项目场景：

CDH集群CM切换hive元数据库报错：

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
        at com.mysql.jdbc.Util.handleNewInstance(Util.java:411)
        at com.mysql.jdbc.Util.getInstance(Util.java:386)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1015)
        at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:989)
Caused by: java.lang.NullPointerException
        at com.mysql.jdbc.ConnectionImpl.getServerCharacterEncoding(ConnectionImpl.java:3281)
        at com.mysql.jdbc.MysqlIO.sendConnectionAttributes(MysqlIO.java:1940)
        at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1866)
        at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1252)
        at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2488)
        at com.mysql.jdbc.ConnectionImpl.connectOneTryOnly(ConnectionImpl.java:2521)

问题描述

hive元数据库进行mysql元数据库切换报错，原因很简单，是切换后的数据库版本和原数据版本不一致，主要记录一下分析过程

原因分析：

寻找启动hive metastore脚本位置:

cd /opt/cloudera/parcels/CDH-6.3.2-1.cdh6.3.2.p0.1605554
vim ./lib/hive/bin/ext/metastore.sh

根据脚本，metastore服务是采用hadoop jar命令启动，通过设置HADOOP_CLIENT_OPTS，修改提交应用程序的jvm参数：

 export HADOOP_CLIENT_OPTS="-agentlib:jdwp=transport=dt_socket,address=18787,server=y,suspend=n"

在idea上配置remote debug即可远程调试程序