Merge branch 'release-v0.16.0' of github.com:matrix-org/synapse v0.16.0

17 files changed, 724 insertions, 84 deletions

diff --git a/synapse/util/__init__.py b/synapse/util/__init__.py
index 3b9da5b34a..2b3f0bef3c 100644
--- a/synapse/util/__init__.py
+++ b/synapse/util/__init__.py
@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from synapse.api.errors import SynapseError
 from synapse.util.logcontext import PreserveLoggingContext
 
 from twisted.internet import defer, reactor, task
@@ -49,9 +50,6 @@ class Clock(object):
         l.start(msec / 1000.0, now=False)
         return l
 
-    def stop_looping_call(self, loop):
-        loop.stop()
-
     def call_later(self, delay, callback, *args, **kwargs):
         """Call something later
 
@@ -83,7 +81,7 @@ class Clock(object):
 
         def timed_out_fn():
             try:
-                ret_deferred.errback(RuntimeError("Timed out"))
+                ret_deferred.errback(SynapseError(504, "Timed out"))
             except:
                 pass
 
diff --git a/synapse/util/async.py b/synapse/util/async.py
index 640fae3890..40be7fe7e3 100644
--- a/synapse/util/async.py
+++ b/synapse/util/async.py
@@ -16,7 +16,12 @@
 
 from twisted.internet import defer, reactor
 
-from .logcontext import PreserveLoggingContext
+from .logcontext import (
+    PreserveLoggingContext, preserve_fn, preserve_context_over_deferred,
+)
+from synapse.util import unwrapFirstError
+
+from contextlib import contextmanager
 
 
 @defer.inlineCallbacks
@@ -97,6 +102,15 @@ class ObservableDeferred(object):
     def observers(self):
         return self._observers
 
+    def has_called(self):
+        return self._result is not None
+
+    def has_succeeded(self):
+        return self._result is not None and self._result[0] is True
+
+    def get_result(self):
+        return self._result[1]
+
     def __getattr__(self, name):
         return getattr(self._deferred, name)
 
@@ -107,3 +121,76 @@ class ObservableDeferred(object):
         return "<ObservableDeferred object at %s, result=%r, _deferred=%r>" % (
             id(self), self._result, self._deferred,
         )
+
+
+def concurrently_execute(func, args, limit):
+    """Executes the function with each argument conncurrently while limiting
+    the number of concurrent executions.
+
+    Args:
+        func (func): Function to execute, should return a deferred.
+        args (list): List of arguments to pass to func, each invocation of func
+            gets a signle argument.
+        limit (int): Maximum number of conccurent executions.
+
+    Returns:
+        deferred: Resolved when all function invocations have finished.
+    """
+    it = iter(args)
+
+    @defer.inlineCallbacks
+    def _concurrently_execute_inner():
+        try:
+            while True:
+                yield func(it.next())
+        except StopIteration:
+            pass
+
+    return defer.gatherResults([
+        preserve_fn(_concurrently_execute_inner)()
+        for _ in xrange(limit)
+    ], consumeErrors=True).addErrback(unwrapFirstError)
+
+
+class Linearizer(object):
+    """Linearizes access to resources based on a key. Useful to ensure only one
+    thing is happening at a time on a given resource.
+
+    Example:
+
+        with (yield linearizer.queue("test_key")):
+            # do some work.
+
+    """
+    def __init__(self):
+        self.key_to_defer = {}
+
+    @defer.inlineCallbacks
+    def queue(self, key):
+        # If there is already a deferred in the queue, we pull it out so that
+        # we can wait on it later.
+        # Then we replace it with a deferred that we resolve *after* the
+        # context manager has exited.
+        # We only return the context manager after the previous deferred has
+        # resolved.
+        # This all has the net effect of creating a chain of deferreds that
+        # wait for the previous deferred before starting their work.
+        current_defer = self.key_to_defer.get(key)
+
+        new_defer = defer.Deferred()
+        self.key_to_defer[key] = new_defer
+
+        if current_defer:
+            yield preserve_context_over_deferred(current_defer)
+
+        @contextmanager
+        def _ctx_manager():
+            try:
+                yield
+            finally:
+                new_defer.callback(None)
+                current_d = self.key_to_defer.get(key)
+                if current_d is new_defer:
+                    self.key_to_defer.pop(key, None)
+
+        defer.returnValue(_ctx_manager())
diff --git a/synapse/util/caches/__init__.py b/synapse/util/caches/__init__.py
index d53569ca49..ebd715c5dc 100644
--- a/synapse/util/caches/__init__.py
+++ b/synapse/util/caches/__init__.py
@@ -24,11 +24,21 @@ DEBUG_CACHES = False
 metrics = synapse.metrics.get_metrics_for("synapse.util.caches")
 
 caches_by_name = {}
-cache_counter = metrics.register_cache(
-    "cache",
-    lambda: {(name,): len(caches_by_name[name]) for name in caches_by_name.keys()},
-    labels=["name"],
-)
+# cache_counter = metrics.register_cache(
+#     "cache",
+#     lambda: {(name,): len(caches_by_name[name]) for name in caches_by_name.keys()},
+#     labels=["name"],
+# )
+
+
+def register_cache(name, cache):
+    caches_by_name[name] = cache
+    return metrics.register_cache(
+        "cache",
+        lambda: len(cache),
+        name,
+    )
+
 
 _string_cache = LruCache(int(5000 * CACHE_SIZE_FACTOR))
 caches_by_name["string_cache"] = _string_cache
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 35544b19fd..f31dfb22b7 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -22,7 +22,7 @@ from synapse.util.logcontext import (
     PreserveLoggingContext, preserve_context_over_deferred, preserve_context_over_fn
 )
 
-from . import caches_by_name, DEBUG_CACHES, cache_counter
+from . import DEBUG_CACHES, register_cache
 
 from twisted.internet import defer
 
@@ -33,6 +33,7 @@ import functools
 import inspect
 import threading
 
+
 logger = logging.getLogger(__name__)
 
 
@@ -43,6 +44,15 @@ CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.1))
 
 
 class Cache(object):
+    __slots__ = (
+        "cache",
+        "max_entries",
+        "name",
+        "keylen",
+        "sequence",
+        "thread",
+        "metrics",
+    )
 
     def __init__(self, name, max_entries=1000, keylen=1, lru=True, tree=False):
         if lru:
@@ -59,7 +69,7 @@ class Cache(object):
         self.keylen = keylen
         self.sequence = 0
         self.thread = None
-        caches_by_name[name] = self.cache
+        self.metrics = register_cache(name, self.cache)
 
     def check_thread(self):
         expected_thread = self.thread
@@ -74,10 +84,10 @@ class Cache(object):
     def get(self, key, default=_CacheSentinel):
         val = self.cache.get(key, _CacheSentinel)
         if val is not _CacheSentinel:
-            cache_counter.inc_hits(self.name)
+            self.metrics.inc_hits()
             return val
 
-        cache_counter.inc_misses(self.name)
+        self.metrics.inc_misses()
 
         if default is _CacheSentinel:
             raise KeyError()
@@ -167,7 +177,8 @@ class CacheDescriptor(object):
                 % (orig.__name__,)
             )
 
-        self.cache = Cache(
+    def __get__(self, obj, objtype=None):
+        cache = Cache(
             name=self.orig.__name__,
             max_entries=self.max_entries,
             keylen=self.num_args,
@@ -175,14 +186,12 @@ class CacheDescriptor(object):
             tree=self.tree,
         )
 
-    def __get__(self, obj, objtype=None):
-
         @functools.wraps(self.orig)
         def wrapped(*args, **kwargs):
             arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs)
             cache_key = tuple(arg_dict[arg_nm] for arg_nm in self.arg_names)
             try:
-                cached_result_d = self.cache.get(cache_key)
+                cached_result_d = cache.get(cache_key)
 
                 observer = cached_result_d.observe()
                 if DEBUG_CACHES:
@@ -204,7 +213,7 @@ class CacheDescriptor(object):
                 # Get the sequence number of the cache before reading from the
                 # database so that we can tell if the cache is invalidated
                 # while the SELECT is executing (SYN-369)
-                sequence = self.cache.sequence
+                sequence = cache.sequence
 
                 ret = defer.maybeDeferred(
                     preserve_context_over_fn,
@@ -213,20 +222,21 @@ class CacheDescriptor(object):
                 )
 
                 def onErr(f):
-                    self.cache.invalidate(cache_key)
+                    cache.invalidate(cache_key)
                     return f
 
                 ret.addErrback(onErr)
 
                 ret = ObservableDeferred(ret, consumeErrors=True)
-                self.cache.update(sequence, cache_key, ret)
+                cache.update(sequence, cache_key, ret)
 
                 return preserve_context_over_deferred(ret.observe())
 
-        wrapped.invalidate = self.cache.invalidate
-        wrapped.invalidate_all = self.cache.invalidate_all
-        wrapped.invalidate_many = self.cache.invalidate_many
-        wrapped.prefill = self.cache.prefill
+        wrapped.invalidate = cache.invalidate
+        wrapped.invalidate_all = cache.invalidate_all
+        wrapped.invalidate_many = cache.invalidate_many
+        wrapped.prefill = cache.prefill
+        wrapped.cache = cache
 
         obj.__dict__[self.orig.__name__] = wrapped
 
@@ -240,11 +250,12 @@ class CacheListDescriptor(object):
     the list of missing keys to the wrapped fucntion.
     """
 
-    def __init__(self, orig, cache, list_name, num_args=1, inlineCallbacks=False):
+    def __init__(self, orig, cached_method_name, list_name, num_args=1,
+                 inlineCallbacks=False):
         """
         Args:
             orig (function)
-            cache (Cache)
+            method_name (str); The name of the chached method.
             list_name (str): Name of the argument which is the bulk lookup list
             num_args (int)
             inlineCallbacks (bool): Whether orig is a generator that should
@@ -263,7 +274,7 @@ class CacheListDescriptor(object):
         self.arg_names = inspect.getargspec(orig).args[1:num_args + 1]
         self.list_pos = self.arg_names.index(self.list_name)
 
-        self.cache = cache
+        self.cached_method_name = cached_method_name
 
         self.sentinel = object()
 
@@ -277,11 +288,13 @@ class CacheListDescriptor(object):
         if self.list_name not in self.arg_names:
             raise Exception(
                 "Couldn't see arguments %r for %r."
-                % (self.list_name, cache.name,)
+                % (self.list_name, cached_method_name,)
             )
 
     def __get__(self, obj, objtype=None):
 
+        cache = getattr(obj, self.cached_method_name).cache
+
         @functools.wraps(self.orig)
         def wrapped(*args, **kwargs):
             arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs)
@@ -290,21 +303,26 @@ class CacheListDescriptor(object):
 
             # cached is a dict arg -> deferred, where deferred results in a
             # 2-tuple (`arg`, `result`)
-            cached = {}
+            results = {}
+            cached_defers = {}
             missing = []
             for arg in list_args:
                 key = list(keyargs)
                 key[self.list_pos] = arg
 
                 try:
-                    res = self.cache.get(tuple(key)).observe()
-                    res.addCallback(lambda r, arg: (arg, r), arg)
-                    cached[arg] = res
+                    res = cache.get(tuple(key))
+                    if not res.has_succeeded():
+                        res = res.observe()
+                        res.addCallback(lambda r, arg: (arg, r), arg)
+                        cached_defers[arg] = res
+                    else:
+                        results[arg] = res.get_result()
                 except KeyError:
                     missing.append(arg)
 
             if missing:
-                sequence = self.cache.sequence
+                sequence = cache.sequence
                 args_to_call = dict(arg_dict)
                 args_to_call[self.list_name] = missing
 
@@ -327,22 +345,31 @@ class CacheListDescriptor(object):
 
                     key = list(keyargs)
                     key[self.list_pos] = arg
-                    self.cache.update(sequence, tuple(key), observer)
+                    cache.update(sequence, tuple(key), observer)
 
                     def invalidate(f, key):
-                        self.cache.invalidate(key)
+                        cache.invalidate(key)
                         return f
                     observer.addErrback(invalidate, tuple(key))
 
                     res = observer.observe()
                     res.addCallback(lambda r, arg: (arg, r), arg)
 
-                    cached[arg] = res
+                    cached_defers[arg] = res
+
+            if cached_defers:
+                def update_results_dict(res):
+                    results.update(res)
+                    return results
 
-            return preserve_context_over_deferred(defer.gatherResults(
-                cached.values(),
-                consumeErrors=True,
-            ).addErrback(unwrapFirstError).addCallback(lambda res: dict(res)))
+                return preserve_context_over_deferred(defer.gatherResults(
+                    cached_defers.values(),
+                    consumeErrors=True,
+                ).addCallback(update_results_dict).addErrback(
+                    unwrapFirstError
+                ))
+            else:
+                return results
 
         obj.__dict__[self.orig.__name__] = wrapped
 
@@ -370,7 +397,7 @@ def cachedInlineCallbacks(max_entries=1000, num_args=1, lru=False, tree=False):
     )
 
 
-def cachedList(cache, list_name, num_args=1, inlineCallbacks=False):
+def cachedList(cached_method_name, list_name, num_args=1, inlineCallbacks=False):
     """Creates a descriptor that wraps a function in a `CacheListDescriptor`.
 
     Used to do batch lookups for an already created cache. A single argument
@@ -400,7 +427,7 @@ def cachedList(cache, list_name, num_args=1, inlineCallbacks=False):
     """
     return lambda orig: CacheListDescriptor(
         orig,
-        cache=cache,
+        cached_method_name=cached_method_name,
         list_name=list_name,
         num_args=num_args,
         inlineCallbacks=inlineCallbacks,
diff --git a/synapse/util/caches/dictionary_cache.py b/synapse/util/caches/dictionary_cache.py
index f92d80542b..b0ca1bb79d 100644
--- a/synapse/util/caches/dictionary_cache.py
+++ b/synapse/util/caches/dictionary_cache.py
@@ -15,7 +15,7 @@
 
 from synapse.util.caches.lrucache import LruCache
 from collections import namedtuple
-from . import caches_by_name, cache_counter
+from . import register_cache
 import threading
 import logging
 
@@ -43,7 +43,7 @@ class DictionaryCache(object):
             __slots__ = []
 
         self.sentinel = Sentinel()
-        caches_by_name[name] = self.cache
+        self.metrics = register_cache(name, self.cache)
 
     def check_thread(self):
         expected_thread = self.thread
@@ -58,7 +58,7 @@ class DictionaryCache(object):
     def get(self, key, dict_keys=None):
         entry = self.cache.get(key, self.sentinel)
         if entry is not self.sentinel:
-            cache_counter.inc_hits(self.name)
+            self.metrics.inc_hits()
 
             if dict_keys is None:
                 return DictionaryEntry(entry.full, dict(entry.value))
@@ -69,7 +69,7 @@ class DictionaryCache(object):
                     if k in entry.value
                 })
 
-        cache_counter.inc_misses(self.name)
+        self.metrics.inc_misses()
         return DictionaryEntry(False, {})
 
     def invalidate(self, key):
diff --git a/synapse/util/caches/expiringcache.py b/synapse/util/caches/expiringcache.py
index 2b68c1ac93..080388958f 100644
--- a/synapse/util/caches/expiringcache.py
+++ b/synapse/util/caches/expiringcache.py
@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.util.caches import cache_counter, caches_by_name
+from synapse.util.caches import register_cache
 
 import logging
 
@@ -49,7 +49,7 @@ class ExpiringCache(object):
 
         self._cache = {}
 
-        caches_by_name[cache_name] = self._cache
+        self.metrics = register_cache(cache_name, self._cache)
 
     def start(self):
         if not self._expiry_ms:
@@ -78,9 +78,9 @@ class ExpiringCache(object):
     def __getitem__(self, key):
         try:
             entry = self._cache[key]
-            cache_counter.inc_hits(self._cache_name)
+            self.metrics.inc_hits()
         except KeyError:
-            cache_counter.inc_misses(self._cache_name)
+            self.metrics.inc_misses()
             raise
 
         if self._reset_expiry_on_get:
diff --git a/synapse/util/caches/response_cache.py b/synapse/util/caches/response_cache.py
new file mode 100644
index 0000000000..36686b479e
--- /dev/null
+++ b/synapse/util/caches/response_cache.py
@@ -0,0 +1,46 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket 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.
+
+from synapse.util.async import ObservableDeferred
+
+
+class ResponseCache(object):
+    """
+    This caches a deferred response. Until the deferred completes it will be
+    returned from the cache. This means that if the client retries the request
+    while the response is still being computed, that original response will be
+    used rather than trying to compute a new response.
+    """
+
+    def __init__(self):
+        self.pending_result_cache = {}  # Requests that haven't finished yet.
+
+    def get(self, key):
+        result = self.pending_result_cache.get(key)
+        if result is not None:
+            return result.observe()
+        else:
+            return None
+
+    def set(self, key, deferred):
+        result = ObservableDeferred(deferred, consumeErrors=True)
+        self.pending_result_cache[key] = result
+
+        def remove(r):
+            self.pending_result_cache.pop(key, None)
+            return r
+
+        result.addBoth(remove)
+        return result.observe()
diff --git a/synapse/util/caches/stream_change_cache.py b/synapse/util/caches/stream_change_cache.py
index ea8a74ca69..3c051dabc4 100644
--- a/synapse/util/caches/stream_change_cache.py
+++ b/synapse/util/caches/stream_change_cache.py
@@ -13,7 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.util.caches import cache_counter, caches_by_name
+from synapse.util.caches import register_cache
 
 
 from blist import sorteddict
@@ -42,7 +42,7 @@ class StreamChangeCache(object):
         self._cache = sorteddict()
         self._earliest_known_stream_pos = current_stream_pos
         self.name = name
-        caches_by_name[self.name] = self._cache
+        self.metrics = register_cache(self.name, self._cache)
 
         for entity, stream_pos in prefilled_cache.items():
             self.entity_has_changed(entity, stream_pos)
@@ -53,19 +53,19 @@ class StreamChangeCache(object):
         assert type(stream_pos) is int
 
         if stream_pos < self._earliest_known_stream_pos:
-            cache_counter.inc_misses(self.name)
+            self.metrics.inc_misses()
             return True
 
         latest_entity_change_pos = self._entity_to_key.get(entity, None)
         if latest_entity_change_pos is None:
-            cache_counter.inc_hits(self.name)
+            self.metrics.inc_hits()
             return False
 
         if stream_pos < latest_entity_change_pos:
-            cache_counter.inc_misses(self.name)
+            self.metrics.inc_misses()
             return True
 
-        cache_counter.inc_hits(self.name)
+        self.metrics.inc_hits()
         return False
 
     def get_entities_changed(self, entities, stream_pos):
@@ -82,10 +82,10 @@ class StreamChangeCache(object):
                 self._cache[k] for k in keys[i:]
             ).intersection(entities)
 
-            cache_counter.inc_hits(self.name)
+            self.metrics.inc_hits()
         else:
             result = entities
-            cache_counter.inc_misses(self.name)
+            self.metrics.inc_misses()
 
         return result
 
diff --git a/synapse/util/distributor.py b/synapse/util/distributor.py
index 8875813de4..d7cccc06b1 100644
--- a/synapse/util/distributor.py
+++ b/synapse/util/distributor.py
@@ -15,7 +15,9 @@
 
 from twisted.internet import defer
 
-from synapse.util.logcontext import PreserveLoggingContext
+from synapse.util.logcontext import (
+    PreserveLoggingContext, preserve_context_over_fn
+)
 
 from synapse.util import unwrapFirstError
 
@@ -25,6 +27,24 @@ import logging
 logger = logging.getLogger(__name__)
 
 
+def registered_user(distributor, user):
+    return distributor.fire("registered_user", user)
+
+
+def user_left_room(distributor, user, room_id):
+    return preserve_context_over_fn(
+        distributor.fire,
+        "user_left_room", user=user, room_id=room_id
+    )
+
+
+def user_joined_room(distributor, user, room_id):
+    return preserve_context_over_fn(
+        distributor.fire,
+        "user_joined_room", user=user, room_id=room_id
+    )
+
+
 class Distributor(object):
     """A central dispatch point for loosely-connected pieces of code to
     register, observe, and fire signals.
diff --git a/synapse/util/httpresourcetree.py b/synapse/util/httpresourcetree.py
new file mode 100644
index 0000000000..45be47159a
--- /dev/null
+++ b/synapse/util/httpresourcetree.py
@@ -0,0 +1,98 @@
+# Copyright 2016 OpenMarket 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.
+
+from twisted.web.resource import Resource
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+def create_resource_tree(desired_tree, root_resource):
+    """Create the resource tree for this Home Server.
+
+    This in unduly complicated because Twisted does not support putting
+    child resources more than 1 level deep at a time.
+
+    Args:
+        web_client (bool): True to enable the web client.
+        root_resource (twisted.web.resource.Resource): The root
+            resource to add the tree to.
+    Returns:
+        twisted.web.resource.Resource: the ``root_resource`` with a tree of
+        child resources added to it.
+    """
+
+    # ideally we'd just use getChild and putChild but getChild doesn't work
+    # unless you give it a Request object IN ADDITION to the name :/ So
+    # instead, we'll store a copy of this mapping so we can actually add
+    # extra resources to existing nodes. See self._resource_id for the key.
+    resource_mappings = {}
+    for full_path, res in desired_tree.items():
+        logger.info("Attaching %s to path %s", res, full_path)
+        last_resource = root_resource
+        for path_seg in full_path.split('/')[1:-1]:
+            if path_seg not in last_resource.listNames():
+                # resource doesn't exist, so make a "dummy resource"
+                child_resource = Resource()
+                last_resource.putChild(path_seg, child_resource)
+                res_id = _resource_id(last_resource, path_seg)
+                resource_mappings[res_id] = child_resource
+                last_resource = child_resource
+            else:
+                # we have an existing Resource, use that instead.
+                res_id = _resource_id(last_resource, path_seg)
+                last_resource = resource_mappings[res_id]
+
+        # ===========================
+        # now attach the actual desired resource
+        last_path_seg = full_path.split('/')[-1]
+
+        # if there is already a resource here, thieve its children and
+        # replace it
+        res_id = _resource_id(last_resource, last_path_seg)
+        if res_id in resource_mappings:
+            # there is a dummy resource at this path already, which needs
+            # to be replaced with the desired resource.
+            existing_dummy_resource = resource_mappings[res_id]
+            for child_name in existing_dummy_resource.listNames():
+                child_res_id = _resource_id(
+                    existing_dummy_resource, child_name
+                )
+                child_resource = resource_mappings[child_res_id]
+                # steal the children
+                res.putChild(child_name, child_resource)
+
+        # finally, insert the desired resource in the right place
+        last_resource.putChild(last_path_seg, res)
+        res_id = _resource_id(last_resource, last_path_seg)
+        resource_mappings[res_id] = res
+
+    return root_resource
+
+
+def _resource_id(resource, path_seg):
+    """Construct an arbitrary resource ID so you can retrieve the mapping
+    later.
+
+    If you want to represent resource A putChild resource B with path C,
+    the mapping should looks like _resource_id(A,C) = B.
+
+    Args:
+        resource (Resource): The *parent* Resourceb
+        path_seg (str): The name of the child Resource to be attached.
+    Returns:
+        str: A unique string which can be a key to the child Resource.
+    """
+    return "%s-%s" % (resource, path_seg)
diff --git a/synapse/util/manhole.py b/synapse/util/manhole.py
new file mode 100644
index 0000000000..97e0f00b67
--- /dev/null
+++ b/synapse/util/manhole.py
@@ -0,0 +1,70 @@
+# Copyright 2016 OpenMarket 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.
+
+from twisted.conch.manhole import ColoredManhole
+from twisted.conch.insults import insults
+from twisted.conch import manhole_ssh
+from twisted.cred import checkers, portal
+from twisted.conch.ssh.keys import Key
+
+PUBLIC_KEY = (
+    "ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAGEArzJx8OYOnJmzf4tfBEvLi8DVPrJ3/c9k2I/Az"
+    "64fxjHf9imyRJbixtQhlH9lfNjUIx+4LmrJH5QNRsFporcHDKOTwTTYLh5KmRpslkYHRivcJS"
+    "kbh/C+BR3utDS555mV"
+)
+
+PRIVATE_KEY = """-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----"""
+
+
+def manhole(username, password, globals):
+    """Starts a ssh listener with password authentication using
+    the given username and password. Clients connecting to the ssh
+    listener will find themselves in a colored python shell with
+    the supplied globals.
+
+    Args:
+        username(str): The username ssh clients should auth with.
+        password(str): The password ssh clients should auth with.
+        globals(dict): The variables to expose in the shell.
+
+    Returns:
+        twisted.internet.protocol.Factory: A factory to pass to ``listenTCP``
+    """
+
+    checker = checkers.InMemoryUsernamePasswordDatabaseDontUse(
+        **{username: password}
+    )
+
+    rlm = manhole_ssh.TerminalRealm()
+    rlm.chainedProtocolFactory = lambda: insults.ServerProtocol(
+        ColoredManhole,
+        dict(globals, __name__="__console__")
+    )
+
+    factory = manhole_ssh.ConchFactory(portal.Portal(rlm, [checker]))
+    factory.publicKeys['ssh-rsa'] = Key.fromString(PUBLIC_KEY)
+    factory.privateKeys['ssh-rsa'] = Key.fromString(PRIVATE_KEY)
+
+    return factory
diff --git a/synapse/util/metrics.py b/synapse/util/metrics.py
index c51b641125..e1f374807e 100644
--- a/synapse/util/metrics.py
+++ b/synapse/util/metrics.py
@@ -50,7 +50,7 @@ block_db_txn_duration = metrics.register_distribution(
 class Measure(object):
     __slots__ = [
         "clock", "name", "start_context", "start", "new_context", "ru_utime",
-        "ru_stime", "db_txn_count", "db_txn_duration"
+        "ru_stime", "db_txn_count", "db_txn_duration", "created_context"
     ]
 
     def __init__(self, clock, name):
@@ -58,14 +58,20 @@ class Measure(object):
         self.name = name
         self.start_context = None
         self.start = None
+        self.created_context = False
 
     def __enter__(self):
         self.start = self.clock.time_msec()
         self.start_context = LoggingContext.current_context()
-        if self.start_context:
-            self.ru_utime, self.ru_stime = self.start_context.get_resource_usage()
-            self.db_txn_count = self.start_context.db_txn_count
-            self.db_txn_duration = self.start_context.db_txn_duration
+        if not self.start_context:
+            logger.warn("Entered Measure without log context: %s", self.name)
+            self.start_context = LoggingContext("Measure")
+            self.start_context.__enter__()
+            self.created_context = True
+
+        self.ru_utime, self.ru_stime = self.start_context.get_resource_usage()
+        self.db_txn_count = self.start_context.db_txn_count
+        self.db_txn_duration = self.start_context.db_txn_duration
 
     def __exit__(self, exc_type, exc_val, exc_tb):
         if exc_type is not None or not self.start_context:
@@ -91,7 +97,12 @@ class Measure(object):
 
         block_ru_utime.inc_by(ru_utime - self.ru_utime, self.name)
         block_ru_stime.inc_by(ru_stime - self.ru_stime, self.name)
-        block_db_txn_count.inc_by(context.db_txn_count - self.db_txn_count, self.name)
+        block_db_txn_count.inc_by(
+            context.db_txn_count - self.db_txn_count, self.name
+        )
         block_db_txn_duration.inc_by(
             context.db_txn_duration - self.db_txn_duration, self.name
         )
+
+        if self.created_context:
+            self.start_context.__exit__(exc_type, exc_val, exc_tb)
diff --git a/synapse/util/presentable_names.py b/synapse/util/presentable_names.py
new file mode 100644
index 0000000000..a6866f6117
--- /dev/null
+++ b/synapse/util/presentable_names.py
@@ -0,0 +1,170 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket 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 re
+import logging
+
+logger = logging.getLogger(__name__)
+
+# intentionally looser than what aliases we allow to be registered since
+# other HSes may allow aliases that we would not
+ALIAS_RE = re.compile(r"^#.*:.+$")
+
+ALL_ALONE = "Empty Room"
+
+
+def calculate_room_name(room_state, user_id, fallback_to_members=True):
+    """
+    Works out a user-facing name for the given room as per Matrix
+    spec recommendations.
+    Does not yet support internationalisation.
+    Args:
+        room_state: Dictionary of the room's state
+        user_id: The ID of the user to whom the room name is being presented
+        fallback_to_members: If False, return None instead of generating a name
+                             based on the room's members if the room has no
+                             title or aliases.
+
+    Returns:
+        (string or None) A human readable name for the room.
+    """
+    # does it have a name?
+    if ("m.room.name", "") in room_state:
+        m_room_name = room_state[("m.room.name", "")]
+        if m_room_name.content and m_room_name.content["name"]:
+            return m_room_name.content["name"]
+
+    # does it have a canonical alias?
+    if ("m.room.canonical_alias", "") in room_state:
+        canon_alias = room_state[("m.room.canonical_alias", "")]
+        if (
+            canon_alias.content and canon_alias.content["alias"] and
+            _looks_like_an_alias(canon_alias.content["alias"])
+        ):
+            return canon_alias.content["alias"]
+
+    # at this point we're going to need to search the state by all state keys
+    # for an event type, so rearrange the data structure
+    room_state_bytype = _state_as_two_level_dict(room_state)
+
+    # right then, any aliases at all?
+    if "m.room.aliases" in room_state_bytype:
+        m_room_aliases = room_state_bytype["m.room.aliases"]
+        if len(m_room_aliases.values()) > 0:
+            first_alias_event = m_room_aliases.values()[0]
+            if first_alias_event.content and first_alias_event.content["aliases"]:
+                the_aliases = first_alias_event.content["aliases"]
+                if len(the_aliases) > 0 and _looks_like_an_alias(the_aliases[0]):
+                    return the_aliases[0]
+
+    if not fallback_to_members:
+        return None
+
+    my_member_event = None
+    if ("m.room.member", user_id) in room_state:
+        my_member_event = room_state[("m.room.member", user_id)]
+
+    if (
+        my_member_event is not None and
+        my_member_event.content['membership'] == "invite"
+    ):
+        if ("m.room.member", my_member_event.sender) in room_state:
+            inviter_member_event = room_state[("m.room.member", my_member_event.sender)]
+            return "Invite from %s" % (name_from_member_event(inviter_member_event),)
+        else:
+            return "Room Invite"
+
+    # we're going to have to generate a name based on who's in the room,
+    # so find out who is in the room that isn't the user.
+    if "m.room.member" in room_state_bytype:
+        all_members = [
+            ev for ev in room_state_bytype["m.room.member"].values()
+            if ev.content['membership'] == "join" or ev.content['membership'] == "invite"
+        ]
+        # Sort the member events oldest-first so the we name people in the
+        # order the joined (it should at least be deterministic rather than
+        # dictionary iteration order)
+        all_members.sort(key=lambda e: e.origin_server_ts)
+        other_members = [m for m in all_members if m.state_key != user_id]
+    else:
+        other_members = []
+        all_members = []
+
+    if len(other_members) == 0:
+        if len(all_members) == 1:
+            # self-chat, peeked room with 1 participant,
+            # or inbound invite, or outbound 3PID invite.
+            if all_members[0].sender == user_id:
+                if "m.room.third_party_invite" in room_state_bytype:
+                    third_party_invites = (
+                        room_state_bytype["m.room.third_party_invite"].values()
+                    )
+
+                    if len(third_party_invites) > 0:
+                        # technically third party invite events are not member
+                        # events, but they are close enough
+
+                        # FIXME: no they're not - they look nothing like a member;
+                        # they have a great big encrypted thing as their name to
+                        # prevent leaking the 3PID name...
+                        # return "Inviting %s" % (
+                        #     descriptor_from_member_events(third_party_invites)
+                        # )
+                        return "Inviting email address"
+                    else:
+                        return ALL_ALONE
+            else:
+                return name_from_member_event(all_members[0])
+        else:
+            return ALL_ALONE
+    else:
+        return descriptor_from_member_events(other_members)
+
+
+def descriptor_from_member_events(member_events):
+    if len(member_events) == 0:
+        return "nobody"
+    elif len(member_events) == 1:
+        return name_from_member_event(member_events[0])
+    elif len(member_events) == 2:
+        return "%s and %s" % (
+            name_from_member_event(member_events[0]),
+            name_from_member_event(member_events[1]),
+        )
+    else:
+        return "%s and %d others" % (
+            name_from_member_event(member_events[0]),
+            len(member_events) - 1,
+        )
+
+
+def name_from_member_event(member_event):
+    if (
+        member_event.content and "displayname" in member_event.content and
+        member_event.content["displayname"]
+    ):
+        return member_event.content["displayname"]
+    return member_event.state_key
+
+
+def _state_as_two_level_dict(state):
+    ret = {}
+    for k, v in state.items():
+        ret.setdefault(k[0], {})[k[1]] = v
+    return ret
+
+
+def _looks_like_an_alias(string):
+    return ALIAS_RE.match(string) is not None
diff --git a/synapse/util/ratelimitutils.py b/synapse/util/ratelimitutils.py
index 4076eed269..1101881a2d 100644
--- a/synapse/util/ratelimitutils.py
+++ b/synapse/util/ratelimitutils.py
@@ -100,20 +100,6 @@ class _PerHostRatelimiter(object):
         self.current_processing = set()
         self.request_times = []
 
-    def is_empty(self):
-        time_now = self.clock.time_msec()
-        self.request_times[:] = [
-            r for r in self.request_times
-            if time_now - r < self.window_size
-        ]
-
-        return not (
-            self.ready_request_queue
-            or self.sleeping_requests
-            or self.current_processing
-            or self.request_times
-        )
-
     @contextlib.contextmanager
     def ratelimit(self):
         # `contextlib.contextmanager` takes a generator and turns it into a
diff --git a/synapse/util/rlimit.py b/synapse/util/rlimit.py
new file mode 100644
index 0000000000..f4a9abf83f
--- /dev/null
+++ b/synapse/util/rlimit.py
@@ -0,0 +1,37 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket 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 resource
+import logging
+
+
+logger = logging.getLogger("synapse.app.homeserver")
+
+
+def change_resource_limit(soft_file_no):
+    try:
+        soft, hard = resource.getrlimit(resource.RLIMIT_NOFILE)
+
+        if not soft_file_no:
+            soft_file_no = hard
+
+        resource.setrlimit(resource.RLIMIT_NOFILE, (soft_file_no, hard))
+        logger.info("Set file limit to: %d", soft_file_no)
+
+        resource.setrlimit(
+            resource.RLIMIT_CORE, (resource.RLIM_INFINITY, resource.RLIM_INFINITY)
+        )
+    except (ValueError, resource.error) as e:
+        logger.warn("Failed to set file or core limit: %s", e)
diff --git a/synapse/util/stringutils.py b/synapse/util/stringutils.py
index b490bb8725..a100f151d4 100644
--- a/synapse/util/stringutils.py
+++ b/synapse/util/stringutils.py
@@ -21,10 +21,6 @@ _string_with_symbols = (
 )
 
 
-def origin_from_ucid(ucid):
-    return ucid.split("@", 1)[1]
-
-
 def random_string(length):
     return ''.join(random.choice(string.ascii_letters) for _ in xrange(length))
 
diff --git a/synapse/util/versionstring.py b/synapse/util/versionstring.py
new file mode 100644
index 0000000000..a4f156cb3b
--- /dev/null
+++ b/synapse/util/versionstring.py
@@ -0,0 +1,84 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket 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 subprocess
+import os
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+def get_version_string(name, module):
+    try:
+        null = open(os.devnull, 'w')
+        cwd = os.path.dirname(os.path.abspath(module.__file__))
+        try:
+            git_branch = subprocess.check_output(
+                ['git', 'rev-parse', '--abbrev-ref', 'HEAD'],
+                stderr=null,
+                cwd=cwd,
+            ).strip()
+            git_branch = "b=" + git_branch
+        except subprocess.CalledProcessError:
+            git_branch = ""
+
+        try:
+            git_tag = subprocess.check_output(
+                ['git', 'describe', '--exact-match'],
+                stderr=null,
+                cwd=cwd,
+            ).strip()
+            git_tag = "t=" + git_tag
+        except subprocess.CalledProcessError:
+            git_tag = ""
+
+        try:
+            git_commit = subprocess.check_output(
+                ['git', 'rev-parse', '--short', 'HEAD'],
+                stderr=null,
+                cwd=cwd,
+            ).strip()
+        except subprocess.CalledProcessError:
+            git_commit = ""
+
+        try:
+            dirty_string = "-this_is_a_dirty_checkout"
+            is_dirty = subprocess.check_output(
+                ['git', 'describe', '--dirty=' + dirty_string],
+                stderr=null,
+                cwd=cwd,
+            ).strip().endswith(dirty_string)
+
+            git_dirty = "dirty" if is_dirty else ""
+        except subprocess.CalledProcessError:
+            git_dirty = ""
+
+        if git_branch or git_tag or git_commit or git_dirty:
+            git_version = ",".join(
+                s for s in
+                (git_branch, git_tag, git_commit, git_dirty,)
+                if s
+            )
+
+            return (
+                "%s/%s (%s)" % (
+                    name, module.__version__, git_version,
+                )
+            ).encode("ascii")
+    except Exception as e:
+        logger.info("Failed to check for git repository: %s", e)
+
+    return ("%s/%s" % (name, module.__version__,)).encode("ascii")