https://community.cloudera.com/t5/Support-Questions/Hive-Metastore-trouble-with-jbdc-mysql/m-p/204782#M166771 <P><A rel="user" href="https://community.cloudera.com/users/45308/xoffey.html" nodeid="45308">@Michael Coffey</A></P><P>We see the following error:</P><PRE>Metastore connection URL: jdbc:mysql://hadoop12.xxxxx.com/hive?createDatabaseIfNotExist=true Metastore Connection Driver : com.mysql.jdbc.Driver Metastore connection User: hive 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 org.apache.hadoop.hive.metastore.HiveMetaException: Failed to get schema version. at org.apache.hive.beeline.HiveSchemaHelper.getConnectionToMetastore(HiveSchemaHelper.java:80) . . org.apache.hive.beeline.HiveSchemaHelper.getConnectionToMetastore(HiveSchemaHelper.java:76) ... 11 more Caused by: java.net.ConnectException: Connection refused (Connection refused) at java.net.PlainSocketImpl.socketConnect(Native Method) at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)</PRE><P>.<BR />Basically this is MySQL connection issue. So you should check the couple of things first:<BR /><BR />1). The machine where you are running the MySQL please check the following, If the MySQL is running:</P><PRE># ssh root@hadoop12.neocortix.com # ps -ef | grep mysql</PRE><P>2). Check if the Port of MySQL is opened or not? By Passing the MySQL server PID to the following command :</P><PRE># netstat -tnlpa | grep `cat /var/run/mysqld/mysqld.pid` tcp6 0 0 :::3306 :::* LISTEN 1235/mysqld </PRE><P>3). Check if using the following kind of Java Utility you are able to establish the JDBC connection to the MySQL from the ambari-server host AND from the same host where mySQL is installed?</P><PRE># /usr/jdk64/jdk1.8.0_112/bin/java -cp /usr/lib/ambari-agent/DBConnectionVerification.jar:/usr/share/java/mysql-connector-java.jar -Djava.library.path=/var/lib/ambari-agent/cache org.apache.ambari.server.DBConnectionVerification "jdbc:mysql://hadoop12.xxxxx.com/hive" "hive" "hive" com.mysql.jdbc.Driver </PRE><P>**NOTE:** The JAR "DBConnectionVerification.jar" is provided by Ambari for DB connection check. You will need to change the JAVA path in the above command. </P><P>Also please use the correct Hostname (and change : hadoop12.xxxxx.com to correct one) to verify the connectivity. (I have masked the hostname)</P><P>Above will isolate the issue of MySQL DB connectivity. </P><P><BR /><EM><STRONG>Usually the "CommunicationsException : Communications link failure" error indicates that there is either some MySQL DB server issue or the N/W issue. </STRONG></EM></P><P>.</P><P>.</P> Tue, 03 Oct 2017 12:23:51 GMT jsensharma 2017-10-03T12:23:51Z