Django: Subprocess Continuous Output To HTML View

Question

I need a HTML webpage in my Django app to load and show the continous output of a script in a scrollable box. Is this possible?

I\'m presently using a subprocess

Answer 1

You could simplify your task using StreamingHttpResponse and Popen:

def test_iterator():
    from subprocess import Popen, PIPE, CalledProcessError

    with Popen(['ping', 'localhost'], stdout=PIPE, bufsize=1, universal_newlines=True) as p:
        for line in p.stdout:
            yield(line + '
') # process line here

    if p.returncode != 0:
        raise CalledProcessError(p.returncode, p.args)

def busy_view(request):
    from django.http import StreamingHttpResponse
    return StreamingHttpResponse(test_iterator())

StreamingHttpResponse expects an iterator as its parameter. An iterator function is one which has a yield expression (or a generator expression), and its return value is a generator object (an iterator).

In this example, I simply echo the ping command to prove it works.

Substitute ['ping', 'localhost'] by a list (it has to be a list if you pass parameters to the command - in this case, localhost). Your original ['python', script] should work.

If you want to know more about generators, I would recommend Trey Hunner's talk, and also strongly that you read chapter 14 of Fluent Python book. Both are amazing sources.

Disclaimer:

Performance considerations

Django is designed for short-lived requests. Streaming responses will tie a worker process for the entire duration of the response. This may result in poor performance.

Generally speaking, you should perform expensive tasks outside of the request-response cycle, rather than resorting to a streamed response.