class Redis::Lock
Class representing a lock. This functions like a proxy class, in that you can say @object.lock_name { block } to use the lock and also @object.counter_name.clear to reset on it. You can use this directly, but it is better to use the lock :foo class method in your class to define a lock.
Public Class Methods
new(key, *args)
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Calls superclass method
Redis::BaseObject::new
# File lib/redis/lock.rb, line 14 def initialize(key, *args) super(key, *args) @options[:timeout] ||= 5 @options[:init] = false if @options[:init].nil? # default :init to false redis.setnx(key, @options[:start]) unless @options[:start] == 0 || @options[:init] === false end
Public Instance Methods
generate_expiration()
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Return expiration in milliseconds
# File lib/redis/lock.rb, line 70 def generate_expiration ((@options[:expiration].nil? ? 1 : @options[:expiration].to_f) * 1000).to_i end
lock() { || ... }
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Get the lock and execute the code block. Any other code that needs the lock (on any server) will spin waiting for the lock up to the :timeout that was specified when the lock was defined.
# File lib/redis/lock.rb, line 28 def lock raise ArgumentError, 'Block not given' unless block_given? expiration_ms = generate_expiration expiration_s = expiration_ms / 1000.0 end_time = nil try_until_timeout do end_time = Time.now.to_i + expiration_s # Set a NX record and use the Redis expiration mechanism. # Empty value because the presence of it is enough to lock # `px` only except an Integer in millisecond break if redis.set(key, nil, px: expiration_ms, nx: true) # Backward compatibility code # TODO: remove at the next major release for performance unless @options[:expiration].nil? old_expiration = redis.get(key).to_f # Check it was not an empty string with `zero?` and # the expiration time is passed. if !old_expiration.zero? && old_expiration < Time.now.to_f expiration_ms = generate_expiration expiration_s = expiration_ms / 1000.0 end_time = Time.now.to_i + expiration_s break if redis.set(key, nil, px: expiration_ms) end end end begin yield ensure # We need to be careful when cleaning up the lock key. If we took a really long # time for some reason, and the lock expired, someone else may have it, and # it's not safe for us to remove it. Check how much time has passed since we # wrote the lock key and only delete it if it hasn't expired (or we're not using # lock expiration) if @options[:expiration].nil? || end_time > Time.now.to_f redis.del(key) end end end
value()
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# File lib/redis/lock.rb, line 21 def value nil end
Private Instance Methods
try_until_timeout() { || ... }
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# File lib/redis/lock.rb, line 76 def try_until_timeout if @options[:timeout] == 0 yield else start = Time.now while Time.now - start < @options[:timeout] yield sleep 0.1 end end raise LockTimeout, "Timeout on lock #{key} exceeded #{@options[:timeout]} sec" end