[PATCH] debug: automate the process of truncating a damaged obsstore
Simon Farnsworth
simonfar at fb.com
Thu Jun 30 14:04:09 UTC 2016
# HG changeset patch
# User Simon Farnsworth <simonfar at fb.com>
# Date 1467295436 25200
# Thu Jun 30 07:03:56 2016 -0700
# Node ID 252cefa0326063bd664f47e3628942df30d08ccf
# Parent c42a3fd5c1fc5193e5f45887bfddaf05ca977fa4
debug: automate the process of truncating a damaged obsstore
We occasionally see users who've had a system crash damage the obsstore file
in their .hg/store directory; this makes all `hg` commands fail until we go
in and remove the damaged section of the obsstore by hand.
Automate the process we use when this happens, as a debug command because it
loses the corrupted data. We only use it in rare circumstances when it's
important to retrieve a user's work and apply it to a fresh clone.
diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -3702,6 +3702,46 @@
displayer.show(repo[r], **props)
displayer.close()
+ at command('debugtruncatestore',
+ [('', 'obsolete', None, _('truncate bad markers in obsstore'))],
+ _('[OPTION]'))
+def debugtruncatestore(ui, repo, **opts):
+ """Fix up repository corruption by truncating damaged files
+
+ Most on-disk data structures are designed to be append-only. A failed write
+ (e.g. due to an unexpected power failure) can leave the file corrupted.
+
+ This command attempts to recover from that situation by replacing the
+ corrupted file with a version that only contains the valid records from the
+ broken file.
+
+ You should normally use :hg:`recover` before resorting to this command.
+ """
+
+ if 'obsolete' in opts:
+ data = repo.svfs.tryread('obsstore')
+ if data:
+ # Slow algorithm - but this is an emergency debug operation
+ version = None
+ corrupt = False
+ while version is None:
+ try:
+ (version, markers) = obsolete._readmarkers(data)
+ except ValueError:
+ corrupt = True
+ version = None
+ data = data[:-1]
+ continue
+ break
+ if corrupt:
+ repo.svfs.write('obsstore', data)
+ ui.write(_('truncated obsstore\n'))
+ else:
+ ui.write(_('no corruption\n'))
+
+ else:
+ ui.write(_('no obsstore\n'))
+
@command('debugwalk', walkopts, _('[OPTION]... [FILE]...'), inferrepo=True)
def debugwalk(ui, repo, *pats, **opts):
"""show how files match on given patterns"""
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