This document describes the current stable version of Celery (4.4). For development docs, go here.

Source code for celery.contrib.rdb

# -*- coding: utf-8 -*-
"""Remote Debugger.


This is a remote debugger for Celery tasks running in multiprocessing
pool workers.  Inspired by a lost post on


.. code-block:: python

    from celery.contrib import rdb
    from celery import task

    def add(x, y):
        result = x + y
        return result

Environment Variables

.. envvar:: CELERY_RDB_HOST


    Hostname to bind to.  Default is '' (only accessible from

.. envvar:: CELERY_RDB_PORT


    Base port to bind to.  Default is 6899.
    The debugger will try to find an available port starting from the
    base port.  The selected port will be logged by the worker.
from __future__ import absolute_import, print_function, unicode_literals

import errno
import os
import socket
import sys
from pdb import Pdb

from billiard.process import current_process

from celery.five import range

__all__ = (
    'Rdb', 'debugger', 'set_trace',


CELERY_RDB_HOST = os.environ.get('CELERY_RDB_HOST') or ''

#: Holds the currently active debugger.
_current = [None]

_frame = getattr(sys, '_getframe')

{self.ident}: Couldn't find an available port.

Please specify one using the CELERY_RDB_PORT environment variable.

BANNER = """\
{self.ident}: Ready to connect: telnet {} {self.port}

Type `exit` in session to continue.

{self.ident}: Waiting for client...

SESSION_STARTED = '{self.ident}: Now in session with {self.remote_addr}.'
SESSION_ENDED = '{self.ident}: Session with {self.remote_addr} ended.'

[docs]class Rdb(Pdb): """Remote debugger.""" me = 'Remote Debugger' _prev_outs = None _sock = None def __init__(self, host=CELERY_RDB_HOST, port=CELERY_RDB_PORT, port_search_limit=100, port_skew=+0, out=sys.stdout): = True self.out = out self._prev_handles = sys.stdin, sys.stdout self._sock, this_port = self.get_avail_port( host, port, port_search_limit, port_skew, ) self._sock.setblocking(1) self._sock.listen(1) self.ident = '{0}:{1}'.format(, this_port) = host self.port = this_port self.say(BANNER.format(self=self)) self._client, address = self._sock.accept() self._client.setblocking(1) self.remote_addr = ':'.join(str(v) for v in address) self.say(SESSION_STARTED.format(self=self)) self._handle = sys.stdin = sys.stdout = self._client.makefile('rw') Pdb.__init__(self, completekey='tab', stdin=self._handle, stdout=self._handle) def get_avail_port(self, host, port, search_limit=100, skew=+0): try: _, skew = current_process().name.split('-') skew = int(skew) except ValueError: pass this_port = None for i in range(search_limit): _sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) _sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) this_port = port + skew + i try: _sock.bind((host, this_port)) except socket.error as exc: if exc.errno in [errno.EADDRINUSE, errno.EINVAL]: continue raise else: return _sock, this_port else: raise Exception(NO_AVAILABLE_PORT.format(self=self)) def say(self, m): print(m, file=self.out) def __enter__(self): return self def __exit__(self, *exc_info): self._close_session() def _close_session(self): self.stdin, self.stdout = sys.stdin, sys.stdout = self._prev_handles if if self._handle is not None: self._handle.close() if self._client is not None: self._client.close() if self._sock is not None: self._sock.close() = False self.say(SESSION_ENDED.format(self=self)) def do_continue(self, arg): self._close_session() self.set_continue() return 1 do_c = do_cont = do_continue def do_quit(self, arg): self._close_session() self.set_quit() return 1 do_q = do_exit = do_quit def set_quit(self): # this raises a BdbQuit exception that we're unable to catch. sys.settrace(None)
[docs]def debugger(): """Return the current debugger instance, or create if none.""" rdb = _current[0] if rdb is None or not rdb = _current[0] = Rdb() return rdb
[docs]def set_trace(frame=None): """Set break-point at current location, or a specified frame.""" if frame is None: frame = _frame().f_back return debugger().set_trace(frame)