Add a /replication API for extracting the updates that happened on

synapse

This is necessary for replicating the data in synapse to be visible to a
separate service because presence and typing notifications aren't stored
in a database so won't be visible to another process.

This API can be used to either get the raw data by requesting the tables
themselves or to just receive notifications for updates by following the
streams meta-stream.

Returns updates for each table requested a JSON array of arrays with a
row for each row in the table.

Each table is prefixed by a header row with the: name of the table,
current stream_id position for the table, number of rows, number of
columns and the names of the columns.
This is followed by the rows that have been added to the server since
the requester last asked.

The API has a timeout and is hooked up to the notifier so that a slave
can long poll for updates.

1 files changed, 320 insertions, 0 deletions

diff --git a/synapse/replication/resource.py b/synapse/replication/resource.py
new file mode 100644
index 0000000000..e0d039518d
--- /dev/null
+++ b/synapse/replication/resource.py
@@ -0,0 +1,320 @@
+# -*- coding: utf-8 -*-
+# Copyright 2015 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.http.servlet import parse_integer, parse_string
+from synapse.http.server import request_handler, finish_request
+
+from twisted.web.resource import Resource
+from twisted.web.server import NOT_DONE_YET
+from twisted.internet import defer
+
+import ujson as json
+
+import collections
+import logging
+
+logger = logging.getLogger(__name__)
+
+REPLICATION_PREFIX = "/_synapse/replication"
+
+STREAM_NAMES = (
+    ("events",),
+    ("presence",),
+    ("typing",),
+    ("receipts",),
+    ("user_account_data", "room_account_data", "tag_account_data",),
+    ("backfill",),
+)
+
+
+class ReplicationResource(Resource):
+    """
+    HTTP endpoint for extracting data from synapse.
+
+    The streams of data returned by the endpoint are controlled by the
+    parameters given to the API. To return a given stream pass a query
+    parameter with a position in the stream to return data from or the
+    special value "-1" to return data from the start of the stream.
+
+    If there is no data for any of the supplied streams after the given
+    position then the request will block until there is data for one
+    of the streams. This allows clients to long-poll this API.
+
+    The possible streams are:
+
+    * "streams": A special stream returing the positions of other streams.
+    * "events": The new events seen on the server.
+    * "presence": Presence updates.
+    * "typing": Typing updates.
+    * "receipts": Receipt updates.
+    * "user_account_data": Top-level per user account data.
+    * "room_account_data: Per room per user account data.
+    * "tag_account_data": Per room per user tags.
+    * "backfill": Old events that have been backfilled from other servers.
+
+    The API takes two additional query parameters:
+
+    * "timeout": How long to wait before returning an empty response.
+    * "limit": The maximum number of rows to return for the selected streams.
+
+    The response is a JSON object with keys for each stream with updates. Under
+    each key is a JSON object with:
+
+    * "postion": The current position of the stream.
+    * "field_names": The names of the fields in each row.
+    * "rows": The updates as an array of arrays.
+
+    There are a number of ways this API could be used:
+
+    1) To replicate the contents of the backing database to another database.
+    2) To be notified when the contents of a shared backing database changes.
+    3) To "tail" the activity happening on a server for debugging.
+
+    In the first case the client would track all of the streams and store it's
+    own copy of the data.
+
+    In the second case the client might theoretically just be able to follow
+    the "streams" stream to track where the other streams are. However in
+    practise it will probably need to get the contents of the streams in
+    order to expire the any in-memory caches. Whether it gets the contents
+    of the streams from this replication API or directly from the backing
+    store is a matter of taste.
+
+    In the third case the client would use the "streams" stream to find what
+    streams are available and their current positions. Then it can start
+    long-polling this replication API for new data on those streams.
+    """
+
+    isLeaf = True
+
+    def __init__(self, hs):
+        Resource.__init__(self)  # Resource is old-style, so no super()
+
+        self.version_string = hs.version_string
+        self.store = hs.get_datastore()
+        self.sources = hs.get_event_sources()
+        self.presence_handler = hs.get_handlers().presence_handler
+        self.typing_handler = hs.get_handlers().typing_notification_handler
+        self.notifier = hs.notifier
+
+    def render_GET(self, request):
+        self._async_render_GET(request)
+        return NOT_DONE_YET
+
+    @defer.inlineCallbacks
+    def current_replication_token(self):
+        stream_token = yield self.sources.get_current_token()
+        backfill_token = yield self.store.get_current_backfill_token()
+
+        defer.returnValue(_ReplicationToken(
+            stream_token.room_stream_id,
+            int(stream_token.presence_key),
+            int(stream_token.typing_key),
+            int(stream_token.receipt_key),
+            int(stream_token.account_data_key),
+            backfill_token,
+        ))
+
+    @request_handler
+    @defer.inlineCallbacks
+    def _async_render_GET(self, request):
+        limit = parse_integer(request, "limit", 100)
+        timeout = parse_integer(request, "timeout", 10 * 1000)
+
+        request.setHeader(b"Content-Type", b"application/json")
+        writer = _Writer(request)
+
+        @defer.inlineCallbacks
+        def replicate():
+            current_token = yield self.current_replication_token()
+            logger.info("Replicating up to %r", current_token)
+
+            yield self.account_data(writer, current_token, limit)
+            yield self.events(writer, current_token, limit)
+            yield self.presence(writer, current_token)  # TODO: implement limit
+            yield self.typing(writer, current_token)  # TODO: implement limit
+            yield self.receipts(writer, current_token, limit)
+            self.streams(writer, current_token)
+
+            logger.info("Replicated %d rows", writer.total)
+            defer.returnValue(writer.total)
+
+        yield self.notifier.wait_for_replication(replicate, timeout)
+
+        writer.finish()
+
+    def streams(self, writer, current_token):
+        request_token = parse_string(writer.request, "streams")
+
+        streams = []
+
+        if request_token is not None:
+            if request_token == "-1":
+                for names, position in zip(STREAM_NAMES, current_token):
+                    streams.extend((name, position) for name in names)
+            else:
+                items = zip(
+                    STREAM_NAMES,
+                    current_token,
+                    _ReplicationToken(request_token)
+                )
+                for names, current_id, last_id in items:
+                    if last_id < current_id:
+                        streams.extend((name, current_id) for name in names)
+
+            if streams:
+                writer.write_header_and_rows(
+                    "streams", streams, ("name", "position"),
+                    position=str(current_token)
+                )
+
+    @defer.inlineCallbacks
+    def events(self, writer, current_token, limit):
+        request_events = parse_integer(writer.request, "events")
+        request_backfill = parse_integer(writer.request, "backfill")
+
+        if request_events is not None or request_backfill is not None:
+            if request_events is None:
+                request_events = current_token.events
+            if request_backfill is None:
+                request_backfill = current_token.backfill
+            events_rows, backfill_rows = yield self.store.get_all_new_events(
+                request_backfill, request_events,
+                current_token.backfill, current_token.events,
+                limit
+            )
+            writer.write_header_and_rows(
+                "events", events_rows, ("position", "internal", "json")
+            )
+            writer.write_header_and_rows(
+                "backfill", backfill_rows, ("position", "internal", "json")
+            )
+
+    @defer.inlineCallbacks
+    def presence(self, writer, current_token):
+        current_position = current_token.presence
+
+        request_presence = parse_integer(writer.request, "presence")
+
+        if request_presence is not None:
+            presence_rows = yield self.presence_handler.get_all_presence_updates(
+                request_presence, current_position
+            )
+            writer.write_header_and_rows("presence", presence_rows, (
+                "position", "user_id", "state", "last_active_ts",
+                "last_federation_update_ts", "last_user_sync_ts",
+                "status_msg", "currently_active",
+            ))
+
+    @defer.inlineCallbacks
+    def typing(self, writer, current_token):
+        current_position = current_token.presence
+
+        request_typing = parse_integer(writer.request, "typing")
+
+        if request_typing is not None:
+            typing_rows = yield self.typing_handler.get_all_typing_updates(
+                request_typing, current_position
+            )
+            writer.write_header_and_rows("typing", typing_rows, (
+                "position", "room_id", "typing"
+            ))
+
+    @defer.inlineCallbacks
+    def receipts(self, writer, current_token, limit):
+        current_position = current_token.receipts
+
+        request_receipts = parse_integer(writer.request, "receipts")
+
+        if request_receipts is not None:
+            receipts_rows = yield self.store.get_all_updated_receipts(
+                request_receipts, current_position, limit
+            )
+            writer.write_header_and_rows("receipts", receipts_rows, (
+                "position", "room_id", "receipt_type", "user_id", "event_id", "data"
+            ))
+
+    @defer.inlineCallbacks
+    def account_data(self, writer, current_token, limit):
+        current_position = current_token.account_data
+
+        user_account_data = parse_integer(writer.request, "user_account_data")
+        room_account_data = parse_integer(writer.request, "room_account_data")
+        tag_account_data = parse_integer(writer.request, "tag_account_data")
+
+        if user_account_data is not None or room_account_data is not None:
+            if user_account_data is None:
+                user_account_data = current_position
+            if room_account_data is None:
+                room_account_data = current_position
+            user_rows, room_rows = yield self.store.get_all_updated_account_data(
+                user_account_data, room_account_data, current_position, limit
+            )
+            writer.write_header_and_rows("user_account_data", user_rows, (
+                "position", "user_id", "type", "content"
+            ))
+            writer.write_header_and_rows("room_account_data", room_rows, (
+                "position", "user_id", "room_id", "type", "content"
+            ))
+
+        if tag_account_data is not None:
+            tag_rows = yield self.store.get_all_updated_tags(
+                tag_account_data, current_position, limit
+            )
+            writer.write_header_and_rows("tag_account_data", tag_rows, (
+                "position", "user_id", "room_id", "tags"
+            ))
+
+
+class _Writer(object):
+    """Writes the streams as a JSON object as the response to the request"""
+    def __init__(self, request):
+        self.streams = {}
+        self.request = request
+        self.total = 0
+
+    def write_header_and_rows(self, name, rows, fields, position=None):
+        if not rows:
+            return
+
+        if position is None:
+            position = rows[-1][0]
+
+        self.streams[name] = {
+            "position": str(position),
+            "field_names": fields,
+            "rows": rows,
+        }
+
+        self.total += len(rows)
+
+    def finish(self):
+        self.request.write(json.dumps(self.streams, ensure_ascii=False))
+        finish_request(self.request)
+
+
+class _ReplicationToken(collections.namedtuple("_ReplicationToken", (
+    "events", "presence", "typing", "receipts", "account_data", "backfill",
+))):
+    __slots__ = []
+
+    def __new__(cls, *args):
+        if len(args) == 1:
+            return cls(*(int(value) for value in args[0].split("_")))
+        else:
+            return super(_ReplicationToken, cls).__new__(cls, *args)
+
+    def __str__(self):
+        return "_".join(str(value) for value in self)