view mercurial/transaction.py @ 2435:ff2bac730b99

http client: support persistent connections.

uses keepalive module from urlgrabber package.  tested against "hg serve",
cgi server, and through http proxy.  used ethereal to verify that only
one tcp connection used during entire "hg pull" sequence.

if server supports keepalive, this makes latency of "hg pull" much lower.

# 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 <[e-mail]>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

import os
from i18n import gettext as _

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

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

        self.count = 1
        self.report = report
        self.opener = opener
        self.after = after
        self.entries = []
        self.map = {}
        self.journal = journal

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

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

    def add(self, file, offset, data=None):
        if file in self.map: return
        self.entries.append((file, offset, data))
        self.map[file] = len(self.entries) - 1
        # add enough data to the journal to do the truncate
        self.file.write("%s\0%d\n" % (file, offset))
        self.file.flush()

    def find(self, file):
        if file in self.map:
            return self.entries[self.map[file]]
        return None

    def replace(self, file, offset, data=None):
        if file not in self.map:
            raise KeyError(file)
        index = self.map[file]
        self.entries[index] = (file, offset, data)
        self.file.write("%s\0%d\n" % (file, offset))
        self.file.flush()

    def nest(self):
        self.count += 1
        return self

    def running(self):
        return self.count > 0

    def close(self):
        self.count -= 1
        if self.count != 0:
            return
        self.file.close()
        self.entries = []
        if self.after:
            self.after()
        else:
            os.unlink(self.journal)
        self.journal = None

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

        self.report(_("transaction abort!\n"))

        for f, o, ignore in self.entries:
            try:
                self.opener(f, "a").truncate(o)
            except:
                self.report(_("failed to truncate %s\n") % f)

        self.entries = []

        self.report(_("rollback completed\n"))

def rollback(opener, file):
    files = {}
    for l in open(file).readlines():
        f, o = l.split('\0')
        files[f] = o
    for f in files:
        o = files[f]
        opener(f, "a").truncate(int(o))
    os.unlink(file)