view hgweb.cgi @ 45035:3862de62d5cf

chg: suppress OSError in _restoreio() and add some logging (issue6330)

According to issue6330, running chg on heavy loaded systems can lead to
following error:

```
Traceback (most recent call last):
  File "path-to-hg/mercurial/commandserver.py", line 650, in _acceptnewconnection
    self._runworker(conn)
  File "path-to-hg/mercurial/commandserver.py", line 701, in _runworker
    prereposetups=[self._reposetup],
  File "path-to-hg/mercurial/commandserver.py", line 470, in _serverequest
    sv.cleanup()
  File "path-to-hg/mercurial/chgserver.py", line 381, in cleanup
    self._restoreio()
  File "path-to-hg/mercurial/chgserver.py", line 444, in _restoreio
    os.dup2(fd, fp.fileno())
OSError: [Errno 16] Device or resource busy
```

[man dup2] indicates that, on Linux, EBUSY comes from a race condition
between open() and dup2().

However it's not clear why open() race occurred for newfd=stdin/out/err.

We suppress the OSError in _restoreio() since the forked worker process will
finish anyway and add some logging.

Thanks to Mitchell Plamann for a detailed bug description and Yuya Nishihara for
suggesting the fix.

#!/usr/bin/env python
#
# An example hgweb CGI script, edit as necessary
# See also https://mercurial-scm.org/wiki/PublishingRepositories

# Path to repo or hgweb config to serve (see 'hg help hgweb')
config = "/path/to/repo/or/config"

# Uncomment and adjust if Mercurial is not installed system-wide
# (consult "installed modules" path from 'hg debuginstall'):
# import sys; sys.path.insert(0, "/path/to/python/lib")

# Uncomment to send python tracebacks to the browser if an error occurs:
# import cgitb; cgitb.enable()

from mercurial import demandimport

demandimport.enable()
from mercurial.hgweb import hgweb, wsgicgi

application = hgweb(config)
wsgicgi.launch(application)