Creating a merge request is sometimes a very slow request

Problem Statement

Creating a merge request on GitLab.com is often very slow, on the order of 30s or more. I suspect this might be caused by disk reads.

I've marked this as confidential for now as I've included links to kibana below, please feel free to change this if they're ok to be public.

Reach

Currently unknown, but it does at least affect me.

Impact

0.5 (pretty annoying but inconsistent)

Confidence

Needs investigation.

Effort

Unknown

Links

Thanks to @smcgivern for these:

• https://dashboards.gitlab.net/d/000000120/rails-controllers?orgId=1&var-action=Projects::MergeRequests::CreationsController%23create&var-database=influxdb-01-inf-gprd
• https://log.gitlab.net/goto/795448891ecde9e161e797cd5b815028
• https://log.gitlab.net/goto/42150c9dfd20571158cd2c6999d3c6ae