在某些主机上将命令与Fabric一起放置在后台不起作用 [英] Putting command in the background with Fabric does not work on some hosts

问题描述

出于测试目的，我使用普通的ssh命令行工具运行以下命令:

For testing purposes, I am running the following command, with plain ssh command line tool:

ssh user@host "nohup sleep 100 >> /tmp/xxx 2>&1 < /dev/null &"

这在我所有的主机中都按预期工作:后台创建了一个睡眠过程，并且ssh立即完成.

This is working as expected, in all my hosts: a sleep process is created in the background, and the ssh finishes immediately.

我正在尝试使用Fabric在python中实现此功能.我最终进行了run呼叫.这是Fabric日志记录报告的内容:

I am trying to implement this functionality in python using Fabric. I end up doing a run call. This is what the Fabric logging is reporting:

[user@host] run: nohup sleep 100 >> /tmp/xxx 2>&1 < /dev/null &

这正是我所期望的.但是，如果我检查主机中正在运行的进程，则sleep 100不是其中之一.更糟糕的是:该问题仅在我的某些主机上发生.

Which is exactly what I expect. But if I check the processes which are running in my host, sleep 100 is not one of them. Worse yet: the problem happens only on some of my hosts.

我还通过添加"\ necho $！"添加了更多信息，以显示已创建的进程.到由Fabric运行的命令.这是据报道:

I also added some more info to show what process has been created, by appending a "\necho $!" to the command to be run by Fabric. This is what was reported:

[user@host] run: nohup sleep 100 >> /tmp/xxx 2>&1 < /dev/null &
echo $!
[user@host] out: 30935

由于Fabric报告已经创建了该进程，所以我对如何进行调试的想法不多了，但是我看不到另一端正在运行任何进程.系统日志报告正在打开和关闭ssh会话:

I am running out of ideas on how to debug this, since Fabric is reporting that the process has been created, but I see no process running in the other end. The syslog reports that an ssh session is being opened and closed:

Dec  6 09:12:09 host sshd[2835]: Accepted publickey for user from 67.133.172.14 port 37732 ssh2
Dec  6 09:12:09 host sshd[2838]: pam_unix(sshd:session): session opened for user user by (uid=0)
Dec  6 09:12:10 host sshd[2838]: pam_unix(sshd:session): session closed for user user

我能以某种方式增加ssh守护程序正在生成的日志记录的数量，以便至少可以看到通过ssh请求的命令是什么吗?

Could I somehow increase the amount of logging that the ssh daemon is producing, so that I can see at least what command is being requested via ssh?

我知道Fabric在

I know that Fabric has some issues with running commands in the background, but that does not seem to be my problem. Could there be other issues with Fabric / ssh / background processes?

我已经在所有系统上安装了dtach. Ubuntu 8.04中打包的版本太旧，不允许通过ssh调用dtach -n(终端问题)，因此我不得不下载并编译 dtach来源.完成之后，我可以使用Fabric运行这样的命令:

I have installed dtach on all my systems. The version packaged in Ubuntu 8.04 is too old, and does not allow calling dtach -n over ssh (problems with terminal), so I had to download and compile the dtach sources. After doing that, I was able to run my command like this, with Fabric:

[user @ host]运行:dtach -n/tmp/Y sleep 100 >>/tmp/xxx 2>& 1

[user@host] run: dtach -n /tmp/Y sleep 100 >> /tmp/xxx 2>&1

这在所有主机上都能正常工作.但这不适合我的情况，因为:

This is working fine in all hosts. But this does not fit my scenario, because:

• dtach创建两个进程:一个用于dtach本身，另一个用于正在运行的进程.
• 我无法获得启动过程的提示

推荐答案

您可能碰到臭名昭著的 织物问题#395 .这些问题最简单的解决方法是使用pty=False运行您的任务.

You are probably bumping into the infamous Fabric issue #395. The easiet workaround for these problems is to run your task with pty=False.

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