DBLock

Gem to obtain and release manual db locks. This can be utilized for example to make sure that certain rake tasks do not run in parallel on the same database (for example when cron jobs run for too long or are accidentally started multiple times). Currently only supports:

• MySQL
• Microsoft SQL Server
• Postgres

Installation

Add this line to your application's Gemfile:

gem 'db_lock'

then run bundle

Usage

DBLock.with_lock('name_of_lock', 5) do
  # code here
end

Before the code block is executed, it will attempt to acquire a db lock for X seconds (5 in this example). If this fails it will raise an DBLock::AlreadyLocked error. The lock is released after the block is executed, even if the block raised an error itself.

The locking will already fail with an error if the current thread already holds a lock via this gem.

Locks are achieved on the database via:

Database	Locking method
MySQL	GET_LOCK
Postgres	pg_advisory_lock
SQLServer	sp_getapplock

Dynamic lock name

If you prefix the lock with a . in a Rails application, . will be automatically replaced with YourAppName.environment (production/development/etc). If the lock name exceeds 64 characters, it will be replaced with a lock name of 64 characters, that consists of a pre- and suffix from the original lock name and a middle MD5 checksum.

Development

Bundle with the adapter you want to use, for example

$ bundle --with mysql

Run rspec with the database url env variables set. It will only run the specs it can run and skip the others.

For example

$ MYSQL_URL=mysql2://root:dummy@localhost/test SQLSERVER_URL=sqlserver://root:dummy@localhost/test rspec