view hgdemandimport/tracing.py @ 40527:1b49b84d5ed5

pycompat: adding Linux detection and fixing Mac

Python 3 recommends detecting OSs with the prefix of the platform, but we were
comparing the full string for macOS. We also didn't have Linux detection, which
is convenient for extensions to use (rather than have some OSs detected by hg
and some by the extension).

Reference:
https://docs.python.org/3/library/sys.html#sys.platform

Differential Revision: https://phab.mercurial-scm.org/D5227

# 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