view hgext/schemes.py @ 30212:260af19891f2

changegroup: increase write buffer size to 128k

By default, Python defers to the operating system for choosing the
default buffer size on opened files. On my Linux machine, the default
is 4k, which is really small for 2016.

This patch bumps the write buffer size when writing
changegroups/bundles to 128k. This matches the 128k read buffer
we already use on revlogs.

It's worth noting that this only impacts when writing to an explicit
file (such as during `hg bundle`). Buffers when writing to bundle
files via the repo vfs or to a temporary file are not impacted.

When producing a none-v2 bundle file of the mozilla-unified repository,
this change caused the number of write() system calls to drop from
952,449 to 29,788. After this change, the most frequent system
calls are fstat(), read(), lseek(), and open(). There were
2,523,672 system calls after this patch (so a net decrease of
~950k is statistically significant).

This change shows no performance change on my system. But I have a
high-end system with a fast SSD. It is quite possible this change
will have a significant impact on network file systems, where
extra network round trips due to excessive I/O system calls could
introduce significant latency.

# Copyright 2009, Alexander Solovyov <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""extend schemes with shortcuts to repository swarms

This extension allows you to specify shortcuts for parent URLs with a
lot of repositories to act like a scheme, for example::

  [schemes]
  py = http://code.python.org/hg/

After that you can use it like::

  hg clone py://trunk/

Additionally there is support for some more complex schemas, for
example used by Google Code::

  [schemes]
  gcode = http://{1}.googlecode.com/hg/

The syntax is taken from Mercurial templates, and you have unlimited
number of variables, starting with ``{1}`` and continuing with
``{2}``, ``{3}`` and so on. This variables will receive parts of URL
supplied, split by ``/``. Anything not specified as ``{part}`` will be
just appended to an URL.

For convenience, the extension adds these schemes by default::

  [schemes]
  py = http://hg.python.org/
  bb = https://bitbucket.org/
  bb+ssh = ssh://[e-mail]/
  gcode = https://{1}.googlecode.com/hg/
  kiln = https://{1}.kilnhg.com/Repo/

You can override a predefined scheme by defining a new scheme with the
same name.
"""
from __future__ import absolute_import

import os
import re

from mercurial.i18n import _
from mercurial import (
    cmdutil,
    error,
    extensions,
    hg,
    templater,
    util,
)

cmdtable = {}
command = cmdutil.command(cmdtable)
# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = 'ships-with-hg-core'


class ShortRepository(object):
    def __init__(self, url, scheme, templater):
        self.scheme = scheme
        self.templater = templater
        self.url = url
        try:
            self.parts = max(map(int, re.findall(r'\{(\d+)\}', self.url)))
        except ValueError:
            self.parts = 0

    def __repr__(self):
        return '<ShortRepository: %s>' % self.scheme

    def instance(self, ui, url, create):
        url = self.resolve(url)
        return hg._peerlookup(url).instance(ui, url, create)

    def resolve(self, url):
        # Should this use the util.url class, or is manual parsing better?
        try:
            url = url.split('://', 1)[1]
        except IndexError:
            raise error.Abort(_("no '://' in scheme url '%s'") % url)
        parts = url.split('/', self.parts)
        if len(parts) > self.parts:
            tail = parts[-1]
            parts = parts[:-1]
        else:
            tail = ''
        context = dict((str(i + 1), v) for i, v in enumerate(parts))
        return ''.join(self.templater.process(self.url, context)) + tail

def hasdriveletter(orig, path):
    if path:
        for scheme in schemes:
            if path.startswith(scheme + ':'):
                return False
    return orig(path)

schemes = {
    'py': 'http://hg.python.org/',
    'bb': 'https://bitbucket.org/',
    'bb+ssh': 'ssh://[e-mail]/',
    'gcode': 'https://{1}.googlecode.com/hg/',
    'kiln': 'https://{1}.kilnhg.com/Repo/'
    }

def extsetup(ui):
    schemes.update(dict(ui.configitems('schemes')))
    t = templater.engine(lambda x: x)
    for scheme, url in schemes.items():
        if (os.name == 'nt' and len(scheme) == 1 and scheme.isalpha()
            and os.path.exists('%s:\\' % scheme)):
            raise error.Abort(_('custom scheme %s:// conflicts with drive '
                               'letter %s:\\\n') % (scheme, scheme.upper()))
        hg.schemes[scheme] = ShortRepository(url, scheme, t)

    extensions.wrapfunction(util, 'hasdriveletter', hasdriveletter)

@command('debugexpandscheme', norepo=True)
def expandscheme(ui, url, **opts):
    """given a repo path, provide the scheme-expanded path
    """
    repo = hg._peerlookup(url)
    if isinstance(repo, ShortRepository):
        url = repo.resolve(url)
    ui.write(url + '\n')