如何在Fabric收到错误时继续执行任务

Question

当我定义要在多个远程服务器上运行的任务时,如果任务在服务器1上运行并退出并出现错误,则Fabric将停止并中止该任务.但是我想让Fabric忽略错误并在下一个服务器上运行任务.我该怎么做呢？

例如:

$ fab site1_service_gw
[site1rpt1] Executing task 'site1_service_gw'

[site1fep1] run: echo 'Nm123!@#' | sudo -S route
[site1fep1] err:
[site1fep1] err: We trust you have received the usual lecture from the local System
[site1fep1] err: Administrator. It usually boils down to these three things:
[site1fep1] err:
[site1fep1] err:     #1) Respect the privacy of others.
[site1fep1] err:     #2) Think before you type.
[site1fep1] err:     #3) With great power comes great responsibility.
[site1fep1] err: root's password:
[site1fep1] err: sudo: route: command not found

Fatal error: run() encountered an error (return code 1) while executing 'echo 'Nm123!@#' | sudo -S route '

Aborting.

Answer 1

来自文档:

... Fabric默认为"fail-fast"行为模式:如果出现任何问题,例如远程程序返回非零返回值或fabfile的Python代码遇到异常,执行将立即停止.

这通常是所需的行为,但规则有很多例外,因此Fabric提供了env.warn_only,一个布尔设置.它默认为False,这意味着错误条件将导致程序立即中止.但是,如果在失败时将env.warn_only设置为True - 例如设置上下文管理器 - Fabric将发出警告消息但继续执行.

看起来您可以通过使用settings上下文管理器对错误被忽略的位置进行细粒度控制,如下所示:

from fabric.api import settings

sudo('mkdir tmp') # can't fail
with settings(warn_only=True):
    sudo('touch tmp/test') # can fail
sudo('rm tmp') # can't fail

Answer 2

从Fabric 1.5开始,有一个ContextManager使这更容易:

from fabric.api import sudo, warn_only

with warn_only():
    sudo('mkdir foo')

更新:我使用以下代码重新确认这在ipython中有效.

from fabric.api import local, warn_only

#aborted with SystemExit after 'bad command'
local('bad command'); local('bad command 2')

#executes both commands, printing errors for each
with warn_only():
    local('bad command'); local('bad command 2')

Answer 3

您还可以将整个脚本的warn_only设置为true

def local():
    env.warn_only = True

Answer 4

您应该设置abort_exception环境变量并捕获异常.

例如:

from fabric.api        import env
from fabric.operations import sudo

class FabricException(Exception):
    pass

env.abort_exception = FabricException
# ... set up the rest of the environment...

try:
    sudo('reboot')
except FabricException:
    pass  # This is expected, we can continue.

您也可以在with块中进行设置.请参阅此处的文档.

Answer 5

至少在Fabric 1.3.2中,您可以通过捕获SystemExit异常来恢复异常.如果您有多个命令在批处理中运行(如部署),并且如果其中一个命令失败,那么这将非常有用.

Answer 6

在面料2.X你可以使用调用的运行与警告=真说法.无论如何,invoke是Fabric 2.x的依赖:

from invoke import run
run('bad command', warn=True)

从任务中:

from invoke import task

@task
def my_task(c):
    c.run('bad command', warn=True)