Since MySQL Proxy 0.7.0 is soon to be released, I thought another brief tutorial would be helpful. Today we ran across a good use case, and so I wanted to pass this along. If you’ve not used Proxy yet, this is a great opportunity to get your feet wet with it and some Lua.
When queries are routed though MySQL Proxy from various servers, the MySQL Server only sees that the query came from the machine Proxy is running on.
So when you are viewing output of SHOW PROCESSLIST, you have no way of telling what server a particular query originated from.
However, this could be very useful information to have, especially to determine which server a particular long-running query is coming from at that particular moment in time.
Output not using Proxy:
mysql> show processlist; +----+------+-----------------+------+---------+------+-------+------------------+ | Id | User | Host | db … |