lock-smith

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.

Usage

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

DynamoDB

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

Options

• 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.
• attempt_interval - Number of seconds to wait between failed attempts (default: 0.1).

PostgreSQL

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

Options

• 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.
• attempt_interval - Number of seconds to wait between failed attempts (default: 0.1).

Hacking on Locksmith

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

License

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.

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.