factory_prof.md

FactoryProf

FactoryProf tracks your factories usage statistics, i.e. how often each factory has been used.

Example output:

[TEST PROF INFO] Factories usage

Total: 15285
Total top-level: 10286
Total time: 299.5937s
Total uniq factories: 119

 total   top-level   total time    time per call      top-level time            name
  6091        2715    115.7671s          0.0426s            50.2517s            user
  2142        2098     93.3152s          0.0444s            92.1915s            post
  ...

It shows both the total number of the factory runs and the number of top-level runs, i.e. not during another factory invocation (e.g. when using associations.)

(@since v0.9.0) It also shows the time spent generating records with factories. (@since v0.11.0) It also shows the amount of time taken per factory call.

NOTE: FactoryProf only tracks the database-persisted factories. In case of FactoryGirl/FactoryBot these are the factories provided by using create strategy. In case of Fabrication - objects that created using create method.

Instructions

FactoryProf can be used with FactoryGirl/FactoryBot or Fabrication - application can be bundled with both gems at the same time.

To activate FactoryProf use FPROF environment variable:

# Simple profiler
FPROF=1 rspec

# or
FPROF=1 bundle exec rake test

Factory Flamegraph

The most useful feature of FactoryProf is the FactoryFlame report. That's the special interpretation of Brendan Gregg's flame graphs which allows you to identify factory cascades.

To generate FactoryFlame report set FPROF environment variable to flamegraph:

FPROF=flamegraph rspec

# or
FPROF=flamegraph bundle exec rake test

That's how a report looks like:

How to read this?

Every column represents a factory stack or cascade, that is a sequence of recursive #create method calls. Consider an example:

factory :comment do
  answer
  author
end

factory :answer do
  question
  author
end

factory :question do
  author
end

create(:comment) #=> creates 5 records

# And the corresponding stack is:
# [:comment, :answer, :question, :author, :author, :author]

The wider column the more often this stack appears.

The root cell shows the total number of create calls.

Acknowledgments

• Thanks to Martin Spier for d3-flame-graph

• Thanks to Sam Saffron for his flame graphs implementation.