hgext/blackbox.py

hgweb: parse WSGI request into a data structure

Currently, our WSGI applications (hgweb_mod and hgwebdir_mod) process
the raw WSGI request instance themselves. This means they have to
talk in terms of system strings. And they need to know details
about what's in the WSGI request. And in the case of hgweb_mod, it
is doing some very funky things with URL parsing to impact
dispatching. The code is difficult to read and maintain.

This commit introduces parsing of the WSGI request into a higher-level
and easier-to-reason-about data structure.

To prove it works, we hook it up to hgweb_mod and use it for populating
the relative URL on the request instance.

We hold off on using it in more places because the logic in hgweb_mod
is crazy and I don't want to involve those changes with review of
the parsing code.

The URL construction code has variations that use the HTTP: Host header
(the canonical WSGI way of reconstructing the URL) and with the use
of SERVER_NAME. We need to differentiate because hgweb is currently
using SERVER_NAME for URL construction.

Differential Revision: https://phab.mercurial-scm.org/D2734

# 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

"""

from __future__ import absolute_import

import errno
import re

from mercurial.i18n import _
from mercurial.node import hex

from mercurial import (
    encoding,
    registrar,
    ui as uimod,
    util,
)
from mercurial.utils import dateutil

# 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: ['*'],
)

lastui = None

def _openlogfile(ui, vfs):
    def rotate(oldpath, newpath):
        try:
            vfs.unlink(newpath)
        except OSError as err:
            if err.errno != errno.ENOENT:
                ui.debug("warning: cannot remove '%s': %s\n" %
                         (newpath, err.strerror))
        try:
            if newpath:
                vfs.rename(oldpath, newpath)
        except OSError as err:
            if err.errno != errno.ENOENT:
                ui.debug("warning: cannot rename '%s' to '%s': %s\n" %
                         (newpath, oldpath, err.strerror))

    maxsize = ui.configbytes('blackbox', 'maxsize')
    name = 'blackbox.log'
    if maxsize > 0:
        try:
            st = vfs.stat(name)
        except OSError:
            pass
        else:
            if st.st_size >= maxsize:
                path = vfs.join(name)
                maxfiles = ui.configint('blackbox', 'maxfiles')
                for i in xrange(maxfiles - 1, 1, -1):
                    rotate(oldpath='%s.%d' % (path, i - 1),
                           newpath='%s.%d' % (path, i))
                rotate(oldpath=path,
                       newpath=maxfiles > 0 and path + '.1')
    return vfs(name, 'a')

def wrapui(ui):
    class blackboxui(ui.__class__):
        @property
        def _bbvfs(self):
            vfs = None
            repo = getattr(self, '_bbrepo', None)
            if repo:
                vfs = repo.vfs
                if not vfs.isdir('.'):
                    vfs = None
            return vfs

        @util.propertycache
        def track(self):
            return self.configlist('blackbox', 'track')

        def debug(self, *msg, **opts):
            super(blackboxui, self).debug(*msg, **opts)
            if self.debugflag:
                self.log('debug', '%s', ''.join(msg))

        def log(self, event, *msg, **opts):
            global lastui
            super(blackboxui, self).log(event, *msg, **opts)

            if not '*' in self.track and not event in self.track:
                return

            if self._bbvfs:
                ui = self
            else:
                # certain ui instances exist outside the context of
                # a repo, so just default to the last blackbox that
                # was seen.
                ui = lastui

            if not ui:
                return
            vfs = ui._bbvfs
            if not vfs:
                return

            repo = getattr(ui, '_bbrepo', None)
            if not lastui or repo:
                lastui = ui
            if getattr(ui, '_bbinlog', False):
                # recursion and failure guard
                return
            ui._bbinlog = True
            default = self.configdate('devel', 'default-date')
            date = dateutil.datestr(default, '%Y/%m/%d %H:%M:%S')
            user = util.getuser()
            pid = '%d' % util.getpid()
            formattedmsg = msg[0] % msg[1:]
            rev = '(unknown)'
            changed = ''
            if repo:
                ctx = 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, formattedmsg)
                with _openlogfile(ui, vfs) as fp:
                    fp.write(fmt % args)
            except (IOError, OSError) as err:
                self.debug('warning: cannot write to blackbox.log: %s\n' %
                           encoding.strtolocal(err.strerror))
                # do not restore _bbinlog intentionally to avoid failed
                # logging again
            else:
                ui._bbinlog = False

        def setrepo(self, repo):
            self._bbrepo = repo

    ui.__class__ = blackboxui
    uimod.ui = blackboxui

def uisetup(ui):
    wrapui(ui)

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

    if util.safehasattr(ui, 'setrepo'):
        ui.setrepo(repo)

        # Set lastui even if ui.log is not called. This gives blackbox a
        # fallback place to log.
        global lastui
        if lastui is None:
            lastui = ui

    repo._wlockfreeprefix.add('blackbox.log')

@command('^blackbox',
    [('l', 'limit', 10, _('the number of events to show')),
    ],
    _('hg blackbox [OPTION]...'))
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)))