deferreddump.py

"""
Dump current deferred state.

>  Anyway, given a tree of deferreds, this will produce a whatever.dot
> file, which can be fed to graphviz' "dot -Tpdf whatever.dot >
> whatever.pdf", >and the pdf has a rather nice-looking graph of the
> deferreds.

http://twistedmatrix.com/pipermail/twisted-python/2012-July/025867.html


have a look at this too:
https://www.twistedmatrix.com/pipermail/twisted-python/2008-October/018535.html

"""
import gc
import sys

import twisted.internet.defer


def escape(callback_type, obj):
    """Escape the callback."""
    dummy = callback_type  # noqa
    return '%s' % (
        str(obj).replace(' ', '_')
        .replace(':', '').replace('<', '').replace('>', ''), )


def dump(outfile=sys.stdout):
    """Dump out data for a moment in time."""
    outfile.write('digraph deferred_digraph {\n')
    for obj in gc.get_objects():
        if isinstance(obj, twisted.internet.defer.Deferred):
            len_callbacks = len(obj.callbacks)
            if obj.callbacks:
                outfile.write(
                    '\t%s -> %s\n' % (
                        escape('', obj),
                        escape('', obj.callbacks[0][0][0])))
                outfile.write(
                    '\t%s -> %s\n' % (
                        escape('', obj),
                        escape('', obj.callbacks[0][1][0])))
            for callbackpairno in range(len_callbacks - 1):
                current_callback = obj.callbacks[callbackpairno][0]
                current_errback = obj.callbacks[callbackpairno][1]
                current_callback_desc = current_callback[0]
                current_errback_desc = current_errback[0]

                next_callback = obj.callbacks[callbackpairno + 1][0]
                next_errback = obj.callbacks[callbackpairno + 1][1]
                next_callback_desc = next_callback[0]
                next_errback_desc = next_errback[0]

                outfile.write(
                    '\t%s -> %s;\n' % (
                        escape('callback', current_callback_desc),
                        escape('callback', next_callback_desc)))

                outfile.write(
                    '\t%s -> %s;\n' % (
                        escape('errback', current_errback_desc),
                        escape('errback', next_errback_desc))
                )

                outfile.write(
                    '\t%s -> %s;\n' % (
                        escape('callback', current_callback_desc),
                        escape('errback', next_errback_desc))
                )
                outfile.write(
                    '\t%s -> %s;\n' % (
                        escape('errback', current_errback_desc),
                        escape('callback', next_callback_desc))
                )

    outfile.write('}\n')