Merge pull request #155 from matrix-org/erikj/perf

Bulk and batch retrieval of events.

1 files changed, 337 insertions, 51 deletions

diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index 4fee155234..b262035fac 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -15,11 +15,12 @@
 
 from _base import SQLBaseStore, _RollbackButIsFineException
 
-from twisted.internet import defer
+from twisted.internet import defer, reactor
 
 from synapse.events import FrozenEvent
 from synapse.events.utils import prune_event
 
+from synapse.util.logcontext import preserve_context_over_deferred
 from synapse.util.logutils import log_function
 from synapse.api.constants import EventTypes
 from synapse.crypto.event_signing import compute_event_reference_hash
@@ -34,6 +35,16 @@ import simplejson as json
 logger = logging.getLogger(__name__)
 
 
+# These values are used in the `enqueus_event` and `_do_fetch` methods to
+# control how we batch/bulk fetch events from the database.
+# The values are plucked out of thing air to make initial sync run faster
+# on jki.re
+# TODO: Make these configurable.
+EVENT_QUEUE_THREADS = 3  # Max number of threads that will fetch events
+EVENT_QUEUE_ITERATIONS = 3  # No. times we block waiting for requests for events
+EVENT_QUEUE_TIMEOUT_S = 0.1  # Timeout when waiting for requests for events
+
+
 class EventsStore(SQLBaseStore):
     @defer.inlineCallbacks
     @log_function
@@ -91,18 +102,17 @@ class EventsStore(SQLBaseStore):
         Returns:
             Deferred : A FrozenEvent.
         """
-        event = yield self.runInteraction(
-            "get_event", self._get_event_txn,
-            event_id,
+        events = yield self._get_events(
+            [event_id],
             check_redacted=check_redacted,
             get_prev_content=get_prev_content,
             allow_rejected=allow_rejected,
         )
 
-        if not event and not allow_none:
+        if not events and not allow_none:
             raise RuntimeError("Could not find event %s" % (event_id,))
 
-        defer.returnValue(event)
+        defer.returnValue(events[0] if events else None)
 
     @log_function
     def _persist_event_txn(self, txn, event, context, backfilled,
@@ -401,28 +411,75 @@ class EventsStore(SQLBaseStore):
             "have_events", f,
         )
 
+    @defer.inlineCallbacks
     def _get_events(self, event_ids, check_redacted=True,
-                    get_prev_content=False):
-        return self.runInteraction(
-            "_get_events", self._get_events_txn, event_ids,
-            check_redacted=check_redacted, get_prev_content=get_prev_content,
+                    get_prev_content=False, allow_rejected=False):
+        if not event_ids:
+            defer.returnValue([])
+
+        event_map = self._get_events_from_cache(
+            event_ids,
+            check_redacted=check_redacted,
+            get_prev_content=get_prev_content,
+            allow_rejected=allow_rejected,
+        )
+
+        missing_events_ids = [e for e in event_ids if e not in event_map]
+
+        if not missing_events_ids:
+            defer.returnValue([
+                event_map[e_id] for e_id in event_ids
+                if e_id in event_map and event_map[e_id]
+            ])
+
+        missing_events = yield self._enqueue_events(
+            missing_events_ids,
+            check_redacted=check_redacted,
+            get_prev_content=get_prev_content,
+            allow_rejected=allow_rejected,
         )
 
+        event_map.update(missing_events)
+
+        defer.returnValue([
+            event_map[e_id] for e_id in event_ids
+            if e_id in event_map and event_map[e_id]
+        ])
+
     def _get_events_txn(self, txn, event_ids, check_redacted=True,
-                        get_prev_content=False):
+                        get_prev_content=False, allow_rejected=False):
         if not event_ids:
             return []
 
-        events = [
-            self._get_event_txn(
-                txn, event_id,
-                check_redacted=check_redacted,
-                get_prev_content=get_prev_content
-            )
-            for event_id in event_ids
-        ]
+        event_map = self._get_events_from_cache(
+            event_ids,
+            check_redacted=check_redacted,
+            get_prev_content=get_prev_content,
+            allow_rejected=allow_rejected,
+        )
+
+        missing_events_ids = [e for e in event_ids if e not in event_map]
+
+        if not missing_events_ids:
+            return [
+                event_map[e_id] for e_id in event_ids
+                if e_id in event_map and event_map[e_id]
+            ]
+
+        missing_events = self._fetch_events_txn(
+            txn,
+            missing_events_ids,
+            check_redacted=check_redacted,
+            get_prev_content=get_prev_content,
+            allow_rejected=allow_rejected,
+        )
 
-        return [e for e in events if e]
+        event_map.update(missing_events)
+
+        return [
+            event_map[e_id] for e_id in event_ids
+            if e_id in event_map and event_map[e_id]
+        ]
 
     def _invalidate_get_event_cache(self, event_id):
         for check_redacted in (False, True):
@@ -433,54 +490,272 @@ class EventsStore(SQLBaseStore):
     def _get_event_txn(self, txn, event_id, check_redacted=True,
                        get_prev_content=False, allow_rejected=False):
 
-        try:
-            ret = self._get_event_cache.get(event_id, check_redacted, get_prev_content)
+        events = self._get_events_txn(
+            txn, [event_id],
+            check_redacted=check_redacted,
+            get_prev_content=get_prev_content,
+            allow_rejected=allow_rejected,
+        )
+
+        return events[0] if events else None
+
+    def _get_events_from_cache(self, events, check_redacted, get_prev_content,
+                               allow_rejected):
+        event_map = {}
+
+        for event_id in events:
+            try:
+                ret = self._get_event_cache.get(
+                    event_id, check_redacted, get_prev_content
+                )
 
-            if allow_rejected or not ret.rejected_reason:
-                return ret
+                if allow_rejected or not ret.rejected_reason:
+                    event_map[event_id] = ret
+                else:
+                    event_map[event_id] = None
+            except KeyError:
+                pass
+
+        return event_map
+
+    def _do_fetch(self, conn):
+        """Takes a database connection and waits for requests for events from
+        the _event_fetch_list queue.
+        """
+        event_list = []
+        i = 0
+        while True:
+            try:
+                with self._event_fetch_lock:
+                    event_list = self._event_fetch_list
+                    self._event_fetch_list = []
+
+                    if not event_list:
+                        single_threaded = self.database_engine.single_threaded
+                        if single_threaded or i > EVENT_QUEUE_ITERATIONS:
+                            self._event_fetch_ongoing -= 1
+                            return
+                        else:
+                            self._event_fetch_lock.wait(EVENT_QUEUE_TIMEOUT_S)
+                            i += 1
+                            continue
+                    i = 0
+
+                event_id_lists = zip(*event_list)[0]
+                event_ids = [
+                    item for sublist in event_id_lists for item in sublist
+                ]
+
+                rows = self._new_transaction(
+                    conn, "do_fetch", [], self._fetch_event_rows, event_ids
+                )
+
+                row_dict = {
+                    r["event_id"]: r
+                    for r in rows
+                }
+
+                # We only want to resolve deferreds from the main thread
+                def fire(lst, res):
+                    for ids, d in lst:
+                        if not d.called:
+                            try:
+                                d.callback([
+                                    res[i]
+                                    for i in ids
+                                    if i in res
+                                ])
+                            except:
+                                logger.exception("Failed to callback")
+                reactor.callFromThread(fire, event_list, row_dict)
+            except Exception as e:
+                logger.exception("do_fetch")
+
+                # We only want to resolve deferreds from the main thread
+                def fire(evs):
+                    for _, d in evs:
+                        if not d.called:
+                            d.errback(e)
+
+                if event_list:
+                    reactor.callFromThread(fire, event_list)
+
+    @defer.inlineCallbacks
+    def _enqueue_events(self, events, check_redacted=True,
+                        get_prev_content=False, allow_rejected=False):
+        """Fetches events from the database using the _event_fetch_list. This
+        allows batch and bulk fetching of events - it allows us to fetch events
+        without having to create a new transaction for each request for events.
+        """
+        if not events:
+            defer.returnValue({})
+
+        events_d = defer.Deferred()
+        with self._event_fetch_lock:
+            self._event_fetch_list.append(
+                (events, events_d)
+            )
+
+            self._event_fetch_lock.notify()
+
+            if self._event_fetch_ongoing < EVENT_QUEUE_THREADS:
+                self._event_fetch_ongoing += 1
+                should_start = True
             else:
-                return None
-        except KeyError:
-            pass
+                should_start = False
 
-        sql = (
-            "SELECT e.internal_metadata, e.json, r.event_id, rej.reason "
-            "FROM event_json as e "
-            "LEFT JOIN redactions as r ON e.event_id = r.redacts "
-            "LEFT JOIN rejections as rej on rej.event_id = e.event_id  "
-            "WHERE e.event_id = ? "
-            "LIMIT 1 "
+        if should_start:
+            self.runWithConnection(
+                self._do_fetch
+            )
+
+        rows = yield preserve_context_over_deferred(events_d)
+
+        if not allow_rejected:
+            rows[:] = [r for r in rows if not r["rejects"]]
+
+        res = yield defer.gatherResults(
+            [
+                self._get_event_from_row(
+                    row["internal_metadata"], row["json"], row["redacts"],
+                    check_redacted=check_redacted,
+                    get_prev_content=get_prev_content,
+                    rejected_reason=row["rejects"],
+                )
+                for row in rows
+            ],
+            consumeErrors=True
         )
 
-        txn.execute(sql, (event_id,))
+        defer.returnValue({
+            e.event_id: e
+            for e in res if e
+        })
 
-        res = txn.fetchone()
+    def _fetch_event_rows(self, txn, events):
+        rows = []
+        N = 200
+        for i in range(1 + len(events) / N):
+            evs = events[i*N:(i + 1)*N]
+            if not evs:
+                break
 
-        if not res:
-            return None
+            sql = (
+                "SELECT "
+                " e.event_id as event_id, "
+                " e.internal_metadata,"
+                " e.json,"
+                " r.redacts as redacts,"
+                " rej.event_id as rejects "
+                " FROM event_json as e"
+                " LEFT JOIN rejections as rej USING (event_id)"
+                " LEFT JOIN redactions as r ON e.event_id = r.redacts"
+                " WHERE e.event_id IN (%s)"
+            ) % (",".join(["?"]*len(evs)),)
+
+            txn.execute(sql, evs)
+            rows.extend(self.cursor_to_dict(txn))
+
+        return rows
+
+    def _fetch_events_txn(self, txn, events, check_redacted=True,
+                          get_prev_content=False, allow_rejected=False):
+        if not events:
+            return {}
+
+        rows = self._fetch_event_rows(
+            txn, events,
+        )
 
-        internal_metadata, js, redacted, rejected_reason = res
+        if not allow_rejected:
+            rows[:] = [r for r in rows if not r["rejects"]]
 
-        result = self._get_event_from_row_txn(
-            txn, internal_metadata, js, redacted,
-            check_redacted=check_redacted,
-            get_prev_content=get_prev_content,
+        res = [
+            self._get_event_from_row_txn(
+                txn,
+                row["internal_metadata"], row["json"], row["redacts"],
+                check_redacted=check_redacted,
+                get_prev_content=get_prev_content,
+                rejected_reason=row["rejects"],
+            )
+            for row in rows
+        ]
+
+        return {
+            r.event_id: r
+            for r in res
+        }
+
+    @defer.inlineCallbacks
+    def _get_event_from_row(self, internal_metadata, js, redacted,
+                            check_redacted=True, get_prev_content=False,
+                            rejected_reason=None):
+        d = json.loads(js)
+        internal_metadata = json.loads(internal_metadata)
+
+        if rejected_reason:
+            rejected_reason = yield self._simple_select_one_onecol(
+                table="rejections",
+                keyvalues={"event_id": rejected_reason},
+                retcol="reason",
+                desc="_get_event_from_row",
+            )
+
+        ev = FrozenEvent(
+            d,
+            internal_metadata_dict=internal_metadata,
             rejected_reason=rejected_reason,
         )
-        self._get_event_cache.prefill(event_id, check_redacted, get_prev_content, result)
 
-        if allow_rejected or not rejected_reason:
-            return result
-        else:
-            return None
+        if check_redacted and redacted:
+            ev = prune_event(ev)
+
+            redaction_id = yield self._simple_select_one_onecol(
+                table="redactions",
+                keyvalues={"redacts": ev.event_id},
+                retcol="event_id",
+                desc="_get_event_from_row",
+            )
+
+            ev.unsigned["redacted_by"] = redaction_id
+            # Get the redaction event.
+
+            because = yield self.get_event(
+                redaction_id,
+                check_redacted=False
+            )
+
+            if because:
+                ev.unsigned["redacted_because"] = because
+
+        if get_prev_content and "replaces_state" in ev.unsigned:
+            prev = yield self.get_event(
+                ev.unsigned["replaces_state"],
+                get_prev_content=False,
+            )
+            if prev:
+                ev.unsigned["prev_content"] = prev.get_dict()["content"]
+
+        self._get_event_cache.prefill(
+            ev.event_id, check_redacted, get_prev_content, ev
+        )
+
+        defer.returnValue(ev)
 
     def _get_event_from_row_txn(self, txn, internal_metadata, js, redacted,
                                 check_redacted=True, get_prev_content=False,
                                 rejected_reason=None):
-
         d = json.loads(js)
         internal_metadata = json.loads(internal_metadata)
 
+        if rejected_reason:
+            rejected_reason = self._simple_select_one_onecol_txn(
+                txn,
+                table="rejections",
+                keyvalues={"event_id": rejected_reason},
+                retcol="reason",
+            )
+
         ev = FrozenEvent(
             d,
             internal_metadata_dict=internal_metadata,
@@ -490,12 +765,19 @@ class EventsStore(SQLBaseStore):
         if check_redacted and redacted:
             ev = prune_event(ev)
 
-            ev.unsigned["redacted_by"] = redacted
+            redaction_id = self._simple_select_one_onecol_txn(
+                txn,
+                table="redactions",
+                keyvalues={"redacts": ev.event_id},
+                retcol="event_id",
+            )
+
+            ev.unsigned["redacted_by"] = redaction_id
             # Get the redaction event.
 
             because = self._get_event_txn(
                 txn,
-                redacted,
+                redaction_id,
                 check_redacted=False
             )
 
@@ -511,6 +793,10 @@ class EventsStore(SQLBaseStore):
             if prev:
                 ev.unsigned["prev_content"] = prev.get_dict()["content"]
 
+        self._get_event_cache.prefill(
+            ev.event_id, check_redacted, get_prev_content, ev
+        )
+
         return ev
 
     def _parse_events(self, rows):