How do I make a spawned process timeout when called from Django?

Question

I have the code below in a Python module; it uses subprocess to start a command line app and reads the output the app writes to stdout.

If the command line app doesn't complete after 15 seconds, I want the code to time out. I have used signal.alarm to try to achieve this.

When testing the module without Django it times out after 15s as expected. However, when I call the code from a Django view it doesn't timeout after 15s, but continues to run until the spawned process times out.

How can I get this to do what I want?

p = get_process() # spawns a process using subproccess and returns the process handle

signal.signal(signal.SIGALRM, alarm_handler)                           
signal.alarm(15)   
try:
    s= p.stdout.read()
except:
    p.kill()
    s = "Operation timed out"

Maybe Django is running your code in a distinct thread? The interrupt will always occur in the main thread, which might not be your code. — Thomas K, Apr 02 '12 at 12:28

score 1 · Accepted Answer · edited May 23 '17 at 10:08

1

This approach, of just spawning a thread for running the subprocess and using a timeout on joining said thread, should avoid any problems with interrupts occurring in the wrong thread and also work on Windows.

edited May 23 '17 at 10:08

Community

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answered Apr 02 '12 at 19:39

Danica

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score 0 · Answer 2 · answered Apr 02 '12 at 19:30

0

Consider using select() call which allows you to specify a timeout for the I/O operation(s).

answered Apr 02 '12 at 19:30

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Just keep in mind that using `select()` with pipes for redirected I/O only works on UNIX-like systems and will not work on Windows, where `select()` only works on sockets. This might or might not be a problem (no OS was specified in the question). – André Caron Apr 02 '12 at 19:34

How do I make a spawned process timeout when called from Django?

2 Answers2