jbertram commented on a change in pull request #3930:
URL: https://github.com/apache/activemq-artemis/pull/3930#discussion_r812335923
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File path: docs/user-manual/en/address-model.md
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@@ -1,455 +1,242 @@
-# Addressing Model
+# Address Model
-Apache ActiveMQ Artemis has a unique addressing model that is both powerful and
-flexible and that offers great performance. The addressing model comprises
-three main concepts: **addresses**, **queues**, and **routing types**.
+Every messaging protocol and API that Apache ActiveMQ Artemis supports defines
+a different set of messaging resources.
+
+ - JMS uses _queues_ and _topics_
+ - STOMP uses generic _destinations_
+ - MQTT uses _topics_
+ - AMQP uses generic _nodes_
+
+In order to deal the the unique semantics and use-cases for each of these the
+broker has a flexible and powerful address model and a _core_ set of resources:
+
+ - **address**
+ - **queue**
+ - **routing type**
### Address
-An address represents a messaging endpoint. Within the configuration, a typical
-address is given a unique name, 0 or more queues, and a routing type.
+Messages are *sent* to an address. An address is given a unique name, a routing
+type, and zero or more queues.
### Queue
-A queue is associated with an address. There can be multiple queues per
-address. Once an incoming message is matched to an address, the message will be
-sent on to one or more of its queues, depending on the routing type configured.
-Queues can be configured to be automatically created and deleted.
+Messages are *consumed* from a queue. A queue is bound to an address. There can
+be zero or more queues bound to one address. When a message is sent to an
+address it is routed to one or more of its queues based on the configured
+routing type.
-### Routing Types
+The name of the queue must be _globally_ unique. For example, you can't have a
+queue named `q1` on address `a1` and also a queue named `q1` address `a2`.
-A routing type determines how messages are sent to the queues associated with
-an address. An Apache ActiveMQ Artemis address can be configured with two
-different routing types.
+### Routing Type
-Table 1. Routing Types
+A routing type determines how messages are routed from an address to the
+queue(s) bound to that address. Two different routing types are supported,
+**anycast** and **multicast**.
If you want your messages routed to...|Use this routing type...
---|---
-A single queue within the matching address, in a point-to-point manner.|Anycast
-Every queue within the matching address, in a publish-subscribe
manner.|Multicast
-
-
-**Note:** It is possible to define more than one routing type per address, but
-this typically results in an anti-pattern and is therefore not recommended. If
-an address does use both routing types, however, and the client does not show a
-preference for either one, the broker typically defaults to the anycast routing
-type.
-
-The one exception is when the client uses the MQTT protocol. In that case, the
-default routing type is multicast.
-
-For additional details about these concepts refer to [the core](core.md)
chapter.
-
-## Basic Address Configuration
-
-The following examples show how to configure basic point to point and publish
-subscribe addresses.
-
-### Point-to-Point Messaging
-
-Point-to-point messaging is a common scenario in which a message sent by a
-producer has only one consumer. AMQP and JMS message producers and consumers
-can make use of point-to-point messaging queues, for example. Define an anycast
-routing type for an address so that its queues receive messages in a
-point-to-point manner.
-
-When a message is received on an address using anycast, Apache ActiveMQ Artemis
-locates the queue associated with the address and routes the message to it.
-When consumers request to consume from the address, the broker locates the
-relevant queue and associates this queue with the appropriate consumers. If
-multiple consumers are connected to the same queue, messages are distributed
-amongst each consumer equally, providing the consumers are equally able to
-handle them.
-
-
-Figure 1. Point to Point Messaging
-
-#### Using the Anycast Routing Type
-
-Open the file `<broker-instance>/etc/broker.xml` for editing.
-
-Add an address configuration element and its associated queue if they do not
-exist already.
+a single queue on the address.|anycast
+every queue on the address.|multicast
-**Note:** For normal Point to Point semantics, the queue name **MUST** match
the
-address name.
-
-```xml
-<addresses>
- <address name="orders">
- <anycast>
- <queue name="orders"/>
- </anycast>
- </address>
-</addresses>
-```
+> **Note:**
+>
+> It is possible to define more than one routing type per address, but this
+> typically results in an anti-pattern and is therefore not recommended.
-### Publish-Subscribe Messaging
+## Automatic Configuration
-In a publish-subscribe scenario, messages are sent to every consumer subscribed
-to an address. JMS topics and MQTT subscriptions are two examples of
-publish-subscribe messaging.
+By default Apache ActiveMQ Artemis will automatically create addresses and
+queues to support the semantics of whatever protocol you're using. The broker
+understands how to support each protocol's functionality with the core
+resources so that in most cases no manual configuration is required. This saves
+you from having to preconfigure each address and queue before a client can
+connect to it.
-To configure an address with publish-subscribe semantics, create an address
-with the multicast routing type.
+The broker can optionally be configured to automatically delete addresses and
+queues when they are no longer in use.
-
-Figure 2. Publish-Subscribe
+Automatic creation and deletion is configured on a per address basis and is
+controlled by the following [`address-setting`](address-settings.md) elements:
-#### Using the Multicast Routing Type
+- `auto-create-addresses`
+- `auto-delete-addresses`
+- `default-address-routing-type`
+- `auto-create-queues`
+- `auto-delete-queues`
+- `default-queue-routing-type`
-Open the file `<broker-instance>/etc/broker.xml` for editing.
+See [the documentation on address settings](address-settings.md) for more
+details on these elements.
-Add an address configuration element with multicast routing type.
+Of course, automatic configuration can be disabled and everything can be
+configured manually. Read on for more details about manual configuration.
-```xml
-<addresses>
- <address name="pubsub.foo">
- <multicast/>
- </address>
-</addresses>
-```
+## Basic Manual Configuration
-When clients connect to an address with the multicast element, a subscription
-queue for the client will be automatically created for the client. It is also
-possible to pre-configure subscription queues and connect to them directly
-using the queue's [Fully Qualified Queue names](#fully-qualified-queue-names).
+The following examples show how to configure resources for basic anycast and
+multicast use-cases.
-Optionally add one or more queue elements to the address and wrap the multicast
-element around them. This step is typically not needed since the broker will
-automatically create a queue for each subscription requested by a client.
-
-```xml
-<addresses>
- <address name="pubsub.foo">
- <multicast>
- <queue name="client123.pubsub.foo"/>
- <queue name="client456.pubsub.foo"/>
- </multicast>
- </address>
-</addresses>
-```
-
-Figure 3. Point-to-Point with Two Queues
+> **Note:**
+>
+> Many of the details of these use-cases are protocol agnostic. The goal here
+> is to demonstrate and explain the basic configuration elements and how the
+> address model works fundamentally.
-### Point-to-Point Address multiple Queues
+### Anycast
-It is actually possible to define more than one queue on an address with an
-anycast routing type. When messages are received on such an address, they are
-firstly distributed evenly across all the defined queues. Using [Fully
-Qualified Queue names](#fully-qualified-queue-names), clients are able to
-select the queue that they would like to subscribe to. Should more than one
-consumer connect directly to a single queue, Apache ActiveMQ Artemis will take
-care of distributing messages between them, as in the example above.
+The most common use-case for anycast semantics, sometimes referred to as
+[point-to-point](messaging-concepts.md#point-to-point), involves applications
+following a "competing consumer" pattern to receive messages from a shared
+queue. The more consumers receiving messages the greater the overall message
+throughput. Multiple Java applications sharing a JMS queue is a classic example
+of this use-case.
-
-Figure 3. Point-to-Point with Two Queues
+In this use-case the broker is configured, for example, with an address,
+`anycast.foo` using the `anycast` routing type with just one queue, `q1`. When
+a producer sends a message to `address.foo` it is then routed to `q1` and
+finally dispatched to one of the consumers.
-**Note:** This is how Apache ActiveMQ Artemis handles load balancing of queues
-across multiple nodes in a cluster. Configuring a Point-to-Point Address with
-two queues, open the file `<broker-instance>/etc/broker.xml` for editing.
+
+Figure 1. Anycast
-Add an address configuration with Anycast routing type element and its
-associated queues.
+This is what the configuration for this use-case would look like in
+`etc/broker.xml`:
```xml
<addresses>
<address name="address.foo">
<anycast>
<queue name="q1"/>
- <queue name="q2"/>
</anycast>
</address>
</addresses>
```
-### Point-to-Point and Publish-Subscribe Addresses
-
-It is possible to define an address with both point-to-point and
-publish-subscribe semantics enabled. While not typically recommend, this can be
-useful when you want, for example, a JMS Queue say orders and a JMS Topic named
-orders. The different routing types make the addresses appear to be distinct.
-
-Using an example of JMS Clients, the messages sent by a JMS message producer
-will be routed using the anycast routing type. Messages sent by a JMS topic
-producer will use the multicast routing type. In addition when a JMS topic
-consumer attaches, it will be attached to it’s own subscription queue. JMS
-queue consumer will be attached to the anycast queue.
-
-
-Figure 4. Point-to-Point and Publish-Subscribe
-
-**Note:** The behavior in this scenario is dependent on the protocol being
-used. For JMS there is a clear distinction between topic and queue producers
-and consumers, which make the logic straight forward. Other protocols like AMQP
-do not make this distinction. A message being sent via AMQP will be routed by
-both anycast and multicast and consumers will default to anycast. For more
-information, please check the behavior of each protocol in the sections on
-protocols.
-
-The XML snippet below is an example of what the configuration for an address
-using both anycast and multicast would look like in
-`<broker-instance>/etc/broker.xml`. Note that subscription queues are typically
-created on demand, so there is no need to list specific queue elements inside
-the multicast routing type.
+For most protocols and APIs which support this kind of use-case (e.g. JMS,
+AMQP, etc.) it is customary to use the _same name_ when sending and consuming
+messages. In that case you'd use a configuration like this:
```xml
<addresses>
- <address name="foo.orders">
+ <address name="orderQueue">
<anycast>
- <queue name="orders"/>
+ <queue name="orderQueue"/>
</anycast>
- <multicast/>
</address>
</addresses>
```
-## How to filter messages
+### Multicast
-Apache ActiveMQ Artemis supports the ability to filter messages using Apache
-Artemis [Filter Expressions](filter-expressions.md).
+The most common use-case for multicast semantics, sometimes referred to as
+[publish/subscribe](messaging-concepts.md#publish-subscribe) or "pub/sub",
+involves each application receiving every message sent to an address. Multiple
+applications consuming from a JMS topic is a classic example of this use-case.
+MQTT subscriptions is another supported example of multicast semantics.
-Filters can be applied in two places, on a queue and on a consumer.
+In this use-case the broker is configured with an address, `anycast.foo` using
+the `multicast` routing type with two queues, `q1` & `q2`. When a producer
+sends a message to `address.foo` it is then routed to *both* `q1` & `q2` so
+that ultimately both consumers receive the same messages.
-### Queue Filter
+
+Figure 2. Multicast
-When a filter is applied to a queue, messages are filtered before they are
sent to
-the queue. To add a queue filter use the filter element when configuring a
-queue. Open up `<broker-instance>/etc/broker.xml` and add an address with a
-queue, using the filter element to configure a filter on this queue.
+This is what the configuration for this use-case would look like in
+`etc/broker.xml`:
```xml
<addresses>
- <address name="filter">
- <queue name="filter">
- <filter string="color='red'"/>
- </queue>
+ <address name="address.foo">
+ <multicast>
+ <queue name="q1"/>
+ <queue name="q2"/>
+ </multicast>
</address>
</addresses>
```
-
-The filter defined above ensures that only messages with an attribute
-`"color='red'"` is sent to this queue.
-
-### Consumer Filters
-
-Consumer filters are applied after messages have reached a queue and are
-defined using the appropriate client APIs. The following JMS example shows how
-consumer filters work.
-
-1. Define an address with a single queue, with no filter applied.
+This basic configuration is simple and straight-forward, but there's a
+problem. In a normal pub/sub use-case like with a JMS topic or with MQTT the
+number of subscribers *isn't known ahead of time*. In that case, this is the
+recommended configuration:
```xml
<addresses>
- <address name="filter">
- <queue name="filter"/>
+ <address name="address.foo">
+ <multicast/>
</address>
</addresses>
```
-
-```java
-...
-// Send some messages
-for (int i = 0; i < 3; i ++) {
- TextMessage redMessage = senderSession.createTextMessage("Red");
- redMessage.setStringProperty("color", "red");
- producer.send(redMessage)
-
- TextMessage greenMessage = senderSession.createTextMessage("Green");
- greenMessage.setStringProperty("color", "green");
- producer.send(greenMessage)
-}
-```
-
-At this point the queue would have 6 messages: red,green,red,green,red,green
-
-```java
-MessageConsumer redConsumer = redSession.createConsumer(queue, "color='red'");
-```
-
-The redConsumer has a filter that only matches "red" messages. The redConsumer
-will receive 3 messages.
-
-```
-red, red, red
-```
-
-The resulting queue would now be
-
-```
-green, green, green
-```
-
-## Automatic Address/Queue Management
-
-You can configure Apache ActiveMQ Artemis to automatically create addresses and
-queues, and then delete them when they are no longer in use. This saves you
-from having to preconfigure each address and queue before a client can connect
-to it. Automatic creation and deletion is configured on a per address basis and
-is controlled by following:
-
-Parameter|Description
----|---
-`auto-create-addresses`|When set to true, the broker will create the address
requested by the client if it does not exist already. The default is `true`.
-`auto-delete-addresses`|When set to true, the broker will be delete any
**auto-created** address once all of it’s queues have been deleted. The default
is `true`
-`default-address-routing-type`|The routing type to use if the client does not
specify one. Possible values are `MULTICAST` and `ANYCAST`. See earlier in this
chapter for more information about routing types. The default value is
`MULTICAST`.
-
-### Auto Address Creation
-
-- Edit the file `<broker-instance>/etc/broker.xml` and add the
- `auto-create-addresses` element to the `address-setting` you want the broker
- to automatically create.
-
-- (Optional) Add the `address-setting` if it does not exist. Use the match
- parameter and the [wildcard syntax](wildcard-syntax.md) to match more than
- one specific address.
-
-- Set `auto-create-addresses` to `true`
-
-- (Optional) Assign `MULTICAST` or `ANYCAST` as the default routing type for
- the address.
-
-The example below configures an `address-setting` to be automatically created
-by the broker. The default routing type to be used if not specified by the
-client is MULTICAST. Note that wildcard syntax is used. Any address starting
-with `/news/politics/` will be automatically created by the broker.
-
-```xml
-<address-setting match="/news/politics/#">
- <auto-create-addresses>true</auto-create-addresses>
- <default-address-routing-type>MULTICAST</default-address-routing-type>
-</address-setting>
-```
-
-### Auto Address Deletion
-
-- Edit the file `<broker-instance>/etc/broker.xml` and add the
- `auto-delete-addresses` element to the `address-setting` you want the broker
to
- automatically delete.
-
-- (Optional) Add the `address-setting` if it does not exist. Use the match
- parameter and the [wildcard syntax](wildcard-syntax.md) to match more than
one
- specific address.
-
-- Set `auto-delete-addresses` to `true`
-
-The example below configures an `address-setting` to be automatically deleted
-by the broker. Note that wildcard syntax is used. Any address request by the
-client that starts with `/news/politics/` is configured to be automatically
-deleted by the broker.
-
-```xml
-<address-setting match="/news/politics/#">
- <auto-delete-addresses>true</auto-delete-addresses>
- <default-address-routing-type>MULTICAST</default-address-routing-type>
-</address-setting>
-```
-
-## "Fully Qualified" Queue Names
-
-Internally the broker maps a client’s request for an address to specific
-queues. The broker decides on behalf of the client which queues to send
-messages to or from which queue to receive messages. However, more advanced use
-cases might require that the client specify a queue directly. In these
-situations the client uses a fully qualified queue name, by specifying both
-the address name and the queue name, separated by `::`.
-
-> **Note**
->
-> The string `::` should only be used for FQQN and not in any other context
-> in address or queue names.
-
-Currently Artemis supports fully qualified queue names on Core, AMQP, JMS,
-OpenWire, MQTT and STOMP protocols for both sending and receiving messages.
-
-### Specifying a Fully Qualified Queue Name
-
-In this example, the address foo is configured with two queues q1, q2 as shown
-in the configuration below.
+Define `<multicast/>` with no queues and the broker will automatically create
+queues for each subscription when the consumers connect to `address.foo`. Then
+when a message is sent to `address.foo` it will be routed to each queue for
+each subscriber and therefore each subscriber will get every message. These
+queues are often referred to as _subscription queues_ for obvious reasons.
+
+These subscription queues are typically named based on the semantics of the
+protocol used to create them. For example, JMS supports durable and non-durable
+subscriptions. The queue for a non-durable subscription is named with a UUID,
+but the queue used for a durable subscription is named according to the JMS
+"client ID" and "subscription name." Similar conventions are used for AMQP,
+MQTT, STOMP, etc.
+
+## Advanced Manual Configuration
+
+### Fully Qualified Queue Names
+
+In most cases it’s not necessary or desirable to statically configure the
+aforementioned subscription queues. However, there are scenarios where a user
+may want to statically configure a subscription queue and later connect to that
+queue directly using a **Fully Qualified Queue Name** (i.e. FQQN).
+
+An FQQN uses a special syntax to specify *both* the address and the queue so
+that applications using protocols and APIs which don't natively understand the
+address/queue separation (e.g. AMQP, JMS, etc.) can send messages or subscribe
+*directly* to a queue rather than being limited to the address. Applications
+simply need to use the address name and the queue name separated by `::` (e.g.
+`address::queue`).
+
+In this example, the address `a1` is configured with two queues: `q1`, `q2` as
+shown in the configuration below.
```xml
<addresses>
- <address name="foo">
- <anycast>
+ <address name="a1">
+ <multicast>
<queue name="q1" />
<queue name="q2" />
- </anycast>
+ </multicast>
</address>
</addresses>
```
-In the client code, use both the address name and the queue name when
-requesting a connection from the broker. Remember to use two colons, `::`, to
-separate the names, as in the example Java code below.
+Here's a snippet of Java code using JMS which demonstrates the FQQN syntax:
```java
-String FQQN = "foo::q1";
+String FQQN = "a1::q1";
Queue q1 session.createQueue(FQQN);
Review comment:
Done.
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