Class: Bosh::Director::Lock

Inherits:
Object show all
Defined in:
lib/bosh/director/lock.rb

Overview

Distributed lock backed by Redis.

Defined Under Namespace

Classes: TimeoutError

Instance Method Summary collapse

Constructor Details

#initialize(name, opts = {}) ⇒ Lock

Creates new lock with the given name.

Parameters:

  • name —

    lock name

  • opts (Hash) (defaults to: {}) —

    a customizable set of options

Options Hash (opts):

  • timeout (Number) —

    how long to wait before giving up

  • expiration (Number) —

    how long to wait before expiring an old lock



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# File 'lib/bosh/director/lock.rb', line 17

def initialize(name, opts = {})
  @name = name
  @id = SecureRandom.uuid
  @timeout = opts[:timeout] || 1.0
  @expiration = opts[:expiration] || 10.0
  @logger = Config.logger
  @refresh_thread = nil
end

Instance Method Details

#lock {|void| ... } ⇒ void

This method returns an undefined value.

Acquire a lock.

Yields:

  • (void) —

    optional block to do work before automatically releasing the lock.



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# File 'lib/bosh/director/lock.rb', line 31

def lock
  acquire

  @refresh_thread = Thread.new do
    redis = Config.redis
    sleep_interval = [1.0, @expiration/2].max
    begin
      loop do
        @logger.debug("Renewing lock: #@name")
        redis.watch(@name)
        existing_lock = redis.get(@name)
        lock_id = existing_lock.split(":")[1]
        break if lock_id != @id
        lock_expiration = Time.now.to_f + @expiration + 1
        redis.multi do
          redis.set(@name, "#{lock_expiration}:#@id")
        end
        sleep(sleep_interval)
      end
    ensure
      @logger.debug("Lock renewal thread exiting")
      redis.quit
    end
  end

  if block_given?
    begin
      yield
    ensure
      release
    end
  end
end

#release ⇒ void

This method returns an undefined value.

Release a lock that was not auto released by the lock method.



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# File 'lib/bosh/director/lock.rb', line 68

def release
  @refresh_thread.exit if @refresh_thread
  delete
end