Module: Resque::Plugins::Retry

Included in:
ExponentialBackoff
Defined in:
lib/resque/plugins/retry.rb

Overview

If you want your job to retry on failure, simply extend your module/class with this module:

class DeliverWebHook
  extend Resque::Plugins::Retry # allows 1 retry by default.
  @queue = :web_hooks

  def self.perform(url, hook_id, hmac_key)
    heavy_lifting
  end
end

Easily do something custom:

class DeliverWebHook
  extend Resque::Plugins::Retry
  @queue = :web_hooks

  @retry_limit = 8          # default: 1
  @retry_delay = 60 # default: 0

  # used to build redis key, for counting job attempts.
  def self.identifier(url, hook_id, hmac_key)
    "#{url}-#{hook_id}"
  end

  def self.perform(url, hook_id, hmac_key)
    heavy_lifting
  end
end

Instance Method Summary collapse

Instance Method Details

#after_perform_retry(*args) ⇒ Object

Resque after_perform hook.

Deletes retry attempt count from Redis.



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# File 'lib/resque/plugins/retry.rb', line 159

def after_perform_retry(*args)
  Resque.redis.del(redis_retry_key(*args))
end

#args_for_retry(*args) ⇒ Array

This method is abstract.

Modify the arguments used to retry the job. Use this to do something other than try the exact same job again.

Returns:

  • (Array) —

    new job arguments



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# File 'lib/resque/plugins/retry.rb', line 96

def args_for_retry(*args)
  args
end

#before_perform_retry(*args) ⇒ Object

Resque before_perform hook.

Increments and sets the ‘@retry_attempt` count.



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# File 'lib/resque/plugins/retry.rb', line 149

def before_perform_retry(*args)
  retry_key = redis_retry_key(*args)
  Resque.redis.setnx(retry_key, -1)             # default to -1 if not set.
  @retry_attempt = Resque.redis.incr(retry_key) # increment by 1.
end

#identifier(*args) ⇒ String

This method is abstract.

You may override to implement a custom identifier, you should consider doing this if your job arguments are many/long or may not cleanly cleanly to strings.

Builds an identifier using the job arguments. This identifier is used as part of the redis key.

Parameters:

  • args (Array) —

    job arguments

Returns:

  • (String) —

    job identifier



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# File 'lib/resque/plugins/retry.rb', line 47

def identifier(*args)
  args_string = args.join('-')
  args_string.empty? ? nil : args_string
end

#on_failure_retry(exception, *args) ⇒ Object

Resque on_failure hook.

Checks if our retry criteria is valid, if it is we try again. Otherwise the retry attempt count is deleted from Redis.



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# File 'lib/resque/plugins/retry.rb', line 168

def on_failure_retry(exception, *args)
  if retry_criteria_valid?(exception, *args)
    try_again(*args)
  else
    Resque.redis.del(redis_retry_key(*args))
  end
end

#redis_retry_key(*args) ⇒ String

Builds the redis key to be used for keeping state of the job attempts.

Returns:

  • (String) —

    redis key



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# File 'lib/resque/plugins/retry.rb', line 57

def redis_retry_key(*args)
  ['resque-retry', name, identifier(*args)].compact.join(":").gsub(/\s/, '')
end

#retry_attempt ⇒ Fixnum

Number of retry attempts used to try and perform the job.

The real value is kept in Redis, it is accessed and incremented using a before_perform hook.

Returns:

  • (Fixnum) —

    number of attempts



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# File 'lib/resque/plugins/retry.rb', line 77

def retry_attempt
  @retry_attempt ||= 0
end

#retry_criteria_valid?(exception, *args) ⇒ Boolean

Test if the retry criteria is valid.

Parameters:

  • exception (Exception)
  • args (Array) —

    job arguments

Returns:

  • (Boolean) 


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# File 'lib/resque/plugins/retry.rb', line 126

def retry_criteria_valid?(exception, *args)
  # FIXME: let people extend retry criteria, give them a chance to say no.
  if retry_limit > 0
    return false if retry_attempt >= retry_limit
  end
  retry_exception?(exception.class)
end

#retry_delay ⇒ Number

This method is abstract.

Number of seconds to delay until the job is retried.

Returns:

  • (Number) —

    number of seconds to delay



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# File 'lib/resque/plugins/retry.rb', line 86

def retry_delay
  @retry_delay ||= 0
end

#retry_exception?(exception) ⇒ Boolean

Convenience method to test whether you may retry on a given exception.

Returns:

  • (Boolean) 


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# File 'lib/resque/plugins/retry.rb', line 104

def retry_exception?(exception)
  return true if retry_exceptions.nil?
  !! retry_exceptions.any? { |ex| ex >= exception }
end

#retry_exceptions ⇒ Array?

This method is abstract.

Controls what exceptions may be retried.

Default: ‘nil` - this will retry all exceptions.

Returns:

  • (Array, nil) 


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# File 'lib/resque/plugins/retry.rb', line 116

def retry_exceptions
  @retry_exceptions ||= nil
end

#retry_limit ⇒ Fixnum

Maximum number of retrys we can attempt to successfully perform the job. A retry limit of 0 or below will retry forever.

Returns:

  • (Fixnum) 


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# File 'lib/resque/plugins/retry.rb', line 66

def retry_limit
  @retry_limit ||= 1
end

#try_again(*args) ⇒ Object

Will retry the job.



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# File 'lib/resque/plugins/retry.rb', line 136

def try_again(*args)
  if retry_delay <= 0
    # If the delay is 0, no point passing it through the scheduler
    Resque.enqueue(self, *args_for_retry(*args))
  else
    Resque.enqueue_in(retry_delay, self, *args_for_retry(*args))
  end
end