1 # Support code for event tracing in Mercurial. Lives in demandimport

     2 # so it can also be used in demandimport.

     3 #

     4 # Copyright 2018 Google LLC.

     5 #

     6 # This software may be used and distributed according to the terms of the

     7 # GNU General Public License version 2 or any later version.

     8 from __future__ import absolute_import

     9 

    10 import contextlib

    11 import os

    12 

    13 _pipe = None

    14 _checked = False

    15 

    16 @contextlib.contextmanager

    17 def log(whencefmt, *whenceargs):

    18     global _pipe, _session, _checked

    19     if _pipe is None:

    20         if _checked:

    21             yield

    22             return

    23         _checked = True

    24         if 'HGCATAPULTSERVERPIPE' not in os.environ:

    25             yield

    26             return

    27         _pipe = open(os.environ['HGCATAPULTSERVERPIPE'], 'w', 1)

    28         _session = os.environ.get('HGCATAPULTSESSION', 'none')

    29     whence = whencefmt % whenceargs

    30     try:

    31         # Both writes to the pipe are wrapped in try/except to ignore

    32         # errors, as we can see mysterious errors in here if the pager

    33         # is active. Presumably other conditions could trigger

    34         # problems too.

    35         try:

    36             _pipe.write('START %s %s\n' % (_session, whence))

    37         except IOError:

    38             pass

    39         yield

    40     finally:

    41         try:

    42             _pipe.write('END %s %s\n' % (_session, whence))

    43         except IOError:

    44             pass