1、背景
在 用zookeeper做 注冊中心時，本地啟動 zookeeper3.4.2 成功，但一直注冊不成功，創建節點失敗， 然后，下載比jar對應的（zookeeper3.5.8）高的 zookeeper3.5.8 版本， 啟動一直 不成功。
2 排查
zookeeper 3.4.2
啟動 報異常：
2020-08-09 22:15:43.872 ERROR 21194 --- [nStateManager-0] o.a.c.x.d.details.ServiceDiscoveryImpl : Could not re-register instances after reconnection
org.apache.zookeeper.KeeperException$UnimplementedException: KeeperErrorCode = Unimplemented for /services/config-client/38d43e04-c2d0-4ca2-90b6-c88720f83755
at org.apache.zookeeper.KeeperException.create(KeeperException.java:103) ~[zookeeper-3.5.3-beta.jar:3.5.3-beta-8ce24f9e675cbefffb8f21a47e06b42864475a60]
at org.apache.zookeeper.KeeperException.create(KeeperException.java:51) ~[zookeeper-3.5.3-beta.jar:3.5.3-beta-8ce24f9e675cbefffb8f21a47e06b42864475a60]
at org.apache.zookeeper.ZooKeeper.create(ZooKeeper.java:1525) ~[zookeeper-3.5.3-beta.jar:3.5.3-beta-8ce24f9e675cbefffb8f21a47e06b42864475a60]
at org.apache.curator.framework.imps.CreateBuilderImpl$17.call(CreateBuilderImpl.java:1181) ~[curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.framework.imps.CreateBuilderImpl$17.call(CreateBuilderImpl.java:1158) ~[curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.connection.StandardConnectionHandlingPolicy.callWithRetry(StandardConnectionHandlingPolicy.java:64) ~[curator-client-4.0.1.jar:na]
at org.apache.curator.RetryLoop.callWithRetry(RetryLoop.java:100) ~[curator-client-4.0.1.jar:na]
at org.apache.curator.framework.imps.CreateBuilderImpl.pathInForeground(CreateBuilderImpl.java:1155) ~[curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.framework.imps.CreateBuilderImpl.protectedPathInForeground(CreateBuilderImpl.java:605) ~[curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.framework.imps.CreateBuilderImpl.forPath(CreateBuilderImpl.java:595) ~[curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.framework.imps.CreateBuilderImpl.forPath(CreateBuilderImpl.java:49) ~[curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.x.discovery.details.ServiceDiscoveryImpl.internalRegisterService(ServiceDiscoveryImpl.java:236) ~[curator-x-discovery-4.0.1.jar:na]
at org.apache.curator.x.discovery.details.ServiceDiscoveryImpl.reRegisterServices(ServiceDiscoveryImpl.java:456) ~[curator-x-discovery-4.0.1.jar:na]
at org.apache.curator.x.discovery.details.ServiceDiscoveryImpl.access$100(ServiceDiscoveryImpl.java:58) ~[curator-x-discovery-4.0.1.jar:na]
at org.apache.curator.x.discovery.details.ServiceDiscoveryImpl$1.stateChanged(ServiceDiscoveryImpl.java:78) ~[curator-x-discovery-4.0.1.jar:na]
at org.apache.curator.framework.state.ConnectionStateManager$2.apply(ConnectionStateManager.java:274) [curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.framework.state.ConnectionStateManager$2.apply(ConnectionStateManager.java:270) [curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.framework.listen.ListenerContainer$1.run(ListenerContainer.java:93) [curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.shaded.com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:435) [curator-client-4.0.1.jar:na]
at org.apache.curator.framework.listen.ListenerContainer.forEach(ListenerContainer.java:85) [curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.framework.state.ConnectionStateManager.processEvents(ConnectionStateManager.java:268) [curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.framework.state.ConnectionStateManager.access$000(ConnectionStateManager.java:44) [curator-framework-4.0.1.jar:4.0.1]
at org.apache.curator.framework.state.ConnectionStateManager$1.call(ConnectionStateManager.java:120) [curator-framework-4.0.1.jar:4.0.1]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_202]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_202]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_202]
at java.lang.Thread.run(Thread.java:748) [na:1.8.0_202]
經過排查，可能是 版本過低導致的，
項目中依賴的 zk：
zookeeper 3.5.8
指定zoo.cfg 文件 啟動， 執行 ps -ef | grep zookeeper 顯示沒有啟動成功。
在log中 發現.
2020-08-09 21:56:25,722 [myid:] - ERROR [main:ZooKeeperServerMain@79] - Unable to start AdminServer, exiting abnormally
org.apache.zookeeper.server.admin.AdminServer$AdminServerException: Problem starting AdminServer on address 0.0.0.0, port 8080 and command URL /commands
查了 google 和 zookeeper 的3.5版本的官方文檔，
同時，在 項目啟動的時候，我也已經使用了 8080端口， 然后修改了應用的 端口，重新啟動， zk上 注冊成功.
在 zk客戶端中可以看到，注冊的 service 實例。
[zk: localhost:2181(CONNECTED) 0] ls /services/config-client/
ada645f6-3034-4b5e-a2d8-02daf8d42872 fbadbdec-ae4c-49f9-bea3-a6ed88d84fe8