mercurial/transaction.py
author mpm@selenic.com
Fri, 24 Jun 2005 22:51:39 -0800
changeset 460 6409d9a0df43
parent 429 688d03d6997a
child 515 03f27b1381f9
permissions -rw-r--r--
add dirstate debugging commands -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 add dirstate debugging commands As I've played with various different merges and more recently rawcommit, I've found the following patch to be very very helpful in figuring out whether the dirstate is being left in a consistent or inconsistent state with respect to the current manifest. I attempted to deduce the invariants that were assumed by the current code, and then check it in this code. I may or may not have captured the design intent in this check; if not, I'd be very happy to hear more clearly what was intended, so that I can write tests to that expectation. Anyway, here's the patch. Not sure if it's a good idea to commit it to the mainline, or just leave it as a debugging aid. I attempted to package it so that it doesn't interfere with normal usage. Michael Fetterman (tweaked by mpm: remove -d magic) manifest hash: 869f5b5f954dc0f46ba27322359e811d5e21d71c -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.0 (GNU/Linux) iD8DBQFCvP77ywK+sNU5EO8RArmtAKCCVuI2slANzWZ26P5edtH/ixdwNwCfZLWl 5P+V+C92II3usO4YW2MULKY= =/Pv4 -----END PGP SIGNATURE-----

# transaction.py - simple journalling scheme for mercurial
#
# This transaction scheme is intended to gracefully handle program
# errors and interruptions. More serious failures like system crashes
# can be recovered with an fsck-like tool. As the whole repository is
# effectively log-structured, this should amount to simply truncating
# anything that isn't referenced in the changelog.
#
# Copyright 2005 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

import os
import util

class transaction:
    def __init__(self, opener, journal, after = None):
        self.journal = None

        # abort here if the journal already exists
        if os.path.exists(journal):
            raise "journal already exists - run hg recover"

        self.opener = opener
        self.after = after
        self.entries = []
        self.map = {}
        self.journal = journal

        self.file = open(self.journal, "w")

    def __del__(self):
        if self.entries: self.abort()
        try: os.unlink(self.journal)
        except: pass

    def add(self, file, offset):
        if file in self.map: return
        self.entries.append((file, offset))
        self.map[file] = 1
        # add enough data to the journal to do the truncate
        self.file.write("%s\0%d\n" % (file, offset))
        self.file.flush()

    def close(self):
        self.file.close()
        self.entries = []
        if self.after:
            util.rename(self.journal, self.after)
        else:
            os.unlink(self.journal)

    def abort(self):
        if not self.entries: return

        print "transaction abort!"

        for f, o in self.entries:
            try:
                self.opener(f, "a").truncate(o)
            except:
                print "failed to truncate", f

        self.entries = []

        print "rollback completed"
        
def rollback(opener, file):
    for l in open(file).readlines():
        f, o = l.split('\0')
        opener(f, "a").truncate(int(o))
    os.unlink(file)