Module: TrackBallast::StopSignal

Defined in:
lib/track_ballast/stop_signal.rb

Overview

StopSignal is a module that provides a way to stop a process while it is running.

It uses Redis to store the stop signal. Please see TrackBallast.redis for more details.

When the stop signal is set, the client process will stop the next time the process manually checks the stopped? method.

Usage

StopSignal can be used via extend or include.

Extend

  • Extend the module in your class

  • Call stopped? to check if the stop signal is set, for example: at the beginning of the perform method in a job class.

  • If desired, add an implementation of the stop_signal_key method. This can be useful for stopping multiple classes with the same stop signal. For example: multiple related jobs. The default implementation is to use the class name.

Then, from another process, you can manipulate the stop signal:

  • Call YourClass.stop! to set the stop signal

  • Call YourClass.go! to remove the stop signal

Example

class YourJob < ApplicationJob
  extend TrackBallast::StopSignal

  def perform
    return if self.class.stopped?

    # Process your job here
  end

  # Optional:
  #
  #     def self.stop_signal_key
  #       "custom_stop_signal_key:stop"
  #     end
end

Include

  • Include the module in your class

  • Call stopped? to check if the stop signal is set, for example: at the beginning of the perform method in a job class.

  • If desired, add an implementation of the stop_signal_key method. This can tie the stop signal to a specific instance of the class, as shown in the example below.

Then, from another process, you can manipulate the stop signal:

  • Call your_model_instance.stop! to set the stop signal

  • Call your_model_instance.go! to remove the stop signal

Example

class YourModel < ApplicationRecord
  include TrackBallast::StopSignal

  # Optional, but recommended for usage via `include`
  def stop_signal_key
    "#{self.class.name}:#{id}:stop"
  end
end

class YourModelService
  def initialize(your_model_instance)
    @your_model_instance = your_model_instance
  end

  def call
    return if your_model_instance.stopped?

    # Process `your_model_instance` here
  end
end

Instance Method Summary collapse

Instance Method Details

#go! ⇒ Boolean

Remove the stop signal

Returns:

  • (Boolean) —

    true if the stop signal was removed

Raises:

  • (StopSignalError) —

    if an error occurred while removing the stop signal



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# File 'lib/track_ballast/stop_signal.rb', line 108

def go!
  redis.del(stop_signal_key)

  true
rescue Redis::CommandError
  raise StopSignalError
end

#stop! ⇒ Boolean

Set the stop signal

Returns:

  • (Boolean) —

    true if the stop signal was set

Raises:



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# File 'lib/track_ballast/stop_signal.rb', line 96

def stop!
  redis.set(stop_signal_key, true)

  true
rescue Redis::CommandError
  raise StopSignalError
end

#stop_signal_key ⇒ String

The key used to store the stop signal.

It defaults to the class name plus “:stop”.

This can be overridden to provide a custom key as described in the StopSignal module documentation.

Returns:

  • (String) —

    the key used to store the stop signal



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# File 'lib/track_ballast/stop_signal.rb', line 133

def stop_signal_key
  "#{name}:stop"
end

#stopped? ⇒ Boolean

Check if the stop signal is set

Returns:

  • (Boolean)

Raises:

  • (StopSignalError) —

    if an error occurred while checking the stop signal



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# File 'lib/track_ballast/stop_signal.rb', line 119

def stopped?
  redis.exists(stop_signal_key).positive?
rescue Redis::CommandError
  raise StopSignalError
end