blackbox: resurrect recursion guard

If I added ui.log() to hg.repository() function, test-merge-subrepos.t
exploded. The problem is that the blackbox may create new repository instance
while logging is active, and the created repository owns its new ui derived
from the baseui, not from the ui which is processing the active logging.

I tried to work around the issue in ui.log(), but that turned out to be not
easy. We shouldn't globally lock the ui.log() since there may be more than
one active repo/ui instances in threaded environment. We could store the
logging state in thread-local storage, but that seems unnecessarily complex.
So this patch reintroduces the _inlog flag to per-repository logger instances.

hgext/blackbox.py

@@ -1,185 +1,198
 # blackbox.py - log repository events to a file for post-mortem debugging
 #
 # Copyright 2010 Nicolas Dumazet
 # Copyright 2013 Facebook, Inc.
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 """log repository events to a blackbox for debugging
 
 Logs event information to .hg/blackbox.log to help debug and diagnose problems.
 The events that get logged can be configured via the blackbox.track config key.
 
 Examples::
 
   [blackbox]
   track = *
   # dirty is *EXPENSIVE* (slow);
   # each log entry indicates `+` if the repository is dirty, like :hg:`id`.
   dirty = True
   # record the source of log messages
   logsource = True
 
   [blackbox]
   track = command, commandfinish, commandexception, exthook, pythonhook
 
   [blackbox]
   track = incoming
 
   [blackbox]
   # limit the size of a log file
   maxsize = 1.5 MB
   # rotate up to N log files when the current one gets too big
   maxfiles = 3
 
   [blackbox]
   # Include nanoseconds in log entries with %f (see Python function
   # datetime.datetime.strftime)
   date-format = '%Y-%m-%d @ %H:%M:%S.%f'
 
 """
 
 from __future__ import absolute_import
 
 import re
 
 from mercurial.i18n import _
 from mercurial.node import hex
 
 from mercurial import (
     encoding,
     loggingutil,
     registrar,
 )
 from mercurial.utils import (
     dateutil,
     procutil,
 )
 
 # Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
 # extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
 # be specifying the version(s) of Mercurial they are tested with, or
 # leave the attribute unspecified.
 testedwith = 'ships-with-hg-core'
 
 cmdtable = {}
 command = registrar.command(cmdtable)
 
 configtable = {}
 configitem = registrar.configitem(configtable)
 
 configitem('blackbox', 'dirty',
     default=False,
 )
 configitem('blackbox', 'maxsize',
     default='1 MB',
 )
 configitem('blackbox', 'logsource',
     default=False,
 )
 configitem('blackbox', 'maxfiles',
     default=7,
 )
 configitem('blackbox', 'track',
     default=lambda: ['*'],
 )
 configitem('blackbox', 'date-format',
     default='%Y/%m/%d %H:%M:%S',
 )
 
 _lastlogger = loggingutil.proxylogger()
 
 class blackboxlogger(object):
     def __init__(self, ui, repo):
         self._repo = repo
         self._trackedevents = set(ui.configlist('blackbox', 'track'))
         self._maxfiles = ui.configint('blackbox', 'maxfiles')
         self._maxsize = ui.configbytes('blackbox', 'maxsize')
+        self._inlog = False
 
     def tracked(self, event):
         return b'*' in self._trackedevents or event in self._trackedevents
 
     def log(self, ui, event, msg, opts):
+        # self._log() -> ctx.dirty() may create new subrepo instance, which
+        # ui is derived from baseui. So the recursion guard in ui.log()
+        # doesn't work as it's local to the ui instance.
+        if self._inlog:
+            return
+        self._inlog = True
+        try:
+            self._log(ui, event, msg, opts)
+        finally:
+            self._inlog = False
+
+    def _log(self, ui, event, msg, opts):
         default = ui.configdate('devel', 'default-date')
         date = dateutil.datestr(default, ui.config('blackbox', 'date-format'))
         user = procutil.getuser()
         pid = '%d' % procutil.getpid()
         rev = '(unknown)'
         changed = ''
         ctx = self._repo[None]
         parents = ctx.parents()
         rev = ('+'.join([hex(p.node()) for p in parents]))
         if (ui.configbool('blackbox', 'dirty') and
             ctx.dirty(missing=True, merge=False, branch=False)):
             changed = '+'
         if ui.configbool('blackbox', 'logsource'):
             src = ' [%s]' % event
         else:
             src = ''
         try:
             fmt = '%s %s @%s%s (%s)%s> %s'
             args = (date, user, rev, changed, pid, src, msg)
             with loggingutil.openlogfile(
                     ui, self._repo.vfs, name='blackbox.log',
                     maxfiles=self._maxfiles, maxsize=self._maxsize) as fp:
                 fp.write(fmt % args)
         except (IOError, OSError) as err:
             # deactivate this to avoid failed logging again
             self._trackedevents.clear()
             ui.debug('warning: cannot write to blackbox.log: %s\n' %
                      encoding.strtolocal(err.strerror))
             return
         _lastlogger.logger = self
 
 def uipopulate(ui):
     ui.setlogger(b'blackbox', _lastlogger)
 
 def reposetup(ui, repo):
     # During 'hg pull' a httppeer repo is created to represent the remote repo.
     # It doesn't have a .hg directory to put a blackbox in, so we don't do
     # the blackbox setup for it.
     if not repo.local():
         return
 
     # Since blackbox.log is stored in the repo directory, the logger should be
     # instantiated per repository.
     logger = blackboxlogger(ui, repo)
     ui.setlogger(b'blackbox', logger)
 
     # Set _lastlogger even if ui.log is not called. This gives blackbox a
     # fallback place to log
     if _lastlogger.logger is None:
         _lastlogger.logger = logger
 
     repo._wlockfreeprefix.add('blackbox.log')
 
 @command('blackbox',
     [('l', 'limit', 10, _('the number of events to show')),
     ],
     _('hg blackbox [OPTION]...'),
     helpcategory=command.CATEGORY_MAINTENANCE,
     helpbasic=True)
 def blackbox(ui, repo, *revs, **opts):
     '''view the recent repository events
     '''
 
     if not repo.vfs.exists('blackbox.log'):
         return
 
     limit = opts.get(r'limit')
     fp = repo.vfs('blackbox.log', 'r')
     lines = fp.read().split('\n')
 
     count = 0
     output = []
     for line in reversed(lines):
         if count >= limit:
             break
 
         # count the commands by matching lines like: 2013/01/23 19:13:36 root>
         if re.match('^\d{4}/\d{2}/\d{2} \d{2}:\d{2}:\d{2} .*> .*', line):
             count += 1
         output.append(line)
 
     ui.status('\n'.join(reversed(output)))