hgdemandimport/tracing.py

flagutil: use it in simplestorerepo

This remove the other code duplication of the `_processflags` code.

To be honest, this code looks very dead since it is not run by either developer
nor buildbot. However, we update the code to make the task of reviving this less
daunting.

Differential Revision: https://phab.mercurial-scm.org/D6799

# 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
_session = 'none'

def _isactive():
    global _pipe, _session, _checked
    if _pipe is None:
        if _checked:
            return False
        _checked = True
        if 'HGCATAPULTSERVERPIPE' not in os.environ:
            return False
        _pipe = open(os.environ['HGCATAPULTSERVERPIPE'], 'w', 1)
        _session = os.environ.get('HGCATAPULTSESSION', 'none')
    return True

@contextlib.contextmanager
def log(whencefmt, *whenceargs):
    if not _isactive():
        yield
        return
    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

def counter(label, amount, *labelargs):
    if not _isactive():
        return
    l = label % labelargs
    # See above in log() for why this is in a try/except.
    try:
        _pipe.write('COUNTER %s %d %s\n' % (_session, amount, l))
    except IOError:
        pass