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new ff3ed92 Create dubbo-zk.md (#1) (#82)
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commit ff3ed92ee56b0feef64268d35b4f8c2a3d933ecf
Author: Mani's hub <[email protected]>
AuthorDate: Thu Aug 9 14:14:30 2018 +0800
Create dubbo-zk.md (#1) (#82)
* Create dubbo-zk.md (#1)
* Update blog.js
* Update blog.js
---
blog/en-us/dubbo-zk.md | 335 +++++++++++++++++++++++++++++++++++++++++++++++++
site_config/blog.js | 7 ++
2 files changed, 342 insertions(+)
diff --git a/blog/en-us/dubbo-zk.md b/blog/en-us/dubbo-zk.md
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+# Using Zookeeper in Dubbo
+
+## Introduction of Zookeeper
+
+### The basic concept
+
+In the mordern distrbuted applications, there are multiple coordination
problems between nodes and nodes, including: leader election, group service,
locking, configuration management, naming and synchronization. Apache
Zookeeper, as its name implied, is a distributed, open-source coordination
service framwork to address these demand.
+
+In order to ensure the high performance, highly available and strictly ordered
access, the performance aspects of ZooKeeper means it can be used in large,
distributed systems and can also be deployed in cluster mode, which called
'ZooKeeper ensemble'. In ZooKeeper ensemble, all write requests from clients
are forwarded to a single server, called the leader, through the ZAB(Zookeeper
Atomic Broadcast Protocol) to make sure the message in each nodes are same.
Clients can access any one of [...]
+
+
+
+*Image Credit : ebook -Zookeeper-Distributed Process Coordination from
O'Reilly*
+
+The method to store the data in Zookeeper is similar as the standard UNIX file
system, as a data model styled after the familiar directory tree structure of
file systems. When we talking about ZooKeeper data nodes, we call it Znodes to
clarify it.
+
+
+*Image Credit : ebook -Zookeeper-Distributed Process Coordination from
O'Reilly*
+
+### Basic Implementation
+
+You could donwload and install Zookeeper directly[^2].
+Or you could use Homebrew [^3] `brew install zookeeper` to install Zookeeper
in Mac OS.
+Considering the versatility, we run the Zookeeper by using docker in this
blog. If you have not installed the docker yet, please prepare the docker
environment first. [^4]
+
+#### 1. Running the Zookeeper
+
+Execute the command to run zookeeper in a docker container
+
+```shell
+docker run --rm --name zookeeper -p 2181:2181 zookeeper
+```
+
+#### 2. Entering the zookeeper container
+
+```shell
+docker exec -it zookeeper bash
+```
+
+In the `bin` directory, there is a command to start zookeeper `zkServer` and
the Management Console `zkCli`
+
+```shell
+bash-4.4# ls -l bin
+total 36
+-rwxr-xr-x 1 zookeepe zookeepe 232 Mar 27 04:32 README.txt
+-rwxr-xr-x 1 zookeepe zookeepe 1937 Mar 27 04:32 zkCleanup.sh
+-rwxr-xr-x 1 zookeepe zookeepe 1056 Mar 27 04:32 zkCli.cmd
+-rwxr-xr-x 1 zookeepe zookeepe 1534 Mar 27 04:32 zkCli.sh
+-rwxr-xr-x 1 zookeepe zookeepe 1759 Mar 27 04:32 zkEnv.cmd
+-rwxr-xr-x 1 zookeepe zookeepe 2696 Mar 27 04:32 zkEnv.sh
+-rwxr-xr-x 1 zookeepe zookeepe 1089 Mar 27 04:32 zkServer.cmd
+-rwxr-xr-x 1 zookeepe zookeepe 6773 Mar 27 04:32 zkServer.sh
+```
+
+#### 3. Entering the zookeeper management interface via zkCli
+
+Since it was started through docker, the process of Zookeeper has been started
and will provide the services to the public via port 2181.
+
+```shell
+bash-4.4# ps
+PID USER TIME COMMAND
+ 1 zookeepe 0:02 /usr/lib/jvm/java-1.8-openjdk/jre/bin/java
-Dzookeeper.log.dir=. -Dzookeeper.root
+ 32 root 0:00 bash
+ 42 root 0:00 ps
+```
+
+So, it allows you to access Zookeeper's console directly through `zkCli ` for
management.
+
+```shell
+bash-4.4# bin/zkCli.sh -server 127.0.0.1:2181
+Connecting to 127.0.0.1:2181
+...
+WATCHER::
+
+WatchedEvent state:SyncConnected type:None path:null
+
+[zk: 127.0.0.1:2181(CONNECTED) 0] help
+ZooKeeper -server host:port cmd args
+ stat path [watch]
+ set path data [version]
+ ls path [watch]
+ delquota [-n|-b] path
+ ls2 path [watch]
+ setAcl path acl
+ setquota -n|-b val path
+ history
+ redo cmdno
+ printwatches on|off
+ delete path [version]
+ sync path
+ listquota path
+ rmr path
+ get path [watch]
+ create [-s] [-e] path data acl
+ addauth scheme auth
+ quit
+ getAcl path
+ close
+ connect host:port
+```
+
+#### 4. Basic Examples on zkCli
+
+Create `/hello-zone` node:
+```shell
+[zk: 127.0.0.1:2181(CONNECTED) 19] create /hello-zone 'world'
+Created /hello-zone
+```
+
+List the child nodes under `/` and confirm that `hello-zone` is created:
+
+```shell
+[zk: 127.0.0.1:2181(CONNECTED) 20] ls /
+[zookeeper, hello-zone]
+```
+
+List the child nodes for `/hello-zone` and verify that it is empty:
+
+```shell
+[zk: 127.0.0.1:2181(CONNECTED) 21] ls /hello-zone
+[]
+```
+
+Get the data stored on the `/hello-zone` node:
+
+```shell
+[zk: 127.0.0.1:2181(CONNECTED) 22] get /hello-zone
+world
+```
+
+## Using Zookeeper in Dubbo
+Zookeeper is used for service registration discovery and configuration
management in Dubbo, and the structure of data in Zookeeper is shown in the
following figure:
+
+
+
+First, all data related to Dubbo is organized under the root node of `/duboo`.
+
+The secondary directory is the service name like `com.foo.BarService`.
+
+The three-level directory has two child nodes, `providers` and `consumers`,
representing the supplier and customers of the service.
+
+The URL information for each application instance associated with the service
will be recorded by the Level 4 directory. The `providers` and `consumer` will
stored the providers information and the consumers information of the services
seperately.
+For example, the service provider of `com.foo.BarService` will register its
URL Information to `/dubbo/com.foo.BarService/providers`; Similarly, service
consumers will register their information under the corresponding `consumer`
node. At the same time, consumers will subscribe to the corresponding
`providers` node to be able to detect the changes of the service provider
address list.
+
+### Prepare the sample code
+
+The code in this document can be found in
https://github.com/dubbo/dubbo-samples/tree/master/dubbo-samples-zookeeper.
+
+#### 1. Interface definition
+
+Define a simple `greetingservice` interface with only one simple method named
`sayHello` to greet to the caller.
+
+```java
+public interface GreetingService {
+ String sayHello(String name);
+}
+```
+
+#### 2. Server: Implementation
+
+Implement the `GreetingService` interface and mark it as a service for Dubbo
via `@Service`.
+
+```java
+@Service
+public class AnnotatedGreetingService implements GreetingService {
+ public String sayHello(String name) {
+ return "hello, " + name;
+ }
+}
+```
+
+#### 3. Server: Assembly
+
+Define ProviderConfiguration to assemble Dubbo services.
+
+```java
+@Configuration
+@EnableDubbo(scanBasePackages = "com.alibaba.dubbo.samples.impl")
+@PropertySource("classpath:/spring/dubbo-provider.properties")
+static class ProviderConfiguration {}
+```
+
+Dubbo-provider.properties is an external configuration in a spring
application, as follows:
+
+```properties
+dubbo.application.name=demo-provider
+dubbo.registry.address=zookeeper://$DOCKER_HOST:2181
+dubbo.protocol.name=dubbo
+dubbo.protocol.port=20880
+```
+
+Since zookeeper runs in a docker container, please be noted that:
+
+* We assumes that Dubbo applications is running on the host machine (outside
the docker container) in this document, and needs to replace the PATH of
Zookeeper with the IP address of the Environment Variable *${DOCKER_HOST}*.
Please find more detail in the official Docker documentation.
+* When the Dubbo application is a docker application, the container's name is
equivalent to Zookeeper's. The container's name is ** zookeeper ** in this
document.
+* Of course, if you don't want to run the Zookeeper in a container mode, just
simply replace *$DOCKER_HOST* with **localhost**.
+
+#### 4. Server: Starting Service
+
+In the `main` method, you could provide the Dubbo service by running a Spring
Context.
+
+
+```java
+public class ProviderBootstrap {
+ public static void main(String[] args) throws Exception {
+ AnnotationConfigApplicationContext context = new
AnnotationConfigApplicationContext(ProviderConfiguration.class);
+ context.start();
+ System.in.read();
+ }
+}
+```
+
+Start the `main` method of server, you will get the following output, which
represents the success of the server's startup, and the `GreetingService`
service is registered on the ZookeeperRegistry:
+
+```sh
+[03/08/18 10:50:33:033 CST] main INFO zookeeper.ZookeeperRegistry: [DUBBO]
Register:
dubbo://192.168.99.1:20880/com.alibaba.dubbo.samples.api.GreetingService?anyhost=true&application=demo-provider&dubbo=2.6.2&generic=false&interface=com.alibaba.dubbo.samples.api.GreetingService&methods=sayHello&pid=12938&side=provider×tamp=1533264631849,
dubbo version: 2.6.2, current host: 192.168.99.1
+```
+
+You could find the registration information of the service provider through
the Zookeeper management terminal:
+
+```sh
+$ docker exec -it zookeeper bash
+bash-4.4# bin/zkCli.sh -server localhost:218
+Connecting to localhost:2181
+...
+Welcome to ZooKeeper!
+JLine support is enabled
+...
+[zk: localhost:2181(CONNECTED) 0] ls
/dubbo/com.alibaba.dubbo.samples.api.GreetingService/providers
+[dubbo%3A%2F%2F192.168.99.1%3A20880%2Fcom.alibaba.dubbo.samples.api.GreetingService%3Fanyhost%3Dtrue%26application%3Ddemo-provider%26dubbo%3D2.6.2%26generic%3Dfalse%26interface%3Dcom.alibaba.dubbo.samples.api.GreetingService%26methods%3DsayHello%26pid%3D12938%26side%3Dprovider%26timestamp%3D1533264631849]
+```
+You could find that the Dubbo services just registered its URL address at the
`providers` node as follows:
+*dubbo://192.168.99.1:20880/com.alibaba.dubbo.samples.api.GreetingService?anyhost=true&application=demo-provider&dubbo=2.6.2&generic=false&interface=com.alibaba.dubbo.samples.api.GreetingService&methods=sayHello&pid=12938&side=provider×tamp=1533264631849*
+
+
+#### 5. Client: Reference Service
+You could declare the reference service by @Reference, while it will generate
a full call. The target address of the service could be queried by the
Zookeeper's `provider` node.
+
+```java
+@Component("annotatedConsumer")
+public class GreetingServiceConsumer {
+ @Reference
+ private GreetingService greetingService;
+
+ public String doSayHello(String name) {
+ return greetingService.sayHello(name);
+ }
+}
+```
+
+#### 6. Client: Assembling
+Define the ConsumerConfiguration to assemble Dubbo service.
+
+```java
+@Configuration
+@EnableDubbo(scanBasePackages = "com.alibaba.dubbo.samples.action")
+@PropertySource("classpath:/spring/dubbo-consumer.properties")
+@ComponentScan(value = {"com.alibaba.dubbo.samples.action"})
+static class ConsumerConfiguration {}
+```
+"dubbo-consumer.properties" is a method of external configuration in a Spring
application, as follows:
+
+```properties
+dubbo.application.name=demo-consumer
+dubbo.registry.address=zookeeper://$DOCKER_HOST:2181
+dubbo.consumer.timeout=3000
+```
+
+Same as **3. Server: Assembling**, You need to modify *$DOCKER_HOST* defined
in *dubbo.registry.address* according to your own environment. You could find
more instructions in step 3.
+
+
+#### 7. Client: Initiating A Remote Call
+Run `main` to initiate a remote call from a existed service provider. Dubbo
first subscribes to the zookeeper service address and then selects one from the
list of returned addresses to invoke the client:
+
+```java
+public class ConsumerBootstrap {
+ public static void main(String[] args) {
+public class ConsumerBootstrap {
+
+ public static void main(String[] args) throws IOException {
+ AnnotationConfigApplicationContext context = new
AnnotationConfigApplicationContext(ConsumerConfiguration.class);
+ context.start();
+ GreetingServiceConsumer greetingServiceConsumer =
context.getBean(GreetingServiceConsumer.class);
+ String hello = greetingServiceConsumer.doSayHello("zookeeper");
+ System.out.println("result: " + hello);
+ System.in.read();
+ }
+}
+```
+
+The output are as follows:
+
+```shell
+[03/08/18 01:42:31:031 CST] main INFO zookeeper.ZookeeperRegistry: [DUBBO]
Register:
consumer://192.168.99.1/com.alibaba.dubbo.samples.api.GreetingService?application=demo-consumer&category=consumers&check=false&default.timeout=3000&dubbo=2.6.2&interface=com.alibaba.dubbo.samples.api.GreetingService&methods=sayHello&pid=82406&side=consumer×tamp=1533274951195,
dubbo version: 2.6.2, current host: 192.168.99.1 #1
+[03/08/18 01:42:31:031 CST] main INFO zookeeper.ZookeeperRegistry: [DUBBO]
Subscribe:
consumer://192.168.99.1/com.alibaba.dubbo.samples.api.GreetingService?application=demo-consumer&category=providers,configurators,routers&default.timeout=3000&dubbo=2.6.2&interface=com.alibaba.dubbo.samples.api.GreetingService&methods=sayHello&pid=82406&side=consumer×tamp=1533274951195,
dubbo version: 2.6.2, current host: 192.168.99.1 #2
+...
+result: hello, zookeeper
+```
+
+Description:
+
+1. **Register**: consumer://192.168.99.1/...&**category=consumers**&： In
Zookeeper, consumers could register their information and store it at the
`consumers` node
+2. **Subscribe**:
consumer://192.168.99.1/...&**category=providers,configurators,routers**&：Consumers
subscribe `providers`, `configurators`, `routers` from Zookeepers. The
`configurations` is related to the Dubbo configuration, and `routers` is
related to routing rules. The providers node subscription should be noted. When
a new service provider to join, due to the relationship between the
subscription, the new address list will be pushed to the subscriber. So service
consumers also dyn [...]
+
+You could find the registration information of the service provider through
the Zookeeper management terminal:
+```sh
+$ docker exec -it zookeeper bash
+bash-4.4# bin/zkCli.sh -server localhost:218
+Connecting to localhost:2181
+...
+Welcome to ZooKeeper!
+JLine support is enabled
+...
+[zk: localhost:2181(CONNECTED) 4] ls
/dubbo/com.alibaba.dubbo.samples.api.GreetingService/consumers
+[consumer%3A%2F%2F192.168.99.1%2Fcom.alibaba.dubbo.samples.api.GreetingService%3Fapplication%3Ddemo-consumer%26category%3Dconsumers%26check%3Dfalse%26default.timeout%3D3000%26dubbo%3D2.6.2%26interface%3Dcom.alibaba.dubbo.samples.api.GreetingService%26methods%3DsayHello%26pid%3D82406%26side%3Dconsumer%26timestamp%3D1533274951195]
+```
+
+You could see that consumers of Dubbo's servicehas registered its URL address
at the `consumers` node:
+
+*consumer://192.168.99.1/com.alibaba.dubbo.samples.api.GreetingService?application=demo-consumer&category=providers,configurators,routers&default.timeout=3000&dubbo=2.6.2&interface=com.alibaba.dubbo.samples.api.GreetingService&methods=sayHello&pid=82406&side=consumer×tamp=1533274951195*
+
+
+## Summary
+This document focuses on how to use ZooKeeper as a registry in Dubbo. This
document also mentioned that the Zookeeper could be a configuration center and
a service management in Dubbo. Zookeeper is a single-node, standalone mode.
However, developers always bulid a Zookeeper server cluster called * Zookeeper
ensemble * in the real world.
+
+Through this document, readers can learn:
+* Basic concepts and applications of ZooKeeper
+* The function of Zookeeper in Dubbo application
+* Learn about Zookeeper's interaction through practical sample codes
+* The storage of service registration and consumption information of Dubbo
with ZooKeeper
+
+[^1]:
https://www.ixiacom.com/company/blog/apache-zab—zookeeper-atomic-broadcast-protocol
+[^2]: https://www.apache.org/dyn/closer.cgi/zookeeper/
+[^3]: https://brew.sh
+[^4]: https://www.docker.com/community-edition
diff --git a/site_config/blog.js b/site_config/blog.js
index 4064fda..2fd9769 100644
--- a/site_config/blog.js
+++ b/site_config/blog.js
@@ -59,6 +59,13 @@ export default {
desc: 'This blog introduces how to use annotations',
link: '/blog/dubbo-annotations.md',
},
+ {
+ title: 'Using Zookeeper in Dubbo',
+ author: 'Mani',
+ dateStr: 'August 7th，2018',
+ desc: 'This blog introduces how to use Zookeeper in Dubbo',
+ link: '/blog/dubbo-zk.md',
+ },
]
},
'zh-cn': {
