mysql connection timeout on small traffic server

How can I set up MySQL so that connections never time out? And how do I even check to see what the current settings for variables such as wait_timeout and interactive_timeout, etc. are? Given that these variables are not defined in the config shown below.

Here is the situation:

A low (micro) traffic web server sometimes does not get a database transaction for a couple of weeks. Mysql is running on the same server box as are a few private web applications. I set autoReconnect=true in the connection string, but when I check back days later, I always notice that the web application cannot connect to the database, and when I open the catalina.out log, it gives the following:

Caused by: java.net.SocketException: Broken pipe
    at java.net.SocketOutputStream.socketWrite0(Native Method) ~[na:1.7.0_75]
    at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:113) ~[na:1.7.0_75]
    at java.net.SocketOutputStream.write(SocketOutputStream.java:159) ~[na:1.7.0_75]
    at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:82) ~[na:1.7.0_75]
    at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:140) ~[na:1.7.0_75]
    at com.mysql.jdbc.MysqlIO.send(MysqlIO.java:3969) ~[mysql-connector-java-5.1.27.jar:na]
    ... 111 common frames omitted

I then restart tomcat and the webapps are able to make database connections again, but the problem repeats, and the long periods involved mean that it is not reasonable to test waiting days to see when the broken pipe error will resurface.

I have read many postings about setting max timeout for mysql, including the tutorial at this link, but they describe variables that are not defined in the conf files on my machine. For example, the mysql config files on the server in question are:

/etc/my.cnf is:

```
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
#

It is bad practice to sit there connected for arbitrarily long. It is better to have wait_timeout be something more like 30 (seconds) and write code to deal with disconnects. Reconnecting to MySQL is quite quick, so it is not a performance issue. If the app is idle for (say) 30 seconds, it should expect to get an error and have to reconnect.

Keep in mind that network glitches, etc, can cause disconnects. Hence, you need to code for disconnects anyway.

Edit

Do not use AUTORECONNECT with InnoDB, it can cause nasty glitches. Instead, catch 'not connected' error after each query and restart the transaction. Another approach is to execute a 'ping' whenever you might be coming back from a long idle period.

StackExchange Database Administrators Q#97158, answer score: 3