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A library of composable Python executors

Project description

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This library is intended for use with the `concurrent.futures <https://docs.python.org/3/library/concurrent.futures.html>`__ module. It includes a collection of Executor implementations in order to extend the behavior of Future objects.

Features

  • Futures with implicit retry

  • Futures with implicit cancel on executor shutdown

  • Futures with implicit cancel after timeout

  • Futures with transformed output values (sync & async)

  • Futures resolved by a caller-provided polling function

  • Throttle the number of futures running at once

  • Synchronous executor

  • Bridge concurrent.futures with asyncio

  • Convenience API for creating executors

See the API documentation for detailed information on usage.

Example

This example combines the map and retry executors to create futures for HTTP requests running concurrently, decoding JSON responses within the future and retrying on error.

import requests
from concurrent.futures import as_completed
from more_executors import Executors


def get_json(response):
    response.raise_for_status()
    return (response.url, response.json())


def fetch_urls(urls):
    # Configure an executor:
    # - run up to 4 requests concurrently, in separate threads
    # - run get_json on each response
    # - retry up to several minutes on any errors
    executor = Executors.\
        thread_pool(max_workers=4).\
        with_map(get_json).\
        with_retry()

    # Submit requests for each given URL
    futures = [executor.submit(requests.get, url)
               for url in urls]

    # Futures API works as normal; we can block on the completed
    # futures and map/retry happens implicitly
    for future in as_completed(futures):
        (url, data) = future.result()
        do_something(url, data)

Changelog

v1.16.0

  • API break: removed new_default methods in retry module

  • Minor usability improvements to retry API

  • Introduced flat_bind (#97)

v1.15.0

  • Fixed possible deadlock in CancelOnShutdownExecutor (#98)

  • Fixed Executors.bind with functools.partial (#96)

  • Fixed ThrottleExecutor thread leak when shutdown() is never called (#93)

v1.14.0

  • API break: removed Executors.wrap class method

  • Fixed thread leaks when shutdown() is never called (#87)

  • Refactors to avoid pylint errors from client code (#86)

v1.13.0

  • Introduced Executors.bind

v1.12.0

  • Introduced FlatMapExecutor

v1.11.0

  • Fixed hangs on executor shutdown

v1.10.0

  • Improved RetryPolicy API

  • Fixed a race condition leading to RetryExecutor hangs

  • Added logger argument to each executor

v1.9.0

  • Introduced ThrottleExecutor

v1.8.0

  • Fixed missing long_description in package

v1.7.0

  • Revised TimeoutExecutor concept to “cancel after timeout”

  • Introduced AsyncioExecutor

v1.6.0

  • Introduce TimeoutExecutor

  • Use monotonic clock in RetryExecutor

  • Avoid some uninterruptible sleeps on Python 2.x

  • Minor improvements to logging

License

GPLv3

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