如何在python请求库中实现重试机制？

Question

我想在python请求库中添加重试机制，因此正在使用它的脚本将重试非致命错误。

目前，我确实认为三种错误是可以恢复的：

• HTTP返回码502、503、504
• 找不到主机（现在不太重要）
• 请求超时

在第一阶段，我想每分钟重试指定的5xx请求。

我希望能够透明地添加此功能，而不必为从这些使用python-requests的脚本或库中进行的每个HTTP调用手动实现恢复。

Answer 1

通过扩展requests.Session类，我可以获得所需的可靠性。

这是代码https://bitbucket.org/bspeakmon/jira-
python/src/a7fca855394402f58507ca4056de87ccdbd6a213/jira/resilientsession.py?at=master

编辑 该代码是：

from requests import Session
from requests.exceptions import ConnectionError
import logging
import time


class ResilientSession(Session):

    """
    This class is supposed to retry requests that do return temporary errors.

    At this moment it supports: 502, 503, 504
    """

    def __recoverable(self, error, url, request, counter=1):
        if hasattr(error,'status_code'):
            if error.status_code in [502, 503, 504]:
                error = "HTTP %s" % error.status_code
            else:
                return False
        DELAY = 10 * counter
        logging.warn("Got recoverable error [%s] from %s %s, retry #%s in %ss" % (error, request, url, counter, DELAY))
        time.sleep(DELAY)
        return True


    def get(self, url, **kwargs):
        counter = 0
        while True:
            counter += 1
            try:
                r = super(ResilientSession, self).get(url, **kwargs)
            except ConnectionError as e:
                r = e.message
            if self.__recoverable(r, url, 'GET', counter):
                continue
            return r

    def post(self, url, **kwargs):
        counter = 0
        while True:
            counter += 1
            try:
                r = super(ResilientSession, self).post(url, **kwargs)
            except ConnectionError as e:
                r = e.message
            if self.__recoverable(r, url, 'POST', counter):
                continue
            return r

    def delete(self, url, **kwargs):
        counter = 0
        while True:
            counter += 1
            try:
                r = super(ResilientSession, self).delete(url, **kwargs)
            except ConnectionError as e:
                r = e.message
            if self.__recoverable(r, url, 'DELETE', counter):
                continue
            return r

    def put(self, url, **kwargs):
        counter = 0
        while True:
            counter += 1
            try:
                r = super(ResilientSession, self).put(url, **kwargs)
            except ConnectionError as e:
                r = e.message

            if self.__recoverable(r, url, 'PUT', counter):
                continue
            return r

    def head(self, url, **kwargs):
        counter = 0
        while True:
            counter += 1
            try:
                r = super(ResilientSession, self).head(url, **kwargs)
            except ConnectionError as e:
                r = e.message
            if self.__recoverable(r, url, 'HEAD', counter):
                continue
            return r

    def patch(self, url, **kwargs):
        counter = 0
        while True:
            counter += 1
            try:
                r = super(ResilientSession, self).patch(url, **kwargs)
            except ConnectionError as e:
                r = e.message

            if self.__recoverable(r, url, 'PATCH', counter):
                continue
            return r

    def options(self, url, **kwargs):
        counter = 0
        while True:
            counter += 1
            try:
                r = super(ResilientSession, self).options(url, **kwargs)
            except ConnectionError as e:
                r = e.message

            if self.__recoverable(r, url, 'OPTIONS', counter):
                continue
            return r