# HG changeset patch
# User Augie Fackler <augie@google.com>
# Date 1535815997 14400
# Node ID 452790284a15414dad1e6e12396d1a621e20173f
# Parent  f57682dca1c13891ca6c9041a76c459f5b1f6dc0
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

diff -r f57682dca1c1 -r 452790284a15 hgdemandimport/tracing.py
--- a/hgdemandimport/tracing.py	Sat Sep 01 11:06:47 2018 -0400
+++ b/hgdemandimport/tracing.py	Sat Sep 01 11:33:17 2018 -0400
@@ -28,7 +28,17 @@
         _session = os.environ.get('HGCATAPULTSESSION', 'none')
     whence = whencefmt % whenceargs
     try:
-        _pipe.write('START %s %s\n' % (_session, whence))
+        # 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:
-        _pipe.write('END %s %s\n' % (_session, whence))
+        try:
+            _pipe.write('END %s %s\n' % (_session, whence))
+        except IOError:
+            pass