wsgi script to get the current tinc graph as png image

tinc-graph.wsgi

# coding: utf-8

import os
import re
import time

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

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

png_graph_all = '/tmp/tinc-graph-all.png'
png_graph_reachable = '/tmp/tinc-graph-reachable.png'

# caching time
max_age = 300


def graph2png(graph, fname):
    # you can also use dot, circo, whatever with different options here
    p = Popen(['/usr/bin/neato', '-Tpng', '-Nfontname=Sans', '-Goverlap=scale', '-Gsplines=true', '-o', fname], stdin=PIPE)
    p.communicate(input=graph)
    return p.returncode


def application(environ, start_response):

    d = parse_qs(environ['QUERY_STRING'])
    mode = d.get('mode', [''])[0]
    fname = png_graph_all if mode == 'all' else png_graph_reachable

    rcs = 0
    if not os.path.isfile(fname) or time.time() - os.path.getmtime(fname) > max_age:
        # this command requires sudo permissions for the user running the wsgi/web service
        graph_all = check_output(['/usr/bin/sudo', '/path/to/tinc', '-n', 'yournetwork', 'dump', 'graph'])
        graph_reachable = re_filter.sub('', graph_all)
        rcs += graph2png(graph_all, png_graph_all)
        rcs += graph2png(graph_reachable, png_graph_reachable)

    if rcs == 0:
        headers = [('Content-Type', 'image/png')]
        with open(fname, 'rb') as png:
            ret = png.read()
    else:
        headers = [('Content-Type', 'text/plain')]
        ret = 'some bad shit went down'

    status = '200 OK'
    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.