commandserver: add new forking server implemented without using SocketServer
SocketServer.ForkingMixIn of Python 2.x has a couple of issues, such as:
- race condition that leads to 100% CPU usage (Python 2.6)
https://bugs.python.org/
issue21491
- can't wait for children belonging to different process groups (Python 2.6)
- leaves at least one zombie process (Python 2.6, 2.7)
https://bugs.python.org/
issue11109
The first two are critical because we do setpgid(0, 0) in child process to
isolate terminal signals. The last one isn't, but ForkingMixIn seems to be
doing silly. So there are two choices:
a) backport and maintain SocketServer until we can drop support for Python 2.x
b) replace SocketServer by simpler one and eliminate glue codes
I chose (b) because it's great time for getting rid of utterly complicated
SocketServer stuff, and preparing for future move towards prefork service.
New unixforkingservice is implemented loosely based on chg
531f8ef64be6. It
is monolithic but much simpler than SocketServer. unixservicehandler provides
customizing points for chg, and it will be shared with future prefork service.
Old unixservice class is still used by chgserver. It will be removed later.
Thanks to Jun Wu for investigating these issues.
# extension to emulate invoking 'dirstate.write()' at the time
# specified by '[fakedirstatewritetime] fakenow', only when
# 'dirstate.write()' is invoked via functions below:
#
# - 'workingctx._checklookup()' (= 'repo.status()')
# - 'committablectx.markcommitted()'
from __future__ import absolute_import
from mercurial import (
context,
dirstate,
extensions,
parsers,
util,
)
def pack_dirstate(fakenow, orig, dmap, copymap, pl, now):
# execute what original parsers.pack_dirstate should do actually
# for consistency
actualnow = int(now)
for f, e in dmap.iteritems():
if e[0] == 'n' and e[3] == actualnow:
e = parsers.dirstatetuple(e[0], e[1], e[2], -1)
dmap[f] = e
return orig(dmap, copymap, pl, fakenow)
def fakewrite(ui, func):
# fake "now" of 'pack_dirstate' only if it is invoked while 'func'
fakenow = ui.config('fakedirstatewritetime', 'fakenow')
if not fakenow:
# Execute original one, if fakenow isn't configured. This is
# useful to prevent subrepos from executing replaced one,
# because replacing 'parsers.pack_dirstate' is also effective
# in subrepos.
return func()
# parsing 'fakenow' in YYYYmmddHHMM format makes comparison between
# 'fakenow' value and 'touch -t YYYYmmddHHMM' argument easy
fakenow = util.parsedate(fakenow, ['%Y%m%d%H%M'])[0]
orig_pack_dirstate = parsers.pack_dirstate
orig_dirstate_getfsnow = dirstate._getfsnow
wrapper = lambda *args: pack_dirstate(fakenow, orig_pack_dirstate, *args)
parsers.pack_dirstate = wrapper
dirstate._getfsnow = lambda *args: fakenow
try:
return func()
finally:
parsers.pack_dirstate = orig_pack_dirstate
dirstate._getfsnow = orig_dirstate_getfsnow
def _checklookup(orig, workingctx, files):
ui = workingctx.repo().ui
return fakewrite(ui, lambda : orig(workingctx, files))
def markcommitted(orig, committablectx, node):
ui = committablectx.repo().ui
return fakewrite(ui, lambda : orig(committablectx, node))
def extsetup(ui):
extensions.wrapfunction(context.workingctx, '_checklookup',
_checklookup)
extensions.wrapfunction(context.committablectx, 'markcommitted',
markcommitted)