how to set expiration and timeout for lock

The below example will be used to test the difference of expiration and timeout of redis-object lock

# in User model
def purchase(item)
  self.purchase_something_lock.lock do
    puts "buy a #{item}"
    sleep 5
  end
end

Expiration

# in User model
lock :purchase_something, expiration: 3

when expiration of former process is reached, the lock will released, a latter process can obtain the lock and do the work.

example:

# execute and result
['book', 'doll'].each do |item|
  Thread.new do
    purchase(item)
  end
end

#=> buy a book
(after 3 sec...)
#=> buy a doll

Lock

# in User model
lock :purchase_something, timeout: 3

when timeout of latter process is reached, the process will exit with a timeout exception.

# execute and result
['book', 'doll'].each do |item|
  Thread.new do
    begin
      purchase(item)
    rescue => e
      puts e
    end
  end
end

#=> buy a book
(after 3 sec...)
#=> Redis::Lock::LockTimeout: Timeout on lock .........