Pond

Pond is a Crystal implementation of a WaitGroup, without channels or explicit counters. Pond automatically keeps track of all its fibers, and waits until all of them complete execution.

Installation

1. Add the dependency to your shard.yml:

   dependencies:
     pond:
       github: GrottoPress/pond
   

2. Run shards install

Usage

• Spawn fibers and wait on them:

  require "pond"
  
  pond = Pond.new
  
  1000.times do |_|
    pond.fill { do_work } # <= Spawns fiber and passes block to it
  end
  
  pond.drain # <= Waits for fibers to complete
  

  The code above is the same as:

  require "pond"
  
  Pond.drain do |pond|
    1000.times do |_|
      pond.fill { do_work }
    end
  end # <= Drains pond automatically at the end of the block
  

• You may spawn nested fibers:

  In this case, all ancestor fibers have to be added to the pond, otherwise Pond can't guarantee any of them would complete.

  require "pond"
  
  pond = Pond.new
  
  pond.fill do
    pond.fill do
      pond.fill { do_work }
    end
  end
  
  pond.drain
  

  Note that, while you can fill a pond that was created in a another fiber, draining has to be done in the same fiber the pond was created in. This is to prevent potential deadlocks.

  require "pond"
  
  pond = Pond.new
  
  pond.fill { do_work }
  
  spawn { pond.drain } # <= Error!
  

Development

Run tests with crystal spec -Dpreview_mt. You may set CRYSTAL_WORKERS environment variable with export CRYSTAL_WORKERS=<number>, before running tests.

Contributing

1. Fork it
2. Switch to the master branch: git checkout master
3. Create your feature branch: git checkout -b my-new-feature
4. Make your changes, updating changelog and documentation as appropriate.
5. Commit your changes: git commit
6. Push to the branch: git push origin my-new-feature
7. Submit a new Pull Request against the GrottoPress:master branch.