dpnova · November 9, 2016 19:29 · Nov 9, 2016
diff --git a/deferreddump.py b/deferreddump.py
@@ -0,0 +1,78 @@
+"""
+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')