tracing: ignore any IOErrors when writing to pipe
When the pager forks off the main process, we can end up with the pipe
closed prematurely. Rather than break hg entirely when that happens
and tracing is active, just let lingering events disappear as needed.
Differential Revision: https://phab.mercurial-scm.org/D4445
# Support code for event tracing in Mercurial. Lives in demandimport
# so it can also be used in demandimport.
#
# Copyright 2018 Google LLC.
#
# 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 contextlib
import os
_pipe = None
_checked = False
@contextlib.contextmanager
def log(whencefmt, *whenceargs):
global _pipe, _session, _checked
if _pipe is None:
if _checked:
yield
return
_checked = True
if 'HGCATAPULTSERVERPIPE' not in os.environ:
yield
return
_pipe = open(os.environ['HGCATAPULTSERVERPIPE'], 'w', 1)
_session = os.environ.get('HGCATAPULTSESSION', 'none')
whence = whencefmt % whenceargs
try:
# Both writes to the pipe are wrapped in try/except to ignore
# errors, as we can see mysterious errors in here if the pager
# is active. Presumably other conditions could trigger
# problems too.
try:
_pipe.write('START %s %s\n' % (_session, whence))
except IOError:
pass
yield
finally:
try:
_pipe.write('END %s %s\n' % (_session, whence))
except IOError:
pass