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Retrying, to retry all the things
=========================
.. image:: https://travis-ci.org/rholder/retrying.png?branch=master
:target: https://travis-ci.org/rholder/retrying
Retrying is an Apache 2.0 licensed general-purpose retrying library, written in
Python, to simplify the task of adding retry behavior to just about anything.
The simplest use case is retrying a flaky function whenever an Exception occurs
until a value is returned.
.. code-block:: python
import random
from retrying import retry
@retry
def do_something_unreliable():
if random.randint(0, 10) > 1:
raise IOError("Broken sauce, everything is hosed!!!111one")
else:
return "Awesome sauce!"
print do_something_unreliable()
Features
--------
- Generic Decorator API
- Specify stop condition (i.e. limit by number of attempts)
- Specify wait condition (i.e. exponential backoff sleeping between attempts)
- Customize retrying on Exceptions
- Customize retrying on expected returned result
Installation
------------
To install retrying, simply:
.. code-block:: bash
$ pip install retrying
Or, if you absolutely must:
.. code-block:: bash
$ easy_install retrying
But, you might regret that later.
Examples
----------
Here are some snippets and parameters for building your own versions of retrying behavior:
.. code-block:: python
@retry
def never_give_up_never_surrender():
print "Retry forever ignoring Exceptions, don't wait between retries"
@retry(stop='stop_after_attempt', stop_max_attempt_number=7)
def stop_after_7_attempts():
print "Stopping after 7 attempts"
@retry(stop='stop_after_delay', stop_max_delay=10000)
def stop_after_10_s():
print "Stopping after 10 seconds"
@retry(wait='fixed_sleep', wait_fixed=2000)
def wait_2_s():
print "Wait 2 second between retries"
@retry(wait='random_sleep', wait_random_min=1000, wait_random_max=2000)
def wait_random_1_to_2_s():
print "Randomly wait 1 to 2 seconds between retries"
@retry(wait='exponential_sleep', wait_exponential_multiplier=1000, wait_exponential_max=10000)
def wait_exponential_1000():
print "Wait 2^x * 1000 milliseconds between each retry, up to 10 seconds, then 10 seconds afterwards"
def retry_if_io_error(exception):
"""Return True if we should retry (in this case when it's an IOError), False otherwise"""
return isinstance(exception, IOError)
@retry(retry_on_exception=retry_if_io_error)
def might_io_error():
print "Retry forever with no wait if an IOError occurs, raise any other errors"
def retry_if_result_none(result):
"""Return True if we should retry (in this case when result is None), False otherwise"""
return result is None
@retry(retry_on_result=retry_if_result_none)
def might_return_none():
print "Retry forever ignoring Exceptions with no wait if return value is None"
@retry(retry_on_exception=retry_if_io_error, wrap_exception=True)
def only_raise_retry_error_when_not_io_error():
print "Retry forever with no wait if an IOError occurs, raise any other errors wrapped in RetryError"
Any combination of stop, wait, etc. are also supported to give you the freedom to mix and match.
Contribute
----------
#. Check for open issues or open a fresh issue to start a discussion around a feature idea or a bug.
#. Fork `the repository`_ on GitHub to start making your changes to the **master** branch (or branch off of it).
#. Write a test which shows that the bug was fixed or that the feature works as expected.
#. Send a pull request and bug the maintainer until it gets merged and published. :) Make sure to add yourself to AUTHORS_.
.. _`the repository`: http://github.com/rholder/retrying
.. _AUTHORS: https://github.com/rholder/retrying/blob/master/AUTHORS.rst
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