resque-retry
A Resque plugin. Requires Resque ~> 1.25 or Resque ~> 2.0 & resque-scheduler ~> 4.0.
This gem provides retry, delay and exponential backoff support for resque jobs.
- Redis backed retry count/limit.
- Retry on all or specific exceptions.
- Exponential backoff (varying the delay between retrys).
- Multiple failure backend with retry suppression & resque-web tab.
- Small & Extendable - plenty of places to override retry logic/settings.
Install & Quick Start
To install:
$ gem install resque-retry
If you're using Bundler to manage your dependencies, you should add
gem 'resque-retry' to your Gemfile.
Add this to your Rakefile:
require 'resque/tasks'
require 'resque/scheduler/tasks'
The delay between retry attempts is provided by resque-scheduler.
You'll want to run the scheduler process, otherwise delayed retry attempts
will never perform:
$ rake resque:scheduler
Use the plugin:
require 'resque-retry'
class ExampleRetryJob
extend Resque::Plugins::Retry
@queue = :example_queue
@retry_limit = 3
@retry_delay = 60
def self.perform(*args)
# your magic/heavy lifting goes here.
end
end
Then start up a resque worker as normal:
$ QUEUE=* rake resque:work
Now if you ExampleRetryJob fails, it will be retried 3 times, with a 60 second
delay between attempts.
For more explanation and examples, please see the remaining documentation.
Failure Backend & Resque Web Additions
Lets say you're using the Redis failure backend of resque (the default).
Every time a job fails, the failure queue is populated with the job and
exception details.
Normally this is useful, but if your jobs retry... it can cause a bit of a mess.
For example: given a job that retried 4 times before completing successful.
You'll have a lot of failures for the same job and you wont be sure if it
actually completed successfully just by just using the resque-web interface.
Failure Backend
MultipleWithRetrySuppression is a multiple failure backend, with retry
suppression.
Here's an example, using the Redis failure backend:
require 'resque-retry'
require 'resque/failure/redis'
# require your jobs & application code.
Resque::Failure::MultipleWithRetrySuppression.classes = [Resque::Failure::Redis]
Resque::Failure.backend = Resque::Failure::MultipleWithRetrySuppression
If a job fails, but can and will retry, the failure details wont be logged
in the Redis failed queue (visible via resque-web).
If the job fails, but can't or won't retry, the failure will be logged in
the Redis failed queue, like a normal failure (without retry) would.
Resque Web Additions
If you're using the MultipleWithRetrySuppression failure backend, you should
also checkout the resque-web additions!
The new Retry tab displays delayed jobs with retry information; the number of
attempts and the exception details from the last failure.
Configuring and running the Resque-Web Interface
Using a Rack configuration:
One alternative is to use a rack configuration file. To use this, make sure you
include this in your config.ru or similar file:
require 'resque-retry'
require 'resque-retry/server'
# Make sure to require your workers & application code below this line:
# require '[path]/[to]/[jobs]/your_worker'
# Run the server
run Resque::Server.new
As an example, you could run this server with the following command:
rackup -p 9292 config.ru
When using bundler, you can also run the server like this:
bundle exec rackup -p 9292 config.ru
Using the 'resque-web' command with a configuration file:
Another alternative is to use resque's built-in 'resque-web' command with the
additional resque-retry tabs. In order to do this, you must first create a
configuration file. For the sake of this example we'll create the configuration
file in a 'config' directory, and name it 'resque_web_config.rb'. In practice
you could rename this configuration file to anything you like and place in your
project in a directory of your choosing. The contents of the configuration file
would look like this:
# [app_dir]/config/resque_web_config.rb
require 'resque-retry'
require 'resque-retry/server'
# Make sure to require your workers & application code below this line:
# require '[path]/[to]/[jobs]/your_worker'
Once you have the configuration file ready, you can pass the configuration file
to the resque-web command as a parameter, like so:
resque-web [app_dir]/config/resque_web_config.rb
Retry Options & Logic
Please take a look at the yardoc/code
for more details on methods you may wish to override.
Customisation is pretty easy, the below examples should give you some ideas =),
adapt for your own usage and feel free to pick and mix!
Here are a list of the options provided (click to jump):
- Retry Defaults
- Custom Retry
- Sleep After Requeuing
- Exponential Backoff
- Retry Specific Exceptions
- Fail Fast For Specific Exceptions
- Custom Retry Criteria Check Callbacks
- Retry Arguments
- Job Retry Identifier/Key
- Expire Retry Counters From Redis
- Try Again and Give Up Callbacks
- Ignored Exceptions
- Debug Plugin Logging
Retry Defaults
Retry the job once on failure, with zero delay.
require 'resque-retry'
class DeliverWebHook
extend Resque::Plugins::Retry
@queue = :web_hooks
def self.perform(url, hook_id, hmac_key)
heavy_lifting
end
end
When a job runs, the number of retry attempts is checked and incremented
in Redis. If your job fails, the number of retry attempts is used to
determine if we can requeue the job for another go.
Custom Retry
class DeliverWebHook
extend Resque::Plugins::Retry
@queue = :web_hooks
@retry_limit = 10
@retry_delay = 120
def self.perform(url, hook_id, hmac_key)
heavy_lifting
end
end
The above modification will allow your job to retry up to 10 times, with a delay
of 120 seconds, or 2 minutes between retry attempts.
You can override the retry_delay method to set the delay value dynamically. For example:
class ExampleJob
extend Resque::Plugins::Retry
@queue = :testing
def self.retry_delay(exception)
if exception == SocketError
10
else
1
end
end
def self.perform(*args)
heavy_lifting
end
end
Or, if you'd like the delay to be dependent on job arguments:
class ExampleJob
extend Resque::Plugins::Retry
@queue = :testing
def self.retry_delay(exception, *args)
# the delay is dependent on the arguments passed to the job
# in this case, "3" is passed as the arg and that is used as the delay
# make sure this method returns a integer
args.first.to_i
end
def self.perform(*args)
heavy_lifting
end
end
Resque.enqueue(ExampleJob, '3')
Sleep After Requeuing
Sometimes it is useful to delay the worker that failed a job attempt, but
still requeue the job for immediate processing by other workers. This can be
done with @sleep_after_requeue:
class DeliverWebHook
extend Resque::Plugins::Retry
@queue = :web_hooks
@sleep_after_requeue = 5
def self.perform(url, hook_id, hmac_key)
heavy_lifting
end
end
This retries the job once and causes the worker that failed to sleep for 5
seconds after requeuing the job. If there are multiple workers in the system
this allows the job to be retried immediately while the original worker heals
itself. For example failed jobs may cause other (non-worker) OS processes to
die. A system monitor such as monit or god can fix the server
while the job is being retried on a different worker.
@sleep_after_requeue is independent of @retry_delay. If you set both, they
both take effect.
You can override the sleep_after_requeue method to set the sleep value
dynamically.
Exponential Backoff
Use this if you wish to vary the delay between retry attempts:
class DeliverSMS
extend Resque::Plugins::ExponentialBackoff
@queue = :mt_messages
def self.perform(mt_id, mobile_number, message)
heavy_lifting
end
end
Default Settings
key: m = minutes, h = hours
0s, 1m, 10m, 1h, 3h, 6h
@backoff_strategy = [0, 60, 600, 3600, 10800, 21600]
@retry_delay_multiplicand_min = 1.0
@retry_delay_multiplicand_max = 1.0
The first delay will be 0 seconds, the 2nd will be 60 seconds, etc... Again,
tweak to your own needs.
The number of retries is equal to the size of the backoff_strategy array,
unless you set retry_limit yourself.
The delay values will be multiplied by a random Float value between
retry_delay_multiplicand_min and retry_delay_multiplicand_max (both have a
default of 1.0). The product (delay_multiplicand) is recalculated on every
attempt. This feature can be useful if you have a lot of jobs fail at the same
time (e.g. rate-limiting/throttling or connectivity issues) and you don't want
them all retried on the same schedule.
Retry Specific Exceptions
The default will allow a retry for any type of exception. You may change it so
only specific exceptions are retried using retry_exceptions:
class DeliverSMS
extend Resque::Plugins::Retry
@queue = :mt_messages
@retry_exceptions = [NetworkError]
def self.perform(mt_id, mobile_number, message)
heavy_lifting
end
end
The above modification will only retry if a NetworkError (or subclass)
exception is thrown.
You may also want to specify different retry delays for different exception
types. You may optionally set @retry_exceptions to a hash where the keys are
your specific exception classes to retry on, and the values are your retry
delays in seconds or an array of retry delays to be used similar to exponential
backoff.
class DeliverSMS
extend Resque::Plugins::Retry
@queue = :mt_messages
@retry_exceptions = { NetworkError => 30, SystemCallError => [120, 240] }
def self.perform(mt_id, mobile_number, message)
heavy_lifting
end
end
In the above example, Resque would retry any DeliverSMS jobs which throw a
NetworkError or SystemCallError. If the job throws a NetworkError it
will be retried 30 seconds later, if it throws SystemCallError it will first
retry 120 seconds later then subsequent retry attempts 240 seconds later.
Fail Fast For Specific Exceptions
The default will allow a retry for any type of exception. You may change
it so specific exceptions fail immediately by using fatal_exceptions:
class DeliverSMS
extend Resque::Plugins::Retry
@queue = :mt_divisions
@fatal_exceptions = [NetworkError]
def self.perform(mt_id, mobile_number, message)
heavy_lifting
end
end
In the above example, Resque would retry any DeliverSMS jobs that throw any
type of error other than NetworkError. If the job throws a NetworkError it
will be marked as "failed" immediately.
You should use either @fatal_exceptions or @retry_exceptions. If you specify @fatal_exceptions the @retry_exceptions are ignored.
Custom Retry Criteria Check Callbacks
You may define custom retry criteria callbacks:
class TurkWorker
extend Resque::Plugins::Retry
@queue = :turk_job_processor
@retry_exceptions = [NetworkError]
retry_criteria_check do, exception, *args, if exception.message =~ /SpecialErrorMessageToRetry/
return true
end
false
end
def self.perform(job_id)
heavy_lifting
end
end
Similar to the previous example, this job will retry if either a
NetworkError (or subclass) exception is thrown or any of the callbacks
return true.
You'll want to return false by default in the retry_criteria_check callback since
the result of this callback is OR'd with the result of your retry_exceptions or
fatal_exceptions configuration. In other words, if you returned true your
retry_exceptions configuration would never be used.
If you want to AND the result of fatal_exceptions or retry_exceptions with
custom retry criteria, you'll need to implement your own logic in a retry_criteria_check
to check for fatal_exceptions or retry_exceptions.
You can also register a retry criteria check with a Symbol if the method is
already defined on the job class:
class AlwaysRetryJob
extend Resque::Plugins::Retry
retry_criteria_check :yes
def self.yes(ex, *args)
true
end
end
Use @retry_exceptions = [] and @fatal_exceptions = [] to only use your custom retry criteria checks
to determine if the job should retry.
NB: Your callback must be able to accept the exception and job arguments as
passed parameters, or else it cannot be called. e.g., in the example above,
defining def self.yes; true; end would not work.
Retry Arguments
You may override retry_args, which is passed the current job arguments, to
modify the arguments for the next retry attempt.
class DeliverViaSMSC
extend Resque::Plugins::Retry
@queue = :mt_smsc_messages
# retry using the emergency SMSC.
def self.retry_args(smsc_id, mt_message)
[999, mt_message]
end
def self.perform(smsc_id, mt_message)
heavy_lifting
end
end
Alternatively, if you require finer control of the args based on the exception
thrown, you may override retry_args_for_exception, which is passed the
exception and the current job arguments, to modify the arguments for the next
retry attempt.
class DeliverViaSMSC
extend Resque::Plugins::Retry
@queue = :mt_smsc_messages
# retry using the emergency SMSC.
def self.retry_args_for_exception(exception, smsc_id, mt_message)
[999, mt_message + exception.message]
end
def self.perform(smsc_id, mt_message)
heavy_lifting
end
end
Custom Retry Queues
By default, when a job is retried, it is added to the @queue specified in the worker. However, you may want to push the job into another (lower or higher priority) queue when the job fails. You can do this by dynamically specifying the retry queue. For example:
class ExampleJob
extend Resque::Plugins::Retry
@queue = :testing
@retry_delay = 1
def self.work(*args)
user_id, user_mode, record_id = *args
Resque.enqueue_to(
target_queue_for_args(user_id, user_mode, record_id),
self,
*args
)
end
def self.retry_queue(exception, *args)
target_queue_for_args(*args)
end
def self.perform(*args)
heavy_lifting
end
def self.target_queue_for_args(*args)
user_id, user_mode, record_id = *args
if user_mode
'high'
else
'low'
end
end
end
Job Retry Identifier/Key
The retry attempt is incremented and stored in a Redis key. The key is built
using the retry_identifier. If you have a lot of arguments or really long
ones, you should consider overriding retry_identifier to define a more precise
or loose custom retry identifier.
The default identifier is just your job arguments joined with a dash '-'.
By default the key uses this format:
'resque-retry:<job class name>:<retry_identifier>'.
Or you can define the entire key by overriding redis_retry_key.
class DeliverSMS
extend Resque::Plugins::Retry
@queue = :mt_messages
def self.retry_identifier(mt_id, mobile_number, message)
"#{mobile_number}:#{mt_id}"
end
def self.perform(mt_id, mobile_number, message)
heavy_lifting
end
end
Expire Retry Counters From Redis
Allow the Redis to expire stale retry counters from the database by setting
@expire_retry_key_after:
class DeliverSMS
extend Resque::Plugins::Retry
@queue = :mt_messages
@expire_retry_key_after = 3600 # expire key after `retry_delay` plus 1 hour
def self.perform(mt_id, mobile_number, message)
heavy_lifting
end
end
This saves you from having to run a "house cleaning" or "errand" job.
The expiary timeout is "pushed forward" or "touched" after each failure to
ensure it's not expired too soon.
Try Again and Give Up Callbacks
Resque's on_failure callbacks are always called, regardless of whether the
job is going to be retried or not. If you want to run a callback only when the
job is being retried, you can add a try_again_callback:
class LoggedJob
extend Resque::Plugins::Retry
try_again_callback do, exception, *args, logger.info("Received #{exception}, retrying job #{self.name} with #{args}")
end
end
Similarly, if you want to run a callback only when the job has failed, and is
not retrying, you can add a give_up_callback:
class LoggedJob
extend Resque::Plugins::Retry
give_up_callback do, exception, *args, logger.error("Received #{exception}, job #{self.name} failed with #{args}")
end
end
You can register a callback with a Symbol if the method is already defined on
the job class:
class LoggedJob
extend Resque::Plugins::Retry
give_up_callback :log_give_up
def self.log_give_up(exception, *args)
logger.error("Received #{exception}, job #{self.name} failed with #{args}")
end
end
You can register multiple callbacks, and they will be called in the order that
they were registered. You can also set callbacks by setting
@try_again_callbacks or @give_up_callbacks to an array where each element
is a Proc or Symbol.
class CallbackJob
extend Resque::Plugins::Retry
@try_again_callbacks = [
:call_me_first,
:call_me_second,
lambda {, *args, call_me_third(*args) }
]
def self.call_me_first(ex, *args); end
def self.call_me_second(ex, *args); end
def self.call_me_third(ex, *args); end
end
Warning: Make sure your callbacks do not throw any exceptions. If they do,
subsequent callbacks will not be triggered, and the job will not be retried
(if it was trying again). The retry counter also will not be reset.
Ignored Exceptions
If there is an exception for which you want to retry, but you don't want it to
increment your retry counter, you can add it to @ignore_exceptions.
One use case: Restarting your workers triggers a Resque::TermException. You
may want your workers to retry the job that they were working on, but without
incrementing the retry counter.
class RestartResilientJob
extend Resque::Plugins::Retry
@retry_exceptions = [Resque::TermException]
@ignore_exceptions = [Resque::TermException]
end
Reminder: @ignore_exceptions should be a subset of @retry_exceptions.
Debug Plugin Logging
The inner-workings of the plugin are output to the Resque Logger
when Resque.logger.level is set to Logger::DEBUG.
Add VVERBOSE=true as an environment variable to easily set the log level to debug.
Testing
To run a specific test and inspect logging output
bundle exec rake TEST=the_test_file.rb VVERBOSE=true
There are many example jobs implementing various use-cases for this gem in test_jobs.rb
Contributing/Pull Requests
- Yes please!
- Fork the project.
- Make your feature addition or bug fix.
- Add tests for it.
- In a seperate commit, update the HISTORY.md file please.
- Send us a pull request. Bonus points for topic branches.
- If you edit the gemspec/version etc, please do so in another commit.