ZooKeeper 开发随笔

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Dubbo 使用 Curator 连接 ZooKeeper 失败

异常日志：

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Caused by: org.apache.zookeeper.KeeperException$UnimplementedException: KeeperErrorCode = Unimplemented for /dubbo/xxx.xxx.service.UserService/providers/dubbo ....

异常分析：ZooKeeper 的版本与 Curator 的版本不兼容所导致，Curator 官网说明如下：

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第一种情况：

Curator 2.x.x
	compatible with both ZooKeeper 3.4.x and ZooKeeper 3.5.x

Curator 3.x.x
	compatible only with ZooKeeper 3.5.x and includes support for new features such as dynamic reconfiguration, etc.

第二种情况：

ZooKeeper 3.5.x
    Curator 4.0 has a hard dependency on ZooKeeper 3.5.x
    If you are using ZooKeeper 3.5.x there's nothing additional to do - just use Curator 4.0

ZooKeeper 3.4.x
    Curator 4.0 supports ZooKeeper 3.4.x ensembles in a soft-compatibility mode. To use this mode you must exclude ZooKeeper when adding Curator to your dependency management tool.

解决方法：针对第二种情况，假设各组件的版本分别为 Dubbo (2.7.0)、ZooKeeper (3.4.13)、Curator-Framework (4.0.1)，则需要排除 Curator-Framework (4.0.1) 默认依赖的高版本 ZooKeeper (3.5.x)，然后指定低版本的 ZooKeeper (3.4.x)，Maven 的 POM 写法如下：

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<dependencies>
  <dependency>
  	<groupId>org.apache.zookeeper</groupId>
  	<artifactId>zookeeper</artifactId>
  	<version>3.4.13</version>
  </dependency>

  <dependency>
  	<groupId>org.apache.curator</groupId>
  	<artifactId>curator-framework</artifactId>
  	<version>4.0.1</version>
  	<exclusions>
  		<exclusion>
  			<groupId>org.apache.zookeeper</groupId>
  			<artifactId>zookeeper</artifactId>
  		</exclusion>
  	</exclusions>
  </dependency>

  <dependency>
  	<groupId>org.apache.curator</groupId>
  	<artifactId>curator-recipes</artifactId>
  	<version>4.0.1</version>
  </dependency>
</dependencies>