SimpleMutex ·

SimpleMutex::Mutex - Redis-based locks with ability to store custom data inside them.

SimpleMutex::SidekiqSupport::JobWrapper - wrapper for Sidekiq jobs that generates locks using job's class name and arguments (optional)

SimpleMutex:SidekiqSupport::JobMixin - mixin for Sidekiq jobs with DSL simplifying usage of SimpleMutex::SidekiqSupport::JobWrapper

SimpleMutex::SidekiqSupport::JobCleaner - cleaner for leftover locks created by SimpleMutex::Job if Sidekiq dies unexpectedly.

SimpleMutex::SidekiqSupport::Batch - wrapper for Sidekiq Pro batches that use SimpleMutex::Mutex to prevent running multiple batch instances.

SimpleMutex:SidekiqSupport::BatchCleaner - cleaner for leftover lock created by SimpleMutex::Batch if Sidekiq dies unexpectedly.

SimpleMutex::Helper - auxiliary class for debugging purposes. Allows to inspect existing locks.

Configuration

Providing Redis instance before using gem is mandatory.

SimpleMutex.redis = Redis.new(
  # ...
)

Providing logger is optional (used by SimpleMutex::SidekiqSupport::JobCleaner and SimpleMutex::SidekiqSupport::BatchCleaner).

SimpleMutex.logger = Logger.new(
  # ...
)

When using gem with Ruby on Rails you can set those in initializers

SimpleMutex::Mutex Usage

Initialization

Arguments

mandatory

• lock_key - string that identifies lock, mandatory. Two pieces of locked code can't be run simultaneously if they use same lock_key. They don't interfere with each other if different lock_key's are used

optional

Keyword arguments are used for optional args.

• expires_in: - mutex TTL in second (or ActiveSupport::Numeric time interval), lock will be removed by redis automatically when expired, lock will expire in 1 hour (3600) if not provided
• signature: - string used to determine ownership of lock, checked when manually deleting lock, will be generated by SecureRandom.uuid if not provided
• payload: - any object that can be serialized as JSON, nil if not provided

Example

SimpleMutex::Mutex
  .new(
  "some_lock_key",
  expires_in: 3600,
  signature: "qwe123",
  payload: { "started_at" => Time.now }
)

Wrapping block in mutex

You can use method #with_lock to wrap code block in mutex

  SimpleMutex::Mutex
    .new(
      "some_lock_key",
      expires_in: 3600,
      signature: "qwe123",
      payload: { "started_at" => Time.now }
    ).with_lock do
    # your code
  end

Method has delegator defined on class, so it can be used without manual instantiation

  SimpleMutex::Mutex
    .with_lock(
      "some_lock_key",
      expires_in: 3600,
      signature: "qwe123",
      payload: { "started_at" => Time.now }
    ) do
    # your code
  end

Manual lock control

Using mutex instance

  mutex = SimpleMutex::Mutex.new(
            "some_lock_key",
             expires_in: 3600,
             signature: "qwe123",
             payload: { "started_at" => Time.now }
          )

  mutex.lock!
  # your code
  mutex.unlock!

If you for some reason don't want exceptions to be raised when obtaining/deleting lock is failed, you can use non-! methods.

  mutex = SimpleMutex::Mutex.new("some_lock_key")
  # obtaining of lock is not guaranteed
  mutex.lock
  # but you can check if it is obtained (true if lock with correct signature exists)
  mutex.lock_obtained?
  # releasing of lock is not guaranteed
  mutex.unlock 

Using without instance

There are ::lock/::lock!/::unlock/::unlock! methods defined on class if you don't want to explicitly use initializer (though it still will be used behind the scenes as ::lock and ::lock! class methods are just delegators).

Mutexes have random signature stored inside to determine ownership. By default it prevents deleting locks with signature different from provided. You can use force: true to ignore signature check.

::lock and ::lock! class methods accept same arguments as in ::new

::unlock and ::unlock! accept next arguments:

• lock_key - same as in ::new
• signature: - same as in ::new
• force: - boolean, signature will be ignored if true, optional, false by default

  SimpleMutex::Mutex.lock!("some_lock_key", signature: "abra_kadabra")

  # This will work because signature is same as in lock
  SimpleMutex::Mutex.unlock!("some_lock_key", signature: "abra_kadabra")

  # This won't work, because signature is missing
  SimpleMutex::Mutex.unlock!("some_lock_key")

  # This won't work, because signature is different
  SimpleMutex::Mutex.unlock!("some_lock_key", signature: "alakazam")

  # This will work because of force: true
  SimpleMutex::Mutex.unlock!("some_lock_key", force: true)

  # This will work because of force: true
  SimpleMutex::Mutex.unlock!("some_lock_key", signature: "alakazam", force: true)

Getting signature from instance

You can get signature from instance if you want. By default it is UUID generated by SecureRandom.

  mutex = SimpleMutex::Mutex.new("some_lock_key")
  mutex.signature

SimpleMutex::SidekiqSupport::JobWrapper Usage

This class made to simplify usage for locking of sidekiq jobs. It will create lock with lock_key based on job's class.name and it's arguments if lock_with_params: true.

Job's ID (jid) and time when job's execution is started will be stored inside mutex value.

  class SomeJob
    include Sidekiq::Worker

    def perform(*args)
      SimpleMutex::SidekiqSupport::JobWrapper.new(
        self,
        params:           args,
        lock_with_params: true,
        expires_in:       1.hour,
        payload:          { this_is_optional: true }
      ).with_redlock do
        # your code
      end
    end
  end

params will be used to generate lock_key if lock_with_params: true.

expires_in: is in seconds, optional, 5 hours by default.

payload: optional serializable object.

SimpleMutex::SidekiqSupport::Batch Usage

This is wrapper for Sidekiq::Batch (from Sidekiq Pro) that helps to prevent running two similar batches.

  batch = SimpleMutex::SidekiqSupport::Batch.new(
      lock_key: "my_batch",
      expires_in: 23.hours.to_i,
    )

    batch.description = "batch of MyJobs"
    batch.on(:success, self.class, {}) # you can add custom callbacks like with Sidekiq::Batch
    batch.on(:death ,  self.class, {})

    batch.jobs do
      set_of_job_attributes.each do |job_attributes|
        MyJob.perform(job_attributes)
      end
    end

• lock_key - manatory lock key
• expires_in: - optional TTL, 6 hours if not provided

SimpleMutex::SidekiqSupport::JobCleaner Usage

If you use SimpleMutex for locking jobs via SimpleMutex::SidekiqSupport::Job, when Sidekiq dies unexpectedely, there can be leftover mutexes for dead jobs. To delete them you can use:

  SimpleMutex::SidekiqSupport::JobCleaner.unlock_dead_jobs

SimpleMutex::SidekiqSupport::BatchCleaner Usage

If you use SimpleMutex for locking Batches via SimpleMutex::SidekiqSupport::Batch, when Sidekiq dies unexpectedely, there can be leftover mutexes for dead batches. To delete them you can use:

  SimpleMutex::SidekiqSupport::BatchCleaner.unlock_dead_batches

SimpleMutex::Helper Usage

Getting lock by lock_key (returns nil if no such lock)

SimpleMutex::Helper.get("some_lock_key")

Listing existing locks.

SimpleMutex::Helper.list(mode: :default)

mode: paramater allows to filter locks by type:

• :all - all locks including manual
• :job - job locks
• :batch - batch locks
• :default - job and batch locks

SimpleMutex::SidekiqSupport::JobMixin Usage

Base Job class

class ApplicationJob
  include Sidekiq::Worker
  include SimpleMutex::SidekiqSupport::JobMixin

  class << self
    def inherited(job_class)
      # Setting default timeout for mutex.
      job_class.set_job_timeout(5 * 60 * 60) # 5 hours

      job_class.prepend(
        Module.new do
          def perform(*args)
              with_redlock(args) { super }
          end
        end,
      )
    end
  end
end

DSL:

• locking! - enables locking with simple_mutex for jobs of this class
• lock_with_params! - locks are specific for set of arguments. Same job with other arguments can still be called.
• skip_locking_error? - suppresses SimpleMutex::Mutex::LockError
• set_job_timeout - redis mutex TTL in seconds (will be removed by redis itself on timeout)

Example:

class SpecificJob < ApplicaionJob
  locking!
  lock_with_params!
  set_job_timeout 6 * 60 * 60

  def perform
    # ...
  end
end

You can also override error processing for SimpleMutex::Mutex::LockError

  # DEFAULT ERROR PROCESSING
  # def process_locking_error(error)
  #   raise error unless self.class.skip_locking_error?
  # end

  class SpecificJob < ApplicaionJob
    locking!

    def perform
      # ...
    end

    def process_locking_error(error)
      SomeLogger.error(error.msg)
      raise error unless self.class.skip_locking_error?
    end
  end

Contributing

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

License

Released under MIT License.

Authors

Team Umbrellio

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