这是一个验证贴，因为社区文档是错误的。
先说结论
Flink1.15仅支持ZooKeeper3.5/3.6，不再支持3.4。FLINK-25146 Drop support for Zookeeper 3.4
社区文档
其中的ZooKeeper Versions描述默认使用3.4，可以自行调整为3.5。从文档上来看自1.11版本就添加了这段描述，到目前最新稳定版本(1.16.0)依然是这么描述的。但是实际我们在flink-1.15.0/lib目录中只看到了flink-shaded-zookeeper-3.5.9.jar，在opt目录中看到了flink-shaded-zookeeper-3.6.3.jar，即默认使用3.5版本，并在opt目录中放置了3.6版本。
其实在1.15的 ReleaseNote 中明确写了，不再支持3.4，只是还是有点不死心，做了如下的验证。
Drop support for Zookeeper 3.4 #
FLINK-25146 #
Support for using Zookeeper 3.4 for HA has been dropped. Users relying on Zookeeper need to upgrade to 3.5/3.6. By default Flink now uses a Zookeeper 3.5 client.
验证一
那么我们是否可以将3.4的版本（flink-1.13.3/lib/flink-shaded-zookeeper-3.4.14.jar）放置到flink-1.15.3/lib目录中，在1.15版本中使用3.4版本呢？
不能
如果我们这么做，将会遇到 java.lang.ClassNotFoundException: org.apache.flink.shaded.curator5.org.apache.curator.framework.api.ACLProvider ，完整堆栈如下：
1 2022-12-08 18:18:05,693 INFO org.apache.flink.runtime.rpc.akka.AkkaRpcService [] - Stopping Akka RPC service. 2 2022-12-08 18:18:05,734 INFO akka.remote.RemoteActorRefProvider$RemotingTerminator [] - Shutting down remote daemon. 3 2022-12-08 18:18:05,736 INFO akka.remote.RemoteActorRefProvider$RemotingTerminator [] - Remote daemon shut down; proceeding with flushing remote transports. 4 2022-12-08 18:18:05,758 INFO akka.remote.RemoteActorRefProvider$RemotingTerminator [] - Remoting shut down. 5 2022-12-08 18:18:05,782 INFO org.apache.flink.runtime.rpc.akka.AkkaRpcService [] - Stopped Akka RPC service. 6 2022-12-08 18:18:05,782 ERROR org.apache.flink.runtime.entrypoint.ClusterEntrypoint [] - Could not start cluster entrypoint YarnApplicationClusterEntryPoint. 7 org.apache.flink.runtime.entrypoint.ClusterEntrypointException: Failed to initialize the cluster entrypoint YarnApplicationClusterEntryPoint. 8 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.startCluster(ClusterEntrypoint.java:250) ~[flink-dist-1.15.3.jar:1.15.3] 9 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.runClusterEntrypoint(ClusterEntrypoint.java:711) [flink-dist-1.15.3.jar:1.15.3] 10 at org.apache.flink.yarn.entrypoint.YarnApplicationClusterEntryPoint.main(YarnApplicationClusterEntryPoint.java:112) [flink-dist-1.15.3.jar:1.15.3] 11 Caused by: java.lang.NoClassDefFoundError: org/apache/flink/shaded/curator5/org/apache/curator/framework/api/ACLProvider 12 at org.apache.flink.runtime.highavailability.HighAvailabilityServicesUtils.createZooKeeperHaServices(HighAvailabilityServicesUtils.java:90) ~[flink-dist-1.15.3.jar:1.15.3] 13 at org.apache.flink.runtime.highavailability.HighAvailabilityServicesUtils.createHighAvailabilityServices(HighAvailabilityServicesUtils.java:140) ~[flink-dist-1.15.3.jar:1.15.3] 14 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.createHaServices(ClusterEntrypoint.java:427) ~[flink-dist-1.15.3.jar:1.15.3] 15 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.initializeServices(ClusterEntrypoint.java:376) ~[flink-dist-1.15.3.jar:1.15.3] 16 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.runCluster(ClusterEntrypoint.java:277) ~[flink-dist-1.15.3.jar:1.15.3] 17 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.lambda$startCluster$1(ClusterEntrypoint.java:227) ~[flink-dist-1.15.3.jar:1.15.3] 18 at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_202] 19 at javax.security.auth.Subject.doAs(Subject.java:422) ~[?:1.8.0_202] 20 at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1875) ~[hadoop-common-3.0.0-cdh6.3.2.jar:?] 21 at org.apache.flink.runtime.security.contexts.HadoopSecurityContext.runSecured(HadoopSecurityContext.java:41) ~[flink-dist-1.15.3.jar:1.15.3] 22 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.startCluster(ClusterEntrypoint.java:224) ~[flink-dist-1.15.3.jar:1.15.3] 23 ... 2 more 24 Caused by: java.lang.ClassNotFoundException: org.apache.flink.shaded.curator5.org.apache.curator.framework.api.ACLProvider 25 at java.net.URLClassLoader.findClass(URLClassLoader.java:382) ~[?:1.8.0_202] 26 at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_202] 27 at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349) ~[?:1.8.0_202] 28 at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_202] 29 at org.apache.flink.runtime.highavailability.HighAvailabilityServicesUtils.createZooKeeperHaServices(HighAvailabilityServicesUtils.java:90) ~[flink-dist-1.15.3.jar:1.15.3] 30 at org.apache.flink.runtime.highavailability.HighAvailabilityServicesUtils.createHighAvailabilityServices(HighAvailabilityServicesUtils.java:140) ~[flink-dist-1.15.3.jar:1.15.3] 31 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.createHaServices(ClusterEntrypoint.java:427) ~[flink-dist-1.15.3.jar:1.15.3] 32 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.initializeServices(ClusterEntrypoint.java:376) ~[flink-dist-1.15.3.jar:1.15.3] 33 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.runCluster(ClusterEntrypoint.java:277) ~[flink-dist-1.15.3.jar:1.15.3] 34 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.lambda$startCluster$1(ClusterEntrypoint.java:227) ~[flink-dist-1.15.3.jar:1.15.3] 35 at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_202] 36 at javax.security.auth.Subject.doAs(Subject.java:422) ~[?:1.8.0_202] 37 at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1875) ~[hadoop-common-3.0.0-cdh6.3.2.jar:?] 38 at org.apache.flink.runtime.security.contexts.HadoopSecurityContext.runSecured(HadoopSecurityContext.java:41) ~[flink-dist-1.15.3.jar:1.15.3] 39 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.startCluster(ClusterEntrypoint.java:224) ~[flink-dist-1.15.3.jar:1.15.3] 40 ... 2 more
验证二
如果使用3.5的客户端访问3.4版本服务端，将会提示 org.apache.flink.shaded.zookeeper3.org.apache.zookeeper.KeeperException$UnimplementedException: KeeperErrorCode = Unimplemented for 异常，完整堆栈如下：
1 2022-12-08 15:10:14,935 ERROR org.apache.flink.runtime.entrypoint.ClusterEntrypoint [] - Fatal error occurred in the cluster entrypoint. 2 org.apache.flink.shaded.zookeeper3.org.apache.zookeeper.KeeperException$UnimplementedException: KeeperErrorCode = Unimplemented for /flink/jm_ha_metadata/application_1666841155139_0173 3 at org.apache.flink.shaded.zookeeper3.org.apache.zookeeper.KeeperException.create(KeeperException.java:106) ~[flink-shaded-zookeeper-3-3.5.9-15.0.jar:3.5.9-15.0] 4 at org.apache.flink.shaded.zookeeper3.org.apache.zookeeper.KeeperException.create(KeeperException.java:54) ~[flink-shaded-zookeeper-3-3.5.9-15.0.jar:3.5.9-15.0] 5 at org.apache.flink.shaded.zookeeper3.org.apache.zookeeper.ZooKeeper.create(ZooKeeper.java:1538) ~[flink-shaded-zookeeper-3-3.5.9-15.0.jar:3.5.9-15.0] 6 at org.apache.flink.shaded.curator5.org.apache.curator.utils.ZKPaths.mkdirs(ZKPaths.java:351) ~[flink-shaded-zookeeper-3-3.5.9-15.0.jar:3.5.9-15.0] 7 at org.apache.flink.shaded.curator5.org.apache.curator.framework.imps.NamespaceImpl$1.call(NamespaceImpl.java:90) ~[flink-shaded-zookeeper-3-3.5.9-15.0.jar:3.5.9-15.0] 8 at org.apache.flink.shaded.curator5.org.apache.curator.RetryLoop.callWithRetry(RetryLoop.java:93) ~[flink-shaded-zookeeper-3-3.5.9-15.0.jar:3.5.9-15.0] 9 at org.apache.flink.shaded.curator5.org.apache.curator.framework.imps.NamespaceImpl.fixForNamespace(NamespaceImpl.java:83) ~[flink-shaded-zookeeper-3-3.5.9-15.0.jar:3.5.9-15.0] 10 at org.apache.flink.shaded.curator5.org.apache.curator.framework.imps.NamespaceImpl.newNamespaceAwareEnsurePath(NamespaceImpl.java:109) ~[flink-shaded-zookeeper-3-3.5.9-15.0.jar:3.5.9-15.0] 11 at org.apache.flink.shaded.curator5.org.apache.curator.framework.imps.CuratorFrameworkImpl.newNamespaceAwareEnsurePath(CuratorFrameworkImpl.java:618) ~[flink-shaded-zookeeper-3-3.5.9-15.0.jar:3.5.9-15.0] 12 at org.apache.flink.runtime.util.ZooKeeperUtils.useNamespaceAndEnsurePath(ZooKeeperUtils.java:729) ~[flink-runtime-1.15.2.jar:1.15.2] 13 at org.apache.flink.runtime.highavailability.zookeeper.ZooKeeperMultipleComponentLeaderElectionHaServices.<init>(ZooKeeperMultipleComponentLeaderElectionHaServices.java:85) ~[flink-runtime-1.15.2.jar:1.15.2] 14 at org.apache.flink.runtime.highavailability.HighAvailabilityServicesUtils.createZooKeeperHaServices(HighAvailabilityServicesUtils.java:96) ~[flink-runtime-1.15.2.jar:1.15.2] 15 at org.apache.flink.runtime.highavailability.HighAvailabilityServicesUtils.createHighAvailabilityServices(HighAvailabilityServicesUtils.java:140) ~[flink-runtime-1.15.2.jar:1.15.2] 16 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.createHaServices(ClusterEntrypoint.java:427) ~[flink-runtime-1.15.2.jar:1.15.2] 17 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.initializeServices(ClusterEntrypoint.java:376) ~[flink-runtime-1.15.2.jar:1.15.2] 18 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.runCluster(ClusterEntrypoint.java:277) ~[flink-runtime-1.15.2.jar:1.15.2] 19 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.lambda$startCluster$1(ClusterEntrypoint.java:227) ~[flink-runtime-1.15.2.jar:1.15.2] 20 at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_202] 21 at javax.security.auth.Subject.doAs(Subject.java:422) [?:1.8.0_202] 22 at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1875) [hadoop-common-3.0.0-cdh6.3.2.jar:?] 23 at org.apache.flink.runtime.security.contexts.HadoopSecurityContext.runSecured(HadoopSecurityContext.java:41) [flink-runtime-1.15.2.jar:1.15.2] 24 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.startCluster(ClusterEntrypoint.java:224) [flink-runtime-1.15.2.jar:1.15.2] 25 at org.apache.flink.runtime.entrypoint.ClusterEntrypoint.runClusterEntrypoint(ClusterEntrypoint.java:711) [flink-runtime-1.15.2.jar:1.15.2] 26 at org.apache.flink.yarn.entrypoint.YarnApplicationClusterEntryPoint.main(YarnApplicationClusterEntryPoint.java:112) [flink-dist-1.15.3.jar:1.15.3] 27 2022-12-08 15:10:14,943 INFO org.apache.flink.runtime.entrypoint.ClusterEntrypoint [] - Shutting YarnApplicationClusterEntryPoint down with application status UNKNOWN. Diagnostics Cluster entrypoint has been closed externally..
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