Using pt-online-schema-change with option --max-load “Threads_running=100”.

According to Percona documentation the process should pause when threads_running is over the calculated threshold. However, my instance aborts.

Is this a known bug in pt-online-schema-change ?

Hello Chris,

I think you’re missing –critical-load option.

The relevant section says


type: Array; default: Threads_running=50

Examine SHOW GLOBAL STATUS after every chunk, and abort if the load is too high.

You might want to add --critical-load “Threads_running=150”.


Thanks for the reply.

However, according to the docs you posted --critical-load will ‘abort’ the operation. I do not want to abort, I want the operation to pause so it will complete.

According to Percona’s docs --max-load will ‘pause’ the operation, but in my case it is aborting it.

I’m wondering if this is a bug in pt-online-schema-change or am I missing something?


Hi Chris,

I wanted to highlight the default value for --critical-load (50) is lower than your --max-load (100). You will need to mention that.

Oh I understand. So I will have to increase critical to above my value for max. This makes sense!

Thanks for this. Will test on my end and hopefully close this out.