Resque::UniqueByArity

Because some jobs have parameters that you do not want to consider for determination of uniqueness.

NOTE:

I rewrote, and renamed, both resque_solo and resque-lonely_job, because they can't be used together. Why? Their redis_key methods directly conflict, among other more subtle issues.

This gem requires use of my rewritten gems for uniqueness enforcement:

Project	Resque::UniqueByArity
gem name	resque-unique_by_arity
license
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Important Note

See lib/resque/unique_by_arity/configuration.rb for all config options. Only a smattering of what is available is documented in this README.

Most Important Note

You must configure this gem after you define the perform class method in your job or an error will be raised thanks to perform not having been defined yet.

Example:

class MyJob
  def self.perform(arg)
    # do stuff
  end
  include Resque::Plugins::UniqueByArity.new(
    arity_for_uniqueness: 1,
    lock_after_execution_period: 60,
    runtime_lock_timeout: 60 * 60 * 24 * 5, # 5 days
    unique_at_runtime: true,
    unique_in_queue: true
  )
end

Installation

Add this line to your application's Gemfile:

gem 'resque-unique_by_arity'

And then execute:

$ bundle

Or install it yourself as:

$ gem install resque-unique_by_arity

Usage

Global Configuration

The following is showing the default values. These global configs are copied into each per-class config unless they are overridden by the class config.

Create an initializer (e.g. config/initializers/resque-unique_by_arity.rb for rails) and customize the following:

  Resque::UniqueByArity.configure do |config|
    config.logger = nil
    config.log_level = :debug
    config.arity_for_uniqueness = 0
    config.unique_at_runtime = false
    config.unique_in_queue = false
    # No need to do the following if keeping default values
    config.runtime_lock_timeout = 60 * 60 * 24 * 5
    config.runtime_requeue_interval = 1
    config.unique_at_runtime_key_base = 'r-uar'.freeze
    config.lock_after_execution_period = 0
    config.ttl = -1
    config.unique_in_queue_key_base = 'r-uiq'.freeze
    # Debug Mode is preferably set via an environment variable:
    #   to one of 'true', 'arity', or 'arity,queue,runtime' for all three tools:
    #     ENV['RESQUE_DEBUG'] = 'true'
    # config.debug_mode = true
  end

Per Job Class Configuration

This gem will take care to set the class instance variables (similar to the familiar @queue class instance variable) that are utilized by resque-unique_in_queue and resque-unique_at_runtime (default values shown):

# For resque-unique_at_runtime
@runtime_lock_timeout = 60 * 60 * 24 * 5
@runtime_requeue_interval = 1
@unique_at_runtime_key_base = 'r-uar'.freeze

# For resque-unique_in_queue
@lock_after_execution_period = 0
@ttl = -1
@unique_in_queue_key_base = 'r-uiq'.freeze

All you need to do is configure this gem accordingly:

  include Resque::Plugins::UniqueByArity.new(
    arity_for_uniqueness: 1,
    # Turn on one or both of the following:
    unique_at_runtime: false,
    unique_in_queue: false,
    # No need to do the following if keeping default values
    runtime_lock_timeout: 60 * 60 * 24 * 5,
    runtime_requeue_interval: 1,
    # would override the global setting, probably a bad idea.
    # unique_at_runtime_key_base: 'r-uar'.freeze,
    lock_after_execution_period: 0,
    ttl: -1,
    # would override the global setting, probably a bad idea.
    # unique_in_queue_key_base: 'r-uiq'.freeze
  )

Arity For Uniqueness

Some jobs have parameters that you do not want to consider for determination of uniqueness. Resque jobs should use simple parameters, not named parameters, so you can just specify the number of parameters, counting from the left, you want to be considered for uniqueness.

class MyJob
  def self.perform(my, cat, is, the, best, opts = {})
    # Only the first 3: [my, cat, is] will be considered for determination of uniqueness
  end
  include Resque::Plugins::UniqueByArity.new(
    arity_for_uniqueness: 3,
    unique_at_runtime: true
  )
end

Arity For Uniqueness Validation

Want this gem to tell you when it is misconfigured? It can.

class MyJob
  def self.perform(my, cat, opts = {})
    # Because the third argument is optional the arity valdiation will not approve.
    # Arguments to be considered for uniqueness should be required arguments.
    # The warning log might look like:
    #
    #    MyJob.perform has the following required parameters: [:my, :cat], which is not enough to satisfy the configured arity_for_uniqueness of 3
  end
  include Resque::Plugins::UniqueByArity.new(
    arity_for_uniqueness: 3,
    arity_validation: :warning, # or :skip, :error, or an error class to be raised, e.g. RuntimeError
    unique_at_runtime: true
  )
end

Lock After Execution

Give the job a break after it finishes running, and don't allow another of the same, with matching args @ configured arity, to start within X seconds.

class MyJob
  def self.perform(arg1)
    # do stuff
  end
  include Resque::Plugins::UniqueByArity.new(
    arity_for_uniqueness: 1,
    lock_after_execution_period: 60,
    unique_at_runtime: true
  )
end

Runtime Lock Timeout

If runtime lock keys get stale, they will expire on their own after some period. You can set the expiration period on a per class basis.

class MyJob
  def self.perform(arg1)
    # do stuff
  end
  include Resque::Plugins::UniqueByArity.new(
    arity_for_uniqueness: 1,
    runtime_lock_timeout: 60 * 60 * 24 * 5, # 5 days
    unique_at_runtime: true
  )
end

Unique At Runtime (across all queues)

Prevent your app from running a job that is already running.

class MyJob
  def self.perform(arg1)
    # do stuff
  end
  include Resque::Plugins::UniqueByArity.new(
    arity_for_uniqueness: 1,
    unique_at_runtime: true
  )
end

Oops, I have stale runtime uniqueness keys for MyJob stored in Redis...

Preventing jobs with matching signatures from running, and they never get dequeued because there is no actual corresponding job to dequeue.

How to deal?

MyJob.purge_unique_at_runtime_redis_keys

Unique At Queue Time

Unique In Job's Specific Queue

Prevent your app from queueing a job that is already queued in the same queue.

class MyJob
  def self.perform(arg1)
    # do stuff
  end
  include Resque::Plugins::UniqueByArity.new(
    arity_for_uniqueness: 1,
    unique_in_queue: true
  )
end

Unique Across All Queues

Prevent your app from queueing a job that is already queued in any queue.

class MyJob
  def self.perform(arg1)
    # do stuff
  end
  include Resque::Plugins::UniqueByArity.new(
    arity_for_uniqueness: 1,
    unique_across_queues: true
  )
end

Oops, I have stale Queue Time uniqueness keys...

Preventing jobs with matching signatures from being queued, and they never get dequeued because there is no actual corresponding job to dequeue.

How to deal?

Option: Rampage

# Delete *all* queued jobs in the queue, and
#   delete *all* uniqueness keys for the queue.
Redis.remove_queue('queue_name')

Option: Butterfly

# Delete *no* queued jobs at all, and
#   delete *all* uniqueness keys for the queue (might then allow duplicates).
Resque::UniqueInQueue::Queue.cleanup('queue_name')

All Together Now

Unique At Runtime (across all queues) AND Unique In Job's Specific Queue

Prevent your app from running a job that is already running, and prevent your app from queueing a job that is already queued in the same queue.

class MyJob
  def self.perform(arg1)
    # do stuff
  end
  include Resque::Plugins::UniqueByArity.new(
    arity_for_uniqueness: 1,
    unique_at_runtime: true,
    runtime_lock_timeout: 60 * 60 * 24 * 5, # 5 days
    unique_in_queue: true
  )
end

Unique At Runtime (across all queues) AND Unique Across All Queues

Prevent your app from running a job that is already running, and prevent your app from queueing a job that is already queued in any queue.

class MyJob
  def self.perform(arg1)
    # do stuff
  end
  include Resque::Plugins::UniqueByArity.new(
    arity_for_uniqueness: 1,
    unique_at_runtime: true,
    runtime_lock_timeout: 60 * 60 * 24 * 5, # 5 days
    unique_across_queues: true
  )
end

Debugging

Run your worker with RESQUE_DEBUG=true to see payloads printed before they are used to determine uniqueness, as well as a lot of other debugging output.

Customize Unique Keys Per Job

Redefine methods to customize all the things. Warning: This might be crazy-making.

class MyJob
  def self.perform(arg1)
    # do stuff
  end
  include Resque::Plugins::UniqueByArity.new(
    #...
  )

  # Core hashing algorithm for a job used for *all 3 types* of uniqueness
  # @return [Array<String, arguments>], where the string is the unique digest, and arguments are the specific args that were used to calculate the digest
  def self.redis_unique_hash(payload, arity_for_uniqueness = 1)
    #       for how the built-in version works
    # uniqueness_args = payload["args"] # over simplified & ignoring arity
    # args = { class: job, args: uniqueness_args }
    # return [Digest::MD5.hexdigest(Resque.encode(args)), uniqueness_args]
  end

  def self.unique_in_queue_redis_key_prefix
    # "unique_job:#{self}" # <= default value
  end

  def self.unique_in_queue_redis_key(queue, payload)
    # arity_for_uniqueness = determine_arity # over simplified & ignoring context-specific arity determination
    # unique_hash, _args_for_uniqueness = redis_unique_hash(payload, arity_for_uniqueness)
    # "#{unique_in_queue_key_namespace(queue)}:#{unique_in_queue_redis_key_prefix}:#{unique_hash}"
  end

  def self.unique_in_queue_key_namespace(queue = nil)
    # definition depends on which type of uniqueness is chosen, be careful if you customize
    # "r-uiq:queue:#{queue}:job" # <= is for unique within queue at queue time
    # "r-uiq:across_queues:job" # <= is for unique across all queues at queue time
  end

  def self.runtime_key_namespace
    # "unique_at_runtime:#{self}"
  end

  def self.unique_at_runtime_redis_key(*args)
    # payload = {"class" => self.to_s, "args" => args}
    # unique_hash, _args_for_uniqueness = redis_unique_hash(payload, configuration.arity_for_uniqueness_at_runtime)
    # key = "#{runtime_key_namespace}:#{unique_hash}" # <= simplified default
  end
end

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/pboling/resque-unique_by_arity. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Added some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request

Code of Conduct

Everyone interacting in the Resque::UniqueByArity project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

Versioning

This library aims to adhere to Semantic Versioning 2.0.0. Violations of this scheme should be reported as bugs. Specifically, if a minor or patch version is released that breaks backward compatibility, a new version should be immediately released that restores compatibility. Breaking changes to the public API will only be introduced with new major versions.

As a result of this policy, you can (and should) specify a dependency on this gem using the Pessimistic Version Constraint with two digits of precision.

For example:

spec.add_dependency 'resque-unique_by_arity', '~> 0.0'

pboling/resque-unique_by_arity