DynamoidLockable

DynamoidLockable provides a interface for pessimistic locking for Dynamoid models.

Installation

Add this line to your application's Gemfile:

gem 'dynamoid_lockable'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install dynamoid_lockable

Usage

class MyModel
  include Dynamoid::Document
  include DynamoidLockable

  # Models may have more than one lock discriminated by name.
  # Creates a lock named :importing, which locks by default for 5 minutes and will refresh the lock every 10 seconds.
  # Default values:
  #  lock_for: 10 minutes
  #  relock_every: 1/3 of lock_for
  locks_with :importing, lock_for: 5 * 60, relock_every: 10
end

thing = MyModel.find('abcd')

# Most basic usage
thing.perform_with_lock(:importing) do
  # do whatever you like in here, record will remain locked as long as this block is executing and the
  # thread is able to do work
end

# Manually locking and unlocking
thing.lock(:importing)
# WARNING! Lock is not persisted, you have 5 minutes to complete your task
do_work(thing)
thing.unlock(:importing)

# You can also search by entities which are lockable (unlocked, locks expired or eleigible for reentry)
search = MyModel.lockable(:importing).first

# Note that `lockable` returns a dynamoid_advanced_where chain, so additional where clauses may be appended

# Locks support reentry from the same thread
thing.lock(:importing)
thing.lock(:importing) # No error

Thread.new do
  thing.lock(:importing) # Error: Concerns::Lockable::CouldNotAcquireLock
end

A note on the options:

• locks_for - should be a reasonably high number, setting it too small will result in excessive DynamoDB usage
• relock_every - should be a positive number, nil or 0 will result in the relock process being disabled

Errors

• If unable to obtain a lock, DynamoidLockable::CouldNotAcquireLock is raised
• If unable to obtain to release a lock, DynamoidLockable::CouldNotUnlock is raised

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/GetTerminus/dynamoid_lockable.