exchange: support transferring .hgtags fnodes mapping
On Mozilla's mozilla-beta repository .hgtags fnodes resolution takes
~18s from a clean cache on my machine. This means that the first time
a user runs `hg tags`, `hg log`, or any other command that displays or
accesses tags data, a ~18s pause will occur. There is no output during
this pause. This results in a poor user experience and perception
that Mercurial is slow.
The .hgtags changeset to filenode mapping is deterministic. This
patch takes advantage of that property by implementing support
for transferring .hgtags filenodes mappings in a dedicated bundle2
part. When a client advertising support for the "hgtagsfnodes"
capability requests a bundle, a mapping of changesets to .hgtags
filenodes will be sent to the client.
Only mappings of head changesets included in the bundle will be sent. The
transfer of this mapping effectively eliminates one time tags cache related
pauses after initial clone.
The mappings are sent as binary data. So, 40 bytes per pair of
SHA-1s. On the aforementioned mozilla-beta repository,
659 * 40 = 26,360 raw bytes of mappings are sent over the wire
(in addition to the bundle part headers). Assuming 18s to populate
the cache, we only need to transfer this extra data faster than
1.5 KB/s for overall clone + tags cache population time to be shorter.
Put into perspective, the mozilla-beta repository is ~1 GB in size.
So, this additional data constitutes <0.01% of the cloned data.
The marginal overhead for a multi-second performance win on clones
in my opinion justifies an on-by-default behavior.
# error.py - Mercurial exceptions
#
# Copyright 2005-2008 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""Mercurial exceptions.
This allows us to catch exceptions at higher levels without forcing
imports.
"""
# Do not import anything here, please
class HintException(Exception):
def __init__(self, *args, **kw):
Exception.__init__(self, *args)
self.hint = kw.get('hint')
class RevlogError(HintException):
pass
class FilteredIndexError(IndexError):
pass
class LookupError(RevlogError, KeyError):
def __init__(self, name, index, message):
self.name = name
self.index = index
# this can't be called 'message' because at least some installs of
# Python 2.6+ complain about the 'message' property being deprecated
self.lookupmessage = message
if isinstance(name, str) and len(name) == 20:
from node import short
name = short(name)
RevlogError.__init__(self, '%s@%s: %s' % (index, name, message))
def __str__(self):
return RevlogError.__str__(self)
class FilteredLookupError(LookupError):
pass
class ManifestLookupError(LookupError):
pass
class CommandError(Exception):
"""Exception raised on errors in parsing the command line."""
class InterventionRequired(Exception):
"""Exception raised when a command requires human intervention."""
class Abort(HintException):
"""Raised if a command needs to print an error and exit."""
pass
class HookAbort(Abort):
"""raised when a validation hook fails, aborting an operation
Exists to allow more specialized catching."""
pass
class ConfigError(Abort):
"""Exception raised when parsing config files"""
class OutOfBandError(Exception):
"""Exception raised when a remote repo reports failure"""
def __init__(self, *args, **kw):
Exception.__init__(self, *args)
self.hint = kw.get('hint')
class ParseError(Exception):
"""Raised when parsing config files and {rev,file}sets (msg[, pos])"""
class UnknownIdentifier(ParseError):
"""Exception raised when a {rev,file}set references an unknown identifier"""
def __init__(self, function, symbols):
from i18n import _
ParseError.__init__(self, _("unknown identifier: %s") % function)
self.function = function
self.symbols = symbols
class RepoError(HintException):
pass
class RepoLookupError(RepoError):
pass
class FilteredRepoLookupError(RepoLookupError):
pass
class CapabilityError(RepoError):
pass
class RequirementError(RepoError):
"""Exception raised if .hg/requires has an unknown entry."""
pass
class LockError(IOError):
def __init__(self, errno, strerror, filename, desc):
IOError.__init__(self, errno, strerror, filename)
self.desc = desc
class LockHeld(LockError):
def __init__(self, errno, filename, desc, locker):
LockError.__init__(self, errno, 'Lock held', filename, desc)
self.locker = locker
class LockUnavailable(LockError):
pass
class ResponseError(Exception):
"""Raised to print an error with part of output and exit."""
class UnknownCommand(Exception):
"""Exception raised if command is not in the command table."""
class AmbiguousCommand(Exception):
"""Exception raised if command shortcut matches more than one command."""
# derived from KeyboardInterrupt to simplify some breakout code
class SignalInterrupt(KeyboardInterrupt):
"""Exception raised on SIGTERM and SIGHUP."""
class SignatureError(Exception):
pass
class PushRaced(RuntimeError):
"""An exception raised during unbundling that indicate a push race"""
# bundle2 related errors
class BundleValueError(ValueError):
"""error raised when bundle2 cannot be processed"""
class UnsupportedPartError(BundleValueError):
def __init__(self, parttype=None, params=()):
self.parttype = parttype
self.params = params
if self.parttype is None:
msg = 'Stream Parameter'
else:
msg = parttype
if self.params:
msg = '%s - %s' % (msg, ', '.join(self.params))
ValueError.__init__(self, msg)
class ReadOnlyPartError(RuntimeError):
"""error raised when code tries to alter a part being generated"""
pass
class CensoredNodeError(RevlogError):
"""error raised when content verification fails on a censored node
Also contains the tombstone data substituted for the uncensored data.
"""
def __init__(self, filename, node, tombstone):
from node import short
RevlogError.__init__(self, '%s:%s' % (filename, short(node)))
self.tombstone = tombstone
class CensoredBaseError(RevlogError):
"""error raised when a delta is rejected because its base is censored
A delta based on a censored revision must be formed as single patch
operation which replaces the entire base with new content. This ensures
the delta may be applied by clones which have not censored the base.
"""