FlamegraphGenerator

A super simple gem that allows you to create flamegraphs that can be opened via speedscope.app.

This differs from tools like stackprof/singed/rack-mini-profiler in that this allow you to specify the events used to create a flamegraph. Whereas those tools automatically create flamegraph based on the call stack.

You might want to use this gem if you've got a need to create flamegraphs from a custom event source.

Installation

Install the gem and add to the application's Gemfile by executing:

$ bundle add flamegraph_generator

If bundler is not being used to manage dependencies, install the gem by executing:

$ gem install flamegraph_generator

Usage

# Initialize generator
#
# Parameters
#  - name: String
#     Optional. Defaults to 'flamegraph'
#  - units: 'none' | 'nanoseconds' | 'microseconds' | 'milliseconds' | 'seconds' | 'bytes'
#     Optional. Defaults to 'seconds'
generator = FlamegraphGenerator.new(name: 'myflamegraph', units: 'seconds')

# Add your events here
generator.add_event(name: 'UsersComponent', start: 0, finish: 100)
generator.add_event(name: 'X', start: 50, finish: 70, file: 'xxx.rb', line: 200, col: 10)
generator.add_event(name: 'Y', start: 112, finish: 130, file: 'yyy.rb', line: 200, col: 10)

# Will save the flamegraph to /tmp/flamegraph.json + open the flamegraph in your browser
generator.save(path: '/tmp/flamegraph.json', open: true)

# You can also get the raw speedscope-compatible flamegraph hash by:
generator.generate_flamegraph

Contrived example

The below example hooks into the notifications dispatched by the view_component library and generates a flamegraph during each request for view components.

class ApplicationController
    around_action :vc_bm

    def vc_bm
        return yield unless Rails.env.development?

        generator = FlamegraphGenerator.new
        callback = lambda do |name, start, finish, id, payload|
            generator.add_event(name: payload[:name], start:, finish:)
        end

        ActiveSupport::Notifications.subscribed(callback, 'render.view_component', monotonic: true) do
            yield
        end

        generator.save(path: Rails.root.join('tmp', 'vc_bm.json'), open: true)
    end
end

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/owaiswiz/flamegraph_generator.

License

The gem is available as open source under the terms of the MIT License.