Netstat shows numerous CLOSE_WAIT states for mysql connections

The output of netstat -an shows many mysql connections in CLOSE_WAIT state and when i checked the processlist in mysql using 'SHOW PROCESSLIST' the connections shown in netstat do not appear. What possible 开发者_运维问答could be the reason for this. I use tomcat with mysql-connector and use a Connection Pool as well.

Is it that the application is not closing the mysql connection or is there any other reason for this behaviour... sometimes the CLOSE_WAIT reaches over 200.

On the application level i made sure that i close all the connections(make sure i issue a close() command in the finally block) created using jdbc.

Any help would be appreciated.

---

If the netstat is done on the application machine, it could mean misconfigured MySQL servers.

Please check following global variables in MySQL server,

  interactive_timeout
  wait_timeout

If any of these are too short, it will cause this problem. We normally set both to 1 hour when pooling is used.

The TCP is stuck in CLOSE_WAIT state when server closes connection but the connection pool hasn't got a chance to close the connection.

---

We had same issue with IIS. On windows machine we had:

$ netstat -on | sed '1,4d' | sed 's/:/ /g' | awk '{print $6}' | sort | uniq -c

287 CLOSE_WAIT

121 ESTABLISHED

2 SYN_SENT

1 TIME_WAIT

On MySQL:

`mysql> show global variables like "interactive_timeout";

interactive_timeout 28800

mysql> show global variables like "wait_timeout";

wait_timeout 1440 `

We change it wait_timeout=3660, will see it it will help.

PS: wait_timeout=1440 was done because db previosly had up to 400 of sleep connections...