Underlying cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException : Communications link fail

连接MySQL数据库出现

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

解决办法

1.修改wait_timeout的参数值

     查看wait_timeout的值，命令：show global variables like 'wait_timeout';

     注意这里带上global这个是全局的。

    修改wait_timeout值，命令： set global wait_timeout=86400;

    检查是否修改成功，继续输入命令show global variables like 'wait_timeout';到这里就修改成功了。

2.修改mysql配置文件： vim /etc/my.cnf

   添加：两行；

  wait_timeout=31536000  

  interactive_timeout=31536000   重启mysql服务后生效。

原因之一这里写错了：你的机器名为mode1 ,写成 mode01jdbc:mysql://mode01/hive_remote?createDatabaseIfNotExist=true  
 

[root@mode2 conf]# schematool -dbType mysql -initSchema
SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/opt/hive-2.3.4/lib/log4j-slf4j-impl-2.6.2.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file:/opt/hadoop-2.6.5/share/hadoop/common/lib/slf4j-log4j12-1.7.5.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.
SLF4J: Actual binding is of type [org.apache.logging.slf4j.Log4jLoggerFactory]
Metastore connection URL:	 jdbc:mysql://mode01/hive_remote?createDatabaseIfNotExist=true
Metastore Connection Driver :	 com.mysql.jdbc.Driver
Metastore connection User:	 root
org.apache.hadoop.hive.metastore.HiveMetaException: Failed to get schema version.
Underlying cause: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException : Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
SQL Error code: 0
Use --verbose for detailed stacktrace.
*** schemaTool failed ***