##// END OF EJS Templates
revlog: add a mechanism to verify expected file position before appending...
revlog: add a mechanism to verify expected file position before appending If someone uses `hg debuglocks`, or some non-hg process writes to the .hg directory without respecting the locks, or if the repo's on a networked filesystem, it's possible for the revlog code to write out corrupted data. The form of this corruption can vary depending on what data was written and how that happened. We are in the "networked filesystem" case (though I've had users also do this to themselves with the "`hg debuglocks`" scenario), and most often see this with the changelog. What ends up happening is we produce two items (let's call them rev1 and rev2) in the .i file that have the same linkrev, baserev, and offset into the .d file, while the data in the .d file is appended properly. rev2's compressed_size is accurate for rev2, but when we go to decompress the data in the .d file, we use the offset that's recorded in the index file, which is the same as rev1, and attempt to decompress rev2.compressed_size bytes of rev1's data. This usually does not succeed. :) When using inline data, this also fails, though I haven't investigated why too closely. This shows up as a "patch decode" error. I believe what's happening there is that we're basically ignoring the offset field, getting the data properly, but since baserev != rev, it thinks this is a delta based on rev (instead of a full text) and can't actually apply it as such. For now, I'm going to make this an optional component and default it to entirely off. I may increase the default severity of this in the future, once I've enabled it for my users and we gain more experience with it. Luckily, most of my users have a versioned filesystem and can roll back to before the corruption has been written, it's just a hassle to do so and not everyone knows how (so it's a support burden). Users on other filesystems will not have that luxury, and this can cause them to have a corrupted repository that they are unlikely to know how to resolve, and they'll see this as a data-loss event. Refusing to create the corruption is a much better user experience. This mechanism is not perfect. There may be false-negatives (racy writes that are not detected). There should not be any false-positives (non-racy writes that are detected as such). This is not a mechanism that makes putting a repo on a networked filesystem "safe" or "supported", just *less* likely to cause corruption. Differential Revision: https://phab.mercurial-scm.org/D9952

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pager.py
83 lines | 2.6 KiB | text/x-python | PythonLexer
# pager.py - display output using a pager
#
# Copyright 2008 David Soria Parra <dsp@php.net>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
#
# To load the extension, add it to your configuration file:
#
# [extension]
# pager =
#
# Run 'hg help pager' to get info on configuration.
'''browse command output with an external pager (DEPRECATED)
Forcibly enable paging for individual commands that don't typically
request pagination with the attend-<command> option. This setting
takes precedence over ignore options and defaults::
[pager]
attend-cat = false
'''
from __future__ import absolute_import
from mercurial import (
cmdutil,
commands,
dispatch,
extensions,
registrar,
)
# 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 = b'ships-with-hg-core'
configtable = {}
configitem = registrar.configitem(configtable)
configitem(
b'pager',
b'attend',
default=lambda: attended,
)
def uisetup(ui):
def pagecmd(orig, ui, options, cmd, cmdfunc):
auto = options[b'pager'] == b'auto'
if auto and not ui.pageractive:
usepager = False
attend = ui.configlist(b'pager', b'attend')
ignore = ui.configlist(b'pager', b'ignore')
cmds, _ = cmdutil.findcmd(cmd, commands.table)
for cmd in cmds:
var = b'attend-%s' % cmd
if ui.config(b'pager', var, None):
usepager = ui.configbool(b'pager', var, True)
break
if cmd in attend or (cmd not in ignore and not attend):
usepager = True
break
if usepager:
# Slight hack: the attend list is supposed to override
# the ignore list for the pager extension, but the
# core code doesn't know about attend, so we have to
# lobotomize the ignore list so that the extension's
# behavior is preserved.
ui.setconfig(b'pager', b'ignore', b'', b'pager')
ui.pager(b'extension-via-attend-' + cmd)
else:
ui.disablepager()
return orig(ui, options, cmd, cmdfunc)
extensions.wrapfunction(dispatch, b'_runcommand', pagecmd)
attended = [b'annotate', b'cat', b'diff', b'export', b'glog', b'log', b'qdiff']