Fetching missing state from the roomserver. (#135)

* Fetching missing state from the roomserver.

Whenever the syncserver receives an event from the room server that adds
state that isn't in the syncserver's local database it should fetch
those state events from the roomserver.

* Fix append

* Put comment back

* Comments

* s/addsStateEvents/lookupStateEvents/

* Fix spelling

* Include the stream position that a state event was added at in the current state tables

* Fix comment

* Review comments

src/github.com/matrix-org/dendrite/syncapi/config/config.go

@@ -20,6 +20,8 @@ import (
 
 // Sync contains the config information necessary to spin up a sync-server process.
 type Sync struct {
+	// Where the room server is listening for queries.
+	RoomserverURL string `yaml:"roomserver_url"`
 	// The topic for events which are written by the room server output log.
 	RoomserverOutputTopic string `yaml:"roomserver_topic"`
 	// A list of URIs to consume events from. These kafka logs should be produced by a Room Server.

src/github.com/matrix-org/dendrite/syncapi/consumers/roomserver.go

@@ -16,6 +16,7 @@ package consumers
 
 import (
 	"encoding/json"
+	"fmt"
 
 	log "github.com/Sirupsen/logrus"
 	"github.com/matrix-org/dendrite/common"
@@ -33,6 +34,7 @@ type OutputRoomEvent struct {
 	roomServerConsumer *common.ContinualConsumer
 	db                 *storage.SyncServerDatabase
 	notifier           *sync.Notifier
+	query              api.RoomserverQueryAPI
 }
 
 // NewOutputRoomEvent creates a new OutputRoomEvent consumer. Call Start() to begin consuming from room servers.
@@ -51,6 +53,7 @@ func NewOutputRoomEvent(cfg *config.Sync, n *sync.Notifier, store *storage.SyncS
 		roomServerConsumer: &consumer,
 		db:                 store,
 		notifier:           n,
+		query:              api.NewRoomserverQueryAPIHTTP(cfg.RoomserverURL, nil),
 	}
 	consumer.ProcessMessage = s.onMessage
 
@@ -84,7 +87,19 @@ func (s *OutputRoomEvent) onMessage(msg *sarama.ConsumerMessage) error {
 		"room_id":  ev.RoomID(),
 	}).Info("received event from roomserver")
 
-	syncStreamPos, err := s.db.WriteEvent(&ev, output.AddsStateEventIDs, output.RemovesStateEventIDs)
+	addsStateEvents, err := s.lookupStateEvents(output.AddsStateEventIDs, ev)
+	if err != nil {
+		log.WithFields(log.Fields{
+			"event":      string(ev.JSON()),
+			log.ErrorKey: err,
+			"add":        output.AddsStateEventIDs,
+			"del":        output.RemovesStateEventIDs,
+		}).Panicf("roomserver output log: state event lookup failure")
+	}
+
+	syncStreamPos, err := s.db.WriteEvent(
+		&ev, addsStateEvents, output.AddsStateEventIDs, output.RemovesStateEventIDs,
+	)
 
 	if err != nil {
 		// panic rather than continue with an inconsistent database
@@ -100,3 +115,74 @@ func (s *OutputRoomEvent) onMessage(msg *sarama.ConsumerMessage) error {
 
 	return nil
 }
+
+// lookupStateEvents looks up the state events that are added by a new event.
+func (s *OutputRoomEvent) lookupStateEvents(
+	addsStateEventIDs []string, event gomatrixserverlib.Event,
+) ([]gomatrixserverlib.Event, error) {
+	// Fast path if there aren't any new state events.
+	if len(addsStateEventIDs) == 0 {
+		return nil, nil
+	}
+
+	// Fast path if the only state event added is the event itself.
+	if len(addsStateEventIDs) == 1 && addsStateEventIDs[0] == event.EventID() {
+		return []gomatrixserverlib.Event{event}, nil
+	}
+
+	// Check if this is re-adding a state events that we previously processed
+	// If we have previously received a state event it may still be in
+	// our event database.
+	result, err := s.db.Events(addsStateEventIDs)
+	if err != nil {
+		return nil, err
+	}
+	missing := missingEventsFrom(result, addsStateEventIDs)
+
+	// Check if event itself is being added.
+	for _, eventID := range missing {
+		if eventID == event.EventID() {
+			result = append(result, event)
+			break
+		}
+	}
+	missing = missingEventsFrom(result, addsStateEventIDs)
+
+	if len(missing) == 0 {
+		return result, nil
+	}
+
+	// At this point the missing events are neither the event itself nor are
+	// they present in our local database. Our only option is to fetch them
+	// from the roomserver using the query API.
+	eventReq := api.QueryEventsByIDRequest{EventIDs: missing}
+	var eventResp api.QueryEventsByIDResponse
+	if err := s.query.QueryEventsByID(&eventReq, &eventResp); err != nil {
+		return nil, err
+	}
+
+	result = append(result, eventResp.Events...)
+	missing = missingEventsFrom(result, addsStateEventIDs)
+
+	if len(missing) != 0 {
+		return nil, fmt.Errorf(
+			"missing %d state events IDs at event %q", len(missing), event.EventID(),
+		)
+	}
+
+	return result, nil
+}
+
+func missingEventsFrom(events []gomatrixserverlib.Event, required []string) []string {
+	have := map[string]bool{}
+	for _, event := range events {
+		have[event.EventID()] = true
+	}
+	var missing []string
+	for _, eventID := range required {
+		if !have[eventID] {
+			missing = append(missing, eventID)
+		}
+	}
+	return missing
+}

src/github.com/matrix-org/dendrite/syncapi/storage/current_room_state_table.go

@@ -16,6 +16,7 @@ package storage
 
 import (
 	"database/sql"
+	"github.com/lib/pq"
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
@@ -35,6 +36,9 @@ CREATE TABLE IF NOT EXISTS current_room_state (
     -- The 'content.membership' value if this event is an m.room.member event. For other
     -- events, this will be NULL.
     membership TEXT,
+    -- The serial ID of the output_room_events table when this event became
+    -- part of the current state of the room.
+    added_at BIGINT,
     -- Clobber based on 3-uple of room_id, type and state_key
     CONSTRAINT room_state_unique UNIQUE (room_id, type, state_key)
 );
@@ -45,9 +49,10 @@ CREATE INDEX IF NOT EXISTS membership_idx ON current_room_state(type, state_key,
 `
 
 const upsertRoomStateSQL = "" +
-	"INSERT INTO current_room_state (room_id, event_id, type, state_key, event_json, membership) VALUES ($1, $2, $3, $4, $5, $6)" +
+	"INSERT INTO current_room_state (room_id, event_id, type, state_key, event_json, membership, added_at)" +
+	" VALUES ($1, $2, $3, $4, $5, $6, $7)" +
 	" ON CONFLICT ON CONSTRAINT room_state_unique" +
-	" DO UPDATE SET event_id = $2, event_json = $5, membership = $6"
+	" DO UPDATE SET event_id = $2, event_json = $5, membership = $6, added_at = $7"
 
 const deleteRoomStateByEventIDSQL = "" +
 	"DELETE FROM current_room_state WHERE event_id = $1"
@@ -61,12 +66,16 @@ const selectCurrentStateSQL = "" +
 const selectJoinedUsersSQL = "" +
 	"SELECT room_id, state_key FROM current_room_state WHERE type = 'm.room.member' AND membership = 'join'"
 
+const selectEventsWithEventIDsSQL = "" +
+	"SELECT added_at, event_json FROM current_room_state WHERE event_id = ANY($1)"
+
 type currentRoomStateStatements struct {
 	upsertRoomStateStmt             *sql.Stmt
 	deleteRoomStateByEventIDStmt    *sql.Stmt
 	selectRoomIDsWithMembershipStmt *sql.Stmt
 	selectCurrentStateStmt          *sql.Stmt
 	selectJoinedUsersStmt           *sql.Stmt
+	selectEventsWithEventIDsStmt    *sql.Stmt
 }
 
 func (s *currentRoomStateStatements) prepare(db *sql.DB) (err error) {
@@ -89,6 +98,9 @@ func (s *currentRoomStateStatements) prepare(db *sql.DB) (err error) {
 	if s.selectJoinedUsersStmt, err = db.Prepare(selectJoinedUsersSQL); err != nil {
 		return
 	}
+	if s.selectEventsWithEventIDsStmt, err = db.Prepare(selectEventsWithEventIDsSQL); err != nil {
+		return
+	}
 	return
 }
 
@@ -141,6 +153,33 @@ func (s *currentRoomStateStatements) selectCurrentState(txn *sql.Tx, roomID stri
 	}
 	defer rows.Close()
 
+	return rowsToEvents(rows)
+}
+
+func (s *currentRoomStateStatements) deleteRoomStateByEventID(txn *sql.Tx, eventID string) error {
+	_, err := txn.Stmt(s.deleteRoomStateByEventIDStmt).Exec(eventID)
+	return err
+}
+
+func (s *currentRoomStateStatements) upsertRoomState(
+	txn *sql.Tx, event gomatrixserverlib.Event, membership *string, addedAt int64,
+) error {
+	_, err := txn.Stmt(s.upsertRoomStateStmt).Exec(
+		event.RoomID(), event.EventID(), event.Type(), *event.StateKey(), event.JSON(), membership, addedAt,
+	)
+	return err
+}
+
+func (s *currentRoomStateStatements) selectEventsWithEventIDs(txn *sql.Tx, eventIDs []string) ([]streamEvent, error) {
+	rows, err := txn.Stmt(s.selectEventsWithEventIDsStmt).Query(pq.StringArray(eventIDs))
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	return rowsToStreamEvents(rows)
+}
+
+func rowsToEvents(rows *sql.Rows) ([]gomatrixserverlib.Event, error) {
 	var result []gomatrixserverlib.Event
 	for rows.Next() {
 		var eventBytes []byte
@@ -156,15 +195,3 @@ func (s *currentRoomStateStatements) selectCurrentState(txn *sql.Tx, roomID stri
 	}
 	return result, nil
 }
-
-func (s *currentRoomStateStatements) deleteRoomStateByEventID(txn *sql.Tx, eventID string) error {
-	_, err := txn.Stmt(s.deleteRoomStateByEventIDStmt).Exec(eventID)
-	return err
-}
-
-func (s *currentRoomStateStatements) upsertRoomState(txn *sql.Tx, event gomatrixserverlib.Event, membership *string) error {
-	_, err := txn.Stmt(s.upsertRoomStateStmt).Exec(
-		event.RoomID(), event.EventID(), event.Type(), *event.StateKey(), event.JSON(), membership,
-	)
-	return err
-}

src/github.com/matrix-org/dendrite/syncapi/storage/output_room_events_table.go

@@ -16,7 +16,6 @@ package storage
 
 import (
 	"database/sql"
-	"fmt"
 
 	log "github.com/Sirupsen/logrus"
 	"github.com/lib/pq"
@@ -193,7 +192,7 @@ func (s *outputRoomEventsStatements) selectRecentEvents(
 		return nil, err
 	}
 	defer rows.Close()
-	events, err := rowsToEvents(rows)
+	events, err := rowsToStreamEvents(rows)
 	if err != nil {
 		return nil, err
 	}
@@ -205,23 +204,19 @@ func (s *outputRoomEventsStatements) selectRecentEvents(
 // Events returns the events for the given event IDs. Returns an error if any one of the event IDs given are missing
 // from the database.
 func (s *outputRoomEventsStatements) selectEvents(txn *sql.Tx, eventIDs []string) ([]streamEvent, error) {
-	rows, err := txn.Stmt(s.selectEventsStmt).Query(pq.StringArray(eventIDs))
+	stmt := s.selectEventsStmt
+	if txn != nil {
+		stmt = txn.Stmt(stmt)
+	}
+	rows, err := stmt.Query(pq.StringArray(eventIDs))
 	if err != nil {
 		return nil, err
 	}
 	defer rows.Close()
-	result, err := rowsToEvents(rows)
-	if err != nil {
-		return nil, err
-	}
-
-	if len(result) != len(eventIDs) {
-		return nil, fmt.Errorf("failed to map all event IDs to events: (got %d, wanted %d)", len(result), len(eventIDs))
-	}
-	return result, nil
+	return rowsToStreamEvents(rows)
 }
 
-func rowsToEvents(rows *sql.Rows) ([]streamEvent, error) {
+func rowsToStreamEvents(rows *sql.Rows) ([]streamEvent, error) {
 	var result []streamEvent
 	for rows.Next() {
 		var (

src/github.com/matrix-org/dendrite/syncapi/storage/syncserver.go

@@ -17,6 +17,7 @@ package storage
 import (
 	"database/sql"
 	"encoding/json"
+	"fmt"
 	// Import the postgres database driver.
 	_ "github.com/lib/pq"
 	"github.com/matrix-org/dendrite/clientapi/events"
@@ -75,10 +76,24 @@ func (d *SyncServerDatabase) AllJoinedUsersInRooms() (map[string][]string, error
 	return d.roomstate.selectJoinedUsers()
 }
 
+// Events lookups a list of event by their event ID.
+// Returns a list of events matching the requested IDs found in the database.
+// If an event is not found in the database then it will be omitted from the list.
+// Returns an error if there was a problem talking with the database
+func (d *SyncServerDatabase) Events(eventIDs []string) ([]gomatrixserverlib.Event, error) {
+	streamEvents, err := d.events.selectEvents(nil, eventIDs)
+	if err != nil {
+		return nil, err
+	}
+	return streamEventsToEvents(streamEvents), nil
+}
+
 // WriteEvent into the database. It is not safe to call this function from multiple goroutines, as it would create races
 // when generating the stream position for this event. Returns the sync stream position for the inserted event.
 // Returns an error if there was a problem inserting this event.
-func (d *SyncServerDatabase) WriteEvent(ev *gomatrixserverlib.Event, addStateEventIDs, removeStateEventIDs []string) (streamPos types.StreamPosition, returnErr error) {
+func (d *SyncServerDatabase) WriteEvent(
+	ev *gomatrixserverlib.Event, addStateEvents []gomatrixserverlib.Event, addStateEventIDs, removeStateEventIDs []string,
+) (streamPos types.StreamPosition, returnErr error) {
 	returnErr = runTransaction(d.db, func(txn *sql.Tx) error {
 		var err error
 		pos, err := d.events.insertEvent(txn, ev, addStateEventIDs, removeStateEventIDs)
@@ -87,31 +102,19 @@ func (d *SyncServerDatabase) WriteEvent(ev *gomatrixserverlib.Event, addStateEve
 		}
 		streamPos = types.StreamPosition(pos)
 
-		if len(addStateEventIDs) == 0 && len(removeStateEventIDs) == 0 {
+		if len(addStateEvents) == 0 && len(removeStateEventIDs) == 0 {
 			// Nothing to do, the event may have just been a message event.
 			return nil
 		}
 
-		// Update the current room state based on the added/removed state event IDs.
-		// In the common case there is a single added event ID which is the state event itself, assuming `ev` is a state event.
-		// However, conflict resolution may result in there being different events being added, or even some removed.
-		if len(removeStateEventIDs) == 0 && len(addStateEventIDs) == 1 && addStateEventIDs[0] == ev.EventID() {
-			// common case
-			return d.updateRoomState(txn, nil, []gomatrixserverlib.Event{*ev})
-		}
-
-		// uncommon case: we need to fetch the full event for each event ID mentioned, then update room state
-		added, err := d.events.selectEvents(txn, addStateEventIDs)
-		if err != nil {
-			return err
-		}
-
-		return d.updateRoomState(txn, removeStateEventIDs, streamEventsToEvents(added))
+		return d.updateRoomState(txn, removeStateEventIDs, addStateEvents, streamPos)
 	})
 	return
 }
 
-func (d *SyncServerDatabase) updateRoomState(txn *sql.Tx, removedEventIDs []string, addedEvents []gomatrixserverlib.Event) error {
+func (d *SyncServerDatabase) updateRoomState(
+	txn *sql.Tx, removedEventIDs []string, addedEvents []gomatrixserverlib.Event, streamPos types.StreamPosition,
+) error {
 	// remove first, then add, as we do not ever delete state, but do replace state which is a remove followed by an add.
 	for _, eventID := range removedEventIDs {
 		if err := d.roomstate.deleteRoomStateByEventID(txn, eventID); err != nil {
@@ -132,7 +135,7 @@ func (d *SyncServerDatabase) updateRoomState(txn *sql.Tx, removedEventIDs []stri
 			}
 			membership = &memberContent.Membership
 		}
-		if err := d.roomstate.upsertRoomState(txn, event, membership); err != nil {
+		if err := d.roomstate.upsertRoomState(txn, event, membership, int64(streamPos)); err != nil {
 			return err
 		}
 	}
@@ -310,7 +313,7 @@ func (d *SyncServerDatabase) fetchStateEvents(txn *sql.Tx, roomIDToEventIDSet ma
 		for _, missingEvIDs := range missingEvents {
 			allMissingEventIDs = append(allMissingEventIDs, missingEvIDs...)
 		}
-		evs, err := d.events.selectEvents(txn, allMissingEventIDs)
+		evs, err := d.fetchMissingStateEvents(txn, allMissingEventIDs)
 		if err != nil {
 			return nil, err
 		}
@@ -323,6 +326,45 @@ func (d *SyncServerDatabase) fetchStateEvents(txn *sql.Tx, roomIDToEventIDSet ma
 	return stateBetween, nil
 }
 
+func (d *SyncServerDatabase) fetchMissingStateEvents(txn *sql.Tx, eventIDs []string) ([]streamEvent, error) {
+	// Fetch from the events table first so we pick up the stream ID for the
+	// event.
+	events, err := d.events.selectEvents(txn, eventIDs)
+	if err != nil {
+		return nil, err
+	}
+
+	have := map[string]bool{}
+	for _, event := range events {
+		have[event.EventID()] = true
+	}
+	var missing []string
+	for _, eventID := range eventIDs {
+		if !have[eventID] {
+			missing = append(missing, eventID)
+		}
+	}
+	if len(missing) == 0 {
+		return events, nil
+	}
+
+	// If they are missing from the events table then they should be state
+	// events that we received from outside the main event stream.
+	// These should be in the room state table.
+	stateEvents, err := d.roomstate.selectEventsWithEventIDs(txn, missing)
+
+	if err != nil {
+		return nil, err
+	}
+	if len(stateEvents) != len(missing) {
+		return nil, fmt.Errorf("failed to map all event IDs to events: (got %d, wanted %d)", len(stateEvents), len(missing))
+	}
+	for _, e := range stateEvents {
+		events = append(events, e)
+	}
+	return events, nil
+}
+
 func (d *SyncServerDatabase) getStateDeltas(txn *sql.Tx, fromPos, toPos types.StreamPosition, userID string) ([]stateDelta, error) {
 	// Implement membership change algorithm: https://github.com/matrix-org/synapse/blob/v0.19.3/synapse/handlers/sync.py#L821
 	// - Get membership list changes for this user in this sync response