on the number of times
they have been seen.
-
-{{< hint info >}}
-All **PersistedValue**, **PersistedTable**, and **PersistedAppendingBuffer**
fields must be marked with a **@Persisted** annotation or they will not be made
fault tolerant by the runtime.
-{{< /hint >}}
+Functions can message other stateful functions and egresses, exit points for
sending messages to the outside world.
+As with other messages, egress messages are always well-typed.
+Additionally, they contain metadata pertinent to the specific egress type.
+{{< tabs "egress" >}}
+{{< tab "Apache Kafka" >}}
```java
-package org.apache.flink.statefun.docs;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.FunctionType;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-import org.apache.flink.statefun.sdk.annotations.Persisted;
-import org.apache.flink.statefun.sdk.state.PersistedValue;
-
-public class FnUserGreeter implements StatefulFunction {
-
- public static FunctionType TYPE = new FunctionType("example",
"greeter");
-
- @Persisted
- private final PersistedValue<Integer> count =
PersistedValue.of("count", Integer.class);
-
- public void invoke(Context context, Object input) {
- String userId = context.self().id();
- int seen = count.getOrDefault(0);
-
- switch (seen) {
- case 0:
- System.out.println(String.format("Hello %s!",
userId));
- break;
- case 1:
- System.out.println("Hello Again!");
- break;
- case 2:
- System.out.println("Third time is the charm
:)");
- break;
- default:
- System.out.println(String.format("Hello for the
%d-th time", seen + 1));
- }
-
- count.set(seen + 1);
- }
-}
-```
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
+import org.apache.flink.statefun.sdk.java.io.KafkaEgressMessage;
-``PersistedValue`` comes with the right primitive methods to build powerful
stateful applications.
-Calling ``PersistedValue#get`` will return the current value of an object
stored in state, or ``null`` if nothing is set.
-Conversely, ``PersistedValue#set`` will update the value in state and
``PersistedValue#clear`` will delete the value from state.
+public class GreeterFn implements StatefulFunction {
-### Collection Types
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
Review comment:
forNameFromString => typeNameFromString
##########
File path: docs/content/docs/sdk/java.md
##########
@@ -29,451 +29,395 @@ under the License.
Stateful functions are the building blocks of applications; they are atomic
units of isolation, distribution, and persistence.
As objects, they encapsulate the state of a single entity (e.g., a specific
user, device, or session) and encode its behavior.
Stateful functions can interact with each other, and external systems, through
message passing.
-The Java SDK is supported as an [embedded module]({{< ref
"docs/sdk/overview#embedded-module" >}}).
To get started, add the Java SDK as a dependency to your application.
-{{< artifact statefun-sdk >}}
+{{< artifact statefun-sdk-java >}}
## Defining A Stateful Function
-A stateful function is any class that implements the ``StatefulFunction``
interface.
-The following is an example of a simple hello world function.
+A stateful function is any class that implements the `StatefulFunction`
interface.
+In the following example, a `StatefulFunction` maintains a count for every user
+of an application, emitting a customized greeting.
```java
-package org.apache.flink.statefun.docs;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-public class FnHelloWorld implements StatefulFunction {
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
- @Override
- public void invoke(Context context, Object input) {
- System.out.println("Hello " + input.toString());
- }
-}
-```
+public class GreeterFn implements StatefulFunction {
-Functions process each incoming message through their ``invoke`` method.
-Input's are untyped and passed through the system as a ``java.lang.Object`` so
one function can potentially process multiple types of messages.
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
-The ``Context`` provides metadata about the current message and function, and
is how you can call other functions or external systems.
-Functions are invoked based on a function type and unique identifier.
+ static final TypeName INBOX =
TypeName.forNameFromString("com.example.fns/inbox");
-### Stateful Match Function
+ static final ValueSpec<Integer> SEEN =
ValueSpec.named("seen").withIntType();
-Stateful functions provide a powerful abstraction for working with events and
state, allowing developers to build components that can react to any kind of
message.
-Commonly, functions only need to handle a known set of message types, and the
``StatefulMatchFunction`` interface provides an opinionated solution to that
problem.
+ @Override
+ CompletableFuture<Void> apply(Context context, Message message) {
+ if (!message.is(User.TYPE)) {
+ throw new IllegalStateException("Unknown type");
+ }
-#### Simple Match Function
+ User user = message.as(User.TYPE);
+ String name = user.getName();
-Stateful match functions are an opinionated variant of stateful functions for
precisely this pattern.
-Developers outline expected types, optional predicates, and well-typed
business logic and let the system dispatch each input to the correct action.
-Variants are bound inside a ``configure`` method that is executed once the
first time an instance is loaded.
+ var storage = context.storage();
+ var seen = storage.get(SEEN).orElse(0);
+ storage.set(SEEN, seen + 1);
-```java
-package org.apache.flink.statefun.docs.match;
+ context.send(
+ MessageBuilder.forAddress(INBOX, name)
+ .withValue("Hello " + name + " for the " + seen + "th time!")
+ .build());
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.match.MatchBinder;
-import org.apache.flink.statefun.sdk.match.StatefulMatchFunction;
+ return context.done();
+ }
+}
+```
-public class FnMatchGreeter extends StatefulMatchFunction {
+This code declares a greeter function that will be
[registered](#exposing-functions) under the logical type name
`com.example.fns/greeter`. Type names must take the form `<namesapce>/<name>`.
+It contains a single `ValueSpec`, which is implicitly scoped to the current
address and stores an integer.
- @Override
- public void configure(MatchBinder binder) {
- binder
- .predicate(Customer.class, this::greetCustomer)
- .predicate(Employee.class, Employee::isManager,
this::greetManager)
- .predicate(Employee.class, this::greetEmployee);
- }
+Every time a message is sent a greeter, it first validates the message
containing a `User` and extracts its name. Both messages and state are strongly
typed - either one of the default [built-in types]({{< ref
"docs/sdk/appendix#types" >}}) - or a [custom type](#types) as in this case.
- private void greetCustomer(Context context, Customer message) {
- System.out.println("Hello customer " + message.getName());
- }
+The function finally builds a custom greeting for the user.
+The number of times that particular user has been seen so far is queried from
the state store and updated
+and the greeting is sent to the users' inbox (another function type).
- private void greetEmployee(Context context, Employee message) {
- System.out.println("Hello employee " + message.getEmployeeId());
- }
+## Types
- private void greetManager(Context context, Employee message) {
- System.out.println("Hello manager " + message.getEmployeeId());
- }
-}
-```
+Stateful Functions strongly types ll messages and state values.
+Because they run in a distributed manner and state values are persisted to
stable storage, Stateful Functions aims to provide efficient and easy to user
serializers.
-#### Making Your Function Complete
+Out of the box, all SDKs offer a set of highly optimized serializers for
common primitive types; boolean, numerics, and strings.
+Additionally, users are encouraged to plug-in custom types to model more
complex data structures.
-Similar to the first example, match functions are partial by default and will
throw an ``IllegalStateException`` on any input that does not match any branch.
-They can be made complete by providing an ``otherwise`` clause that serves as
a catch-all for unmatched input, think of it as a default clause in a Java
switch statement.
-The ``otherwise`` action takes its message as an untyped ``java.lang.Object``,
allowing you to handle any unexpected messages.
+In the [example above](#defining-a-stateful-function), the greeter function
consumes `User` messages, a POJO type containing several fields.
+By defining a custom type, this object can be passed transparently between
functions and stored in state.
+And because the type is tied to a logical typename, instead of the physical
Java class, it can be passed to functions written in other langauge SDKs.
```java
-package org.apache.flink.statefun.docs.match;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.match.MatchBinder;
-import org.apache.flink.statefun.sdk.match.StatefulMatchFunction;
-
-public class FnMatchGreeterWithCatchAll extends StatefulMatchFunction {
-
- @Override
- public void configure(MatchBinder binder) {
- binder
- .predicate(Customer.class, this::greetCustomer)
- .predicate(Employee.class, Employee::isManager,
this::greetManager)
- .predicate(Employee.class, this::greetEmployee)
- .otherwise(this::catchAll);
- }
-
- private void greetCustomer(Context context, Customer message) {
- System.out.println("Hello customer " + message.getName());
- }
-
- private void greetEmployee(Context context, Employee message) {
- System.out.println("Hello employee " + message.getEmployeeId());
- }
-
- private void greetManager(Context context, Employee message) {
- System.out.println("Hello manager " + message.getEmployeeId());
- }
-
- private void catchAll(Context context, Object message) {
- System.out.println("Hello unexpected message");
- }
-}
-```
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.types.SimpleType;
+import org.apache.flink.statefun.sdk.java.types.Type;
+import java.util.Objects;
-#### Action Resolution Order
+public class User {
-Match functions will always match actions from most to least specific using
the following resolution rules.
+ private static final ObjectMapper mapper = new ObjectMapper();
-First, find an action that matches the type and predicate. If two predicates
will return true for a particular input, the one registered in the binder first
wins.
-Next, search for an action that matches the type but does not have an
associated predicate.
-Finally, if a catch-all exists, it will be executed or an
``IllegalStateException`` will be thrown.
+ public static final Type<User> TYPE = SimpleType.simpleImmutableTypeFrom(
+ TypeName.typeNameFromString("com.example/User"),
+ mapper:writeValueAsBytes,
+ bytes -> mapper.readValue(byes, User.class));
-## Function Types and Messaging
+ private final String name;
-In Java, function types are defined as logical pointers composed of a
namespace and name.
-The type is bound to the implementing class in the [module]({{< ref
"docs/sdk/overview#embedded-module" >}}) definition.
-Below is an example function type for the hello world function.
+ private final String favoriteColor;
-```java
-package org.apache.flink.statefun.docs;
+ @JsonCreator
+ public User(
+ @JsonProperty("name") String name,
+ @JsonProperty("favorite_color" String favoriteColor)) {
-import org.apache.flink.statefun.sdk.FunctionType;
+ this.name = Objects.requireNonNull(name);
+ this.favoriteColor = Objects.requireNonNull(favoriteColor);
+ }
-/** A function type that will be bound to {@link FnHelloWorld}. */
-public class Identifiers {
+ public String getName() {
+ return name;
+ }
- public static final FunctionType HELLO_TYPE = new
FunctionType("apache/flink", "hello");
-}
+ public String getFavoriteColor() {
+ return favoriteColor;
+ }
+
+ @Override
+ public String toString() {
+ return "User{name=" name + ",favoriteColor=" favoriteColor + "}"
+ }
```
-This type can then be referenced from other functions to create an address and
message a particular instance.
+## State
-```java
-package org.apache.flink.statefun.docs;
+Stateful Functions treats state as a first class citizen and so all functions
can easily define state that is automatically made fault tolerant by the
runtime.
+State declaration is as simple as defining one or more `ValueSpec`'s
describing your state values.
+Value specifications are defined with a unique (to the function) name and
[type](#types).
+At runtime, functions can `get`, `set`, and `remove` state values scoped to
the address of the current message.
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-/** A simple stateful function that sends a message to the user with id
"user1" */
-public class FnCaller implements StatefulFunction {
+{{< hint info >}}
+All value specificiations must be earerly registered in the
`StatefulFuctionSpec` when composing
+the applications [RequestReplyHandler](#exposing-functions).
+{{< /hint >}}
- @Override
- public void invoke(Context context, Object input) {
- context.send(Identifiers.HELLO_TYPE, "user1", new MyUserMessage());
- }
-}
+```java
+// Value specification for a state named `seen`
+// with the primitive integer type
+ValueSpec
+ .named("seen")
+ .withIntType();
+
+// Value specification with a custom type
+ValueSpec
+ .name("user")
+ .withCustomType(User.TYPE);
```
-## Sending Delayed Messages
+### State Expiration
-Functions are able to send messages on a delay so that they will arrive after
some duration.
-Functions may even send themselves delayed messages that can serve as a
callback.
-The delayed message is non-blocking so functions will continue to process
records between the time a delayed message is sent and received.
+By default, state values are persisted until manually `remove`d by the user.
+Optionally, they may be configured to expire and be automatically deleted
after a specified duration.
```java
-package org.apache.flink.statefun.docs.delay;
-
-import java.time.Duration;
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-public class FnDelayedMessage implements StatefulFunction {
-
- @Override
- public void invoke(Context context, Object input) {
- if (input instanceof Message) {
- System.out.println("Hello");
- context.sendAfter(Duration.ofMinutes(1),
context.self(), new DelayedMessage());
- }
-
- if (input instanceof DelayedMessage) {
- System.out.println("Welcome to the future!");
- }
- }
-}
+// Value specification that will automatically
+// delete the value if the function instance goes
+// more than 30 minutes without being called
+ValueSpec
+ .named("seen")
+ .thatExpiresAfterCall(Duration.ofDays(1))
+ .withIntType();
+
+// Value specification that will automatically
+// delete the value if it goes more than 1 day
+// without being written
+ValueSpec
+ .named("seen")
+ .thatExpireAfterWrite(Duration.ofDays(1))
+ .withIntType();
```
-## Completing Async Requests
-
-When interacting with external systems, such as a database or API, one needs
to take care that communication delay with the external system does not
dominate the application’s total work.
-Stateful Functions allows registering a Java ``CompletableFuture`` that will
resolve to a value at some point in the future.
-Future's are registered along with a metadata object that provides additional
context about the caller.
+## Sending Delayed Messages
-When the future completes, either successfully or exceptionally, the caller
function type and id will be invoked with a ``AsyncOperationResult``.
-An asynchronous result can complete in one of three states:
+Functions can send messages on a delay so that they will arrive after some
duration.
+They may even send themselves delayed messages that can serve as a callback.
+The delayed message is non-blocking, so functions will continue to process
records between when a delayed message is sent and received.
+Additionally, they are fault-tolerant and never lost, even when recovering
from failure.
-### Success
+This example sends a response back to the calling function after a 30 minute
delay.
-The asynchronous operation has succeeded, and the produced result can be
obtained via ``AsyncOperationResult#value``.
+```java
+import java.util.concurrent.CompletableFuture;
+import java.time.Duration;
-### Failure
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.message.Message;
-The asynchronous operation has failed, and the cause can be obtained via
``AsyncOperationResult#throwable``.
+public class DelayedFn implements StatefulFunction {
-### Unknown
+ private static final Logger LOG = LoggerFactory.getLogger(DelayedFn.class);
-The stateful function was restarted, possibly on a different machine, before
the ``CompletableFuture`` was completed, therefore it is unknown what is the
status of the asynchronous operation.
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/delayed");
-```java
-package org.apache.flink.statefun.docs.async;
+ @Override
+ CompletableFuture<Void> apply(Context context, Message message) {
+ if (!context.caller().isPresent()) {
+ LOG.debug("Message has no known caller meaning it was sent
directly from an ingress");
+ return;
+ }
-import java.util.concurrent.CompletableFuture;
-import org.apache.flink.statefun.sdk.AsyncOperationResult;
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-@SuppressWarnings("unchecked")
-public class EnrichmentFunction implements StatefulFunction {
-
- private final QueryService client;
-
- public EnrichmentFunction(QueryService client) {
- this.client = client;
- }
-
- @Override
- public void invoke(Context context, Object input) {
- if (input instanceof User) {
- onUser(context, (User) input);
- } else if (input instanceof AsyncOperationResult) {
- onAsyncResult((AsyncOperationResult) input);
- }
- }
-
- private void onUser(Context context, User user) {
- CompletableFuture<UserEnrichment> future =
client.getDataAsync(user.getUserId());
- context.registerAsyncOperation(user, future);
- }
-
- private void onAsyncResult(AsyncOperationResult<User, UserEnrichment>
result) {
- if (result.successful()) {
- User metadata = result.metadata();
- UserEnrichment value = result.value();
- System.out.println(
- String.format("Successfully completed future:
%s %s", metadata, value));
- } else if (result.failure()) {
- System.out.println(
- String.format("Something has gone terribly
wrong %s", result.throwable()));
- } else {
- System.out.println("Not sure what happened, maybe
retry");
- }
- }
+ var caller = context.caller().get();
+ context.sendAfter(Duration.ofMinutes(30), MessageBuilder
+ .forAddress(caller)
+ .withValue("Hello from the future!"));
+ }
}
```
-## Persistence
-
-Stateful Functions treats state as a first class citizen and so all stateful
functions can easily define state that is automatically made fault tolerant by
the runtime.
-All stateful functions may contain state by merely defining one or more
persisted fields.
+## Egress
-The simplest way to get started is with a ``PersistedValue``, which is defined
by its name and the class of the type that it stores.
-The data is always scoped to a specific function type and identifier.
-Below is a stateful function that greets users based on the number of times
they have been seen.
-
-{{< hint info >}}
-All **PersistedValue**, **PersistedTable**, and **PersistedAppendingBuffer**
fields must be marked with a **@Persisted** annotation or they will not be made
fault tolerant by the runtime.
-{{< /hint >}}
+Functions can message other stateful functions and egresses, exit points for
sending messages to the outside world.
+As with other messages, egress messages are always well-typed.
+Additionally, they contain metadata pertinent to the specific egress type.
+{{< tabs "egress" >}}
+{{< tab "Apache Kafka" >}}
```java
-package org.apache.flink.statefun.docs;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.FunctionType;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-import org.apache.flink.statefun.sdk.annotations.Persisted;
-import org.apache.flink.statefun.sdk.state.PersistedValue;
-
-public class FnUserGreeter implements StatefulFunction {
-
- public static FunctionType TYPE = new FunctionType("example",
"greeter");
-
- @Persisted
- private final PersistedValue<Integer> count =
PersistedValue.of("count", Integer.class);
-
- public void invoke(Context context, Object input) {
- String userId = context.self().id();
- int seen = count.getOrDefault(0);
-
- switch (seen) {
- case 0:
- System.out.println(String.format("Hello %s!",
userId));
- break;
- case 1:
- System.out.println("Hello Again!");
- break;
- case 2:
- System.out.println("Third time is the charm
:)");
- break;
- default:
- System.out.println(String.format("Hello for the
%d-th time", seen + 1));
- }
-
- count.set(seen + 1);
- }
-}
-```
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
+import org.apache.flink.statefun.sdk.java.io.KafkaEgressMessage;
-``PersistedValue`` comes with the right primitive methods to build powerful
stateful applications.
-Calling ``PersistedValue#get`` will return the current value of an object
stored in state, or ``null`` if nothing is set.
-Conversely, ``PersistedValue#set`` will update the value in state and
``PersistedValue#clear`` will delete the value from state.
+public class GreeterFn implements StatefulFunction {
-### Collection Types
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
-Along with ``PersistedValue``, the Java SDK supports two persisted collection
types.
-``PersistedTable`` is a collection of keys and values, and
``PersistedAppendingBuffer`` is an append-only buffer.
+ static final TypeName KAFKA_EGRESS =
TypeName.forNameFromString("com.example/greets");
-These types are functionally equivalent to ``PersistedValue<Map>`` and
``PersistedValue<Collection>`` respectively but may provide better performance
in some situations.
+ static final ValueSpec<Integer> SEEN =
ValueSpec.named("seen").withIntType();
-```java
-@Persisted
-PersistedTable<String, Integer> table = PersistedTable.of("my-table",
String.class, Integer.class);
+ @Override
+ CompletableFuture<Void> apply(Context context, Message message) {
+ if (!message.is(User.TYPE)) {
+ throw new IllegalStateException("Unknown type");
+ }
-@Persisted
-PersistedAppendingBuffer<Integer> buffer =
PersistedAppendingBuffer.of("my-buffer", Integer.class);
-```
+ User user = message.as(User.TYPE);
+ String name = user.getName();
-### Dynamic State Registration
+ var storage = context.storage();
+ var seen = storage.get(SEEN).orElse(0);
+ storage.set(SEEN, seen + 1);
-Using the above state types, a function's persisted state must be defined
eagerly. You cannot use those state types to
-register a new persisted state during invocations (i.e., in the ``invoke``
method) or after the function instance is created.
+ context.send(
+ KafkaEgressMessage.forEgress(KAFKA_EGRESS)
+ .withTopic("greetings")
+ .withUtf8Key(name)
+ .withUtf8Value("Hello " + name + " for the " + seen + "th
time!")
+ .build());
-If dynamic state registration is required, it can be achieved using a
``PersistedStateRegistry``:
-
-```java
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.FunctionType;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-import org.apache.flink.statefun.sdk.annotations.Persisted;
-import org.apache.flink.statefun.sdk.state.PersistedStateRegistry;
-import org.apache.flink.statefun.sdk.state.PersistedValue;
-
-public class MyFunction implements StatefulFunction {
-
- @Persisted
- private final PersistedStateRegistry registry = new
PersistedStateRegistry();
-
- private PersistedValue<Integer> value;
-
- public void invoke(Context context, Object input) {
- if (value == null) {
- value = PersistedValue.of("my-value", Integer.class);
- registry.registerValue(value);
- }
- int count = value.getOrDefault(0);
- // ...
- }
+ return context.done();
+ }
}
```
-
-Note how the ``PersistedValue`` field doesn't need to be annotated with the
``@Persisted`` annotations, and is initially
-empty. The state object is dynamically created during invocation and
registered with the ``PersistedStateRegistry`` so
-that the system picks it up to be managed for fault-tolerance.
-
-### State Expiration
-
-Persisted states may be configured to expire and be deleted after a specified
duration.
-This is supported by all types of state:
-
+{{< /tab >}}
+{{< tab "Amazon Kinesis" >}}
```java
-@Persisted
-PersistedValue<Integer> value = PersistedValue.of(
- "my-value",
- Integer.class,
- Expiration.expireAfterWriting(Duration.ofHours(1)));
-
-@Persisted
-PersistedTable<String, Integer> table = PersistedTable.of(
- "my-table",
- String.class,
- Integer.class,
- Expiration.expireAfterWriting(Duration.ofMinutes(5)));
-
-@Persisted
-PersistedAppendingBuffer<Integer> buffer = PersistedAppendingBuffer.of(
- "my-buffer",
- Integer.class,
- Expiration.expireAfterWriting(Duration.ofSeconds(30)));
-```
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
+import org.apache.flink.statefun.sdk.java.io.KinesisEgressMessage;
-There are two expiration modes supported:
+public class GreeterFn implements StatefulFunction {
-```java
-Expiration.expireAfterWriting(...)
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
-Expiration.expireAfterReadingOrWriting(...)
-```
+ static final TypeName KINESIS_EGRESS =
TypeName.forNameFromString("com.example/greets");
Review comment:
forNameFromString => typeNameFromString
##########
File path: docs/content/docs/sdk/java.md
##########
@@ -29,451 +29,395 @@ under the License.
Stateful functions are the building blocks of applications; they are atomic
units of isolation, distribution, and persistence.
As objects, they encapsulate the state of a single entity (e.g., a specific
user, device, or session) and encode its behavior.
Stateful functions can interact with each other, and external systems, through
message passing.
-The Java SDK is supported as an [embedded module]({{< ref
"docs/sdk/overview#embedded-module" >}}).
To get started, add the Java SDK as a dependency to your application.
-{{< artifact statefun-sdk >}}
+{{< artifact statefun-sdk-java >}}
## Defining A Stateful Function
-A stateful function is any class that implements the ``StatefulFunction``
interface.
-The following is an example of a simple hello world function.
+A stateful function is any class that implements the `StatefulFunction`
interface.
+In the following example, a `StatefulFunction` maintains a count for every user
+of an application, emitting a customized greeting.
```java
-package org.apache.flink.statefun.docs;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-public class FnHelloWorld implements StatefulFunction {
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
- @Override
- public void invoke(Context context, Object input) {
- System.out.println("Hello " + input.toString());
- }
-}
-```
+public class GreeterFn implements StatefulFunction {
-Functions process each incoming message through their ``invoke`` method.
-Input's are untyped and passed through the system as a ``java.lang.Object`` so
one function can potentially process multiple types of messages.
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
-The ``Context`` provides metadata about the current message and function, and
is how you can call other functions or external systems.
-Functions are invoked based on a function type and unique identifier.
+ static final TypeName INBOX =
TypeName.forNameFromString("com.example.fns/inbox");
-### Stateful Match Function
+ static final ValueSpec<Integer> SEEN =
ValueSpec.named("seen").withIntType();
-Stateful functions provide a powerful abstraction for working with events and
state, allowing developers to build components that can react to any kind of
message.
-Commonly, functions only need to handle a known set of message types, and the
``StatefulMatchFunction`` interface provides an opinionated solution to that
problem.
+ @Override
+ CompletableFuture<Void> apply(Context context, Message message) {
+ if (!message.is(User.TYPE)) {
+ throw new IllegalStateException("Unknown type");
+ }
-#### Simple Match Function
+ User user = message.as(User.TYPE);
+ String name = user.getName();
-Stateful match functions are an opinionated variant of stateful functions for
precisely this pattern.
-Developers outline expected types, optional predicates, and well-typed
business logic and let the system dispatch each input to the correct action.
-Variants are bound inside a ``configure`` method that is executed once the
first time an instance is loaded.
+ var storage = context.storage();
+ var seen = storage.get(SEEN).orElse(0);
+ storage.set(SEEN, seen + 1);
-```java
-package org.apache.flink.statefun.docs.match;
+ context.send(
+ MessageBuilder.forAddress(INBOX, name)
+ .withValue("Hello " + name + " for the " + seen + "th time!")
+ .build());
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.match.MatchBinder;
-import org.apache.flink.statefun.sdk.match.StatefulMatchFunction;
+ return context.done();
+ }
+}
+```
-public class FnMatchGreeter extends StatefulMatchFunction {
+This code declares a greeter function that will be
[registered](#exposing-functions) under the logical type name
`com.example.fns/greeter`. Type names must take the form `<namesapce>/<name>`.
+It contains a single `ValueSpec`, which is implicitly scoped to the current
address and stores an integer.
- @Override
- public void configure(MatchBinder binder) {
- binder
- .predicate(Customer.class, this::greetCustomer)
- .predicate(Employee.class, Employee::isManager,
this::greetManager)
- .predicate(Employee.class, this::greetEmployee);
- }
+Every time a message is sent a greeter, it first validates the message
containing a `User` and extracts its name. Both messages and state are strongly
typed - either one of the default [built-in types]({{< ref
"docs/sdk/appendix#types" >}}) - or a [custom type](#types) as in this case.
- private void greetCustomer(Context context, Customer message) {
- System.out.println("Hello customer " + message.getName());
- }
+The function finally builds a custom greeting for the user.
+The number of times that particular user has been seen so far is queried from
the state store and updated
+and the greeting is sent to the users' inbox (another function type).
- private void greetEmployee(Context context, Employee message) {
- System.out.println("Hello employee " + message.getEmployeeId());
- }
+## Types
- private void greetManager(Context context, Employee message) {
- System.out.println("Hello manager " + message.getEmployeeId());
- }
-}
-```
+Stateful Functions strongly types ll messages and state values.
+Because they run in a distributed manner and state values are persisted to
stable storage, Stateful Functions aims to provide efficient and easy to user
serializers.
-#### Making Your Function Complete
+Out of the box, all SDKs offer a set of highly optimized serializers for
common primitive types; boolean, numerics, and strings.
+Additionally, users are encouraged to plug-in custom types to model more
complex data structures.
-Similar to the first example, match functions are partial by default and will
throw an ``IllegalStateException`` on any input that does not match any branch.
-They can be made complete by providing an ``otherwise`` clause that serves as
a catch-all for unmatched input, think of it as a default clause in a Java
switch statement.
-The ``otherwise`` action takes its message as an untyped ``java.lang.Object``,
allowing you to handle any unexpected messages.
+In the [example above](#defining-a-stateful-function), the greeter function
consumes `User` messages, a POJO type containing several fields.
+By defining a custom type, this object can be passed transparently between
functions and stored in state.
+And because the type is tied to a logical typename, instead of the physical
Java class, it can be passed to functions written in other langauge SDKs.
```java
-package org.apache.flink.statefun.docs.match;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.match.MatchBinder;
-import org.apache.flink.statefun.sdk.match.StatefulMatchFunction;
-
-public class FnMatchGreeterWithCatchAll extends StatefulMatchFunction {
-
- @Override
- public void configure(MatchBinder binder) {
- binder
- .predicate(Customer.class, this::greetCustomer)
- .predicate(Employee.class, Employee::isManager,
this::greetManager)
- .predicate(Employee.class, this::greetEmployee)
- .otherwise(this::catchAll);
- }
-
- private void greetCustomer(Context context, Customer message) {
- System.out.println("Hello customer " + message.getName());
- }
-
- private void greetEmployee(Context context, Employee message) {
- System.out.println("Hello employee " + message.getEmployeeId());
- }
-
- private void greetManager(Context context, Employee message) {
- System.out.println("Hello manager " + message.getEmployeeId());
- }
-
- private void catchAll(Context context, Object message) {
- System.out.println("Hello unexpected message");
- }
-}
-```
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.types.SimpleType;
+import org.apache.flink.statefun.sdk.java.types.Type;
+import java.util.Objects;
-#### Action Resolution Order
+public class User {
-Match functions will always match actions from most to least specific using
the following resolution rules.
+ private static final ObjectMapper mapper = new ObjectMapper();
-First, find an action that matches the type and predicate. If two predicates
will return true for a particular input, the one registered in the binder first
wins.
-Next, search for an action that matches the type but does not have an
associated predicate.
-Finally, if a catch-all exists, it will be executed or an
``IllegalStateException`` will be thrown.
+ public static final Type<User> TYPE = SimpleType.simpleImmutableTypeFrom(
+ TypeName.typeNameFromString("com.example/User"),
+ mapper:writeValueAsBytes,
+ bytes -> mapper.readValue(byes, User.class));
-## Function Types and Messaging
+ private final String name;
-In Java, function types are defined as logical pointers composed of a
namespace and name.
-The type is bound to the implementing class in the [module]({{< ref
"docs/sdk/overview#embedded-module" >}}) definition.
-Below is an example function type for the hello world function.
+ private final String favoriteColor;
-```java
-package org.apache.flink.statefun.docs;
+ @JsonCreator
+ public User(
+ @JsonProperty("name") String name,
+ @JsonProperty("favorite_color" String favoriteColor)) {
-import org.apache.flink.statefun.sdk.FunctionType;
+ this.name = Objects.requireNonNull(name);
+ this.favoriteColor = Objects.requireNonNull(favoriteColor);
+ }
-/** A function type that will be bound to {@link FnHelloWorld}. */
-public class Identifiers {
+ public String getName() {
+ return name;
+ }
- public static final FunctionType HELLO_TYPE = new
FunctionType("apache/flink", "hello");
-}
+ public String getFavoriteColor() {
+ return favoriteColor;
+ }
+
+ @Override
+ public String toString() {
+ return "User{name=" name + ",favoriteColor=" favoriteColor + "}"
+ }
```
-This type can then be referenced from other functions to create an address and
message a particular instance.
+## State
-```java
-package org.apache.flink.statefun.docs;
+Stateful Functions treats state as a first class citizen and so all functions
can easily define state that is automatically made fault tolerant by the
runtime.
+State declaration is as simple as defining one or more `ValueSpec`'s
describing your state values.
+Value specifications are defined with a unique (to the function) name and
[type](#types).
+At runtime, functions can `get`, `set`, and `remove` state values scoped to
the address of the current message.
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-/** A simple stateful function that sends a message to the user with id
"user1" */
-public class FnCaller implements StatefulFunction {
+{{< hint info >}}
+All value specificiations must be earerly registered in the
`StatefulFuctionSpec` when composing
+the applications [RequestReplyHandler](#exposing-functions).
+{{< /hint >}}
- @Override
- public void invoke(Context context, Object input) {
- context.send(Identifiers.HELLO_TYPE, "user1", new MyUserMessage());
- }
-}
+```java
+// Value specification for a state named `seen`
+// with the primitive integer type
+ValueSpec
+ .named("seen")
+ .withIntType();
+
+// Value specification with a custom type
+ValueSpec
+ .name("user")
+ .withCustomType(User.TYPE);
```
-## Sending Delayed Messages
+### State Expiration
-Functions are able to send messages on a delay so that they will arrive after
some duration.
-Functions may even send themselves delayed messages that can serve as a
callback.
-The delayed message is non-blocking so functions will continue to process
records between the time a delayed message is sent and received.
+By default, state values are persisted until manually `remove`d by the user.
+Optionally, they may be configured to expire and be automatically deleted
after a specified duration.
```java
-package org.apache.flink.statefun.docs.delay;
-
-import java.time.Duration;
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-public class FnDelayedMessage implements StatefulFunction {
-
- @Override
- public void invoke(Context context, Object input) {
- if (input instanceof Message) {
- System.out.println("Hello");
- context.sendAfter(Duration.ofMinutes(1),
context.self(), new DelayedMessage());
- }
-
- if (input instanceof DelayedMessage) {
- System.out.println("Welcome to the future!");
- }
- }
-}
+// Value specification that will automatically
+// delete the value if the function instance goes
+// more than 30 minutes without being called
+ValueSpec
+ .named("seen")
+ .thatExpiresAfterCall(Duration.ofDays(1))
+ .withIntType();
+
+// Value specification that will automatically
+// delete the value if it goes more than 1 day
+// without being written
+ValueSpec
+ .named("seen")
+ .thatExpireAfterWrite(Duration.ofDays(1))
+ .withIntType();
```
-## Completing Async Requests
-
-When interacting with external systems, such as a database or API, one needs
to take care that communication delay with the external system does not
dominate the application’s total work.
-Stateful Functions allows registering a Java ``CompletableFuture`` that will
resolve to a value at some point in the future.
-Future's are registered along with a metadata object that provides additional
context about the caller.
+## Sending Delayed Messages
-When the future completes, either successfully or exceptionally, the caller
function type and id will be invoked with a ``AsyncOperationResult``.
-An asynchronous result can complete in one of three states:
+Functions can send messages on a delay so that they will arrive after some
duration.
+They may even send themselves delayed messages that can serve as a callback.
+The delayed message is non-blocking, so functions will continue to process
records between when a delayed message is sent and received.
+Additionally, they are fault-tolerant and never lost, even when recovering
from failure.
-### Success
+This example sends a response back to the calling function after a 30 minute
delay.
-The asynchronous operation has succeeded, and the produced result can be
obtained via ``AsyncOperationResult#value``.
+```java
+import java.util.concurrent.CompletableFuture;
+import java.time.Duration;
-### Failure
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.message.Message;
-The asynchronous operation has failed, and the cause can be obtained via
``AsyncOperationResult#throwable``.
+public class DelayedFn implements StatefulFunction {
-### Unknown
+ private static final Logger LOG = LoggerFactory.getLogger(DelayedFn.class);
-The stateful function was restarted, possibly on a different machine, before
the ``CompletableFuture`` was completed, therefore it is unknown what is the
status of the asynchronous operation.
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/delayed");
-```java
-package org.apache.flink.statefun.docs.async;
+ @Override
+ CompletableFuture<Void> apply(Context context, Message message) {
+ if (!context.caller().isPresent()) {
+ LOG.debug("Message has no known caller meaning it was sent
directly from an ingress");
+ return;
+ }
-import java.util.concurrent.CompletableFuture;
-import org.apache.flink.statefun.sdk.AsyncOperationResult;
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-@SuppressWarnings("unchecked")
-public class EnrichmentFunction implements StatefulFunction {
-
- private final QueryService client;
-
- public EnrichmentFunction(QueryService client) {
- this.client = client;
- }
-
- @Override
- public void invoke(Context context, Object input) {
- if (input instanceof User) {
- onUser(context, (User) input);
- } else if (input instanceof AsyncOperationResult) {
- onAsyncResult((AsyncOperationResult) input);
- }
- }
-
- private void onUser(Context context, User user) {
- CompletableFuture<UserEnrichment> future =
client.getDataAsync(user.getUserId());
- context.registerAsyncOperation(user, future);
- }
-
- private void onAsyncResult(AsyncOperationResult<User, UserEnrichment>
result) {
- if (result.successful()) {
- User metadata = result.metadata();
- UserEnrichment value = result.value();
- System.out.println(
- String.format("Successfully completed future:
%s %s", metadata, value));
- } else if (result.failure()) {
- System.out.println(
- String.format("Something has gone terribly
wrong %s", result.throwable()));
- } else {
- System.out.println("Not sure what happened, maybe
retry");
- }
- }
+ var caller = context.caller().get();
+ context.sendAfter(Duration.ofMinutes(30), MessageBuilder
+ .forAddress(caller)
+ .withValue("Hello from the future!"));
+ }
}
```
-## Persistence
-
-Stateful Functions treats state as a first class citizen and so all stateful
functions can easily define state that is automatically made fault tolerant by
the runtime.
-All stateful functions may contain state by merely defining one or more
persisted fields.
+## Egress
-The simplest way to get started is with a ``PersistedValue``, which is defined
by its name and the class of the type that it stores.
-The data is always scoped to a specific function type and identifier.
-Below is a stateful function that greets users based on the number of times
they have been seen.
-
-{{< hint info >}}
-All **PersistedValue**, **PersistedTable**, and **PersistedAppendingBuffer**
fields must be marked with a **@Persisted** annotation or they will not be made
fault tolerant by the runtime.
-{{< /hint >}}
+Functions can message other stateful functions and egresses, exit points for
sending messages to the outside world.
+As with other messages, egress messages are always well-typed.
+Additionally, they contain metadata pertinent to the specific egress type.
+{{< tabs "egress" >}}
+{{< tab "Apache Kafka" >}}
```java
-package org.apache.flink.statefun.docs;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.FunctionType;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-import org.apache.flink.statefun.sdk.annotations.Persisted;
-import org.apache.flink.statefun.sdk.state.PersistedValue;
-
-public class FnUserGreeter implements StatefulFunction {
-
- public static FunctionType TYPE = new FunctionType("example",
"greeter");
-
- @Persisted
- private final PersistedValue<Integer> count =
PersistedValue.of("count", Integer.class);
-
- public void invoke(Context context, Object input) {
- String userId = context.self().id();
- int seen = count.getOrDefault(0);
-
- switch (seen) {
- case 0:
- System.out.println(String.format("Hello %s!",
userId));
- break;
- case 1:
- System.out.println("Hello Again!");
- break;
- case 2:
- System.out.println("Third time is the charm
:)");
- break;
- default:
- System.out.println(String.format("Hello for the
%d-th time", seen + 1));
- }
-
- count.set(seen + 1);
- }
-}
-```
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
+import org.apache.flink.statefun.sdk.java.io.KafkaEgressMessage;
-``PersistedValue`` comes with the right primitive methods to build powerful
stateful applications.
-Calling ``PersistedValue#get`` will return the current value of an object
stored in state, or ``null`` if nothing is set.
-Conversely, ``PersistedValue#set`` will update the value in state and
``PersistedValue#clear`` will delete the value from state.
+public class GreeterFn implements StatefulFunction {
-### Collection Types
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
-Along with ``PersistedValue``, the Java SDK supports two persisted collection
types.
-``PersistedTable`` is a collection of keys and values, and
``PersistedAppendingBuffer`` is an append-only buffer.
+ static final TypeName KAFKA_EGRESS =
TypeName.forNameFromString("com.example/greets");
Review comment:
forNameFromString => typeNameFromString
##########
File path: docs/content/docs/sdk/java.md
##########
@@ -29,451 +29,395 @@ under the License.
Stateful functions are the building blocks of applications; they are atomic
units of isolation, distribution, and persistence.
As objects, they encapsulate the state of a single entity (e.g., a specific
user, device, or session) and encode its behavior.
Stateful functions can interact with each other, and external systems, through
message passing.
-The Java SDK is supported as an [embedded module]({{< ref
"docs/sdk/overview#embedded-module" >}}).
To get started, add the Java SDK as a dependency to your application.
-{{< artifact statefun-sdk >}}
+{{< artifact statefun-sdk-java >}}
## Defining A Stateful Function
-A stateful function is any class that implements the ``StatefulFunction``
interface.
-The following is an example of a simple hello world function.
+A stateful function is any class that implements the `StatefulFunction`
interface.
+In the following example, a `StatefulFunction` maintains a count for every user
+of an application, emitting a customized greeting.
```java
-package org.apache.flink.statefun.docs;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-public class FnHelloWorld implements StatefulFunction {
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
- @Override
- public void invoke(Context context, Object input) {
- System.out.println("Hello " + input.toString());
- }
-}
-```
+public class GreeterFn implements StatefulFunction {
-Functions process each incoming message through their ``invoke`` method.
-Input's are untyped and passed through the system as a ``java.lang.Object`` so
one function can potentially process multiple types of messages.
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
-The ``Context`` provides metadata about the current message and function, and
is how you can call other functions or external systems.
-Functions are invoked based on a function type and unique identifier.
+ static final TypeName INBOX =
TypeName.forNameFromString("com.example.fns/inbox");
-### Stateful Match Function
+ static final ValueSpec<Integer> SEEN =
ValueSpec.named("seen").withIntType();
-Stateful functions provide a powerful abstraction for working with events and
state, allowing developers to build components that can react to any kind of
message.
-Commonly, functions only need to handle a known set of message types, and the
``StatefulMatchFunction`` interface provides an opinionated solution to that
problem.
+ @Override
+ CompletableFuture<Void> apply(Context context, Message message) {
+ if (!message.is(User.TYPE)) {
+ throw new IllegalStateException("Unknown type");
+ }
-#### Simple Match Function
+ User user = message.as(User.TYPE);
+ String name = user.getName();
-Stateful match functions are an opinionated variant of stateful functions for
precisely this pattern.
-Developers outline expected types, optional predicates, and well-typed
business logic and let the system dispatch each input to the correct action.
-Variants are bound inside a ``configure`` method that is executed once the
first time an instance is loaded.
+ var storage = context.storage();
+ var seen = storage.get(SEEN).orElse(0);
+ storage.set(SEEN, seen + 1);
-```java
-package org.apache.flink.statefun.docs.match;
+ context.send(
+ MessageBuilder.forAddress(INBOX, name)
+ .withValue("Hello " + name + " for the " + seen + "th time!")
+ .build());
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.match.MatchBinder;
-import org.apache.flink.statefun.sdk.match.StatefulMatchFunction;
+ return context.done();
+ }
+}
+```
-public class FnMatchGreeter extends StatefulMatchFunction {
+This code declares a greeter function that will be
[registered](#exposing-functions) under the logical type name
`com.example.fns/greeter`. Type names must take the form `<namesapce>/<name>`.
+It contains a single `ValueSpec`, which is implicitly scoped to the current
address and stores an integer.
- @Override
- public void configure(MatchBinder binder) {
- binder
- .predicate(Customer.class, this::greetCustomer)
- .predicate(Employee.class, Employee::isManager,
this::greetManager)
- .predicate(Employee.class, this::greetEmployee);
- }
+Every time a message is sent a greeter, it first validates the message
containing a `User` and extracts its name. Both messages and state are strongly
typed - either one of the default [built-in types]({{< ref
"docs/sdk/appendix#types" >}}) - or a [custom type](#types) as in this case.
- private void greetCustomer(Context context, Customer message) {
- System.out.println("Hello customer " + message.getName());
- }
+The function finally builds a custom greeting for the user.
+The number of times that particular user has been seen so far is queried from
the state store and updated
+and the greeting is sent to the users' inbox (another function type).
- private void greetEmployee(Context context, Employee message) {
- System.out.println("Hello employee " + message.getEmployeeId());
- }
+## Types
- private void greetManager(Context context, Employee message) {
- System.out.println("Hello manager " + message.getEmployeeId());
- }
-}
-```
+Stateful Functions strongly types ll messages and state values.
+Because they run in a distributed manner and state values are persisted to
stable storage, Stateful Functions aims to provide efficient and easy to user
serializers.
-#### Making Your Function Complete
+Out of the box, all SDKs offer a set of highly optimized serializers for
common primitive types; boolean, numerics, and strings.
+Additionally, users are encouraged to plug-in custom types to model more
complex data structures.
-Similar to the first example, match functions are partial by default and will
throw an ``IllegalStateException`` on any input that does not match any branch.
-They can be made complete by providing an ``otherwise`` clause that serves as
a catch-all for unmatched input, think of it as a default clause in a Java
switch statement.
-The ``otherwise`` action takes its message as an untyped ``java.lang.Object``,
allowing you to handle any unexpected messages.
+In the [example above](#defining-a-stateful-function), the greeter function
consumes `User` messages, a POJO type containing several fields.
+By defining a custom type, this object can be passed transparently between
functions and stored in state.
+And because the type is tied to a logical typename, instead of the physical
Java class, it can be passed to functions written in other langauge SDKs.
```java
-package org.apache.flink.statefun.docs.match;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.match.MatchBinder;
-import org.apache.flink.statefun.sdk.match.StatefulMatchFunction;
-
-public class FnMatchGreeterWithCatchAll extends StatefulMatchFunction {
-
- @Override
- public void configure(MatchBinder binder) {
- binder
- .predicate(Customer.class, this::greetCustomer)
- .predicate(Employee.class, Employee::isManager,
this::greetManager)
- .predicate(Employee.class, this::greetEmployee)
- .otherwise(this::catchAll);
- }
-
- private void greetCustomer(Context context, Customer message) {
- System.out.println("Hello customer " + message.getName());
- }
-
- private void greetEmployee(Context context, Employee message) {
- System.out.println("Hello employee " + message.getEmployeeId());
- }
-
- private void greetManager(Context context, Employee message) {
- System.out.println("Hello manager " + message.getEmployeeId());
- }
-
- private void catchAll(Context context, Object message) {
- System.out.println("Hello unexpected message");
- }
-}
-```
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.types.SimpleType;
+import org.apache.flink.statefun.sdk.java.types.Type;
+import java.util.Objects;
-#### Action Resolution Order
+public class User {
-Match functions will always match actions from most to least specific using
the following resolution rules.
+ private static final ObjectMapper mapper = new ObjectMapper();
-First, find an action that matches the type and predicate. If two predicates
will return true for a particular input, the one registered in the binder first
wins.
-Next, search for an action that matches the type but does not have an
associated predicate.
-Finally, if a catch-all exists, it will be executed or an
``IllegalStateException`` will be thrown.
+ public static final Type<User> TYPE = SimpleType.simpleImmutableTypeFrom(
+ TypeName.typeNameFromString("com.example/User"),
+ mapper:writeValueAsBytes,
+ bytes -> mapper.readValue(byes, User.class));
-## Function Types and Messaging
+ private final String name;
-In Java, function types are defined as logical pointers composed of a
namespace and name.
-The type is bound to the implementing class in the [module]({{< ref
"docs/sdk/overview#embedded-module" >}}) definition.
-Below is an example function type for the hello world function.
+ private final String favoriteColor;
-```java
-package org.apache.flink.statefun.docs;
+ @JsonCreator
+ public User(
+ @JsonProperty("name") String name,
+ @JsonProperty("favorite_color" String favoriteColor)) {
-import org.apache.flink.statefun.sdk.FunctionType;
+ this.name = Objects.requireNonNull(name);
+ this.favoriteColor = Objects.requireNonNull(favoriteColor);
+ }
-/** A function type that will be bound to {@link FnHelloWorld}. */
-public class Identifiers {
+ public String getName() {
+ return name;
+ }
- public static final FunctionType HELLO_TYPE = new
FunctionType("apache/flink", "hello");
-}
+ public String getFavoriteColor() {
+ return favoriteColor;
+ }
+
+ @Override
+ public String toString() {
+ return "User{name=" name + ",favoriteColor=" favoriteColor + "}"
+ }
```
-This type can then be referenced from other functions to create an address and
message a particular instance.
+## State
-```java
-package org.apache.flink.statefun.docs;
+Stateful Functions treats state as a first class citizen and so all functions
can easily define state that is automatically made fault tolerant by the
runtime.
+State declaration is as simple as defining one or more `ValueSpec`'s
describing your state values.
+Value specifications are defined with a unique (to the function) name and
[type](#types).
+At runtime, functions can `get`, `set`, and `remove` state values scoped to
the address of the current message.
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-/** A simple stateful function that sends a message to the user with id
"user1" */
-public class FnCaller implements StatefulFunction {
+{{< hint info >}}
+All value specificiations must be earerly registered in the
`StatefulFuctionSpec` when composing
+the applications [RequestReplyHandler](#exposing-functions).
+{{< /hint >}}
- @Override
- public void invoke(Context context, Object input) {
- context.send(Identifiers.HELLO_TYPE, "user1", new MyUserMessage());
- }
-}
+```java
+// Value specification for a state named `seen`
+// with the primitive integer type
+ValueSpec
+ .named("seen")
+ .withIntType();
+
+// Value specification with a custom type
+ValueSpec
+ .name("user")
+ .withCustomType(User.TYPE);
```
-## Sending Delayed Messages
+### State Expiration
-Functions are able to send messages on a delay so that they will arrive after
some duration.
-Functions may even send themselves delayed messages that can serve as a
callback.
-The delayed message is non-blocking so functions will continue to process
records between the time a delayed message is sent and received.
+By default, state values are persisted until manually `remove`d by the user.
+Optionally, they may be configured to expire and be automatically deleted
after a specified duration.
```java
-package org.apache.flink.statefun.docs.delay;
-
-import java.time.Duration;
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-public class FnDelayedMessage implements StatefulFunction {
-
- @Override
- public void invoke(Context context, Object input) {
- if (input instanceof Message) {
- System.out.println("Hello");
- context.sendAfter(Duration.ofMinutes(1),
context.self(), new DelayedMessage());
- }
-
- if (input instanceof DelayedMessage) {
- System.out.println("Welcome to the future!");
- }
- }
-}
+// Value specification that will automatically
+// delete the value if the function instance goes
+// more than 30 minutes without being called
+ValueSpec
+ .named("seen")
+ .thatExpiresAfterCall(Duration.ofDays(1))
+ .withIntType();
+
+// Value specification that will automatically
+// delete the value if it goes more than 1 day
+// without being written
+ValueSpec
+ .named("seen")
+ .thatExpireAfterWrite(Duration.ofDays(1))
+ .withIntType();
```
-## Completing Async Requests
-
-When interacting with external systems, such as a database or API, one needs
to take care that communication delay with the external system does not
dominate the application’s total work.
-Stateful Functions allows registering a Java ``CompletableFuture`` that will
resolve to a value at some point in the future.
-Future's are registered along with a metadata object that provides additional
context about the caller.
+## Sending Delayed Messages
-When the future completes, either successfully or exceptionally, the caller
function type and id will be invoked with a ``AsyncOperationResult``.
-An asynchronous result can complete in one of three states:
+Functions can send messages on a delay so that they will arrive after some
duration.
+They may even send themselves delayed messages that can serve as a callback.
+The delayed message is non-blocking, so functions will continue to process
records between when a delayed message is sent and received.
+Additionally, they are fault-tolerant and never lost, even when recovering
from failure.
-### Success
+This example sends a response back to the calling function after a 30 minute
delay.
-The asynchronous operation has succeeded, and the produced result can be
obtained via ``AsyncOperationResult#value``.
+```java
+import java.util.concurrent.CompletableFuture;
+import java.time.Duration;
-### Failure
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.message.Message;
-The asynchronous operation has failed, and the cause can be obtained via
``AsyncOperationResult#throwable``.
+public class DelayedFn implements StatefulFunction {
-### Unknown
+ private static final Logger LOG = LoggerFactory.getLogger(DelayedFn.class);
-The stateful function was restarted, possibly on a different machine, before
the ``CompletableFuture`` was completed, therefore it is unknown what is the
status of the asynchronous operation.
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/delayed");
-```java
-package org.apache.flink.statefun.docs.async;
+ @Override
+ CompletableFuture<Void> apply(Context context, Message message) {
+ if (!context.caller().isPresent()) {
+ LOG.debug("Message has no known caller meaning it was sent
directly from an ingress");
+ return;
+ }
-import java.util.concurrent.CompletableFuture;
-import org.apache.flink.statefun.sdk.AsyncOperationResult;
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-
-@SuppressWarnings("unchecked")
-public class EnrichmentFunction implements StatefulFunction {
-
- private final QueryService client;
-
- public EnrichmentFunction(QueryService client) {
- this.client = client;
- }
-
- @Override
- public void invoke(Context context, Object input) {
- if (input instanceof User) {
- onUser(context, (User) input);
- } else if (input instanceof AsyncOperationResult) {
- onAsyncResult((AsyncOperationResult) input);
- }
- }
-
- private void onUser(Context context, User user) {
- CompletableFuture<UserEnrichment> future =
client.getDataAsync(user.getUserId());
- context.registerAsyncOperation(user, future);
- }
-
- private void onAsyncResult(AsyncOperationResult<User, UserEnrichment>
result) {
- if (result.successful()) {
- User metadata = result.metadata();
- UserEnrichment value = result.value();
- System.out.println(
- String.format("Successfully completed future:
%s %s", metadata, value));
- } else if (result.failure()) {
- System.out.println(
- String.format("Something has gone terribly
wrong %s", result.throwable()));
- } else {
- System.out.println("Not sure what happened, maybe
retry");
- }
- }
+ var caller = context.caller().get();
+ context.sendAfter(Duration.ofMinutes(30), MessageBuilder
+ .forAddress(caller)
+ .withValue("Hello from the future!"));
+ }
}
```
-## Persistence
-
-Stateful Functions treats state as a first class citizen and so all stateful
functions can easily define state that is automatically made fault tolerant by
the runtime.
-All stateful functions may contain state by merely defining one or more
persisted fields.
+## Egress
-The simplest way to get started is with a ``PersistedValue``, which is defined
by its name and the class of the type that it stores.
-The data is always scoped to a specific function type and identifier.
-Below is a stateful function that greets users based on the number of times
they have been seen.
-
-{{< hint info >}}
-All **PersistedValue**, **PersistedTable**, and **PersistedAppendingBuffer**
fields must be marked with a **@Persisted** annotation or they will not be made
fault tolerant by the runtime.
-{{< /hint >}}
+Functions can message other stateful functions and egresses, exit points for
sending messages to the outside world.
+As with other messages, egress messages are always well-typed.
+Additionally, they contain metadata pertinent to the specific egress type.
+{{< tabs "egress" >}}
+{{< tab "Apache Kafka" >}}
```java
-package org.apache.flink.statefun.docs;
-
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.FunctionType;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-import org.apache.flink.statefun.sdk.annotations.Persisted;
-import org.apache.flink.statefun.sdk.state.PersistedValue;
-
-public class FnUserGreeter implements StatefulFunction {
-
- public static FunctionType TYPE = new FunctionType("example",
"greeter");
-
- @Persisted
- private final PersistedValue<Integer> count =
PersistedValue.of("count", Integer.class);
-
- public void invoke(Context context, Object input) {
- String userId = context.self().id();
- int seen = count.getOrDefault(0);
-
- switch (seen) {
- case 0:
- System.out.println(String.format("Hello %s!",
userId));
- break;
- case 1:
- System.out.println("Hello Again!");
- break;
- case 2:
- System.out.println("Third time is the charm
:)");
- break;
- default:
- System.out.println(String.format("Hello for the
%d-th time", seen + 1));
- }
-
- count.set(seen + 1);
- }
-}
-```
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
+import org.apache.flink.statefun.sdk.java.io.KafkaEgressMessage;
-``PersistedValue`` comes with the right primitive methods to build powerful
stateful applications.
-Calling ``PersistedValue#get`` will return the current value of an object
stored in state, or ``null`` if nothing is set.
-Conversely, ``PersistedValue#set`` will update the value in state and
``PersistedValue#clear`` will delete the value from state.
+public class GreeterFn implements StatefulFunction {
-### Collection Types
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
-Along with ``PersistedValue``, the Java SDK supports two persisted collection
types.
-``PersistedTable`` is a collection of keys and values, and
``PersistedAppendingBuffer`` is an append-only buffer.
+ static final TypeName KAFKA_EGRESS =
TypeName.forNameFromString("com.example/greets");
-These types are functionally equivalent to ``PersistedValue<Map>`` and
``PersistedValue<Collection>`` respectively but may provide better performance
in some situations.
+ static final ValueSpec<Integer> SEEN =
ValueSpec.named("seen").withIntType();
-```java
-@Persisted
-PersistedTable<String, Integer> table = PersistedTable.of("my-table",
String.class, Integer.class);
+ @Override
+ CompletableFuture<Void> apply(Context context, Message message) {
+ if (!message.is(User.TYPE)) {
+ throw new IllegalStateException("Unknown type");
+ }
-@Persisted
-PersistedAppendingBuffer<Integer> buffer =
PersistedAppendingBuffer.of("my-buffer", Integer.class);
-```
+ User user = message.as(User.TYPE);
+ String name = user.getName();
-### Dynamic State Registration
+ var storage = context.storage();
+ var seen = storage.get(SEEN).orElse(0);
+ storage.set(SEEN, seen + 1);
-Using the above state types, a function's persisted state must be defined
eagerly. You cannot use those state types to
-register a new persisted state during invocations (i.e., in the ``invoke``
method) or after the function instance is created.
+ context.send(
+ KafkaEgressMessage.forEgress(KAFKA_EGRESS)
+ .withTopic("greetings")
+ .withUtf8Key(name)
+ .withUtf8Value("Hello " + name + " for the " + seen + "th
time!")
+ .build());
-If dynamic state registration is required, it can be achieved using a
``PersistedStateRegistry``:
-
-```java
-import org.apache.flink.statefun.sdk.Context;
-import org.apache.flink.statefun.sdk.FunctionType;
-import org.apache.flink.statefun.sdk.StatefulFunction;
-import org.apache.flink.statefun.sdk.annotations.Persisted;
-import org.apache.flink.statefun.sdk.state.PersistedStateRegistry;
-import org.apache.flink.statefun.sdk.state.PersistedValue;
-
-public class MyFunction implements StatefulFunction {
-
- @Persisted
- private final PersistedStateRegistry registry = new
PersistedStateRegistry();
-
- private PersistedValue<Integer> value;
-
- public void invoke(Context context, Object input) {
- if (value == null) {
- value = PersistedValue.of("my-value", Integer.class);
- registry.registerValue(value);
- }
- int count = value.getOrDefault(0);
- // ...
- }
+ return context.done();
+ }
}
```
-
-Note how the ``PersistedValue`` field doesn't need to be annotated with the
``@Persisted`` annotations, and is initially
-empty. The state object is dynamically created during invocation and
registered with the ``PersistedStateRegistry`` so
-that the system picks it up to be managed for fault-tolerance.
-
-### State Expiration
-
-Persisted states may be configured to expire and be deleted after a specified
duration.
-This is supported by all types of state:
-
+{{< /tab >}}
+{{< tab "Amazon Kinesis" >}}
```java
-@Persisted
-PersistedValue<Integer> value = PersistedValue.of(
- "my-value",
- Integer.class,
- Expiration.expireAfterWriting(Duration.ofHours(1)));
-
-@Persisted
-PersistedTable<String, Integer> table = PersistedTable.of(
- "my-table",
- String.class,
- Integer.class,
- Expiration.expireAfterWriting(Duration.ofMinutes(5)));
-
-@Persisted
-PersistedAppendingBuffer<Integer> buffer = PersistedAppendingBuffer.of(
- "my-buffer",
- Integer.class,
- Expiration.expireAfterWriting(Duration.ofSeconds(30)));
-```
+import java.util.concurrent.CompletableFuture;
+import org.apache.flink.statefun.sdk.java.Context;
+import org.apache.flink.statefun.sdk.java.StatefulFunction;
+import org.apache.flink.statefun.sdk.java.TypeName;
+import org.apache.flink.statefun.sdk.java.ValueSpec;
+import org.apache.flink.statefun.sdk.java.message.Message;
+import org.apache.flink.statefun.sdk.java.io.KinesisEgressMessage;
-There are two expiration modes supported:
+public class GreeterFn implements StatefulFunction {
-```java
-Expiration.expireAfterWriting(...)
+ static final TypeName TYPE =
TypeName.forNameFromString("com.example.fns/greeter");
Review comment:
forNameFromString => typeNameFromString
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