As people are getting back from vacations and application traffic is going back and hitting database backend hard, it is a good time to think about performance and prepare for the winter holiday spike. Whenever you are on-premise or in the cloud, questions are the same:

• Are we satisfied with the current MySQL performance?
• How much traffic are we currently serving?
• Is there enough capacity to stay stable as traffic increases?
• What would be the best way to stay cost-effective as we grow?

Unfortunately, the answers are not so obvious and require a thorough performance analysis. However, there is a chance that your problem has already been solved by someone else. I do not mean StackOverflow (which is a beautiful place, by the way), but some higher level questions which people usually discuss at conferences, and we have several of them ongoing or just a couple of weeks away.

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There are few easy ticks to see what is stuck inside MySQL instance. All these techniques will not give you whole picture, but might help to find queries that block performance. Let’s start from what exactly doing your MySQL server right now.

Which queries are running now?

This will give you an idea what’s running right now so you can find long running queries which slowing down MySQL and/or causing replication lag:

mysql -e "SHOW PROCESSLIST" | grep -v -i "sleep"

It is more convenient than just run “SHOW PROCESSLIST” as it’s hiding all connected threads in “Sleep” state so you’ll get a clean output. Also you can get same output but updating each second:

watch -n1 'mysql -e "SHOW FULL PROCESSLIST" | grep -v -i "Sleep"'

What to look for? This is complex output but you can start with Time and State columns. When you see a query running for more …