gitlab-org--gitlab-foss/doc/development/profiling.md
2015-10-15 12:15:18 +02:00

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Profiling

To make it easier to track down performance problems GitLab comes with a set of profiling tools, some of these are available by default while others need to be explicitly enabled.

rack-mini-profiler

This Gem is enabled by default in development only. It allows you to see the timings of the various components that made up a web request (e.g. the SQL queries executed and their execution timings).

Bullet

Bullet is a Gem that can be used to track down N+1 query problems. Because Bullet adds quite a bit of logging noise it's disabled by default. To enable Bullet, set the environment variable ENABLE_BULLET to a non-empty value before starting GitLab. For example:

ENABLE_BULLET=true bundle exec rails s

Bullet will log query problems to both the Rails log as well as the Chrome console.

ActiveRecord Query Trace

This Gem adds backtraces for every ActiveRecord query in the Rails console. This can be useful to track down where a query was executed. Because this Gem adds quite a bit of noise (5-10 extra lines per ActiveRecord query) it's disabled by default. To use this Gem you'll need to set ENABLE_QUERY_TRACE to a non empty file before starting GitLab. For example:

ENABLE_QUERY_TRACE=true bundle exec rails s

rack-lineprof

This is a Gem that can trace the execution time of code on a per line basis. Because this Gem can add quite a bit of overhead it's disabled by default. To enable it, set the environment variable ENABLE_LINEPROF to a non-empty value. For example:

ENABLE_LINEPROF=true bundle exec rails s

Once enabled you'll need to add a query string parameter to a request to actually profile code execution. The name of the parameter is lineprof and should be set to a regular expression (minus the starting/ending slash) used to select what files to profile. To profile all files containing "foo" somewhere in the path you'd use the following parameter:

?lineprof=foo

Or when filtering for files containing "foo" and "bar" in their path:

?lineprof=foo|bar

Once set the profiling output will be displayed in your terminal.