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

Source code for celery.utils.debug

# -*- coding: utf-8 -*-
"""Utilities for debugging memory usage, blocking calls, etc."""
from __future__ import absolute_import, print_function, unicode_literals

import os
import sys
import traceback
from contextlib import contextmanager
from functools import partial
from pprint import pprint

from celery.five import WhateverIO, items, range
from celery.platforms import signals

    from psutil import Process
except ImportError:
    Process = None  # noqa

__all__ = (
    'blockdetection', 'sample_mem', 'memdump', 'sample',
    'humanbytes', 'mem_rss', 'ps', 'cry',

    (2 ** 40.0, 'TB'),
    (2 ** 30.0, 'GB'),
    (2 ** 20.0, 'MB'),
    (2 ** 10.0, 'KB'),
    (0.0, 'b'),

_process = None
_mem_sample = []

def _on_blocking(signum, frame):
    import inspect
    raise RuntimeError(
        'Blocking detection timed-out at: {0}'.format(

def blockdetection(timeout):
    """Context that raises an exception if process is blocking.

    Uses ``SIGALRM`` to detect blocking functions.
    if not timeout:
        old_handler = signals['ALRM']
        old_handler = None if old_handler == _on_blocking else old_handler

        signals['ALRM'] = _on_blocking

            yield signals.arm_alarm(timeout)
            if old_handler:
                signals['ALRM'] = old_handler

[docs]def sample_mem(): """Sample RSS memory usage. Statistics can then be output by calling :func:`memdump`. """ current_rss = mem_rss() _mem_sample.append(current_rss) return current_rss
def _memdump(samples=10): # pragma: no cover S = _mem_sample prev = list(S) if len(S) <= samples else sample(S, samples) _mem_sample[:] = [] import gc gc.collect() after_collect = mem_rss() return prev, after_collect
[docs]def memdump(samples=10, file=None): # pragma: no cover """Dump memory statistics. Will print a sample of all RSS memory samples added by calling :func:`sample_mem`, and in addition print used RSS memory after :func:`gc.collect`. """ say = partial(print, file=file) if ps() is None: say('- rss: (psutil not installed).') return prev, after_collect = _memdump(samples) if prev: say('- rss (sample):') for mem in prev: say('- > {0},'.format(mem)) say('- rss (end): {0}.'.format(after_collect))
[docs]def sample(x, n, k=0): """Given a list `x` a sample of length ``n`` of that list is returned. For example, if `n` is 10, and `x` has 100 items, a list of every tenth. item is returned. ``k`` can be used as offset. """ j = len(x) // n for _ in range(n): try: yield x[k] except IndexError: break k += j
def hfloat(f, p=5): """Convert float to value suitable for humans. Arguments: f (float): The floating point number. p (int): Floating point precision (default is 5). """ i = int(f) return i if i == f else '{0:.{p}}'.format(f, p=p) def humanbytes(s): """Convert bytes to human-readable form (e.g., KB, MB).""" return next( '{0}{1}'.format(hfloat(s / div if div else s), unit) for div, unit in UNITS if s >= div )
[docs]def mem_rss(): """Return RSS memory usage as a humanized string.""" p = ps() if p is not None: return humanbytes(_process_memory_info(p).rss)
[docs]def ps(): # pragma: no cover """Return the global :class:`psutil.Process` instance. Note: Returns :const:`None` if :pypi:`psutil` is not installed. """ global _process if _process is None and Process is not None: _process = Process(os.getpid()) return _process
def _process_memory_info(process): try: return process.memory_info() except AttributeError: return process.get_memory_info() def cry(out=None, sepchr='=', seplen=49): # pragma: no cover """Return stack-trace of all active threads. See Also: Taken from """ import threading out = WhateverIO() if out is None else out P = partial(print, file=out) # get a map of threads by their ID so we can print their names # during the traceback dump tmap = {t.ident: t for t in threading.enumerate()} sep = sepchr * seplen for tid, frame in items(sys._current_frames()): thread = tmap.get(tid) if not thread: # skip old junk (left-overs from a fork) continue P('{}'.format(thread)) P(sep) traceback.print_stack(frame, file=out) P(sep) P('LOCAL VARIABLES') P(sep) pprint(frame.f_locals, stream=out) P('\n') return out.getvalue()