require "active_support/core_ext/numeric/time" module ActiveJob # Provides behavior for retrying and discarding jobs on exceptions. module Exceptions extend ActiveSupport::Concern module ClassMethods # 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. # # ==== Options # * :wait - Re-enqueues the job with a delay specified either in seconds (default: 3 seconds), # as a computing proc that the number of executions so far as an argument, or as a symbol reference of # :exponentially_longer<>, which applies the wait algorithm of (executions ** 4) + 2 # (first wait 3s, then 18s, then 83s, etc) # * :attempts - Re-enqueues the job the specified number of times (default: 5 attempts) # * :queue - Re-enqueues the job on a different queue # * :priority - Re-enqueues the job with a different priority # # ==== Examples # # class RemoteServiceJob < ActiveJob::Base # retry_on CustomAppException # defaults to 3s wait, 5 attempts # retry_on AnotherCustomAppException, wait: ->(executions) { executions * 2 } # retry_on(YetAnotherCustomAppException) do |job, exception| # ExceptionNotifier.caught(exception) # end # retry_on ActiveRecord::Deadlocked, wait: 5.seconds, attempts: 3 # retry_on Net::OpenTimeout, wait: :exponentially_longer, attempts: 10 # # 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 when the remote service is down # end # end def retry_on(exception, wait: 3.seconds, attempts: 5, queue: nil, priority: nil) rescue_from exception do |error| if executions < attempts logger.error "Retrying #{self.class} in #{wait} seconds, due to a #{exception}. The original exception was #{error.cause.inspect}." retry_job wait: determine_delay(wait), queue: queue, priority: priority else if block_given? yield self, exception else logger.error "Stopped retrying #{self.class} due to a #{exception}, which reoccurred on #{executions} attempts. The original exception was #{error.cause.inspect}." raise error end end end end # 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. # # ==== Example # # class SearchIndexingJob < ActiveJob::Base # discard_on ActiveJob::DeserializationError # # def perform(record) # # Will raise ActiveJob::DeserializationError if the record can't be deserialized # end # end def discard_on(exception) rescue_from exception do |error| logger.error "Discarded #{self.class} due to a #{exception}. The original exception was #{error.cause.inspect}." end end end # Reschedules the job to be re-executed. This is useful in combination # with the +rescue_from+ option. When you rescue an exception from your job # you can ask Active Job to retry performing your job. # # ==== Options # * :wait - Enqueues the job with the specified delay in seconds # * :wait_until - Enqueues the job at the time specified # * :queue - Enqueues the job on the specified queue # * :priority - Enqueues the job with the specified priority # # ==== Examples # # class SiteScraperJob < ActiveJob::Base # rescue_from(ErrorLoadingSite) do # retry_job queue: :low_priority # end # # def perform(*args) # # raise ErrorLoadingSite if cannot scrape # end # end def retry_job(options = {}) enqueue options end private def determine_delay(seconds_or_duration_or_algorithm) case seconds_or_duration_or_algorithm when :exponentially_longer (executions ** 4) + 2 when ActiveSupport::Duration duration = seconds_or_duration_or_algorithm duration.to_i when Integer seconds = seconds_or_duration_or_algorithm seconds when Proc algorithm = seconds_or_duration_or_algorithm algorithm.call(executions) else raise "Couldn't determine a delay based on #{seconds_or_duration_or_algorithm.inspect}" end end end end