mercurial/httppeer.py

revlog: use existing file handle when reading during _addrevision

_addrevision() may need to read from revlogs as part of computing
deltas. Previously, we would flush existing file handles and open
a new, short-lived file handle to perform the reading.

If we have an existing file handle, it seems logical to reuse it
for reading instead of opening a new file handle. This patch
makes that the new behavior.

After this patch, revlog files are only reopened when adding
revisions if the revlog is switched from inline to non-inline.

On Linux when unbundling a bundle of the mozilla-central repo, this
patch has the following impact on system call counts:

Call     Before     After       Delta
write    827,639    673,390   -154,249
open     700,103    684,089    -16,014
read      74,489     74,489          0
fstat    493,924    461,896    -32,028
close    249,131    233,117    -16,014
stat     242,001    242,001          0
lstat     18,676     18,676          0
lseek     20,268     20,268          0
ioctl     14,652     13,173     -1,479
TOTAL  3,180,758  2,930,679   -250,079

It's worth noting that many of the open() calls fail due to missing
files. That's why there are many more open() calls than close().

Despite the significant system call reduction, this change does not
seem to have a significant performance impact on Linux.

On Windows 10 (not a VM, on a SSD), this patch appears to reduce
unbundle time for mozilla-central from ~960s to ~920s. This isn't
as significant as I was hoping. But a decrease it is nonetheless.
Still, Windows unbundle performance is still >2x slower than Linux.

Despite the lack of significant gains, fewer system calls is fewer
system calls. If nothing else, this will narrow the focus of potential
areas to optimize in the future.

# httppeer.py - HTTP repository proxy classes for mercurial
#
# Copyright 2005, 2006 Matt Mackall <[e-mail]>
# Copyright 2006 Vadim Gelfer <[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.

from __future__ import absolute_import

import errno
import httplib
import os
import socket
import tempfile
import urllib
import urllib2
import zlib

from .i18n import _
from .node import nullid
from . import (
    changegroup,
    error,
    httpconnection,
    statichttprepo,
    url,
    util,
    wireproto,
)

def zgenerator(f):
    zd = zlib.decompressobj()
    try:
        for chunk in util.filechunkiter(f):
            while chunk:
                yield zd.decompress(chunk, 2**18)
                chunk = zd.unconsumed_tail
    except httplib.HTTPException:
        raise IOError(None, _('connection ended unexpectedly'))
    yield zd.flush()

class httppeer(wireproto.wirepeer):
    def __init__(self, ui, path):
        self.path = path
        self.caps = None
        self.handler = None
        self.urlopener = None
        self.requestbuilder = None
        u = util.url(path)
        if u.query or u.fragment:
            raise util.Abort(_('unsupported URL component: "%s"') %
                             (u.query or u.fragment))

        # urllib cannot handle URLs with embedded user or passwd
        self._url, authinfo = u.authinfo()

        self.ui = ui
        self.ui.debug('using %s\n' % self._url)

        self.urlopener = url.opener(ui, authinfo)
        self.requestbuilder = urllib2.Request

    def __del__(self):
        if self.urlopener:
            for h in self.urlopener.handlers:
                h.close()
                getattr(h, "close_all", lambda : None)()

    def url(self):
        return self.path

    # look up capabilities only when needed

    def _fetchcaps(self):
        self.caps = set(self._call('capabilities').split())

    def _capabilities(self):
        if self.caps is None:
            try:
                self._fetchcaps()
            except error.RepoError:
                self.caps = set()
            self.ui.debug('capabilities: %s\n' %
                          (' '.join(self.caps or ['none'])))
        return self.caps

    def lock(self):
        raise util.Abort(_('operation not supported over http'))

    def _callstream(self, cmd, **args):
        if cmd == 'pushkey':
            args['data'] = ''
        data = args.pop('data', None)
        size = 0
        if util.safehasattr(data, 'length'):
            size = data.length
        elif data is not None:
            size = len(data)
        headers = args.pop('headers', {})
        if data is not None and 'Content-Type' not in headers:
            headers['Content-Type'] = 'application/mercurial-0.1'


        if size and self.ui.configbool('ui', 'usehttp2', False):
            headers['Expect'] = '100-Continue'
            headers['X-HgHttp2'] = '1'

        self.ui.debug("sending %s command\n" % cmd)
        q = [('cmd', cmd)]
        headersize = 0
        if len(args) > 0:
            httpheader = self.capable('httpheader')
            if httpheader:
                headersize = int(httpheader.split(',')[0])
        if headersize > 0:
            # The headers can typically carry more data than the URL.
            encargs = urllib.urlencode(sorted(args.items()))
            headerfmt = 'X-HgArg-%s'
            contentlen = headersize - len(headerfmt % '000' + ': \r\n')
            headernum = 0
            for i in xrange(0, len(encargs), contentlen):
                headernum += 1
                header = headerfmt % str(headernum)
                headers[header] = encargs[i:i + contentlen]
            varyheaders = [headerfmt % str(h) for h in range(1, headernum + 1)]
            headers['Vary'] = ','.join(varyheaders)
        else:
            q += sorted(args.items())
        qs = '?%s' % urllib.urlencode(q)
        cu = "%s%s" % (self._url, qs)
        req = self.requestbuilder(cu, data, headers)
        if data is not None:
            self.ui.debug("sending %s bytes\n" % size)
            req.add_unredirected_header('Content-Length', '%d' % size)
        try:
            resp = self.urlopener.open(req)
        except urllib2.HTTPError as inst:
            if inst.code == 401:
                raise util.Abort(_('authorization failed'))
            raise
        except httplib.HTTPException as inst:
            self.ui.debug('http error while sending %s command\n' % cmd)
            self.ui.traceback()
            raise IOError(None, inst)
        except IndexError:
            # this only happens with Python 2.3, later versions raise URLError
            raise util.Abort(_('http error, possibly caused by proxy setting'))
        # record the url we got redirected to
        resp_url = resp.geturl()
        if resp_url.endswith(qs):
            resp_url = resp_url[:-len(qs)]
        if self._url.rstrip('/') != resp_url.rstrip('/'):
            if not self.ui.quiet:
                self.ui.warn(_('real URL is %s\n') % resp_url)
        self._url = resp_url
        try:
            proto = resp.getheader('content-type')
        except AttributeError:
            proto = resp.headers.get('content-type', '')

        safeurl = util.hidepassword(self._url)
        if proto.startswith('application/hg-error'):
            raise error.OutOfBandError(resp.read())
        # accept old "text/plain" and "application/hg-changegroup" for now
        if not (proto.startswith('application/mercurial-') or
                (proto.startswith('text/plain')
                 and not resp.headers.get('content-length')) or
                proto.startswith('application/hg-changegroup')):
            self.ui.debug("requested URL: '%s'\n" % util.hidepassword(cu))
            raise error.RepoError(
                _("'%s' does not appear to be an hg repository:\n"
                  "---%%<--- (%s)\n%s\n---%%<---\n")
                % (safeurl, proto or 'no content-type', resp.read(1024)))

        if proto.startswith('application/mercurial-'):
            try:
                version = proto.split('-', 1)[1]
                version_info = tuple([int(n) for n in version.split('.')])
            except ValueError:
                raise error.RepoError(_("'%s' sent a broken Content-Type "
                                        "header (%s)") % (safeurl, proto))
            if version_info > (0, 1):
                raise error.RepoError(_("'%s' uses newer protocol %s") %
                                      (safeurl, version))

        return resp

    def _call(self, cmd, **args):
        fp = self._callstream(cmd, **args)
        try:
            return fp.read()
        finally:
            # if using keepalive, allow connection to be reused
            fp.close()

    def _callpush(self, cmd, cg, **args):
        # have to stream bundle to a temp file because we do not have
        # http 1.1 chunked transfer.

        types = self.capable('unbundle')
        try:
            types = types.split(',')
        except AttributeError:
            # servers older than d1b16a746db6 will send 'unbundle' as a
            # boolean capability. They only support headerless/uncompressed
            # bundles.
            types = [""]
        for x in types:
            if x in changegroup.bundletypes:
                type = x
                break

        tempname = changegroup.writebundle(self.ui, cg, None, type)
        fp = httpconnection.httpsendfile(self.ui, tempname, "rb")
        headers = {'Content-Type': 'application/mercurial-0.1'}

        try:
            r = self._call(cmd, data=fp, headers=headers, **args)
            vals = r.split('\n', 1)
            if len(vals) < 2:
                raise error.ResponseError(_("unexpected response:"), r)
            return vals
        except socket.error as err:
            if err.args[0] in (errno.ECONNRESET, errno.EPIPE):
                raise util.Abort(_('push failed: %s') % err.args[1])
            raise util.Abort(err.args[1])
        finally:
            fp.close()
            os.unlink(tempname)

    def _calltwowaystream(self, cmd, fp, **args):
        fh = None
        fp_ = None
        filename = None
        try:
            # dump bundle to disk
            fd, filename = tempfile.mkstemp(prefix="hg-bundle-", suffix=".hg")
            fh = os.fdopen(fd, "wb")
            d = fp.read(4096)
            while d:
                fh.write(d)
                d = fp.read(4096)
            fh.close()
            # start http push
            fp_ = httpconnection.httpsendfile(self.ui, filename, "rb")
            headers = {'Content-Type': 'application/mercurial-0.1'}
            return self._callstream(cmd, data=fp_, headers=headers, **args)
        finally:
            if fp_ is not None:
                fp_.close()
            if fh is not None:
                fh.close()
                os.unlink(filename)

    def _callcompressable(self, cmd, **args):
        stream =  self._callstream(cmd, **args)
        return util.chunkbuffer(zgenerator(stream))

    def _abort(self, exception):
        raise exception

class httpspeer(httppeer):
    def __init__(self, ui, path):
        if not url.has_https:
            raise util.Abort(_('Python support for SSL and HTTPS '
                               'is not installed'))
        httppeer.__init__(self, ui, path)

def instance(ui, path, create):
    if create:
        raise util.Abort(_('cannot create new http repository'))
    try:
        if path.startswith('https:'):
            inst = httpspeer(ui, path)
        else:
            inst = httppeer(ui, path)
        try:
            # Try to do useful work when checking compatibility.
            # Usually saves a roundtrip since we want the caps anyway.
            inst._fetchcaps()
        except error.RepoError:
            # No luck, try older compatibility check.
            inst.between([(nullid, nullid)])
        return inst
    except error.RepoError as httpexception:
        try:
            r = statichttprepo.instance(ui, "static-" + path, create)
            ui.note('(falling back to static-http)\n')
            return r
        except error.RepoError:
            raise httpexception # use the original http RepoError instead