How to coordinate distributed work with MySQL's GET_LOCK
The linked article explains how to get a database-wide lock without creating table rows:
This article explains how I replaced file-based methods to ensure only one running instance of a program with MySQL’s GET_LOCK function. The result is mutual exclusivity that works in a distributed environment, and it’s dead simple to implement.
An implementation as a Rubygem seems to be with_advisory_lock. It has support for MySQL, PostgreSQL and SQLite.
Unfortunately, it has a horrible caveat in MySQL:
With MySQL (at least <= v5.5), if you ask for a different advisory lock within a with_advisory_lock block, you will be releasing the parent lock (!!!). A
NestedAdvisoryLockErrorwill be raised in this case. If you ask for the same lock name, with_advisory_lock won't ask for the lock again, and the block given will be yielded to.
If you're using MySQL, maybe you'd like to use our table-backed lock instead.