Locksy

Locksy provides support for creating and managing time-limited distributed locks.

Currently there is a local in-memory implementation for single-process testing and an AWS dynamodb-backed implementation.

Usage

To create and use a lock:

lock = lock_class.new(lock_name: 'my_lock')

begin
  lock.with_lock do
    # safe code
  end
rescue Locksy::LockNotOwnedError => ex
  # handle the case where the lock cannot be obtained
end

Because the implementations all follow the same interface, it is generally expected that you would separate out the choice of which implementation to use from the code that uses the lock. In the above example, lock_class provides the class name of the implementation to use. The benefit of this is that it allows you to do local testing with, for example, Locksy::Memory implementation which is fast and hreadsafe but does not provide protection when multiple processes are involved and use the Locksy::DynamoDB implementation in production.

To avoid loading many unnecessary dependencies for all implementaitons, it is necessary to require the lock implementation that you actually need from within your code.

Logging

Locksy does some logging, which by default, will push to STDOUT. If you want to control the logging, you can either provide an instance of a logger object that meets the ruby logger interface in to the lock instance (lock.logger = logger) or you can control it for all lock instances by passing in a logger object by calling Locksy.logger = logger.

To make locksy less chatty, things like Locksy.logger = ::Logger.WARN also work.

Dynamo DB locks

For local development when working with Dynamo DB, it is most useful to work with the AWS-provided dynamodb docker container and to configure the endpoint to point to that instance instead of the "real" AWS instance.

To get set up, install docker then:

docker pull amazon/dynamodb-local
docker run -p 8000:8000 amazon/dynamodb-local

Then set Locksy to use your local Dynamo DB instance:

require 'locksy/dynamodb'

dynamo_client = Aws::DynamoDB::Client.new(endpoint: 'http://localhost:8000')

lock = Locksy::DynamoDB.new(lock_name: 'my_lock', dynamo_client: dynamo_client)