Class: Redlock::Client

Inherits:
Object
  • Object
show all
Defined in:
lib/redlock/client.rb,
lib/redlock/testing.rb

Defined Under Namespace

Classes: RedisInstance

Constant Summary collapse

DEFAULT_REDIS_URLS = 
['redis://localhost:6379']
DEFAULT_REDIS_TIMEOUT = 
0.1
DEFAULT_RETRY_COUNT = 
3
DEFAULT_RETRY_DELAY = 
200
DEFAULT_RETRY_JITTER = 
50
CLOCK_DRIFT_FACTOR = 
0.01

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(servers = DEFAULT_REDIS_URLS, options = {}) ⇒ Client

Create a distributed lock manager implementing redlock algorithm. Params:

servers

The array of redis connection URLs or Redis connection instances. Or a mix of both.

options

You can override the default value for ‘retry_count`, `retry_delay` and `retry_gitter`.

* `retry_count`   being how many times it'll try to lock a resource (default: 3)
* `retry_delay`   being how many ms to sleep before try to lock again (default: 200)
* `retry_jitter`  being how many ms to jitter retry delay (default: 50)
* `redis_timeout` being how the Redis timeout will be set in seconds (default: 0.1)



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# File 'lib/redlock/client.rb', line 21

def initialize(servers = DEFAULT_REDIS_URLS, options = {})
  redis_timeout = options[:redis_timeout] || DEFAULT_REDIS_TIMEOUT
  @servers = servers.map do |server|
    if server.is_a?(String)
      RedisInstance.new(url: server, timeout: redis_timeout)
    else
      RedisInstance.new(server)
    end
  end
  @quorum = servers.length / 2 + 1
  @retry_count = options[:retry_count] || DEFAULT_RETRY_COUNT
  @retry_delay = options[:retry_delay] || DEFAULT_RETRY_DELAY
  @retry_jitter = options[:retry_jitter] || DEFAULT_RETRY_JITTER
end

Instance Attribute Details

#testing_mode=(value) ⇒ Object (writeonly)

Sets the attribute testing_mode

Parameters:

  • value —

    the value to set the attribute testing_mode to.



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# File 'lib/redlock/testing.rb', line 3

def testing_mode=(value)
  @testing_mode = value
end

Instance Method Details

#lock(resource, ttl, options = {}, &block) ⇒ Object

Locks a resource for a given time. Params:

resource

the resource (or key) string to be locked.

ttl

The time-to-live in ms for the lock.

options

Hash of optional parameters

* +extend+: A lock ("lock_info") to extend.
* +extend_only_if_life+: If +extend+ is given, only acquire lock if currently held
block

an optional block to be executed; after its execution, the lock (if successfully

acquired) is automatically unlocked.



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# File 'lib/redlock/client.rb', line 45

def lock(resource, ttl, options = {}, &block)
  lock_info = try_lock_instances(resource, ttl, options)

  if block_given?
    begin
      yield lock_info
      !!lock_info
    ensure
      unlock(lock_info) if lock_info
    end
  else
    lock_info
  end
end

#lock!(*args) ⇒ Object

Locks a resource, executing the received block only after successfully acquiring the lock, and returning its return value as a result. See Redlock::Client#lock for parameters.



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# File 'lib/redlock/client.rb', line 70

def lock!(*args)
  fail 'No block passed' unless block_given?

  lock(*args) do |lock_info|
    raise LockError, 'failed to acquire lock' unless lock_info
    return yield
  end
end

#try_lock_instances(resource, ttl, options) ⇒ Object 



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# File 'lib/redlock/client.rb', line 149

def try_lock_instances(resource, ttl, options)
  tries = options[:extend] ? 1 : @retry_count

  tries.times do |attempt_number|
    # Wait a random delay before retrying.
    sleep((@retry_delay + rand(@retry_jitter)).to_f / 1000) if attempt_number > 0

    lock_info = lock_instances(resource, ttl, options)
    return lock_info if lock_info
  end

  false
end

#try_lock_instances_without_testing ⇒ Object 



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# File 'lib/redlock/testing.rb', line 5

def try_lock_instances(resource, ttl, options)
  tries = options[:extend] ? 1 : @retry_count

  tries.times do |attempt_number|
    # Wait a random delay before retrying.
    sleep((@retry_delay + rand(@retry_jitter)).to_f / 1000) if attempt_number > 0

    lock_info = lock_instances(resource, ttl, options)
    return lock_info if lock_info
  end

  false
end

#unlock(lock_info) ⇒ Object

Unlocks a resource. Params:

lock_info

the lock that has been acquired when you locked the resource.



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# File 'lib/redlock/client.rb', line 63

def unlock(lock_info)
  @servers.each { |s| s.unlock(lock_info[:resource], lock_info[:value]) }
end

#unlock_without_testing ⇒ Object

Unlocks a resource. Params:

lock_info

the lock that has been acquired when you locked the resource.



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# File 'lib/redlock/testing.rb', line 21

def unlock(lock_info)
  @servers.each { |s| s.unlock(lock_info[:resource], lock_info[:value]) }
end