Mercurial > hg
view mercurial/worker.py @ 37290:cc5a040fe150
wireproto: syntax for encoding CBOR into frames
We just vendored a library for encoding and decoding the CBOR
data format. While the intent of that vendor was to support state
files, CBOR is really a nice data format. It is extensible and
compact.
I've been feeling dirty inventing my own data formats for
frame payloads. While custom formats can always beat out a generic
format, there is a cost to be paid in terms of implementation,
comprehension, etc. CBOR is compact enough that I'm not too
worried about efficiency loss. I think the benefits of using
a standardized format outweigh rolling our own formats. So
I plan to make heavy use of CBOR in the wire protocol going
forward.
This commit introduces support for encoding CBOR data in frame
payloads to our function to make a frame from a human string.
We do need to employ some low-level Python code in order to
evaluate a string as a Python expression. But other than that,
this should hopefully be pretty straightforward.
Unit tests for this function have been added.
Differential Revision: https://phab.mercurial-scm.org/D2948
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 28 Mar 2018 15:05:39 -0700 |
parents | 5bc7ff103081 |
children | 8fb9985382be |
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# worker.py - master-slave parallelism support # # Copyright 2013 Facebook, Inc. # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. from __future__ import absolute_import import errno import os import signal import sys import threading import time from .i18n import _ from . import ( encoding, error, pycompat, scmutil, util, ) def countcpus(): '''try to count the number of CPUs on the system''' # posix try: n = int(os.sysconf(r'SC_NPROCESSORS_ONLN')) if n > 0: return n except (AttributeError, ValueError): pass # windows try: n = int(encoding.environ['NUMBER_OF_PROCESSORS']) if n > 0: return n except (KeyError, ValueError): pass return 1 def _numworkers(ui): s = ui.config('worker', 'numcpus') if s: try: n = int(s) if n >= 1: return n except ValueError: raise error.Abort(_('number of cpus must be an integer')) return min(max(countcpus(), 4), 32) if pycompat.isposix or pycompat.iswindows: _startupcost = 0.01 else: _startupcost = 1e30 def worthwhile(ui, costperop, nops): '''try to determine whether the benefit of multiple processes can outweigh the cost of starting them''' linear = costperop * nops workers = _numworkers(ui) benefit = linear - (_startupcost * workers + linear / workers) return benefit >= 0.15 def worker(ui, costperarg, func, staticargs, args): '''run a function, possibly in parallel in multiple worker processes. returns a progress iterator costperarg - cost of a single task func - function to run staticargs - arguments to pass to every invocation of the function args - arguments to split into chunks, to pass to individual workers ''' enabled = ui.configbool('worker', 'enabled') if enabled and worthwhile(ui, costperarg, len(args)): return _platformworker(ui, func, staticargs, args) return func(*staticargs + (args,)) def _posixworker(ui, func, staticargs, args): rfd, wfd = os.pipe() workers = _numworkers(ui) oldhandler = signal.getsignal(signal.SIGINT) signal.signal(signal.SIGINT, signal.SIG_IGN) pids, problem = set(), [0] def killworkers(): # unregister SIGCHLD handler as all children will be killed. This # function shouldn't be interrupted by another SIGCHLD; otherwise pids # could be updated while iterating, which would cause inconsistency. signal.signal(signal.SIGCHLD, oldchldhandler) # if one worker bails, there's no good reason to wait for the rest for p in pids: try: os.kill(p, signal.SIGTERM) except OSError as err: if err.errno != errno.ESRCH: raise def waitforworkers(blocking=True): for pid in pids.copy(): p = st = 0 while True: try: p, st = os.waitpid(pid, (0 if blocking else os.WNOHANG)) break except OSError as e: if e.errno == errno.EINTR: continue elif e.errno == errno.ECHILD: # child would already be reaped, but pids yet been # updated (maybe interrupted just after waitpid) pids.discard(pid) break else: raise if not p: # skip subsequent steps, because child process should # be still running in this case continue pids.discard(p) st = _exitstatus(st) if st and not problem[0]: problem[0] = st def sigchldhandler(signum, frame): waitforworkers(blocking=False) if problem[0]: killworkers() oldchldhandler = signal.signal(signal.SIGCHLD, sigchldhandler) ui.flush() parentpid = os.getpid() for pargs in partition(args, workers): # make sure we use os._exit in all worker code paths. otherwise the # worker may do some clean-ups which could cause surprises like # deadlock. see sshpeer.cleanup for example. # override error handling *before* fork. this is necessary because # exception (signal) may arrive after fork, before "pid =" assignment # completes, and other exception handler (dispatch.py) can lead to # unexpected code path without os._exit. ret = -1 try: pid = os.fork() if pid == 0: signal.signal(signal.SIGINT, oldhandler) signal.signal(signal.SIGCHLD, oldchldhandler) def workerfunc(): os.close(rfd) for i, item in func(*(staticargs + (pargs,))): os.write(wfd, '%d %s\n' % (i, item)) return 0 ret = scmutil.callcatch(ui, workerfunc) except: # parent re-raises, child never returns if os.getpid() == parentpid: raise exctype = sys.exc_info()[0] force = not issubclass(exctype, KeyboardInterrupt) ui.traceback(force=force) finally: if os.getpid() != parentpid: try: ui.flush() except: # never returns, no re-raises pass finally: os._exit(ret & 255) pids.add(pid) os.close(wfd) fp = os.fdopen(rfd, r'rb', 0) def cleanup(): signal.signal(signal.SIGINT, oldhandler) waitforworkers() signal.signal(signal.SIGCHLD, oldchldhandler) status = problem[0] if status: if status < 0: os.kill(os.getpid(), -status) sys.exit(status) try: for line in util.iterfile(fp): l = line.split(' ', 1) yield int(l[0]), l[1][:-1] except: # re-raises killworkers() cleanup() raise cleanup() def _posixexitstatus(code): '''convert a posix exit status into the same form returned by os.spawnv returns None if the process was stopped instead of exiting''' if os.WIFEXITED(code): return os.WEXITSTATUS(code) elif os.WIFSIGNALED(code): return -os.WTERMSIG(code) def _windowsworker(ui, func, staticargs, args): class Worker(threading.Thread): def __init__(self, taskqueue, resultqueue, func, staticargs, group=None, target=None, name=None, verbose=None): threading.Thread.__init__(self, group=group, target=target, name=name, verbose=verbose) self._taskqueue = taskqueue self._resultqueue = resultqueue self._func = func self._staticargs = staticargs self._interrupted = False self.daemon = True self.exception = None def interrupt(self): self._interrupted = True def run(self): try: while not self._taskqueue.empty(): try: args = self._taskqueue.get_nowait() for res in self._func(*self._staticargs + (args,)): self._resultqueue.put(res) # threading doesn't provide a native way to # interrupt execution. handle it manually at every # iteration. if self._interrupted: return except util.empty: break except Exception as e: # store the exception such that the main thread can resurface # it as if the func was running without workers. self.exception = e raise threads = [] def trykillworkers(): # Allow up to 1 second to clean worker threads nicely cleanupend = time.time() + 1 for t in threads: t.interrupt() for t in threads: remainingtime = cleanupend - time.time() t.join(remainingtime) if t.is_alive(): # pass over the workers joining failure. it is more # important to surface the inital exception than the # fact that one of workers may be processing a large # task and does not get to handle the interruption. ui.warn(_("failed to kill worker threads while " "handling an exception\n")) return workers = _numworkers(ui) resultqueue = util.queue() taskqueue = util.queue() # partition work to more pieces than workers to minimize the chance # of uneven distribution of large tasks between the workers for pargs in partition(args, workers * 20): taskqueue.put(pargs) for _i in range(workers): t = Worker(taskqueue, resultqueue, func, staticargs) threads.append(t) t.start() try: while len(threads) > 0: while not resultqueue.empty(): yield resultqueue.get() threads[0].join(0.05) finishedthreads = [_t for _t in threads if not _t.is_alive()] for t in finishedthreads: if t.exception is not None: raise t.exception threads.remove(t) except (Exception, KeyboardInterrupt): # re-raises trykillworkers() raise while not resultqueue.empty(): yield resultqueue.get() if pycompat.iswindows: _platformworker = _windowsworker else: _platformworker = _posixworker _exitstatus = _posixexitstatus def partition(lst, nslices): '''partition a list into N slices of roughly equal size The current strategy takes every Nth element from the input. If we ever write workers that need to preserve grouping in input we should consider allowing callers to specify a partition strategy. mpm is not a fan of this partitioning strategy when files are involved. In his words: Single-threaded Mercurial makes a point of creating and visiting files in a fixed order (alphabetical). When creating files in order, a typical filesystem is likely to allocate them on nearby regions on disk. Thus, when revisiting in the same order, locality is maximized and various forms of OS and disk-level caching and read-ahead get a chance to work. This effect can be quite significant on spinning disks. I discovered it circa Mercurial v0.4 when revlogs were named by hashes of filenames. Tarring a repo and copying it to another disk effectively randomized the revlog ordering on disk by sorting the revlogs by hash and suddenly performance of my kernel checkout benchmark dropped by ~10x because the "working set" of sectors visited no longer fit in the drive's cache and the workload switched from streaming to random I/O. What we should really be doing is have workers read filenames from a ordered queue. This preserves locality and also keeps any worker from getting more than one file out of balance. ''' for i in range(nslices): yield lst[i::nslices]