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-rw-r--r--synapse/http/__init__.py22
-rw-r--r--synapse/http/additional_resource.py7
-rw-r--r--synapse/http/client.py45
-rw-r--r--synapse/http/endpoint.py116
-rw-r--r--synapse/http/matrixfederationclient.py69
-rw-r--r--synapse/http/request_metrics.py273
-rw-r--r--synapse/http/server.py361
-rw-r--r--synapse/http/site.py115
8 files changed, 614 insertions, 394 deletions
diff --git a/synapse/http/__init__.py b/synapse/http/__init__.py
index bfebb0f644..054372e179 100644
--- a/synapse/http/__init__.py
+++ b/synapse/http/__init__.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -12,3 +13,24 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from twisted.internet.defer import CancelledError
+from twisted.python import failure
+
+from synapse.api.errors import SynapseError
+
+
+class RequestTimedOutError(SynapseError):
+    """Exception representing timeout of an outbound request"""
+    def __init__(self):
+        super(RequestTimedOutError, self).__init__(504, "Timed out")
+
+
+def cancelled_to_request_timed_out_error(value, timeout):
+    """Turns CancelledErrors into RequestTimedOutErrors.
+
+    For use with async.add_timeout_to_deferred
+    """
+    if isinstance(value, failure.Failure):
+        value.trap(CancelledError)
+        raise RequestTimedOutError()
+    return value
diff --git a/synapse/http/additional_resource.py b/synapse/http/additional_resource.py
index 343e932cb1..a797396ade 100644
--- a/synapse/http/additional_resource.py
+++ b/synapse/http/additional_resource.py
@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.http.server import wrap_request_handler
+from synapse.http.server import wrap_json_request_handler
 from twisted.web.resource import Resource
 from twisted.web.server import NOT_DONE_YET
 
@@ -42,14 +42,13 @@ class AdditionalResource(Resource):
         Resource.__init__(self)
         self._handler = handler
 
-        # these are required by the request_handler wrapper
-        self.version_string = hs.version_string
+        # required by the request_handler wrapper
         self.clock = hs.get_clock()
 
     def render(self, request):
         self._async_render(request)
         return NOT_DONE_YET
 
-    @wrap_request_handler
+    @wrap_json_request_handler
     def _async_render(self, request):
         return self._handler(request)
diff --git a/synapse/http/client.py b/synapse/http/client.py
index f3e4973c2e..4d4eee3d64 100644
--- a/synapse/http/client.py
+++ b/synapse/http/client.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -18,10 +19,10 @@ from OpenSSL.SSL import VERIFY_NONE
 from synapse.api.errors import (
     CodeMessageException, MatrixCodeMessageException, SynapseError, Codes,
 )
+from synapse.http import cancelled_to_request_timed_out_error
+from synapse.util.async import add_timeout_to_deferred
 from synapse.util.caches import CACHE_SIZE_FACTOR
 from synapse.util.logcontext import make_deferred_yieldable
-from synapse.util import logcontext
-import synapse.metrics
 from synapse.http.endpoint import SpiderEndpoint
 
 from canonicaljson import encode_canonical_json
@@ -38,8 +39,9 @@ from twisted.web.http import PotentialDataLoss
 from twisted.web.http_headers import Headers
 from twisted.web._newclient import ResponseDone
 
-from StringIO import StringIO
+from six import StringIO
 
+from prometheus_client import Counter
 import simplejson as json
 import logging
 import urllib
@@ -47,16 +49,9 @@ import urllib
 
 logger = logging.getLogger(__name__)
 
-metrics = synapse.metrics.get_metrics_for(__name__)
-
-outgoing_requests_counter = metrics.register_counter(
-    "requests",
-    labels=["method"],
-)
-incoming_responses_counter = metrics.register_counter(
-    "responses",
-    labels=["method", "code"],
-)
+outgoing_requests_counter = Counter("synapse_http_client_requests", "", ["method"])
+incoming_responses_counter = Counter("synapse_http_client_responses", "",
+                                     ["method", "code"])
 
 
 class SimpleHttpClient(object):
@@ -93,32 +88,28 @@ class SimpleHttpClient(object):
     def request(self, method, uri, *args, **kwargs):
         # A small wrapper around self.agent.request() so we can easily attach
         # counters to it
-        outgoing_requests_counter.inc(method)
+        outgoing_requests_counter.labels(method).inc()
 
-        def send_request():
+        logger.info("Sending request %s %s", method, uri)
+
+        try:
             request_deferred = self.agent.request(
                 method, uri, *args, **kwargs
             )
-
-            return self.clock.time_bound_deferred(
+            add_timeout_to_deferred(
                 request_deferred,
-                time_out=60,
+                60, cancelled_to_request_timed_out_error,
             )
+            response = yield make_deferred_yieldable(request_deferred)
 
-        logger.info("Sending request %s %s", method, uri)
-
-        try:
-            with logcontext.PreserveLoggingContext():
-                response = yield send_request()
-
-            incoming_responses_counter.inc(method, response.code)
+            incoming_responses_counter.labels(method, response.code).inc()
             logger.info(
                 "Received response to  %s %s: %s",
                 method, uri, response.code
             )
             defer.returnValue(response)
         except Exception as e:
-            incoming_responses_counter.inc(method, "ERR")
+            incoming_responses_counter.labels(method, "ERR").inc()
             logger.info(
                 "Error sending request to  %s %s: %s %s",
                 method, uri, type(e).__name__, e.message
@@ -509,7 +500,7 @@ class SpiderHttpClient(SimpleHttpClient):
                     reactor,
                     SpiderEndpointFactory(hs)
                 )
-            ), [('gzip', GzipDecoder)]
+            ), [(b'gzip', GzipDecoder)]
         )
         # We could look like Chrome:
         # self.user_agent = ("Mozilla/5.0 (%s) (KHTML, like Gecko)
diff --git a/synapse/http/endpoint.py b/synapse/http/endpoint.py
index 87639b9151..87a482650d 100644
--- a/synapse/http/endpoint.py
+++ b/synapse/http/endpoint.py
@@ -12,8 +12,6 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-import socket
-
 from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
 from twisted.internet import defer, reactor
 from twisted.internet.error import ConnectError
@@ -33,7 +31,7 @@ SERVER_CACHE = {}
 
 # our record of an individual server which can be tried to reach a destination.
 #
-# "host" is actually a dotted-quad or ipv6 address string. Except when there's
+# "host" is the hostname acquired from the SRV record. Except when there's
 # no SRV record, in which case it is the original hostname.
 _Server = collections.namedtuple(
     "_Server", "priority weight host port expires"
@@ -117,10 +115,15 @@ class _WrappedConnection(object):
         if time.time() - self.last_request >= 2.5 * 60:
             self.abort()
             # Abort the underlying TLS connection. The abort() method calls
-            # loseConnection() on the underlying TLS connection which tries to
+            # loseConnection() on the TLS connection which tries to
             # shutdown the connection cleanly. We call abortConnection()
-            # since that will promptly close the underlying TCP connection.
-            self.transport.abortConnection()
+            # since that will promptly close the TLS connection.
+            #
+            # In Twisted >18.4; the TLS connection will be None if it has closed
+            # which will make abortConnection() throw. Check that the TLS connection
+            # is not None before trying to close it.
+            if self.transport.getHandle() is not None:
+                self.transport.abortConnection()
 
     def request(self, request):
         self.last_request = time.time()
@@ -288,7 +291,7 @@ def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE, clock=t
         if (len(answers) == 1
                 and answers[0].type == dns.SRV
                 and answers[0].payload
-                and answers[0].payload.target == dns.Name('.')):
+                and answers[0].payload.target == dns.Name(b'.')):
             raise ConnectError("Service %s unavailable" % service_name)
 
         for answer in answers:
@@ -297,20 +300,13 @@ def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE, clock=t
 
             payload = answer.payload
 
-            hosts = yield _get_hosts_for_srv_record(
-                dns_client, str(payload.target)
-            )
-
-            for (ip, ttl) in hosts:
-                host_ttl = min(answer.ttl, ttl)
-
-                servers.append(_Server(
-                    host=ip,
-                    port=int(payload.port),
-                    priority=int(payload.priority),
-                    weight=int(payload.weight),
-                    expires=int(clock.time()) + host_ttl,
-                ))
+            servers.append(_Server(
+                host=str(payload.target),
+                port=int(payload.port),
+                priority=int(payload.priority),
+                weight=int(payload.weight),
+                expires=int(clock.time()) + answer.ttl,
+            ))
 
         servers.sort()
         cache[service_name] = list(servers)
@@ -328,81 +324,3 @@ def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE, clock=t
             raise e
 
     defer.returnValue(servers)
-
-
-@defer.inlineCallbacks
-def _get_hosts_for_srv_record(dns_client, host):
-    """Look up each of the hosts in a SRV record
-
-    Args:
-        dns_client (twisted.names.dns.IResolver):
-        host (basestring): host to look up
-
-    Returns:
-        Deferred[list[(str, int)]]: a list of (host, ttl) pairs
-
-    """
-    ip4_servers = []
-    ip6_servers = []
-
-    def cb(res):
-        # lookupAddress and lookupIP6Address return a three-tuple
-        # giving the answer, authority, and additional sections of the
-        # response.
-        #
-        # we only care about the answers.
-
-        return res[0]
-
-    def eb(res, record_type):
-        if res.check(DNSNameError):
-            return []
-        logger.warn("Error looking up %s for %s: %s", record_type, host, res)
-        return res
-
-    # no logcontexts here, so we can safely fire these off and gatherResults
-    d1 = dns_client.lookupAddress(host).addCallbacks(
-        cb, eb, errbackArgs=("A", ))
-    d2 = dns_client.lookupIPV6Address(host).addCallbacks(
-        cb, eb, errbackArgs=("AAAA", ))
-    results = yield defer.DeferredList(
-        [d1, d2], consumeErrors=True)
-
-    # if all of the lookups failed, raise an exception rather than blowing out
-    # the cache with an empty result.
-    if results and all(s == defer.FAILURE for (s, _) in results):
-        defer.returnValue(results[0][1])
-
-    for (success, result) in results:
-        if success == defer.FAILURE:
-            continue
-
-        for answer in result:
-            if not answer.payload:
-                continue
-
-            try:
-                if answer.type == dns.A:
-                    ip = answer.payload.dottedQuad()
-                    ip4_servers.append((ip, answer.ttl))
-                elif answer.type == dns.AAAA:
-                    ip = socket.inet_ntop(
-                        socket.AF_INET6, answer.payload.address,
-                    )
-                    ip6_servers.append((ip, answer.ttl))
-                else:
-                    # the most likely candidate here is a CNAME record.
-                    # rfc2782 says srvs may not point to aliases.
-                    logger.warn(
-                        "Ignoring unexpected DNS record type %s for %s",
-                        answer.type, host,
-                    )
-                    continue
-            except Exception as e:
-                logger.warn("Ignoring invalid DNS response for %s: %s",
-                            host, e)
-                continue
-
-    # keep the ipv4 results before the ipv6 results, mostly to match historical
-    # behaviour.
-    defer.returnValue(ip4_servers + ip6_servers)
diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index 9145405cb0..821aed362b 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2018 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -12,17 +13,19 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-import synapse.util.retryutils
 from twisted.internet import defer, reactor, protocol
 from twisted.internet.error import DNSLookupError
 from twisted.web.client import readBody, HTTPConnectionPool, Agent
 from twisted.web.http_headers import Headers
 from twisted.web._newclient import ResponseDone
 
+from synapse.http import cancelled_to_request_timed_out_error
 from synapse.http.endpoint import matrix_federation_endpoint
-from synapse.util.async import sleep
-from synapse.util import logcontext
 import synapse.metrics
+from synapse.util.async import sleep, add_timeout_to_deferred
+from synapse.util import logcontext
+from synapse.util.logcontext import make_deferred_yieldable
+import synapse.util.retryutils
 
 from canonicaljson import encode_canonical_json
 
@@ -38,22 +41,19 @@ import logging
 import random
 import sys
 import urllib
-import urlparse
+from six.moves.urllib import parse as urlparse
+from six import string_types
+
 
+from prometheus_client import Counter
 
 logger = logging.getLogger(__name__)
 outbound_logger = logging.getLogger("synapse.http.outbound")
 
-metrics = synapse.metrics.get_metrics_for(__name__)
-
-outgoing_requests_counter = metrics.register_counter(
-    "requests",
-    labels=["method"],
-)
-incoming_responses_counter = metrics.register_counter(
-    "responses",
-    labels=["method", "code"],
-)
+outgoing_requests_counter = Counter("synapse_http_matrixfederationclient_requests",
+                                    "", ["method"])
+incoming_responses_counter = Counter("synapse_http_matrixfederationclient_responses",
+                                     "", ["method", "code"])
 
 
 MAX_LONG_RETRIES = 10
@@ -184,21 +184,20 @@ class MatrixFederationHttpClient(object):
                         producer = body_callback(method, http_url_bytes, headers_dict)
 
                     try:
-                        def send_request():
-                            request_deferred = self.agent.request(
-                                method,
-                                url_bytes,
-                                Headers(headers_dict),
-                                producer
-                            )
-
-                            return self.clock.time_bound_deferred(
-                                request_deferred,
-                                time_out=timeout / 1000. if timeout else 60,
-                            )
-
-                        with logcontext.PreserveLoggingContext():
-                            response = yield send_request()
+                        request_deferred = self.agent.request(
+                            method,
+                            url_bytes,
+                            Headers(headers_dict),
+                            producer
+                        )
+                        add_timeout_to_deferred(
+                            request_deferred,
+                            timeout / 1000. if timeout else 60,
+                            cancelled_to_request_timed_out_error,
+                        )
+                        response = yield make_deferred_yieldable(
+                            request_deferred,
+                        )
 
                         log_result = "%d %s" % (response.code, response.phrase,)
                         break
@@ -286,7 +285,8 @@ class MatrixFederationHttpClient(object):
         headers_dict[b"Authorization"] = auth_headers
 
     @defer.inlineCallbacks
-    def put_json(self, destination, path, data={}, json_data_callback=None,
+    def put_json(self, destination, path, args={}, data={},
+                 json_data_callback=None,
                  long_retries=False, timeout=None,
                  ignore_backoff=False,
                  backoff_on_404=False):
@@ -296,6 +296,7 @@ class MatrixFederationHttpClient(object):
             destination (str): The remote server to send the HTTP request
                 to.
             path (str): The HTTP path.
+            args (dict): query params
             data (dict): A dict containing the data that will be used as
                 the request body. This will be encoded as JSON.
             json_data_callback (callable): A callable returning the dict to
@@ -342,6 +343,7 @@ class MatrixFederationHttpClient(object):
             path,
             body_callback=body_callback,
             headers_dict={"Content-Type": ["application/json"]},
+            query_bytes=encode_query_args(args),
             long_retries=long_retries,
             timeout=timeout,
             ignore_backoff=ignore_backoff,
@@ -373,6 +375,7 @@ class MatrixFederationHttpClient(object):
                 giving up. None indicates no timeout.
             ignore_backoff (bool): true to ignore the historical backoff data and
                 try the request anyway.
+            args (dict): query params
         Returns:
             Deferred: Succeeds when we get a 2xx HTTP response. The result
             will be the decoded JSON body.
@@ -548,7 +551,7 @@ class MatrixFederationHttpClient(object):
 
         encoded_args = {}
         for k, vs in args.items():
-            if isinstance(vs, basestring):
+            if isinstance(vs, string_types):
                 vs = [vs]
             encoded_args[k] = [v.encode("UTF-8") for v in vs]
 
@@ -663,7 +666,7 @@ def check_content_type_is_json(headers):
         RuntimeError if the
 
     """
-    c_type = headers.getRawHeaders("Content-Type")
+    c_type = headers.getRawHeaders(b"Content-Type")
     if c_type is None:
         raise RuntimeError(
             "No Content-Type header"
@@ -680,7 +683,7 @@ def check_content_type_is_json(headers):
 def encode_query_args(args):
     encoded_args = {}
     for k, vs in args.items():
-        if isinstance(vs, basestring):
+        if isinstance(vs, string_types):
             vs = [vs]
         encoded_args[k] = [v.encode("UTF-8") for v in vs]
 
diff --git a/synapse/http/request_metrics.py b/synapse/http/request_metrics.py
new file mode 100644
index 0000000000..dc06f6c443
--- /dev/null
+++ b/synapse/http/request_metrics.py
@@ -0,0 +1,273 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2018 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import logging
+
+from prometheus_client.core import Counter, Histogram
+from synapse.metrics import LaterGauge
+
+from synapse.util.logcontext import LoggingContext
+
+logger = logging.getLogger(__name__)
+
+
+# total number of responses served, split by method/servlet/tag
+response_count = Counter(
+    "synapse_http_server_response_count", "", ["method", "servlet", "tag"]
+)
+
+requests_counter = Counter(
+    "synapse_http_server_requests_received", "", ["method", "servlet"]
+)
+
+outgoing_responses_counter = Counter(
+    "synapse_http_server_responses", "", ["method", "code"]
+)
+
+response_timer = Histogram(
+    "synapse_http_server_response_time_seconds", "sec", ["method", "servlet", "tag"]
+)
+
+response_ru_utime = Counter(
+    "synapse_http_server_response_ru_utime_seconds", "sec", ["method", "servlet", "tag"]
+)
+
+response_ru_stime = Counter(
+    "synapse_http_server_response_ru_stime_seconds", "sec", ["method", "servlet", "tag"]
+)
+
+response_db_txn_count = Counter(
+    "synapse_http_server_response_db_txn_count", "", ["method", "servlet", "tag"]
+)
+
+# seconds spent waiting for db txns, excluding scheduling time, when processing
+# this request
+response_db_txn_duration = Counter(
+    "synapse_http_server_response_db_txn_duration_seconds",
+    "",
+    ["method", "servlet", "tag"],
+)
+
+# seconds spent waiting for a db connection, when processing this request
+response_db_sched_duration = Counter(
+    "synapse_http_server_response_db_sched_duration_seconds",
+    "",
+    ["method", "servlet", "tag"],
+)
+
+# size in bytes of the response written
+response_size = Counter(
+    "synapse_http_server_response_size", "", ["method", "servlet", "tag"]
+)
+
+# In flight metrics are incremented while the requests are in flight, rather
+# than when the response was written.
+
+in_flight_requests_ru_utime = Counter(
+    "synapse_http_server_in_flight_requests_ru_utime_seconds",
+    "",
+    ["method", "servlet"],
+)
+
+in_flight_requests_ru_stime = Counter(
+    "synapse_http_server_in_flight_requests_ru_stime_seconds",
+    "",
+    ["method", "servlet"],
+)
+
+in_flight_requests_db_txn_count = Counter(
+    "synapse_http_server_in_flight_requests_db_txn_count", "", ["method", "servlet"]
+)
+
+# seconds spent waiting for db txns, excluding scheduling time, when processing
+# this request
+in_flight_requests_db_txn_duration = Counter(
+    "synapse_http_server_in_flight_requests_db_txn_duration_seconds",
+    "",
+    ["method", "servlet"],
+)
+
+# seconds spent waiting for a db connection, when processing this request
+in_flight_requests_db_sched_duration = Counter(
+    "synapse_http_server_in_flight_requests_db_sched_duration_seconds",
+    "",
+    ["method", "servlet"],
+)
+
+# The set of all in flight requests, set[RequestMetrics]
+_in_flight_requests = set()
+
+
+def _get_in_flight_counts():
+    """Returns a count of all in flight requests by (method, server_name)
+
+    Returns:
+        dict[tuple[str, str], int]
+    """
+    for rm in _in_flight_requests:
+        rm.update_metrics()
+
+    # Map from (method, name) -> int, the number of in flight requests of that
+    # type
+    counts = {}
+    for rm in _in_flight_requests:
+        key = (rm.method, rm.name,)
+        counts[key] = counts.get(key, 0) + 1
+
+    return counts
+
+
+LaterGauge(
+    "synapse_http_request_metrics_in_flight_requests_count",
+    "",
+    ["method", "servlet"],
+    _get_in_flight_counts,
+)
+
+
+class RequestMetrics(object):
+    def start(self, time_sec, name, method):
+        self.start = time_sec
+        self.start_context = LoggingContext.current_context()
+        self.name = name
+        self.method = method
+
+        self._request_stats = _RequestStats.from_context(self.start_context)
+
+        _in_flight_requests.add(self)
+
+    def stop(self, time_sec, request):
+        _in_flight_requests.discard(self)
+
+        context = LoggingContext.current_context()
+
+        tag = ""
+        if context:
+            tag = context.tag
+
+            if context != self.start_context:
+                logger.warn(
+                    "Context have unexpectedly changed %r, %r",
+                    context, self.start_context
+                )
+                return
+
+        outgoing_responses_counter.labels(request.method, str(request.code)).inc()
+
+        response_count.labels(request.method, self.name, tag).inc()
+
+        response_timer.labels(request.method, self.name, tag).observe(
+            time_sec - self.start
+        )
+
+        ru_utime, ru_stime = context.get_resource_usage()
+
+        response_ru_utime.labels(request.method, self.name, tag).inc(ru_utime)
+        response_ru_stime.labels(request.method, self.name, tag).inc(ru_stime)
+        response_db_txn_count.labels(request.method, self.name, tag).inc(
+            context.db_txn_count
+        )
+        response_db_txn_duration.labels(request.method, self.name, tag).inc(
+            context.db_txn_duration_sec
+        )
+        response_db_sched_duration.labels(request.method, self.name, tag).inc(
+            context.db_sched_duration_sec
+        )
+
+        response_size.labels(request.method, self.name, tag).inc(request.sentLength)
+
+        # We always call this at the end to ensure that we update the metrics
+        # regardless of whether a call to /metrics while the request was in
+        # flight.
+        self.update_metrics()
+
+    def update_metrics(self):
+        """Updates the in flight metrics with values from this request.
+        """
+        diff = self._request_stats.update(self.start_context)
+
+        in_flight_requests_ru_utime.labels(self.method, self.name).inc(diff.ru_utime)
+        in_flight_requests_ru_stime.labels(self.method, self.name).inc(diff.ru_stime)
+
+        in_flight_requests_db_txn_count.labels(self.method, self.name).inc(
+            diff.db_txn_count
+        )
+
+        in_flight_requests_db_txn_duration.labels(self.method, self.name).inc(
+            diff.db_txn_duration_sec
+        )
+
+        in_flight_requests_db_sched_duration.labels(self.method, self.name).inc(
+            diff.db_sched_duration_sec
+        )
+
+
+class _RequestStats(object):
+    """Keeps tracks of various metrics for an in flight request.
+    """
+
+    __slots__ = [
+        "ru_utime",
+        "ru_stime",
+        "db_txn_count",
+        "db_txn_duration_sec",
+        "db_sched_duration_sec",
+    ]
+
+    def __init__(
+        self, ru_utime, ru_stime, db_txn_count, db_txn_duration_sec, db_sched_duration_sec
+    ):
+        self.ru_utime = ru_utime
+        self.ru_stime = ru_stime
+        self.db_txn_count = db_txn_count
+        self.db_txn_duration_sec = db_txn_duration_sec
+        self.db_sched_duration_sec = db_sched_duration_sec
+
+    @staticmethod
+    def from_context(context):
+        ru_utime, ru_stime = context.get_resource_usage()
+
+        return _RequestStats(
+            ru_utime, ru_stime,
+            context.db_txn_count,
+            context.db_txn_duration_sec,
+            context.db_sched_duration_sec,
+        )
+
+    def update(self, context):
+        """Updates the current values and returns the difference between the
+        old and new values.
+
+        Returns:
+            _RequestStats: The difference between the old and new values
+        """
+        new = _RequestStats.from_context(context)
+
+        diff = _RequestStats(
+            new.ru_utime - self.ru_utime,
+            new.ru_stime - self.ru_stime,
+            new.db_txn_count - self.db_txn_count,
+            new.db_txn_duration_sec - self.db_txn_duration_sec,
+            new.db_sched_duration_sec - self.db_sched_duration_sec,
+        )
+
+        self.ru_utime = new.ru_utime
+        self.ru_stime = new.ru_stime
+        self.db_txn_count = new.db_txn_count
+        self.db_txn_duration_sec = new.db_txn_duration_sec
+        self.db_sched_duration_sec = new.db_sched_duration_sec
+
+        return diff
diff --git a/synapse/http/server.py b/synapse/http/server.py
index e64aa92729..bc09b8b2be 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -13,11 +13,15 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
+import cgi
+from six.moves import http_client
 
 from synapse.api.errors import (
     cs_exception, SynapseError, CodeMessageException, UnrecognizedRequestError, Codes
 )
+from synapse.http.request_metrics import (
+    requests_counter,
+)
 from synapse.util.logcontext import LoggingContext, PreserveLoggingContext
 from synapse.util.caches import intern_dict
 from synapse.util.metrics import Measure
@@ -41,173 +45,174 @@ import simplejson
 
 logger = logging.getLogger(__name__)
 
-metrics = synapse.metrics.get_metrics_for(__name__)
-
-# total number of responses served, split by method/servlet/tag
-response_count = metrics.register_counter(
-    "response_count",
-    labels=["method", "servlet", "tag"],
-    alternative_names=(
-        # the following are all deprecated aliases for the same metric
-        metrics.name_prefix + x for x in (
-            "_requests",
-            "_response_time:count",
-            "_response_ru_utime:count",
-            "_response_ru_stime:count",
-            "_response_db_txn_count:count",
-            "_response_db_txn_duration:count",
-        )
-    )
-)
+HTML_ERROR_TEMPLATE = """<!DOCTYPE html>
+<html lang=en>
+  <head>
+    <meta charset="utf-8">
+    <title>Error {code}</title>
+  </head>
+  <body>
+     <p>{msg}</p>
+  </body>
+</html>
+"""
 
-requests_counter = metrics.register_counter(
-    "requests_received",
-    labels=["method", "servlet", ],
-)
 
-outgoing_responses_counter = metrics.register_counter(
-    "responses",
-    labels=["method", "code"],
-)
+def wrap_json_request_handler(h):
+    """Wraps a request handler method with exception handling.
 
-response_timer = metrics.register_counter(
-    "response_time_seconds",
-    labels=["method", "servlet", "tag"],
-    alternative_names=(
-        metrics.name_prefix + "_response_time:total",
-    ),
-)
+    Also adds logging as per wrap_request_handler_with_logging.
 
-response_ru_utime = metrics.register_counter(
-    "response_ru_utime_seconds", labels=["method", "servlet", "tag"],
-    alternative_names=(
-        metrics.name_prefix + "_response_ru_utime:total",
-    ),
-)
+    The handler method must have a signature of "handle_foo(self, request)",
+    where "self" must have a "clock" attribute (and "request" must be a
+    SynapseRequest).
 
-response_ru_stime = metrics.register_counter(
-    "response_ru_stime_seconds", labels=["method", "servlet", "tag"],
-    alternative_names=(
-        metrics.name_prefix + "_response_ru_stime:total",
-    ),
-)
+    The handler must return a deferred. If the deferred succeeds we assume that
+    a response has been sent. If the deferred fails with a SynapseError we use
+    it to send a JSON response with the appropriate HTTP reponse code. If the
+    deferred fails with any other type of error we send a 500 reponse.
+    """
 
-response_db_txn_count = metrics.register_counter(
-    "response_db_txn_count", labels=["method", "servlet", "tag"],
-    alternative_names=(
-        metrics.name_prefix + "_response_db_txn_count:total",
-    ),
-)
+    @defer.inlineCallbacks
+    def wrapped_request_handler(self, request):
+        try:
+            yield h(self, request)
+        except CodeMessageException as e:
+            code = e.code
+            if isinstance(e, SynapseError):
+                logger.info(
+                    "%s SynapseError: %s - %s", request, code, e.msg
+                )
+            else:
+                logger.exception(e)
+            respond_with_json(
+                request, code, cs_exception(e), send_cors=True,
+                pretty_print=_request_user_agent_is_curl(request),
+            )
 
-# seconds spent waiting for db txns, excluding scheduling time, when processing
-# this request
-response_db_txn_duration = metrics.register_counter(
-    "response_db_txn_duration_seconds", labels=["method", "servlet", "tag"],
-    alternative_names=(
-        metrics.name_prefix + "_response_db_txn_duration:total",
-    ),
-)
+        except Exception:
+            # failure.Failure() fishes the original Failure out
+            # of our stack, and thus gives us a sensible stack
+            # trace.
+            f = failure.Failure()
+            logger.error(
+                "Failed handle request via %r: %r: %s",
+                h,
+                request,
+                f.getTraceback().rstrip(),
+            )
+            respond_with_json(
+                request,
+                500,
+                {
+                    "error": "Internal server error",
+                    "errcode": Codes.UNKNOWN,
+                },
+                send_cors=True,
+                pretty_print=_request_user_agent_is_curl(request),
+            )
 
-# seconds spent waiting for a db connection, when processing this request
-response_db_sched_duration = metrics.register_counter(
-    "response_db_sched_duration_seconds", labels=["method", "servlet", "tag"]
-)
+    return wrap_request_handler_with_logging(wrapped_request_handler)
 
-_next_request_id = 0
 
+def wrap_html_request_handler(h):
+    """Wraps a request handler method with exception handling.
 
-def request_handler(include_metrics=False):
-    """Decorator for ``wrap_request_handler``"""
-    return lambda request_handler: wrap_request_handler(request_handler, include_metrics)
+    Also adds logging as per wrap_request_handler_with_logging.
 
+    The handler method must have a signature of "handle_foo(self, request)",
+    where "self" must have a "clock" attribute (and "request" must be a
+    SynapseRequest).
+    """
+    def wrapped_request_handler(self, request):
+        d = defer.maybeDeferred(h, self, request)
+        d.addErrback(_return_html_error, request)
+        return d
 
-def wrap_request_handler(request_handler, include_metrics=False):
-    """Wraps a method that acts as a request handler with the necessary logging
-    and exception handling.
+    return wrap_request_handler_with_logging(wrapped_request_handler)
 
-    The method must have a signature of "handle_foo(self, request)". The
-    argument "self" must have "version_string" and "clock" attributes. The
-    argument "request" must be a twisted HTTP request.
 
-    The method must return a deferred. If the deferred succeeds we assume that
-    a response has been sent. If the deferred fails with a SynapseError we use
-    it to send a JSON response with the appropriate HTTP reponse code. If the
-    deferred fails with any other type of error we send a 500 reponse.
+def _return_html_error(f, request):
+    """Sends an HTML error page corresponding to the given failure
 
-    We insert a unique request-id into the logging context for this request and
-    log the response and duration for this request.
+    Args:
+        f (twisted.python.failure.Failure):
+        request (twisted.web.iweb.IRequest):
     """
+    if f.check(CodeMessageException):
+        cme = f.value
+        code = cme.code
+        msg = cme.msg
+
+        if isinstance(cme, SynapseError):
+            logger.info(
+                "%s SynapseError: %s - %s", request, code, msg
+            )
+        else:
+            logger.error(
+                "Failed handle request %r: %s",
+                request,
+                f.getTraceback().rstrip(),
+            )
+    else:
+        code = http_client.INTERNAL_SERVER_ERROR
+        msg = "Internal server error"
+
+        logger.error(
+            "Failed handle request %r: %s",
+            request,
+            f.getTraceback().rstrip(),
+        )
+
+    body = HTML_ERROR_TEMPLATE.format(
+        code=code, msg=cgi.escape(msg),
+    ).encode("utf-8")
+    request.setResponseCode(code)
+    request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
+    request.setHeader(b"Content-Length", b"%i" % (len(body),))
+    request.write(body)
+    finish_request(request)
+
+
+def wrap_request_handler_with_logging(h):
+    """Wraps a request handler to provide logging and metrics
 
+    The handler method must have a signature of "handle_foo(self, request)",
+    where "self" must have a "clock" attribute (and "request" must be a
+    SynapseRequest).
+
+    As well as calling `request.processing` (which will log the response and
+    duration for this request), the wrapped request handler will insert the
+    request id into the logging context.
+    """
     @defer.inlineCallbacks
     def wrapped_request_handler(self, request):
-        global _next_request_id
-        request_id = "%s-%s" % (request.method, _next_request_id)
-        _next_request_id += 1
+        """
+        Args:
+            self:
+            request (synapse.http.site.SynapseRequest):
+        """
 
+        request_id = request.get_request_id()
         with LoggingContext(request_id) as request_context:
+            request_context.request = request_id
             with Measure(self.clock, "wrapped_request_handler"):
-                request_metrics = RequestMetrics()
                 # we start the request metrics timer here with an initial stab
                 # at the servlet name. For most requests that name will be
                 # JsonResource (or a subclass), and JsonResource._async_render
                 # will update it once it picks a servlet.
                 servlet_name = self.__class__.__name__
-                request_metrics.start(self.clock, name=servlet_name)
-
-                request_context.request = request_id
-                with request.processing():
-                    try:
-                        with PreserveLoggingContext(request_context):
-                            if include_metrics:
-                                yield request_handler(self, request, request_metrics)
-                            else:
-                                requests_counter.inc(request.method, servlet_name)
-                                yield request_handler(self, request)
-                    except CodeMessageException as e:
-                        code = e.code
-                        if isinstance(e, SynapseError):
-                            logger.info(
-                                "%s SynapseError: %s - %s", request, code, e.msg
-                            )
-                        else:
-                            logger.exception(e)
-                        outgoing_responses_counter.inc(request.method, str(code))
-                        respond_with_json(
-                            request, code, cs_exception(e), send_cors=True,
-                            pretty_print=_request_user_agent_is_curl(request),
-                            version_string=self.version_string,
-                        )
-                    except Exception:
-                        # failure.Failure() fishes the original Failure out
-                        # of our stack, and thus gives us a sensible stack
-                        # trace.
-                        f = failure.Failure()
-                        logger.error(
-                            "Failed handle request %s.%s on %r: %r: %s",
-                            request_handler.__module__,
-                            request_handler.__name__,
-                            self,
-                            request,
-                            f.getTraceback().rstrip(),
-                        )
-                        respond_with_json(
-                            request,
-                            500,
-                            {
-                                "error": "Internal server error",
-                                "errcode": Codes.UNKNOWN,
-                            },
-                            send_cors=True,
-                            pretty_print=_request_user_agent_is_curl(request),
-                            version_string=self.version_string,
-                        )
-                    finally:
-                        try:
-                            request_metrics.stop(
-                                self.clock, request
-                            )
-                        except Exception as e:
-                            logger.warn("Failed to stop metrics: %r", e)
+                with request.processing(servlet_name):
+                    with PreserveLoggingContext(request_context):
+                        d = defer.maybeDeferred(h, self, request)
+
+                        # record the arrival of the request *after*
+                        # dispatching to the handler, so that the handler
+                        # can update the servlet name in the request
+                        # metrics
+                        requests_counter.labels(request.method,
+                                                request.request_metrics.name).inc()
+                        yield d
     return wrapped_request_handler
 
 
@@ -257,7 +262,6 @@ class JsonResource(HttpServer, resource.Resource):
         self.canonical_json = canonical_json
         self.clock = hs.get_clock()
         self.path_regexs = {}
-        self.version_string = hs.version_string
         self.hs = hs
 
     def register_paths(self, method, path_patterns, callback):
@@ -273,13 +277,9 @@ class JsonResource(HttpServer, resource.Resource):
         self._async_render(request)
         return server.NOT_DONE_YET
 
-    # Disable metric reporting because _async_render does its own metrics.
-    # It does its own metric reporting because _async_render dispatches to
-    # a callback and it's the class name of that callback we want to report
-    # against rather than the JsonResource itself.
-    @request_handler(include_metrics=True)
+    @wrap_json_request_handler
     @defer.inlineCallbacks
-    def _async_render(self, request, request_metrics):
+    def _async_render(self, request):
         """ This gets called from render() every time someone sends us a request.
             This checks if anyone has registered a callback for that method and
             path.
@@ -291,9 +291,7 @@ class JsonResource(HttpServer, resource.Resource):
             servlet_classname = servlet_instance.__class__.__name__
         else:
             servlet_classname = "%r" % callback
-
-        request_metrics.name = servlet_classname
-        requests_counter.inc(request.method, servlet_classname)
+        request.request_metrics.name = servlet_classname
 
         # Now trigger the callback. If it returns a response, we send it
         # here. If it throws an exception, that is handled by the wrapper
@@ -324,7 +322,7 @@ class JsonResource(HttpServer, resource.Resource):
                 register_paths, so will return (possibly via Deferred) either
                 None, or a tuple of (http code, response body).
         """
-        if request.method == "OPTIONS":
+        if request.method == b"OPTIONS":
             return _options_handler, {}
 
         # Loop through all the registered callbacks to check if the method
@@ -340,15 +338,12 @@ class JsonResource(HttpServer, resource.Resource):
 
     def _send_response(self, request, code, response_json_object,
                        response_code_message=None):
-        outgoing_responses_counter.inc(request.method, str(code))
-
         # TODO: Only enable CORS for the requests that need it.
         respond_with_json(
             request, code, response_json_object,
             send_cors=True,
             response_code_message=response_code_message,
             pretty_print=_request_user_agent_is_curl(request),
-            version_string=self.version_string,
             canonical_json=self.canonical_json,
         )
 
@@ -381,52 +376,6 @@ def _unrecognised_request_handler(request):
     raise UnrecognizedRequestError()
 
 
-class RequestMetrics(object):
-    def start(self, clock, name):
-        self.start = clock.time_msec()
-        self.start_context = LoggingContext.current_context()
-        self.name = name
-
-    def stop(self, clock, request):
-        context = LoggingContext.current_context()
-
-        tag = ""
-        if context:
-            tag = context.tag
-
-            if context != self.start_context:
-                logger.warn(
-                    "Context have unexpectedly changed %r, %r",
-                    context, self.start_context
-                )
-                return
-
-        response_count.inc(request.method, self.name, tag)
-
-        response_timer.inc_by(
-            clock.time_msec() - self.start, request.method,
-            self.name, tag
-        )
-
-        ru_utime, ru_stime = context.get_resource_usage()
-
-        response_ru_utime.inc_by(
-            ru_utime, request.method, self.name, tag
-        )
-        response_ru_stime.inc_by(
-            ru_stime, request.method, self.name, tag
-        )
-        response_db_txn_count.inc_by(
-            context.db_txn_count, request.method, self.name, tag
-        )
-        response_db_txn_duration.inc_by(
-            context.db_txn_duration_ms / 1000., request.method, self.name, tag
-        )
-        response_db_sched_duration.inc_by(
-            context.db_sched_duration_ms / 1000., request.method, self.name, tag
-        )
-
-
 class RootRedirect(resource.Resource):
     """Redirects the root '/' path to another path."""
 
@@ -445,7 +394,7 @@ class RootRedirect(resource.Resource):
 
 def respond_with_json(request, code, json_object, send_cors=False,
                       response_code_message=None, pretty_print=False,
-                      version_string="", canonical_json=True):
+                      canonical_json=True):
     # could alternatively use request.notifyFinish() and flip a flag when
     # the Deferred fires, but since the flag is RIGHT THERE it seems like
     # a waste.
@@ -461,19 +410,17 @@ def respond_with_json(request, code, json_object, send_cors=False,
         if canonical_json or synapse.events.USE_FROZEN_DICTS:
             json_bytes = encode_canonical_json(json_object)
         else:
-            # ujson doesn't like frozen_dicts.
             json_bytes = simplejson.dumps(json_object)
 
     return respond_with_json_bytes(
         request, code, json_bytes,
         send_cors=send_cors,
         response_code_message=response_code_message,
-        version_string=version_string
     )
 
 
 def respond_with_json_bytes(request, code, json_bytes, send_cors=False,
-                            version_string="", response_code_message=None):
+                            response_code_message=None):
     """Sends encoded JSON in response to the given request.
 
     Args:
@@ -487,8 +434,8 @@ def respond_with_json_bytes(request, code, json_bytes, send_cors=False,
 
     request.setResponseCode(code, message=response_code_message)
     request.setHeader(b"Content-Type", b"application/json")
-    request.setHeader(b"Server", version_string)
     request.setHeader(b"Content-Length", b"%d" % (len(json_bytes),))
+    request.setHeader(b"Cache-Control", b"no-cache, no-store, must-revalidate")
 
     if send_cors:
         set_cors_headers(request)
@@ -536,9 +483,9 @@ def finish_request(request):
 
 def _request_user_agent_is_curl(request):
     user_agents = request.requestHeaders.getRawHeaders(
-        "User-Agent", default=[]
+        b"User-Agent", default=[]
     )
     for user_agent in user_agents:
-        if "curl" in user_agent:
+        if b"curl" in user_agent:
             return True
     return False
diff --git a/synapse/http/site.py b/synapse/http/site.py
index e422c8dfae..60299657b9 100644
--- a/synapse/http/site.py
+++ b/synapse/http/site.py
@@ -12,27 +12,51 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.util.logcontext import LoggingContext
-from twisted.web.server import Site, Request
-
 import contextlib
 import logging
 import re
 import time
 
-ACCESS_TOKEN_RE = re.compile(r'(\?.*access(_|%5[Ff])token=)[^&]*(.*)$')
+from twisted.web.server import Site, Request
+
+from synapse.http.request_metrics import RequestMetrics
+from synapse.util.logcontext import LoggingContext
+
+logger = logging.getLogger(__name__)
+
+ACCESS_TOKEN_RE = re.compile(br'(\?.*access(_|%5[Ff])token=)[^&]*(.*)$')
+
+_next_request_seq = 0
 
 
 class SynapseRequest(Request):
+    """Class which encapsulates an HTTP request to synapse.
+
+    All of the requests processed in synapse are of this type.
+
+    It extends twisted's twisted.web.server.Request, and adds:
+     * Unique request ID
+     * Redaction of access_token query-params in __repr__
+     * Logging at start and end
+     * Metrics to record CPU, wallclock and DB time by endpoint.
+
+    It provides a method `processing` which should be called by the Resource
+    which is handling the request, and returns a context manager.
+
+    """
     def __init__(self, site, *args, **kw):
         Request.__init__(self, *args, **kw)
         self.site = site
         self.authenticated_entity = None
         self.start_time = 0
 
+        global _next_request_seq
+        self.request_seq = _next_request_seq
+        _next_request_seq += 1
+
     def __repr__(self):
         # We overwrite this so that we don't log ``access_token``
-        return '<%s at 0x%x method=%s uri=%s clientproto=%s site=%s>' % (
+        return '<%s at 0x%x method=%r uri=%r clientproto=%r site=%r>' % (
             self.__class__.__name__,
             id(self),
             self.method,
@@ -41,16 +65,30 @@ class SynapseRequest(Request):
             self.site.site_tag,
         )
 
+    def get_request_id(self):
+        return "%s-%i" % (self.method, self.request_seq)
+
     def get_redacted_uri(self):
         return ACCESS_TOKEN_RE.sub(
-            r'\1<redacted>\3',
+            br'\1<redacted>\3',
             self.uri
         )
 
     def get_user_agent(self):
-        return self.requestHeaders.getRawHeaders("User-Agent", [None])[-1]
+        return self.requestHeaders.getRawHeaders(b"User-Agent", [None])[-1]
+
+    def render(self, resrc):
+        # override the Server header which is set by twisted
+        self.setHeader("Server", self.site.server_version_string)
+        return Request.render(self, resrc)
+
+    def _started_processing(self, servlet_name):
+        self.start_time = time.time()
+        self.request_metrics = RequestMetrics()
+        self.request_metrics.start(
+            self.start_time, name=servlet_name, method=self.method,
+        )
 
-    def started_processing(self):
         self.site.access_logger.info(
             "%s - %s - Received request: %s %s",
             self.getClientIP(),
@@ -58,32 +96,32 @@ class SynapseRequest(Request):
             self.method,
             self.get_redacted_uri()
         )
-        self.start_time = int(time.time() * 1000)
-
-    def finished_processing(self):
 
+    def _finished_processing(self):
         try:
             context = LoggingContext.current_context()
             ru_utime, ru_stime = context.get_resource_usage()
             db_txn_count = context.db_txn_count
-            db_txn_duration_ms = context.db_txn_duration_ms
-            db_sched_duration_ms = context.db_sched_duration_ms
+            db_txn_duration_sec = context.db_txn_duration_sec
+            db_sched_duration_sec = context.db_sched_duration_sec
         except Exception:
             ru_utime, ru_stime = (0, 0)
-            db_txn_count, db_txn_duration_ms = (0, 0)
+            db_txn_count, db_txn_duration_sec = (0, 0)
+
+        end_time = time.time()
 
         self.site.access_logger.info(
             "%s - %s - {%s}"
-            " Processed request: %dms (%dms, %dms) (%dms/%dms/%d)"
+            " Processed request: %.3fsec (%.3fsec, %.3fsec) (%.3fsec/%.3fsec/%d)"
             " %sB %s \"%s %s %s\" \"%s\"",
             self.getClientIP(),
             self.site.site_tag,
             self.authenticated_entity,
-            int(time.time() * 1000) - self.start_time,
-            int(ru_utime * 1000),
-            int(ru_stime * 1000),
-            db_sched_duration_ms,
-            db_txn_duration_ms,
+            end_time - self.start_time,
+            ru_utime,
+            ru_stime,
+            db_sched_duration_sec,
+            db_txn_duration_sec,
             int(db_txn_count),
             self.sentLength,
             self.code,
@@ -93,11 +131,38 @@ class SynapseRequest(Request):
             self.get_user_agent(),
         )
 
+        try:
+            self.request_metrics.stop(end_time, self)
+        except Exception as e:
+            logger.warn("Failed to stop metrics: %r", e)
+
     @contextlib.contextmanager
-    def processing(self):
-        self.started_processing()
+    def processing(self, servlet_name):
+        """Record the fact that we are processing this request.
+
+        Returns a context manager; the correct way to use this is:
+
+        @defer.inlineCallbacks
+        def handle_request(request):
+            with request.processing("FooServlet"):
+                yield really_handle_the_request()
+
+        This will log the request's arrival. Once the context manager is
+        closed, the completion of the request will be logged, and the various
+        metrics will be updated.
+
+        Args:
+            servlet_name (str): the name of the servlet which will be
+                processing this request. This is used in the metrics.
+
+                It is possible to update this afterwards by updating
+                self.request_metrics.servlet_name.
+        """
+        # TODO: we should probably just move this into render() and finish(),
+        # to save having to call a separate method.
+        self._started_processing(servlet_name)
         yield
-        self.finished_processing()
+        self._finished_processing()
 
 
 class XForwardedForRequest(SynapseRequest):
@@ -135,7 +200,8 @@ class SynapseSite(Site):
     Subclass of a twisted http Site that does access logging with python's
     standard logging
     """
-    def __init__(self, logger_name, site_tag, config, resource, *args, **kwargs):
+    def __init__(self, logger_name, site_tag, config, resource,
+                 server_version_string, *args, **kwargs):
         Site.__init__(self, resource, *args, **kwargs)
 
         self.site_tag = site_tag
@@ -143,6 +209,7 @@ class SynapseSite(Site):
         proxied = config.get("x_forwarded", False)
         self.requestFactory = SynapseRequestFactory(self, proxied)
         self.access_logger = logging.getLogger(logger_name)
+        self.server_version_string = server_version_string
 
     def log(self, request):
         pass