largefiles: getlfile must hit end of HTTP chunked streams to reuse connections

We did read the exactly the right number of bytes from the response body. But
if the response came in chunked encoding then that meant that the HTTP layer
still hadn't read the last 0-sized chunk and expected the app layer to read
more data from the stream. The app layer was however happy and sent another
request which had to be sent on another HTTP connection while the old one was
lingering until some other event closed the connection.

Adding an extra read where we expect to hit the end of file makes the HTTP
connection ready for reuse. This thus plugs a real socket leak.

To distinguish HTTP from SSH we look at self's class, just like it is done in
putlfile.

hgext/largefiles/proto.py

@@ -1,167 +1,174
 # Copyright 2011 Fog Creek Software
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 import os
 import urllib2
 
 from mercurial import error, httppeer, util, wireproto
 from mercurial.wireproto import batchable, future
 from mercurial.i18n import _
 
 import lfutil
 
 LARGEFILES_REQUIRED_MSG = ('\nThis repository uses the largefiles extension.'
                            '\n\nPlease enable it in your Mercurial config '
                            'file.\n')
 
 # these will all be replaced by largefiles.uisetup
 capabilitiesorig = None
 ssholdcallstream = None
 httpoldcallstream = None
 
 def putlfile(repo, proto, sha):
     '''Put a largefile into a repository's local store and into the
     user cache.'''
     proto.redirect()
 
     path = lfutil.storepath(repo, sha)
     util.makedirs(os.path.dirname(path))
     tmpfp = util.atomictempfile(path, createmode=repo.store.createmode)
 
     try:
         try:
             proto.getfile(tmpfp)
             tmpfp._fp.seek(0)
             if sha != lfutil.hexsha1(tmpfp._fp):
                 raise IOError(0, _('largefile contents do not match hash'))
             tmpfp.close()
             lfutil.linktousercache(repo, sha)
         except IOError, e:
             repo.ui.warn(_('largefiles: failed to put %s into store: %s') %
                          (sha, e.strerror))
             return wireproto.pushres(1)
     finally:
         tmpfp.discard()
 
     return wireproto.pushres(0)
 
 def getlfile(repo, proto, sha):
     '''Retrieve a largefile from the repository-local cache or system
     cache.'''
     filename = lfutil.findfile(repo, sha)
     if not filename:
         raise util.Abort(_('requested largefile %s not present in cache') % sha)
     f = open(filename, 'rb')
     length = os.fstat(f.fileno())[6]
 
     # Since we can't set an HTTP content-length header here, and
     # Mercurial core provides no way to give the length of a streamres
     # (and reading the entire file into RAM would be ill-advised), we
     # just send the length on the first line of the response, like the
     # ssh proto does for string responses.
     def generator():
         yield '%d\n' % length
         for chunk in f:
             yield chunk
     return wireproto.streamres(generator())
 
 def statlfile(repo, proto, sha):
     '''Return '2\n' if the largefile is missing, '0\n' if it seems to be in
     good condition.
 
     The value 1 is reserved for mismatched checksum, but that is too expensive
     to be verified on every stat and must be caught be running 'hg verify'
     server side.'''
     filename = lfutil.findfile(repo, sha)
     if not filename:
         return '2\n'
     return '0\n'
 
 def wirereposetup(ui, repo):
     class lfileswirerepository(repo.__class__):
         def putlfile(self, sha, fd):
             # unfortunately, httprepository._callpush tries to convert its
             # input file-like into a bundle before sending it, so we can't use
             # it ...
             if issubclass(self.__class__, httppeer.httppeer):
                 res = None
                 try:
                     res = self._call('putlfile', data=fd, sha=sha,
                         headers={'content-type':'application/mercurial-0.1'})
                     d, output = res.split('\n', 1)
                     for l in output.splitlines(True):
                         self.ui.warn(_('remote: '), l, '\n')
                     return int(d)
                 except (ValueError, urllib2.HTTPError):
                     self.ui.warn(_('unexpected putlfile response: %s') % res)
                     return 1
             # ... but we can't use sshrepository._call because the data=
             # argument won't get sent, and _callpush does exactly what we want
             # in this case: send the data straight through
             else:
                 try:
                     ret, output = self._callpush("putlfile", fd, sha=sha)
                     if ret == "":
                         raise error.ResponseError(_('putlfile failed:'),
                                 output)
                     return int(ret)
                 except IOError:
                     return 1
                 except ValueError:
                     raise error.ResponseError(
                         _('putlfile failed (unexpected response):'), ret)
 
         def getlfile(self, sha):
             """returns an iterable with the chunks of the file with sha sha"""
             stream = self._callstream("getlfile", sha=sha)
             length = stream.readline()
             try:
                 length = int(length)
             except ValueError:
                 self._abort(error.ResponseError(_("unexpected response:"),
                                                 length))
 
             # SSH streams will block if reading more than length
             for chunk in util.filechunkiter(stream, 128 * 1024, length):
                 yield chunk
+            # HTTP streams must hit the end to process the last empty
+            # chunk of Chunked-Encoding so the connection can be reused.
+            if issubclass(self.__class__, httppeer.httppeer):
+                chunk = stream.read(1)
+                if chunk:
+                    self._abort(error.ResponseError(_("unexpected response:"),
+                                                    chunk))
 
         @batchable
         def statlfile(self, sha):
             f = future()
             result = {'sha': sha}
             yield result, f
             try:
                 yield int(f.value)
             except (ValueError, urllib2.HTTPError):
                 # If the server returns anything but an integer followed by a
                 # newline, newline, it's not speaking our language; if we get
                 # an HTTP error, we can't be sure the largefile is present;
                 # either way, consider it missing.
                 yield 2
 
     repo.__class__ = lfileswirerepository
 
 # advertise the largefiles=serve capability
 def capabilities(repo, proto):
     return capabilitiesorig(repo, proto) + ' largefiles=serve'
 
 def heads(repo, proto):
     if lfutil.islfilesrepo(repo):
         return wireproto.ooberror(LARGEFILES_REQUIRED_MSG)
     return wireproto.heads(repo, proto)
 
 def sshrepocallstream(self, cmd, **args):
     if cmd == 'heads' and self.capable('largefiles'):
         cmd = 'lheads'
     if cmd == 'batch' and self.capable('largefiles'):
         args['cmds'] = args['cmds'].replace('heads ', 'lheads ')
     return ssholdcallstream(self, cmd, **args)
 
 def httprepocallstream(self, cmd, **args):
     if cmd == 'heads' and self.capable('largefiles'):
         cmd = 'lheads'
     if cmd == 'batch' and self.capable('largefiles'):
         args['cmds'] = args['cmds'].replace('heads ', 'lheads ')
     return httpoldcallstream(self, cmd, **args)