How can I track/fix memory leak in tornado-redis using pympler?

Question

I've been trying to use tornado-redis (which is basically a fork of brükva slightly modified to work with tornado.gen interface instead of adisp) in order to deliver events by using redis' pubsub.

So I wrote down a little script to test things out inspired by this example.

import os

from tornado import ioloop, gen
import tornadoredis


print os.getpid()

def on_message(msg):
    print msg

@gen.engine
def listen():
    c = tornadoredis.Client()
    c.connect()
    yield gen.Task(c.subscribe, 'channel')
    c.listen(on_message)

listen()

ioloop.IOLoop.instance().start()

Unfortunately, as I PUBLISHed through redis-climemory usage kept on rising.

In order to profile memory usage I first tried to use guppy-pe but it wouldn’t work under python 2.7 (Yes even tried trunk) so I fell back to pympler.

import os

from pympler import tracker
from tornado import ioloop, gen
import tornadoredis


print os.getpid()

class MessageHandler(object):

    def __init__(self):
        self.memory_tracker = tracker.SummaryTracker()

    def on_message(self, msg):
        self.memory_tracker.print_diff()

@gen.engine
def listen():
    c = tornadoredis.Client()
    c.connect()
    yield gen.Task(c.subscribe, 'channel')
    c.listen(MessageHandler().on_message)

listen()

ioloop.IOLoop.instance().start()

Now each time I PUBLISHed I could see that some objects were never released:

                                            types |   # objects |   total size
===================================================== | =========== | ============
                                                 dict |          32 |     14.75 KB
                                                tuple |          41 |      3.66 KB
                                                  set |           8 |      1.81 KB
                                       instancemethod |          16 |      1.25 KB
                                                 cell |          22 |      1.20 KB
                          function (handle_exception) |           8 |    960     B
                                     function (inner) |           7 |    840     B
                                            generator |           8 |    640     B
                             <class 'tornado.gen.Task |           8 |    512     B
                           <class 'tornado.gen.Runner |           8 |    512     B
  <class 'tornado.stack_context.ExceptionStackContext |           8 |    512     B
                                                 list |           3 |    504     B
                                                  str |           7 |    353     B
                                                  int |           7 |    168     B
                           builtin_function_or_method |           2 |    144     B
                                                types |   # objects |   total size
===================================================== | =========== | ============
                                                 dict |          32 |     14.75 KB
                                                tuple |          42 |      4.23 KB
                                                  set |           8 |      1.81 KB
                                                 cell |          24 |      1.31 KB
                                       instancemethod |          16 |      1.25 KB
                          function (handle_exception) |           8 |    960     B
                                     function (inner) |           8 |    960     B
                                            generator |           8 |    640     B
                             <class 'tornado.gen.Task |           8 |    512     B
                           <class 'tornado.gen.Runner |           8 |    512     B
  <class 'tornado.stack_context.ExceptionStackContext |           8 |    512     B
                                               object |           8 |    128     B
                                                  str |           2 |    116     B
                                                  int |           1 |     24     B
                                                types |   # objects |   total size
===================================================== | =========== | ============
                                                 dict |          32 |     14.75 KB
                                                tuple |          42 |      4.73 KB
                                                  set |           8 |      1.81 KB
                                                 cell |          24 |      1.31 KB
                                       instancemethod |          16 |      1.25 KB
                          function (handle_exception) |           8 |    960     B
                                     function (inner) |           8 |    960     B
                                            generator |           8 |    640     B
                             <class 'tornado.gen.Task |           8 |    512     B
                           <class 'tornado.gen.Runner |           8 |    512     B
  <class 'tornado.stack_context.ExceptionStackContext |           8 |    512     B
                                                 list |           0 |    240     B
                                               object |           8 |    128     B
                                                  int |          -1 |    -24     B
                                                  str |           0 |    -34     B

Now that I know there's really a memory leak, how do I track where those objects are created? I guess I should start here?

Answer 1

Upgrading Tornado to version 2.3 should fix this issue.

I was having the same issue where ExceptionStackContext were leaking very quickly. It was related to this bug report: https://github.com/facebook/tornado/issues/507 and fixed in this commit: https://github.com/facebook/tornado/commit/57a3f83fc6b6fa4d9c207dc078a337260863ff99. Upgrading to 2.3 took care of the issue for me.