How to debug Lock wait timeout exceeded on MySQL?

Question

In my production error logs I occasionally see:

SQLSTATE[HY000]: General error: 1205 Lock wait timeout exceeded; try restarting transaction

Answer 1

You can use:

show full processlist

which will list all the connections in MySQL and the current state of connection as well as the query being executed. There's also a shorter variant show processlist; which displays the truncated query as well as the connection stats.