Module: ActiveJob::Exceptions::ClassMethods

Defined in:
lib/active_job/exceptions.rb

Instance Method Summary collapse

Instance Method Details

#after_discard(&blk) ⇒ Object

A block to run when a job is about to be discarded for any reason.

Example

class WorkJob < ActiveJob::Base
  after_discard do |job, exception|
    ExceptionNotifier.report(exception)
  end

  ...

end



124
125
126
 
# File 'lib/active_job/exceptions.rb', line 124

def after_discard(&blk)
  self.after_discard_procs += [blk]
end

#discard_on(*exceptions) ⇒ Object

Discard the job with no attempts to retry, if the exception is raised. This is useful when the subject of the job, like an Active Record, is no longer available, and the job is thus no longer relevant.

You can also pass a block that’ll be invoked. This block is yielded with the job instance as the first and the error instance as the second parameter.

retry_on and discard_on handlers are searched from bottom to top, and up the class hierarchy. The handler of the first class for which exception.is_a?(klass) holds true is the one invoked, if any.

Example

class SearchIndexingJob < ActiveJob::Base
  discard_on ActiveJob::DeserializationError
  discard_on(CustomAppException) do |job, error|
    ExceptionNotifier.caught(error)
  end

  def perform(record)
    # Will raise ActiveJob::DeserializationError if the record can't be deserialized
    # Might raise CustomAppException for something domain specific
  end
end



103
104
105
106
107
108
109
110
 
# File 'lib/active_job/exceptions.rb', line 103

def discard_on(*exceptions)
  rescue_from(*exceptions) do |error|
    instrument :discard, error: error do
      yield self, error if block_given?
      run_after_discard_procs(error)
    end
  end
end

#retry_on(*exceptions, wait: 3.seconds, attempts: 5, queue: nil, priority: nil, jitter: JITTER_DEFAULT) ⇒ Object

Catch the exception and reschedule job for re-execution after so many seconds, for a specific number of attempts. If the exception keeps getting raised beyond the specified number of attempts, the exception is allowed to bubble up to the underlying queuing system, which may have its own retry mechanism or place it in a holding queue for inspection.

You can also pass a block that’ll be invoked if the retry attempts fail for custom logic rather than letting the exception bubble up. This block is yielded with the job instance as the first and the error instance as the second parameter.

retry_on and discard_on handlers are searched from bottom to top, and up the class hierarchy. The handler of the first class for which exception.is_a?(klass) holds true is the one invoked, if any.

Options

  • :wait - Re-enqueues the job with a delay specified either in seconds (default: 3 seconds), as a computing proc that takes the number of executions so far as an argument, or as a symbol reference of :polynomially_longer, which applies the wait algorithm of ((executions**4) + (Kernel.rand * (executions**4) * jitter)) + 2 (first wait ~3s, then ~18s, then ~83s, etc)

  • :attempts - Enqueues the job the specified number of times (default: 5 attempts) or a symbol reference of :unlimited to retry the job until it succeeds. The number of attempts includes the original job execution.

  • :queue - Re-enqueues the job on a different queue

  • :priority - Re-enqueues the job with a different priority

  • :jitter - A random delay of wait time used when calculating backoff. The default is 15% (0.15) which represents the upper bound of possible wait time (expressed as a percentage)

Examples

class RemoteServiceJob < ActiveJob::Base
  retry_on CustomAppException # defaults to ~3s wait, 5 attempts
  retry_on AnotherCustomAppException, wait: ->(executions) { executions * 2 }
  retry_on CustomInfrastructureException, wait: 5.minutes, attempts: :unlimited

  retry_on ActiveRecord::Deadlocked, wait: 5.seconds, attempts: 3
  retry_on Net::OpenTimeout, Timeout::Error, wait: :polynomially_longer, attempts: 10 # retries at most 10 times for Net::OpenTimeout and Timeout::Error combined
  # To retry at most 10 times for each individual exception:
  # retry_on Net::OpenTimeout, wait: :polynomially_longer, attempts: 10
  # retry_on Net::ReadTimeout, wait: 5.seconds, jitter: 0.30, attempts: 10
  # retry_on Timeout::Error, wait: :polynomially_longer, attempts: 10

  retry_on(YetAnotherCustomAppException) do |job, error|
    ExceptionNotifier.caught(error)
  end

  def perform(*args)
    # Might raise CustomAppException, AnotherCustomAppException, or YetAnotherCustomAppException for something domain specific
    # Might raise ActiveRecord::Deadlocked when a local db deadlock is detected
    # Might raise Net::OpenTimeout or Timeout::Error when the remote service is down
  end
end



62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
 
# File 'lib/active_job/exceptions.rb', line 62

def retry_on(*exceptions, wait: 3.seconds, attempts: 5, queue: nil, priority: nil, jitter: JITTER_DEFAULT)
  rescue_from(*exceptions) do |error|
    executions = executions_for(exceptions)
    if attempts == :unlimited || executions < attempts
      retry_job wait: determine_delay(seconds_or_duration_or_algorithm: wait, executions: executions, jitter: jitter), queue: queue, priority: priority, error: error
    else
      if block_given?
        instrument :retry_stopped, error: error do
          yield self, error
        end
        run_after_discard_procs(error)
      else
        instrument :retry_stopped, error: error
        run_after_discard_procs(error)
        raise error
      end
    end
  end
end