nworkers.cr

nworkers.cr is an experimental library in Crystal programming language that allows you to change the number of worker threads at runtime.

See Crystal Forum : How to add command line options to specify the number of threads?

Installation

1. Add the dependency to your shard.yml:

   dependencies:
     nworkers:
       github: kojix2/nworkers.cr
   

2. Run shards install

Usage

This is an experimental library. It is intended for use where the number of workers is changed immediately after startup and not changed afterwards. For example, in a command line tool, where the number of threads is set as an option.

• NWorkers.set_worker(n : Int): Sets the number of worker threads to n.
• NWorkers.add_worker(n : Int): Adds n worker threads.
• NWorkers.remove_worker(n : Int): Removes n worker threads.

Here's an example:

require "nworkers"

# set the number of workers to 4
NWorkers.set_worker(4)

# add 2 more workers
NWorkers.add_worker(2)

# remove 1 worker
NWorkers.remove_worker

Documentation

Development

• Crystal creates the number of workers specified by the environment variable ENV [“CRYSTAL_WORKERS”] only once at the beginning.
  • See scheduler.cr.
• This library will add workers later in the same manner.
• The author has used this library to create several small command line tools to verify that parallel processing with additional workers actually works.
• However, that there is no guarantee that adding or removing workers after the fact will work correctly.
• The author does not have sufficient knowledge or experience to examine whether this method will work well for long-running processes such as web applications.
• Pull requests and comments are always welcome!

Contributing

1. Fork it (https://github.com/kojix2/nworkers.cr/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributions are welcome! Please feel free to submit a Pull Request if you find a bug or you want to propose a new feature.