一、问题描述
基于CDH5.7.0的solr构建solr cloud
1.准备配置solr-4.10.3-cdh5.7.0/zookeeper-3.4.5-cdh5.7.0/apache-tomcat-8.5.12/jdk1.7
2.配置好zookeeper集群后，开启tomcat1-4，发现tomcat1自动关闭，无法连接，查看日志报错：
tail -f solrcloud/tomcat1/logs/catalina.out
01-May-2019 09:08:46.041 WARNING [localhost-startStop-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [solr] appears to have started a thread named [localhost-startStop-1-SendThread(hadoop01:2182)] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Thread.sleep(Native Method)
org.apache.zookeeper.ClientCnxnSocketNIO.cleanup(ClientCnxnSocketNIO.java:219)
org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1185)
org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1122)
12088 [OverseerExitThread] ERROR org.apache.solr.cloud.Overseer – could not read the data
org.apache.zookeeper.KeeperException$SessionExpiredException: KeeperErrorCode = Session expired for /overseer_elect/leader
at org.apache.zookeeper.KeeperException.create(KeeperException.java:127)
at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
at org.apache.zookeeper.ZooKeeper.getData(ZooKeeper.java:1151)
at org.apache.solr.common.cloud.SolrZkClient$7.execute(SolrZkClient.java:349)
at org.apache.solr.common.cloud.SolrZkClient$7.execute(SolrZkClient.java:346)
at org.apache.solr.common.cloud.ZkCmdExecutor.retryOperation(ZkCmdExecutor.java:61)
at org.apache.solr.common.cloud.SolrZkClient.getData(SolrZkClient.java:346)
at org.apache.solr.cloud.Overseer$ClusterStateUpdater.checkIfIamStillLeader(Overseer.java:322)
at org.apache.solr.cloud.Overseer$ClusterStateUpdater.access$300(Overseer.java:91)
at org.apache.solr.cloud.Overseer$ClusterStateUpdater$1.run(Overseer.java:294)
01-May-2019 09:08:46.050 WARNING [localhost-startStop-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [solr] appears to have started a thread named [OverseerExitThread] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
01-May-2019 09:08:46.084 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deployment of web application directory /opt/modules/solrcloud/tomcat2/webapps/solr has finished in 24,458 ms
01-May-2019 09:08:46.090 INFO [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployDirectory Deploying web application directory /opt/modules/solrcloud/tomcat2/webapps/docs
01-May-2019 09:08:46.104 INFO [localhost-startStop-1-SendThread(hadoop01:2182)] org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading Illegal access: this web application instance has been stopped already. Could not load [org.apache.zookeeper.server.ZooTrace]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load [org.apache.zookeeper.server.ZooTrace]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading(WebappClassLoaderBase.java:1305)
at org.apache.catalina.loader.WebappClassLoaderBase.checkStateForClassLoading(WebappClassLoaderBase.java:1293)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1158)
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1119)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1128)
查找很多资料，始终无法解决。最终无奈翻官方文档，才有解决的思路。
二、问题原因
官方文档：http://archive.apache.org/dist/lucene/solr/ref-guide/apache-solr-ref-guide-4.10.pdf，找到版本兼容性问题问题。solr-4.10.3以上应当使用zookeeper3.4.6，而现在cdh5.7.0使用的是zookeeper-3.4.5-cdh5.7.0！！！真是坑爹！还是官方靠谱。
三、解决办法
1.尝试只替换zookeeper为zookeeper-3.4.6，但是还是不能连接，报错
solr-4.10.3-cdh5.7.0/zookeeper-3.4.6/apache-tomcat-8.5.12/jdk1.7
2.最终方法，不用cdh版本的solr，全部替换为apache版本
solr-4.10.3/zookeeper-3.4.6/apache-tomcat-8.5.12/jdk1.7
然后，重新配置solr cloud，结果世界清静了！
四、总结
1.注意版本兼容性问题！这个在大数据平台很常见！
2.官网才是王道！