SentrySmartSampler

Smart sampler for sentry-ruby with rate limiting/throttling and sampling specific errors.

Installation

Add this line to your application's Gemfile:

gem 'sentry-smart-sampler'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install sentry-smart-sampler

Usage

Inside Sentry initializer:

Rails.application.config.to_prepare do
  SentrySmartSampler.configure do |config|
    config.cache_storage = Rails.cache # ideally a Rails cache backed by Redis. But could be anything responding to the same interface
    config.logger = Rails.logger
    config.default_sample_rate = 0.5 # defaults to 1
    config.declare_sampling_rate_per_error do
      declare Faraday::ClientError, sample_rate: 0.1
      declare ActiveRecord::RecordInvalid, sample_rate: 0.2
      declare /message pattern as regexp/, sample_rate: 0.3
      declare "message pattern as string", sample_rate: 0.4
    end
    
    config.default_throttling_errors_number_threshold = 100 # do not set it if you don't want errors to be throttled
    config.default_throttling_time_unit = :minute  # do not set it if you don't want errors to be throttled, other options: [:second, :minute, :hour, :day]
    # this config means that at most 100 errors of the same type can be sent withing a minute
    
    config.declare_throttling_per_error do
      declare ActiveRecord::StatementInvalid, time_unit: :hour, threshold: 50
      declare /message pattern as regexp/, time_unit: :hour, threshold: 100
      declare "message pattern as string", time_unit: :hour, threshold: 200
    end
    
    config.after_throttling_threshold_reached = lambda do |event, hint|
      # do something when the threshold is reached, e.g. send a Slack notification. This callback will be fired at most once, when the threshold is reached. Not required
      # when not provided, the error will be logged using logger
    end
    
    # not-required and not recommended to set unless you really know what you are doing
    # the default definition of of reaching threshold is when the number of errors reaches the provided threshold for a given error within a given time unit
    # if you really want to customize it (because you want e.g. to have another notification delivered from `after_throttling_threshold_reached` when you reach 10x of the threshold
    # you need create an object that responds to `reached?` method taking 3 arguments: rate_limit, throttling_registration, error
    # check `SentrySmartSampler::ThrottlingThresholdReachedDefinition` for more details
    config.throttling_threshold_reached_definition = SomeCustomClassImplementingThrottlingThresholdReachedDefinition.new 
  end
end

Sentry.init do |config| 
  config.dsn = ENV["SENTRY_DSN"]
  
  config.before_send = lambda do |event, hint|
    SentrySmartSampler.call(event, hint) # returns event or nil if the event should be dropped
  end
end

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec 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/[USERNAME]/sentry-smart-sampler.

License

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