A library of locking algorithms for a variety of data stores. Supported Data Stores:

• DynamoDB *
• PostgreSQL

* The DynamoDB code uses a TTL based lock expiration. You should be comfortable with the implications outlined here.

There is only 1 public method:

lock(name, opts, &blk)

Install using the gem. The gem does not depend on the data store drivers, you will need to install those for yourself.

$ gem install pg
$ gem install lock-smith

Create a DynamoDB table named Locks with a hash key Name.

ENV["AWS_ID"] = "id"
ENV["AWS_SECRET"] = "secret"

require 'aws/dynamo_db'
require 'locksmith/dynamodb'
Locksmith::Dynamodb.lock("my-resource") do
  puts("locked my-resource with DynamoDB")
end

• ttl - Sets TTL on the DynamoDB item & Wraps your block in a timeout. Be sure to handle Timeout::Error.
• attempts - Number of attempts to create DynamoDB item. Your code will only run once.

Locksmith will use pg_try_advisory_lock to lock, no need for table creation.

ENV["DATABASE_URL"] = "postgresql://user:pass@localhost/database_name"

require 'pg'
require 'locksmith/pg'
Locksmith::Pg.lock("my-resource") do
  puts("locked my-resource with PostgreSQL")
end

• lspace - This defines which lock space lock-smith will use. This is handy if you have multiple applications using advisory locks.
• ttl - Wraps your block in a timeout. Be sure to handle Timeout::Error.
• attempts - Number of attempts to try advisory lock. Your code will only run once.

There are still some Data Stores to implement, follow the pattern for PostgreSQLand DynamoDB and submit a pull request.

Copyright (C) 2012 Ryan Smith

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.

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