Python 进程挂起，直到子进程使用 tee 方案终止
我有以下与进程同步相关的问题。
有一个Python脚本startup.py、一个可执行的maestro和一个可执行的tee。 我的Python脚本startup.py启动maestro程序，并使用tee将maestro的stderr/stdout通过管道传输到日志文件中，并写入控制台。
我使用以下代码实现了这一点：
cmd = "maestro"
mae_err_log = "output.txt"
maestro = subprocess.Popen(cmd, stderr = subprocess.STDOUT, stdout=subprocess.PIPE)
tee = subprocess.Popen(['tee', mae_err_log], stdin = maestro.stdout)
maestro.stdout.close()
tee.communicate()
maestro_status = maestro.returncode
sys.exit(maestro_status)
我的 maestro 程序是一个 gui 程序，当我退出 maestro 程序时，它在内部调用 posix system("maestro_cleanup &") api 并立即退出。我注意到，尽管我在后台运行 maestro_cleanup，但在 maestro_cleanup 程序终止之前，我的 maestro 程序不会释放控制台。我需要在后台运行 maestro_cleanup，因为这需要时间，并且我不想在 maestro_cleanup 完成之前保持控制台。使用上面的代码，maestro 程序在 maestro_cleanup 完成之前不会终止。
我看到“ps -elf”显示如下：
0 S j 16876 6678 0 75 0 - 65307 wait 18:56 pts/53 00:00:00 python startup.py
0 Z j 17230 16876 4 76 0 - 0 exit 18:56 pts/53 00:00:04 [maestro] <defunct>
0 S j 17231 16876 0 77 0 - 948 pipe_w 18:56 pts/53 00:00:00 /usr/bin/tee output.txt
0 S j 17424 1 0 77 0 - 948 - 18:57 pts/53 00:00:00 maestro_cleanup
您可以看到 maestro_cleanup 父进程是会话进程 id 而不是 maestro，因为我在后台使用系统 api 启动了 maestro_cleanup。
知道为什么 maestro 在 maestro_cleanup 完成之前不会终止吗？
任何帮助将不胜感激。
-维宾
I have a following problem related to process synchronization.
There is a python script startup.py, an executable maestro, and an executable tee.
My python script startup.py starts maestro program and pipes the stderr/stdout of maestro into the log file using tee as well write into the console.
I achieved this using following code:
cmd = "maestro"
mae_err_log = "output.txt"
maestro = subprocess.Popen(cmd, stderr = subprocess.STDOUT, stdout=subprocess.PIPE)
tee = subprocess.Popen(['tee', mae_err_log], stdin = maestro.stdout)
maestro.stdout.close()
tee.communicate()
maestro_status = maestro.returncode
sys.exit(maestro_status)
My maestro program is a gui program when I exit from the maestro program, it internally call posix system("maestro_cleanup &") api and immediately exit. I noticed that my maestro program does not release the console until maestro_cleanup program terminate although I am running maestro_cleanup in the background. I need to run maestro_cleanup in the background as it takes time and I do not want to hold the console for the period until maestro_cleanup finishes. Using above code, maestro program does not terminate until maestro_cleanup finishes.
I see "ps -elf" shows following:
0 S j 16876 6678 0 75 0 - 65307 wait 18:56 pts/53 00:00:00 python startup.py
0 Z j 17230 16876 4 76 0 - 0 exit 18:56 pts/53 00:00:04 [maestro] <defunct>
0 S j 17231 16876 0 77 0 - 948 pipe_w 18:56 pts/53 00:00:00 /usr/bin/tee output.txt
0 S j 17424 1 0 77 0 - 948 - 18:57 pts/53 00:00:00 maestro_cleanup
You can see the maestro_cleanup parent process is session process id instead maestro because I started maestro_cleanup using system api in background.
Any idea why maestro does not terminate until maestro_cleanup finishes?
Any help would be appreciated.
-Vipin
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评论（2）
那么 subprocess.Popen 文档 确实说 tee.communicate() 将“等待进程终止”；您的调用也与 这个人确实说他的子进程在后台运行，所以看起来没问题。所以这种退出前阻塞听起来像是子进程的限制。
尝试 'Python 生成子子进程，分离，并退出'，它引用了 ActiveState 配方：'以 Python 方式创建守护程序'：将进程与控制终端分离并在后台作为守护程序运行的 Python 方法。
Well the subprocess.Popen documentation does say tee.communicate() will "Wait for process to terminate"; also your invocation is the same as this guy who does say his child process runs in the background, so that seems ok. So this blocking-before-exit sounds like a limitation of subprocess.
Try the links in 'Python spawn off a child subprocess, detach, and exit' which references the ActiveState recipe: 'Creating a daemon the Python way': The Python way to detach a process from the controlling terminal and run it in the background as a daemon.
我会说使用
close_fd=True。它应该可以解决问题。I'd say use
close_fd=True. It should do the trick.