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| IO.write(f, 'Hello, world!') end
/tmp/my-file.txt.lock will be created and used as an entrance lock.
will won't be deleted afterwards.
If you are not planning to write to the file, it is recommended to get
a non-exclusive/shared access to it, by providing
false to the method
require 'futex' Futex.new('/tmp/my-file.txt').open(false) |f| IO.read(f) end
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
trueif 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;
How to contribute
$ bundle update $ rake
If it's clean and you don't see any error messages, submit your pull request.
(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:
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