httppeer: use compression engine API for decompressing responses

In preparation for supporting multiple compression formats on the
wire protocol, we need all users of the wire protocol to use
compression engine APIs.

This commit ports the HTTP wire protocol client to use the
compression engine API.

The code for handling the HTTPException is a bit hacky. Essentially,
HTTPException could be thrown by any read() from the socket. However,
as part of porting the API, we no longer have a generator wrapping
the socket and we don't have a single place where we can trap the
exception. We solve this by introducing a proxy class that intercepts
read() and converts the exception appropriately.

In the future, we could introduce a new compression engine API that
supports emitting a generator of decompressed chunks. This would
eliminate the need for the proxy class. As I said when I introduced
the decompressorreader() API, I'm not fond of it and would support
transitioning to something better. This can be done as a follow-up,
preferably once all the code is using the compression engine API and
we have a better idea of the API needs of all the consumers.

mercurial/httppeer.py

@@ -1,311 +1,320
 # 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 os
 import socket
 import tempfile
-import zlib
 
 from .i18n import _
 from .node import nullid
 from . import (
     bundle2,
     error,
     httpconnection,
     statichttprepo,
     url,
     util,
     wireproto,
 )
 
 httplib = util.httplib
 urlerr = util.urlerr
 urlreq = util.urlreq
 
-def zgenerator(f):
-    zd = zlib.decompressobj()
+# FUTURE: consider refactoring this API to use generators. This will
+# require a compression engine API to emit generators.
+def decompressresponse(response, engine):
     try:
-        for chunk in util.filechunkiter(f):
-            while chunk:
-                yield zd.decompress(chunk, 2**18)
-                chunk = zd.unconsumed_tail
+        reader = engine.decompressorreader(response)
     except httplib.HTTPException:
         raise IOError(None, _('connection ended unexpectedly'))
-    yield zd.flush()
+
+    # We need to wrap reader.read() so HTTPException on subsequent
+    # reads is also converted.
+    origread = reader.read
+    class readerproxy(reader.__class__):
+        def read(self, *args, **kwargs):
+            try:
+                return origread(*args, **kwargs)
+            except httplib.HTTPException:
+                raise IOError(None, _('connection ended unexpectedly'))
+
+    reader.__class__ = readerproxy
+    return reader
 
 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 error.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 = urlreq.request
 
     def __del__(self):
         urlopener = getattr(self, 'urlopener', None)
         if urlopener:
             for h in 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 error.Abort(_('operation not supported over http'))
 
     def _callstream(self, cmd, _compressible=False, **args):
         if cmd == 'pushkey':
             args['data'] = ''
         data = args.pop('data', None)
         headers = args.pop('headers', {})
 
         self.ui.debug("sending %s command\n" % cmd)
         q = [('cmd', cmd)]
         headersize = 0
         # Important: don't use self.capable() here or else you end up
         # with infinite recursion when trying to look up capabilities
         # for the first time.
         postargsok = self.caps is not None and 'httppostargs' in self.caps
         # TODO: support for httppostargs when data is a file-like
         # object rather than a basestring
         canmungedata = not data or isinstance(data, basestring)
         if postargsok and canmungedata:
             strargs = urlreq.urlencode(sorted(args.items()))
             if strargs:
                 if not data:
                     data = strargs
                 elif isinstance(data, basestring):
                     data = strargs + data
                 headers['X-HgArgs-Post'] = len(strargs)
         else:
             if len(args) > 0:
                 httpheader = self.capable('httpheader')
                 if httpheader:
                     headersize = int(httpheader.split(',', 1)[0])
             if headersize > 0:
                 # The headers can typically carry more data than the URL.
                 encargs = urlreq.urlencode(sorted(args.items()))
                 headerfmt = 'X-HgArg-%s'
                 contentlen = headersize - len(headerfmt % '000' + ': \r\n')
                 headernum = 0
                 varyheaders = []
                 for i in xrange(0, len(encargs), contentlen):
                     headernum += 1
                     header = headerfmt % str(headernum)
                     headers[header] = encargs[i:i + contentlen]
                     varyheaders.append(header)
                 headers['Vary'] = ','.join(varyheaders)
             else:
                 q += sorted(args.items())
         qs = '?%s' % urlreq.urlencode(q)
         cu = "%s%s" % (self._url, qs)
         size = 0
         if util.safehasattr(data, 'length'):
             size = data.length
         elif data is not None:
             size = len(data)
         if size and self.ui.configbool('ui', 'usehttp2', False):
             headers['Expect'] = '100-Continue'
             headers['X-HgHttp2'] = '1'
         if data is not None and 'Content-Type' not in headers:
             headers['Content-Type'] = 'application/mercurial-0.1'
         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 urlerr.httperror as inst:
             if inst.code == 401:
                 raise error.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 error.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))
 
         if _compressible:
-            return util.chunkbuffer(zgenerator(resp))
+            return decompressresponse(resp, util.compengines['zlib'])
 
         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 bundle2.bundletypes:
                 type = x
                 break
 
         tempname = bundle2.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 error.Abort(_('push failed: %s') % err.args[1])
             raise error.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):
         return self._callstream(cmd, _compressible=True, **args)
 
     def _abort(self, exception):
         raise exception
 
 class httpspeer(httppeer):
     def __init__(self, ui, path):
         if not url.has_https:
             raise error.Abort(_('Python support for SSL and HTTPS '
                                'is not installed'))
         httppeer.__init__(self, ui, path)
 
 def instance(ui, path, create):
     if create:
         raise error.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