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Sometimes you need to synchronize your block of code, but Mutex is too coarse-grained, because it always locks, no matter what objects your code accesses. The Futex (from "file mutex") is more fine-grained and uses a file as an entrance lock to your code.

First, install it:

$ gem install futex

Then, use it like this:

require 'futex'
Futex.new('/tmp/my-file.txt').open |f|
  File.write(f, 'Hello, world!')
end

The file /tmp/my-file.txt.lock will be created and used as an entrance lock. It will won't be deleted afterwards.

For better traceability you can provide a few arguments to the constructor of the Futex class, including:

  • log: an object that implements debug() method, which will receive supplementary messages from the locking mechanism;

  • logging: set it to true if you want to see logs;

  • timeout: the number of seconds to wait for the lock availability (an exception is raised when the wait is expired);

  • sleep: the number of seconds to wait between attempts to acquire the lock file (the smaller the number, the more reactive is the software, but the higher the load for the file system and the CPU);

  • lock: the absolute path of the lock file;

That's it.

How to contribute

Read these guidelines. Make sure you build is green before you contribute your pull request. You will need to have Ruby 2.3+ and Bundler installed. Then:

$ bundle update
$ rake

If it's clean and you don't see any error messages, submit your pull request.

License

(The MIT License)

Copyright (c) 2018 Yegor Bugayenko

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.