How to profile a Decidim app
The development_app includes a bunch of gems that profile the application. Run the following command in the decidim root’s folder:
bundle exec rake development_app
and then move into it and boot the server
bundle exec rails s
Bullet detects N+1 queries and suggests how to fix them, although it does not catch them all. It is currently configured in
config/initializers/bullet.rb to log in the regular rails log and also in its own
log/bullet.log. You will now see entries like the following:
USE eager loading detected
Decidim::Comments::Comment => [:author]
Add to your query: .includes([:author])
It also warns you when there is an unnecessary eager load.
More details: https://github.com/flyerhzm/bullet
This gem can analyze memory, database, and call stack with flamegraphs. It will show up in development on the top left corner and it gives you all sorts of profiling insights about that page. It will tell you where the response time was spend on in the call stack.
This gem is further enhanced with the
memory_profiler gems which provide more detailed analysis. Try out by appending
?pp=analyze-memory to the URL. You can read more about these options at https://github.com/MiniProfiler/rack-mini-profiler#flamegraphs.
More details: https://github.com/MiniProfiler/rack-mini-profiler
You need to take the insights of these gems with a grain of salt though, if you run this in development. Rails' development settings have nothing to do with a production set up where classes are not reloaded and assets are precompiled and served from a web server. Therefore, you should mimic these settings as much as possible if you want your findings to be realistic.