Review comments

5 files changed, 119 insertions, 158 deletions

diff --git a/synapse/rest/client/transactions.py b/synapse/rest/client/transactions.py
new file mode 100644
index 0000000000..1db972a378
--- /dev/null
+++ b/synapse/rest/client/transactions.py
@@ -0,0 +1,85 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014-2016 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.
+
+"""This module contains logic for storing HTTP PUT transactions. This is used
+to ensure idempotency when performing PUTs using the REST API."""
+import logging
+
+from synapse.api.auth import get_access_token_from_request
+from synapse.util.async import ObservableDeferred
+
+logger = logging.getLogger(__name__)
+
+
+def get_transaction_key(request):
+    """A helper function which returns a transaction key that can be used
+    with TransactionCache for idempotent requests.
+
+    Idempotency is based on the returned key being the same for separate
+    requests to the same endpoint. The key is formed from the HTTP request
+    path and the access_token for the requesting user.
+
+    Args:
+        request (twisted.web.http.Request): The incoming request. Must
+        contain an access_token.
+    Returns:
+        str: A transaction key
+    """
+    token = get_access_token_from_request(request)
+    return request.path + "/" + token
+
+
+class HttpTransactionCache(object):
+
+    def __init__(self):
+        self.transactions = {
+            # $txn_key: ObservableDeferred<(res_code, res_json_body)>
+        }
+
+    def fetch_or_execute_request(self, request, fn, *args, **kwargs):
+        """A helper function for fetch_or_execute which extracts
+        a transaction key from the given request.
+
+        See:
+            fetch_or_execute
+        """
+        return self.fetch_or_execute(
+            get_transaction_key(request), fn, *args, **kwargs
+        )
+
+    def fetch_or_execute(self, txn_key, fn, *args, **kwargs):
+        """Fetches the response for this transaction, or executes the given function
+        to produce a response for this transaction.
+
+        Args:
+            txn_key (str): A key to ensure idempotency should fetch_or_execute be
+            called again at a later point in time.
+            fn (function): A function which returns a tuple of
+            (response_code, response_dict)d
+            *args: Arguments to pass to fn.
+            **kwargs: Keyword arguments to pass to fn.
+        Returns:
+            synapse.util.async.ObservableDeferred which resolves to a tuple
+            of (response_code, response_dict).
+        """
+        try:
+            return self.transactions[txn_key]
+        except KeyError:
+            pass  # execute the function instead.
+
+        deferred = fn(*args, **kwargs)
+        observable = ObservableDeferred(deferred)
+        self.transactions[txn_key] = observable
+        return observable
diff --git a/synapse/rest/client/v1/base.py b/synapse/rest/client/v1/base.py
index 22c740c30c..07ff5b218c 100644
--- a/synapse/rest/client/v1/base.py
+++ b/synapse/rest/client/v1/base.py
@@ -18,7 +18,8 @@
 
 from synapse.http.servlet import RestServlet
 from synapse.api.urls import CLIENT_PREFIX
-from .transactions import HttpTransactionCache
+from synapse.rest.client.transactions import HttpTransactionCache
+
 import re
 
 import logging
diff --git a/synapse/rest/client/v1/room.py b/synapse/rest/client/v1/room.py
index 7af4077721..0622e64380 100644
--- a/synapse/rest/client/v1/room.py
+++ b/synapse/rest/client/v1/room.py
@@ -22,7 +22,6 @@ from synapse.streams.config import PaginationConfig
 from synapse.api.constants import EventTypes, Membership
 from synapse.api.filtering import Filter
 from synapse.types import UserID, RoomID, RoomAlias
-from synapse.util.async import ObservableDeferred
 from synapse.events.utils import serialize_event, format_event_for_client_v2
 from synapse.http.servlet import (
     parse_json_object_from_request, parse_string, parse_integer
@@ -56,17 +55,11 @@ class RoomCreateRestServlet(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def on_PUT(self, request, txn_id):
-        try:
-            res_deferred = self.txns.get_client_transaction(request, txn_id)
-            res = yield res_deferred.observe()
-            defer.returnValue(res)
-        except KeyError:
-            pass
-
-        res_deferred = ObservableDeferred(self.on_POST(request))
-        self.txns.store_client_transaction(request, txn_id, res_deferred)
-        response = yield res_deferred.observe()
-        defer.returnValue(response)
+        observable = self.txns.fetch_or_execute_request(
+            request, self.on_POST, request
+        )
+        res = yield observable.observe()
+        defer.returnValue(res)
 
     @defer.inlineCallbacks
     def on_POST(self, request):
@@ -217,19 +210,11 @@ class RoomSendEventRestServlet(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def on_PUT(self, request, room_id, event_type, txn_id):
-        try:
-            res_deferred = self.txns.get_client_transaction(request, txn_id)
-            res = yield res_deferred.observe()
-            defer.returnValue(res)
-        except KeyError:
-            pass
-
-        res_deferred = ObservableDeferred(
-            self.on_POST(request, room_id, event_type, txn_id)
+        observable = self.txns.fetch_or_execute_request(
+            request, self.on_POST, request, room_id, event_type, txn_id
         )
-        self.txns.store_client_transaction(request, txn_id, res_deferred)
-        response = yield res_deferred.observe()
-        defer.returnValue(response)
+        res = yield observable.observe()
+        defer.returnValue(res)
 
 
 # TODO: Needs unit testing for room ID + alias joins
@@ -288,17 +273,11 @@ class JoinRoomAliasServlet(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def on_PUT(self, request, room_identifier, txn_id):
-        try:
-            res_deferred = self.txns.get_client_transaction(request, txn_id)
-            res = yield res_deferred.observe()
-            defer.returnValue(res)
-        except KeyError:
-            pass
-
-        res_deferred = ObservableDeferred(self.on_POST(request, room_identifier, txn_id))
-        self.txns.store_client_transaction(request, txn_id, res_deferred)
-        response = yield res_deferred.observe()
-        defer.returnValue(response)
+        observable = self.txns.fetch_or_execute_request(
+            request, self.on_POST, request, room_identifier, txn_id
+        )
+        res = yield observable.observe()
+        defer.returnValue(res)
 
 
 # TODO: Needs unit testing
@@ -542,17 +521,11 @@ class RoomForgetRestServlet(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def on_PUT(self, request, room_id, txn_id):
-        try:
-            res_deferred = self.txns.get_client_transaction(request, txn_id)
-            res = yield res_deferred.observe()
-            defer.returnValue(res)
-        except KeyError:
-            pass
-
-        res_deferred = ObservableDeferred(self.on_POST(request, room_id, txn_id))
-        self.txns.store_client_transaction(request, txn_id, res_deferred)
-        response = yield res_deferred.observe()
-        defer.returnValue(response)
+        observable = self.txns.fetch_or_execute_request(
+            request, self.on_POST, request, room_id, txn_id
+        )
+        res = yield observable.observe()
+        defer.returnValue(res)
 
 
 # TODO: Needs unit testing
@@ -626,19 +599,11 @@ class RoomMembershipRestServlet(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def on_PUT(self, request, room_id, membership_action, txn_id):
-        try:
-            res_deferred = self.txns.get_client_transaction(request, txn_id)
-            res = yield res_deferred.observe()
-            defer.returnValue(res)
-        except KeyError:
-            pass
-
-        res_deferred = ObservableDeferred(
-            self.on_POST(request, room_id, membership_action, txn_id)
+        observable = self.txns.fetch_or_execute_request(
+            request, self.on_POST, request, room_id, membership_action, txn_id
         )
-        self.txns.store_client_transaction(request, txn_id, res_deferred)
-        response = yield res_deferred.observe()
-        defer.returnValue(response)
+        res = yield observable.observe()
+        defer.returnValue(res)
 
 
 class RoomRedactEventRestServlet(ClientV1RestServlet):
@@ -672,19 +637,11 @@ class RoomRedactEventRestServlet(ClientV1RestServlet):
 
     @defer.inlineCallbacks
     def on_PUT(self, request, room_id, event_id, txn_id):
-        try:
-            res_deferred = self.txns.get_client_transaction(request, txn_id)
-            res = yield res_deferred.observe()
-            defer.returnValue(res)
-        except KeyError:
-            pass
-
-        res_deferred = ObservableDeferred(
-            self.on_POST(request, room_id, event_id, txn_id)
+        observable = self.txns.fetch_or_execute_request(
+            request, self.on_POST, request, room_id, event_id, txn_id
         )
-        self.txns.store_client_transaction(request, txn_id, res_deferred)
-        response = yield res_deferred.observe()
-        defer.returnValue(response)
+        res = yield observable.observe()
+        defer.returnValue(res)
 
 
 class RoomTypingRestServlet(ClientV1RestServlet):
diff --git a/synapse/rest/client/v1/transactions.py b/synapse/rest/client/v1/transactions.py
deleted file mode 100644
index 774430458a..0000000000
--- a/synapse/rest/client/v1/transactions.py
+++ /dev/null
@@ -1,75 +0,0 @@
-# -*- coding: utf-8 -*-
-# Copyright 2014-2016 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.
-
-"""This module contains logic for storing HTTP PUT transactions. This is used
-to ensure idempotency when performing PUTs using the REST API."""
-import logging
-
-from synapse.api.auth import get_access_token_from_request
-
-logger = logging.getLogger(__name__)
-
-
-class HttpTransactionCache(object):
-
-    def __init__(self):
-        # { key : (txn_id, res_observ_defer) }
-        self.transactions = {}
-
-    def _get_response(self, key, txn_id):
-        try:
-            (last_txn_id, res_observ_defer) = self.transactions[key]
-            if txn_id == last_txn_id:
-                logger.info("get_response: Returning a response for %s", txn_id)
-                return res_observ_defer
-        except KeyError:
-            pass
-        return None
-
-    def _store_response(self, key, txn_id, res_observ_defer):
-        self.transactions[key] = (txn_id, res_observ_defer)
-
-    def store_client_transaction(self, request, txn_id, res_observ_defer):
-        """Stores the request/Promise<response> pair of an HTTP transaction.
-
-        Args:
-            request (twisted.web.http.Request): The twisted HTTP request. This
-            request must have the transaction ID as the last path segment.
-            res_observ_defer (Promise<tuple>): A tuple of (response code, response dict)
-            txn_id (str): The transaction ID for this request.
-        """
-        self._store_response(self._get_key(request), txn_id, res_observ_defer)
-
-    def get_client_transaction(self, request, txn_id):
-        """Retrieves a stored response if there was one.
-
-        Args:
-            request (twisted.web.http.Request): The twisted HTTP request. This
-            request must have the transaction ID as the last path segment.
-            txn_id (str): The transaction ID for this request.
-        Returns:
-            Promise: Resolves to the response tuple.
-        Raises:
-            KeyError if the transaction was not found.
-        """
-        res_observ_defer = self._get_response(self._get_key(request), txn_id)
-        if res_observ_defer is None:
-            raise KeyError("Transaction not found.")
-        return res_observ_defer
-
-    def _get_key(self, request):
-        token = get_access_token_from_request(request)
-        path_without_txn_id = request.path.rsplit("/", 1)[0]
-        return path_without_txn_id + "/" + token
diff --git a/synapse/rest/client/v2_alpha/sendtodevice.py b/synapse/rest/client/v2_alpha/sendtodevice.py
index 31167ba535..2ce038c6cd 100644
--- a/synapse/rest/client/v2_alpha/sendtodevice.py
+++ b/synapse/rest/client/v2_alpha/sendtodevice.py
@@ -19,8 +19,7 @@ from twisted.internet import defer
 
 from synapse.http import servlet
 from synapse.http.servlet import parse_json_object_from_request
-from synapse.rest.client.v1.transactions import HttpTransactionCache
-from synapse.util.async import ObservableDeferred
+from synapse.rest.client.transactions import HttpTransactionCache
 
 from ._base import client_v2_patterns
 
@@ -46,16 +45,10 @@ class SendToDeviceRestServlet(servlet.RestServlet):
 
     @defer.inlineCallbacks
     def on_PUT(self, request, message_type, txn_id):
-        try:
-            res_deferred = self.txns.get_client_transaction(request, txn_id)
-            res = yield res_deferred.observe()
-            defer.returnValue(res)
-        except KeyError:
-            pass
-
-        res_deferred = ObservableDeferred(self._put(request, message_type, txn_id))
-        self.txns.store_client_transaction(request, txn_id, res_deferred)
-        res = yield res_deferred.observe()
+        observable = self.txns.fetch_or_execute_request(
+            request, self._put, request, message_type, txn_id
+        )
+        res = yield observable.observe()
         defer.returnValue(res)
 
     @defer.inlineCallbacks