com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: The last packet successfully received from the server was 52,445,041 milliseconds ago. The last packet sent successfully to the server was 52,445,045 milliseconds ago. is longer than the server configured value of'wait_timeout'. You should consider either expiring and/or testing connection validity before use in your application, increasing the server configured values for client timeouts, orusing the Connector/J connection property 'autoReconnect=true' to avoid this problem.
flink连接mysql，在过了一定时间后，就断开连接了，设置'autoReconnect=true’也不管用
