extend network protocol to stop clients from locking servers
now all repositories have capabilities slot, tuple with list of names.
if 'unbundle' capability present, repo supports push where client does
not need to lock server. repository classes that have unbundle capability
also have unbundle method.
implemented for ssh now, will be base for push over http.
unbundle protocol acts this way. server tells client what heads it
has during normal negotiate step. client starts unbundle by repeat
server's heads back to it. if server has new heads, abort immediately.
otherwise, transfer changes to server. once data transferred, server
locks and checks heads again. if heads same, changes can be added.
else someone else added heads, and server aborts.
if client wants to force server to add heads, sends special heads list of
'force'.
# 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
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)