README.rst
riprova |PyPI| |Coverage Status| |Documentation Status| |Quality| |Versions|
============================================================================
``riprova`` (meaning ``retry`` in Italian) is a small, general-purpose and versatile `Python`_ library
that provides retry mechanisms with multiple backoff strategies for any sort of failed operations.
It's domain agnostic, highly customizable, extensible and provides a minimal API that's easy to instrument in any code base via decorators, context managers or raw API consumption.
For a brief introduction about backoff mechanisms for potential failed operations, `read this article`_.
Features
--------
- Retry decorator for simple and idiomatic consumption.
- Simple Pythonic programmatic interface.
- Maximum retry timeout support.
- Supports error `whitelisting`_ and `blacklisting`_.
- Supports custom `error evaluation`_ retry logic (useful to retry only in specific cases).
- Automatically retry operations on raised exceptions.
- Supports `asynchronous coroutines`_ with both ``async/await`` and ``yield from`` syntax.
- Configurable maximum number of retry attempts.
- Highly configurable supporting max retries, timeouts or retry notifier callback.
- Built-in backoff strategies: constant, `fibonacci`_ and `exponential`_ backoffs.
- Supports sync/async context managers.
- Pluggable custom backoff strategies.
- Lightweight library with almost zero embedding cost.
- Works with Python +2.6, 3.0+ and PyPy.
Backoff strategies
------------------
List of built-in backoff strategies.
- `Constant backoff`_
- `Fibonacci backoff`_
- `Exponential backoff`_
You can also implement your own one easily.
See `ConstantBackoff`_ for an implementation reference.
Installation
------------
Using ``pip`` package manager (requires pip 1.9+. Upgrade it running: ``pip install -U pip``):
.. code-block:: bash
pip install -U riprova
Or install the latest sources from Github:
.. code-block:: bash
pip install -e git+git://github.com/h2non/riprova.git#egg=riprova
API
---
- riprova.retry_
- riprova.Retrier_
- riprova.AsyncRetrier_
- riprova.Backoff_
- riprova.ConstantBackoff_
- riprova.FibonacciBackoff_
- riprova.ExponentialBackoff_
- riprova.ErrorWhitelist_
- riprova.ErrorBlacklist_
- riprova.add_whitelist_error_
- riprova.RetryError_
- riprova.RetryTimeoutError_
- riprova.MaxRetriesExceeded_
- riprova.NotRetriableError_
.. _riprova.retry: http://riprova.readthedocs.io/en/latest/api.html#riprova.retry
.. _riprova.Retrier: http://riprova.readthedocs.io/en/latest/api.html#riprova.Retrier
.. _riprova.AsyncRetrier: http://riprova.readthedocs.io/en/latest/api.html#riprova.AsyncRetrier
.. _riprova.Backoff: http://riprova.readthedocs.io/en/latest/api.html#riprova.Backoff
.. _riprova.ConstantBackoff: http://riprova.readthedocs.io/en/latest/api.html#riprova.ConstantBackoff
.. _riprova.FibonacciBackoff: http://riprova.readthedocs.io/en/latest/api.html#riprova.FibonacciBackoff
.. _riprova.ExponentialBackoff: http://riprova.readthedocs.io/en/latest/api.html#riprova.ExponentialBackoff
.. _riprova.ErrorWhitelist: http://riprova.readthedocs.io/en/latest/api.html#riprova.ErrorWhitelist
.. _riprova.ErrorBlacklist: http://riprova.readthedocs.io/en/latest/api.html#riprova.ErrorBlacklist
.. _riprova.add_whitelist_error: http://riprova.readthedocs.io/en/latest/api.html#riprova.add_whitelist_error
.. _riprova.RetryError: http://riprova.readthedocs.io/en/latest/api.html#riprova.RetryError
.. _riprova.RetryTimeoutError: http://riprova.readthedocs.io/en/latest/api.html#riprova.RetryTimeoutError
.. _riprova.MaxRetriesExceeded: http://riprova.readthedocs.io/en/latest/api.html#riprova.MaxRetriesExceeded
.. _riprova.NotRetriableError: http://riprova.readthedocs.io/en/latest/api.html#riprova.NotRetriableError
Examples
^^^^^^^^
You can see more featured examples from the `documentation` site.
**Basic usage examples**:
.. code-block:: python
import riprova
@riprova.retry
def task():
"""Retry operation if it fails with constant backoff (default)"""
@riprova.retry(backoff=riprova.ConstantBackoff(retries=5))
def task():
"""Retry operation if it fails with custom max number of retry attempts"""
@riprova.retry(backoff=riprova.ExponentialBackOff(factor=0.5))
def task():
"""Retry operation if it fails using exponential backoff"""
@riprova.retry(timeout=10)
def task():
"""Raises a TimeoutError if the retry loop exceeds from 10 seconds"""
def on_retry(err, next_try):
print('Operation error: {}'.format(err))
print('Next try in: {}ms'.format(next_try))
@riprova.retry(on_retry=on_retry)
def task():
"""Subscribe via function callback to every retry attempt"""
def evaluator(response):
# Force retry operation if not a valid response
if response.status >= 400:
raise RuntimeError('invalid response status') # or simple return True
# Otherwise return False, meaning no retry
return False
@riprova.retry(evaluator=evaluator)
def task():
"""Use a custom evaluator function to determine if the operation failed or not"""
@riprova.retry
async def task():
"""Asynchronous coroutines are also supported :)"""
**Retry failed HTTP requests**:
.. code-block:: python
import pook
import requests
from riprova import retry
# Define HTTP mocks to simulate failed requests
pook.get('server.com').times(3).reply(503)
pook.get('server.com').times(1).reply(200).json({'hello': 'world'})
# Retry evaluator function used to determine if the operated failed or not
def evaluator(response):
if response != 200:
return Exception('failed request') # you can also simply return True
return False
# On retry even subscriptor
def on_retry(err, next_try):
print('Operation error {}'.format(err))
print('Next try in {}ms'.format(next_try))
# Register retriable operation
@retry(evaluator=evaluator, on_retry=on_retry)
def fetch(url):
return requests.get(url)
# Run task that might fail
fetch('http://server.com')
License
-------
MIT - Tomas Aparicio
.. _exponential: https://en.wikipedia.org/wiki/Exponential_backoff
.. _fibonacci: https://en.wikipedia.org/wiki/Fibonacci_number
.. _asyncio: https://docs.python.org/3.5/library/asyncio.html
.. _Python: http://python.org
.. _annotated API reference: https://h2non.github.io/paco
.. _async/await: https://www.python.org/dev/peps/pep-0492/
.. _yield from: https://www.python.org/dev/peps/pep-0380/
.. _documentation: http://riprova.readthedocs.io/en/latest/examples.html
.. _read this article: http://dthain.blogspot.ie/2009/02/exponential-backoff-in-distributed.html
.. _Constant backoff: http://riprova.readthedocs.io/en/latest/api.html#riprova.ConstantBackoff
.. _Fibonacci backoff: http://riprova.readthedocs.io/en/latest/api.html#riprova.FibonacciBackoff
.. _Exponential backoff: http://riprova.readthedocs.io/en/latest/api.html#riprova.ExponentialBackOff
.. _ConstantBackoff: https://github.com/h2non/riprova/blob/master/riprova/strategies/constant.py
.. _whitelisting: https://github.com/h2non/riprova/blob/master/examples/whitelisting_errors.py
.. _blacklisting: https://github.com/h2non/riprova/blob/master/examples/blacklisting_errors.py
.. _error evaluation: https://github.com/h2non/riprova/blob/master/examples/http_request.py
.. _asynchronous coroutines: https://github.com/h2non/riprova/blob/master/examples/http_asyncio.py
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