python – Fabric：处理异常,所以我可以在try块中捕获它

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我试图找到一种方法来处理Fabric错误.

示例：如果我的远程主机停机进行维护,并且我的应用程序正在运行,尝试完成一些工作,我从Fabric获得了一个例外.这阻止了我的应用程序,并打印出可怕的堆栈跟踪.

为了避免这种情况,因为我需要知道主机何时关闭,我将我的请求包装到远程,使用try块,但我不确定应该在except块中放入什么,以便仅捕获来自Fabric的异常(比如networkError和类似的).

使用Fabric处理try-except块的正确方法是什么？或者更具体地说,我将什么放在“except”块中,因此它将捕获来自结构的任何异常,并避免让整个应用程序退出并打印出堆栈错误？

解决方法:

在捕获错误后,logging.exception将输出回溯：

import logging

try:
    1/0
except Exception as e:
    logging.exception(e)

ERROR:root:division by zero
Traceback (most recent call last):
  File "/home/padraic/Dropbox/python/py3/size.py", line 105, in <module>
    1/0
ZeroDivisionError: division by zero

Process finished with exit code 0

如果您查看文档中的failure-handling,您将看到您可以使用上下文管理器仅在您获得非零退出状态时发出警告.

Once the task list has been constructed, Fabric will start executing them as outlined in Execution strategy, until all tasks have been run on the entirety of their host lists. However, Fabric defaults to a “fail-fast” behavior pattern: if anything goes wrong, such as a remote program returning a nonzero return value or your fabfile’s Python code encountering an exception, execution will halt immediately.

This is typically the desired behavior, but there are many exceptions to the rule, so Fabric provides env.warn_only, a Boolean setting. It defaults to False, meaning an error condition will result in the program aborting immediately. However, if env.warn_only is set to True at the time of failure – with, say, the settings context manager – Fabric will emit a warning message but continue executing.

from fabric.api import settings

with settings(warn_only=True):
    p = run('sudo foo')
    if p.return_code ==  0:
       ...
    elif p.return_code ==  1:
       ....

还有一个env.abort_exception：

默认值：无

Fabric normally handles aborting by printing an error message to stderr and calling sys.exit(1). This setting allows you to override that behavior (which is what happens when env.abort_exception is None.)

Give it a callable which takes a string (the error message that would have been printed) and returns an exception instance. That exception object is then raised instead of SystemExit (which is what sys.exit does.)

Much of the time you’ll want to simply set this to an exception class, as those fit the above description perfectly (callable, take a string, return an exception instance.) E.g. env.abort_exception = MyExceptionClass.

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