Zookeeper与Curator二三事【坑爹】

起因：我的Dubbo服务起不来：我本地Zookeeper3.4.11，Curator4.1

Caused by: org.apache.zookeeper.KeeperException$UnimplementedException: KeeperErrorCode = Unimplemented for /dubbo/com.demo.common.service.DemoService
    at org.apache.zookeeper.KeeperException.create(KeeperException.java:) ~[zookeeper-3.5.-beta.jar:3.5.-beta-7f51e5b68cf2f80176ff944a9ebd2abbc65e7327]
    at org.apache.zookeeper.KeeperException.create(KeeperException.java:) ~[zookeeper-3.5.-beta.jar:3.5.-beta-7f51e5b68cf2f80176ff944a9ebd2abbc65e7327]
    at org.apache.zookeeper.ZooKeeper.create(ZooKeeper.java:) ~[zookeeper-3.5.-beta.jar:3.5.-beta-7f51e5b68cf2f80176ff944a9ebd2abbc65e7327]
    at org.apache.curator.framework.imps.CreateBuilderImpl$.call(CreateBuilderImpl.java:) ~[curator-framework-4.1..jar:4.1.]
    at org.apache.curator.framework.imps.CreateBuilderImpl$.call(CreateBuilderImpl.java:) ~[curator-framework-4.1..jar:4.1.]
    at org.apache.curator.connection.StandardConnectionHandlingPolicy.callWithRetry(StandardConnectionHandlingPolicy.java:) ~[curator-client-4.1..jar:na]
    at org.apache.curator.RetryLoop.callWithRetry(RetryLoop.java:) ~[curator-client-4.1..jar:na]
    at org.apache.curator.framework.imps.CreateBuilderImpl.pathInForeground(CreateBuilderImpl.java:) ~[curator-framework-4.1..jar:4.1.]
    at org.apache.curator.framework.imps.CreateBuilderImpl.protectedPathInForeground(CreateBuilderImpl.java:) ~[curator-framework-4.1..jar:4.1.]
    at org.apache.curator.framework.imps.CreateBuilderImpl.forPath(CreateBuilderImpl.java:) ~[curator-framework-4.1..jar:4.1.]
    at org.apache.curator.framework.imps.CreateBuilderImpl.forPath(CreateBuilderImpl.java:) ~[curator-framework-4.1..jar:4.1.]
    at org.apache.curator.framework.imps.CreateBuilderImpl.forPath(CreateBuilderImpl.java:) ~[curator-framework-4.1..jar:4.1.]
    at com.alibaba.dubbo.remoting.zookeeper.curator.CuratorZookeeperClient.createPersistent(CuratorZookeeperClient.java:) ~[dubbo-2.6..jar:2.6.]
    ...  common frames omitted

于是去了解这个版本对应关系如下：

Curator作为zookeeper的客户端，并不是最新版的就没问题，因为它的版本和zookeeper的版本有对应关系。

ZooKeeper 3.5.x

Curator4.0十分依赖Zookeeper3.5.X

ZooKeeper 3.4.x

Curator4.0在软兼容模式下支持Zookeeper3.4.X，但是需要依赖排除zookeeper

<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>${curator-version}</version>
    <exclusions>
        <exclusion>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
        </exclusion>
    </exclusions>
</dependency>

同时必须加入Zookeeper3.4.X的依赖，并且呢，因为是软兼容模式，一些3.4.X不具备的新特性是不能使用的。

低版本

对于Curator2.X是支持Zookeeper3.4.X的，所以如果目前你是Zookeeper3.4.X的版本，还是使用Curator2.X的吧，比如：

<!-- https://mvnrepository.com/artifact/org.apache.zookeeper/zookeeper -->
<dependency>
    <groupId>org.apache.zookeeper</groupId>
    <artifactId>zookeeper</artifactId>
    <version>3.4.13</version>
    <type>pom</type>
</dependency>

版本列表

同一个项目有三个版本也是醉了，貌似现在2.X和4.X是主打了，3.X被边缘了？