sigurd

Small gem to manage executing looping processes and signal handling.

Gem Version

Installation

Add this line to your application's Gemfile:

gem 'sigurd'

And then execute:

$ bundle

Or install it yourself as:

$ gem install sigurd

Versioning

We use a version of semver for this gem. Any change in previous behavior (something works differently or something old no longer works) is denoted with a bump in the minor version (0.4 -> 0.5). Patch versions are for bugfixes or new functionality which does not affect existing code. You should be locking your Gemfile to the minor version:

gem 'sigurd', '0.0.3'

Usage

Sigurd exposes two classes for use with a third class. The ideas is as follows:

  • You have any object which responds to the start and stop methods. This object is called a "Runner". When the stop method is called, the runner should gracefully shut down.
  • You create an Executor class - this manages a thread pool for a list of runners.
  • You create a SignalHandler which is the topmost object. This will handle the signals sent by the system and gracefully forward the requests. You pass the executor into the SignalHandler.
  • Finally, you call start on the SignalHandler to begin the execution.

Sample code:

class TestRunner

def start
  loop do
    break if @signal_to_stop
    # do some logic here
  end
end

  def stop
    @signal_to_stop = true
  end
end

runners = (1..2).map { TestRunner.new }
executor = Sigurd::Executor.new(runners, sleep_seconds: 5, logger: Logger.new(STDOUT))
Sigurd::SignalHandler.new(executor).run!

If you have only a single runner, you can pass it into the SignalHandler directly, without using an Executor:

  Sigurd::SignalHandler.new(runner).run!

By default, if any of your runners fails, Sigurd will use an exponential backoff to wait before restarting it. You can instead use the sleep_seconds setting to always sleep a fixed amount of time before retrying. There is no limit to retries.

Configuration

By default, sigurd will exit the process when a TERM, KILL or QUIT signal is received. You can change this behavior to instead raise the original SignalException by setting

Sigurd.exit_on_signal = true

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/flipp-oss/sigurd .

Linting

Sigurd uses Rubocop to lint the code. Please run Rubocop on your code before submitting a PR.

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