wsgi script to get the current tinc graph as png image

tinc-graph.wsgi

# coding: utf-8

import re

from subprocess import Popen, PIPE, check_output
from urlparse import parse_qs

re_filter = re.compile(r' \w+ \[label = "[^"]+", color = "red"];\n')

def application(environ, start_response):

    d = parse_qs(environ['QUERY_STRING'])
    mode = d.get('mode', [''])[0]

    # this command requires sudo permissions for the user running the wsgi/web service
    graph = check_output(["/usr/bin/sudo", "/path/to/tinc", "-n", "yournetwork", "dump", "graph"])

    if mode != "all":
        # remove unreachable nodes
        graph = re_filter.sub('', graph)

    # you can also use dot, circo, whatever with different options here
    p = Popen(["/usr/bin/neato", "-Tpng", "-Nfontname=Sans", "-Goverlap=scale", "-Gsplines=true"], stdin=PIPE, stdout=PIPE)
    data, _ = p.communicate(input=graph)

    status = '200 OK'

    if p.returncode == 0:
        headers = [('Content-Type', 'image/png')]
        ret = data
    else:
        headers = [('Content-Type', 'text/plain')]
        ret = "some bad shit went down"

    start_response(status, headers)

    return [ret]

Revision 3 writes image files to disk for caching.
Revision 1 keeps everything in memory but calls tinc every single time a request is made.