Merge branch 'master' into kegan/http-auth

.travis.yml

@@ -1,13 +1,26 @@
 language: go
 go:
  - 1.7
+
+sudo: false
+
+# Use trusty for postgres 9.5 support
+dist: trusty
+
+addons:
+  postgresql: "9.5"
+
+services:
+  - postgresql
+
 install:
  - go get github.com/constabulary/gb/...
  - go get github.com/golang/lint/golint
  - go get github.com/fzipp/gocyclo
+ - ./travis-install-kafka.sh
 
 script:
- - gb build github.com/matrix-org/dendrite/roomserver/roomserver && ./hooks/pre-commit
+ - ./travis-test.sh
 
 notifications:
     webhooks:

README.md

@@ -37,7 +37,7 @@ complications for this model.
  3) A client can query the current state of the room from a reader.
 
 The writers and readers cannot extract the necessary information directly from
-the event logs because it would take to long to extract the information as the
+the event logs because it would take too long to extract the information as the
 state is built up by collecting individual state events from the event history.
 
 The writers and readers therefore need access to something that stores copies

src/github.com/matrix-org/dendrite/roomserver/api/output.go

@@ -0,0 +1,85 @@
+package api
+
+import (
+	"encoding/json"
+)
+
+// An OutputRoomEvent is written when the roomserver receives a new event.
+type OutputRoomEvent struct {
+	// The JSON bytes of the event.
+	Event []byte
+	// The state event IDs needed to determine who can see this event.
+	// This can be used to tell which users to send the event to.
+	VisibilityEventIDs []string
+	// The latest events in the room after this event.
+	// This can be used to set the prev events for new events in the room.
+	// This also can be used to get the full current state after this event.
+	LatestEventIDs []string
+	// The state event IDs that were added to the state of the room by this event.
+	// Together with RemovesStateEventIDs this allows the receiver to keep an up to date
+	// view of the current state of the room.
+	AddsStateEventIDs []string
+	// The state event IDs that were removed from the state of the room by this event.
+	RemovesStateEventIDs []string
+	// The ID of the event that was output before this event.
+	// Or the empty string if this is the first event output for this room.
+	// This is used by consumers to check if they can safely update their
+	// current state using the delta supplied in AddsStateEventIDs and
+	// RemovesStateEventIDs.
+	// If the LastSentEventID doesn't match what they were expecting it to be
+	// they can use the LatestEventIDs to request the full current state.
+	LastSentEventID string
+}
+
+// UnmarshalJSON implements json.Unmarshaller
+func (ore *OutputRoomEvent) UnmarshalJSON(data []byte) error {
+	// Create a struct rather than unmarshalling directly into the OutputRoomEvent
+	// so that we can use json.RawMessage.
+	// We use json.RawMessage so that the event JSON is sent as JSON rather than
+	// being base64 encoded which is the default for []byte.
+	var content struct {
+		Event                *json.RawMessage
+		VisibilityEventIDs   []string
+		LatestEventIDs       []string
+		AddsStateEventIDs    []string
+		RemovesStateEventIDs []string
+		LastSentEventID      string
+	}
+	if err := json.Unmarshal(data, &content); err != nil {
+		return err
+	}
+	if content.Event != nil {
+		ore.Event = []byte(*content.Event)
+	}
+	ore.VisibilityEventIDs = content.VisibilityEventIDs
+	ore.LatestEventIDs = content.LatestEventIDs
+	ore.AddsStateEventIDs = content.AddsStateEventIDs
+	ore.RemovesStateEventIDs = content.RemovesStateEventIDs
+	ore.LastSentEventID = content.LastSentEventID
+	return nil
+}
+
+// MarshalJSON implements json.Marshaller
+func (ore OutputRoomEvent) MarshalJSON() ([]byte, error) {
+	// Create a struct rather than marshalling directly from the OutputRoomEvent
+	// so that we can use json.RawMessage.
+	// We use json.RawMessage so that the event JSON is sent as JSON rather than
+	// being base64 encoded which is the default for []byte.
+	event := json.RawMessage(ore.Event)
+	content := struct {
+		Event                *json.RawMessage
+		VisibilityEventIDs   []string
+		LatestEventIDs       []string
+		AddsStateEventIDs    []string
+		RemovesStateEventIDs []string
+		LastSentEventID      string
+	}{
+		Event:                &event,
+		VisibilityEventIDs:   ore.VisibilityEventIDs,
+		LatestEventIDs:       ore.LatestEventIDs,
+		AddsStateEventIDs:    ore.AddsStateEventIDs,
+		RemovesStateEventIDs: ore.RemovesStateEventIDs,
+		LastSentEventID:      ore.LastSentEventID,
+	}
+	return json.Marshal(&content)
+}

src/github.com/matrix-org/dendrite/roomserver/api/query.go

@@ -0,0 +1,102 @@
+package api
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"github.com/matrix-org/gomatrixserverlib"
+	"net/http"
+)
+
+// StateKeyTuple is a pair of an event type and state_key.
+// This is used when requesting parts of the state of a room.
+type StateKeyTuple struct {
+	// The "type" key
+	EventType string
+	// The "state_key" of a matrix event.
+	// The empty string is a legitimate value for the "state_key" in matrix
+	// so take care to initialise this field lest you accidentally request a
+	// "state_key" with the go default of the empty string.
+	EventStateKey string
+}
+
+// QueryLatestEventsAndStateRequest is a request to QueryLatestEventsAndState
+type QueryLatestEventsAndStateRequest struct {
+	// The roomID to query the latest events for.
+	RoomID string
+	// The state key tuples to fetch from the room current state.
+	// If this list is empty or nil then no state events are returned.
+	StateToFetch []StateKeyTuple
+}
+
+// QueryLatestEventsAndStateResponse is a response to QueryLatestEventsAndState
+type QueryLatestEventsAndStateResponse struct {
+	// Copy of the request for debugging.
+	QueryLatestEventsAndStateRequest
+	// Does the room exist?
+	// If the room doesn't exist this will be false and LatestEvents will be empty.
+	RoomExists bool
+	// The latest events in the room.
+	LatestEvents []gomatrixserverlib.EventReference
+	// The state events requested.
+	StateEvents []gomatrixserverlib.Event
+}
+
+// RoomserverQueryAPI is used to query information from the room server.
+type RoomserverQueryAPI interface {
+	// Query the latest events and state for a room from the room server.
+	QueryLatestEventsAndState(
+		request *QueryLatestEventsAndStateRequest,
+		response *QueryLatestEventsAndStateResponse,
+	) error
+}
+
+// RoomserverQueryLatestEventsAndStatePath is the HTTP path for the QueryLatestEventsAndState API.
+const RoomserverQueryLatestEventsAndStatePath = "/api/roomserver/QueryLatestEventsAndState"
+
+// NewRoomserverQueryAPIHTTP creates a RoomserverQueryAPI implemented by talking to a HTTP POST API.
+// If httpClient is nil then it uses the http.DefaultClient
+func NewRoomserverQueryAPIHTTP(roomserverURL string, httpClient *http.Client) RoomserverQueryAPI {
+	if httpClient == nil {
+		httpClient = http.DefaultClient
+	}
+	return &httpRoomserverQueryAPI{roomserverURL, *httpClient}
+}
+
+type httpRoomserverQueryAPI struct {
+	roomserverURL string
+	httpClient    http.Client
+}
+
+// QueryLatestEventsAndState implements RoomserverQueryAPI
+func (h *httpRoomserverQueryAPI) QueryLatestEventsAndState(
+	request *QueryLatestEventsAndStateRequest,
+	response *QueryLatestEventsAndStateResponse,
+) error {
+	apiURL := h.roomserverURL + RoomserverQueryLatestEventsAndStatePath
+	return postJSON(h.httpClient, apiURL, request, response)
+}
+
+func postJSON(httpClient http.Client, apiURL string, request, response interface{}) error {
+	jsonBytes, err := json.Marshal(request)
+	if err != nil {
+		return err
+	}
+	res, err := httpClient.Post(apiURL, "application/json", bytes.NewReader(jsonBytes))
+	if res != nil {
+		defer res.Body.Close()
+	}
+	if err != nil {
+		return err
+	}
+	if res.StatusCode != 200 {
+		var errorBody struct {
+			Message string `json:"message"`
+		}
+		if err = json.NewDecoder(res.Body).Decode(&errorBody); err != nil {
+			return err
+		}
+		return fmt.Errorf("api: %d: %s", res.StatusCode, errorBody.Message)
+	}
+	return json.NewDecoder(res.Body).Decode(response)
+}

src/github.com/matrix-org/dendrite/roomserver/input/consumer.go

@@ -34,15 +34,33 @@ type Consumer struct {
 	// But any equivalent event streaming protocol could be made to implement the same interface.
 	Consumer sarama.Consumer
 	// The database used to store the room events.
-	DB ConsumerDatabase
+	DB       ConsumerDatabase
+	Producer sarama.SyncProducer
 	// The kafkaesque topic to consume room events from.
 	// This is the name used in kafka to identify the stream to consume events from.
-	RoomEventTopic string
+	InputRoomEventTopic string
+	// The kafkaesque topic to output new room events to.
+	// This is the name used in kafka to identify the stream to write events to.
+	OutputRoomEventTopic string
 	// The ErrorLogger for this consumer.
 	// If left as nil then the consumer will panic when it encounters an error
 	ErrorLogger ErrorLogger
 }
 
+// WriteOutputRoomEvent implements OutputRoomEventWriter
+func (c *Consumer) WriteOutputRoomEvent(output api.OutputRoomEvent) error {
+	var m sarama.ProducerMessage
+	value, err := json.Marshal(output)
+	if err != nil {
+		return err
+	}
+	m.Topic = c.OutputRoomEventTopic
+	m.Key = sarama.StringEncoder("")
+	m.Value = sarama.ByteEncoder(value)
+	_, _, err = c.Producer.SendMessage(&m)
+	return err
+}
+
 // Start starts the consumer consuming.
 // Starts up a goroutine for each partition in the kafka stream.
 // Returns nil once all the goroutines are started.
@@ -50,7 +68,7 @@ type Consumer struct {
 func (c *Consumer) Start() error {
 	offsets := map[int32]int64{}
 
-	partitions, err := c.Consumer.Partitions(c.RoomEventTopic)
+	partitions, err := c.Consumer.Partitions(c.InputRoomEventTopic)
 	if err != nil {
 		return err
 	}
@@ -59,7 +77,7 @@ func (c *Consumer) Start() error {
 		offsets[partition] = sarama.OffsetOldest
 	}
 
-	storedOffsets, err := c.DB.PartitionOffsets(c.RoomEventTopic)
+	storedOffsets, err := c.DB.PartitionOffsets(c.InputRoomEventTopic)
 	if err != nil {
 		return err
 	}
@@ -70,7 +88,7 @@ func (c *Consumer) Start() error {
 
 	var partitionConsumers []sarama.PartitionConsumer
 	for partition, offset := range offsets {
-		pc, err := c.Consumer.ConsumePartition(c.RoomEventTopic, partition, offset)
+		pc, err := c.Consumer.ConsumePartition(c.InputRoomEventTopic, partition, offset)
 		if err != nil {
 			for _, p := range partitionConsumers {
 				p.Close()
@@ -95,7 +113,7 @@ func (c *Consumer) consumePartition(pc sarama.PartitionConsumer) {
 			// If the message is invalid then log it and move onto the next message in the stream.
 			c.logError(message, err)
 		} else {
-			if err := processRoomEvent(c.DB, input); err != nil {
+			if err := processRoomEvent(c.DB, c, input); err != nil {
 				// If there was an error processing the message then log it and
 				// move onto the next message in the stream.
 				// TODO: If the error was due to a problem talking to the database
@@ -105,7 +123,7 @@ func (c *Consumer) consumePartition(pc sarama.PartitionConsumer) {
 			}
 		}
 		// Advance our position in the stream so that we will start at the right position after a restart.
-		if err := c.DB.SetPartitionOffset(c.RoomEventTopic, message.Partition, message.Offset); err != nil {
+		if err := c.DB.SetPartitionOffset(c.InputRoomEventTopic, message.Partition, message.Offset); err != nil {
 			c.logError(message, err)
 		}
 	}

src/github.com/matrix-org/dendrite/roomserver/input/events.go

@@ -36,11 +36,20 @@ type RoomEventDatabase interface {
 	SetState(eventNID types.EventNID, stateNID types.StateSnapshotNID) error
 	// Lookup the latest events in a room in preparation for an update.
 	// The RoomRecentEventsUpdater must have Commit or Rollback called on it if this doesn't return an error.
+	// Returns the latest events in the room and the last eventID sent to the log along with an updater.
 	// If this returns an error then no further action is required.
-	GetLatestEventsForUpdate(roomNID types.RoomNID) ([]types.StateAtEventAndReference, types.RoomRecentEventsUpdater, error)
+	GetLatestEventsForUpdate(roomNID types.RoomNID) (updater types.RoomRecentEventsUpdater, err error)
+	// Lookup the string event IDs for a list of numeric event IDs
+	EventIDs(eventNIDs []types.EventNID) (map[types.EventNID]string, error)
 }
 
-func processRoomEvent(db RoomEventDatabase, input api.InputRoomEvent) error {
+// OutputRoomEventWriter has the APIs needed to write an event to the output logs.
+type OutputRoomEventWriter interface {
+	// Write an event.
+	WriteOutputRoomEvent(output api.OutputRoomEvent) error
+}
+
+func processRoomEvent(db RoomEventDatabase, ow OutputRoomEventWriter, input api.InputRoomEvent) error {
 	// Parse and validate the event JSON
 	event, err := gomatrixserverlib.NewEventFromUntrustedJSON(input.Event)
 	if err != nil {
@@ -82,7 +91,7 @@ func processRoomEvent(db RoomEventDatabase, input api.InputRoomEvent) error {
 			}
 		} else {
 			// We haven't been told what the state at the event is so we need to calculate it from the prev_events
-			if stateAtEvent.BeforeStateSnapshotNID, err = calculateAndStoreState(db, event, roomNID); err != nil {
+			if stateAtEvent.BeforeStateSnapshotNID, err = calculateAndStoreStateBeforeEvent(db, event, roomNID); err != nil {
 				return err
 			}
 		}
@@ -95,7 +104,7 @@ func processRoomEvent(db RoomEventDatabase, input api.InputRoomEvent) error {
 	}
 
 	// Update the extremities of the event graph for the room
-	if err := updateLatestEvents(db, roomNID, stateAtEvent, event); err != nil {
+	if err := updateLatestEvents(db, ow, roomNID, stateAtEvent, event); err != nil {
 		return err
 	}
 

src/github.com/matrix-org/dendrite/roomserver/input/latest_events.go

@@ -2,11 +2,13 @@ package input
 
 import (
 	"bytes"
+	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/roomserver/types"
 	"github.com/matrix-org/gomatrixserverlib"
 )
 
-// updateLatestEvents updates the list of latest events for this room.
+// updateLatestEvents updates the list of latest events for this room in the database and writes the
+// event to the output log.
 // The latest events are the events that aren't referenced by another event in the database:
 //
 //     Time goes down the page. 1 is the m.room.create event (root).
@@ -22,9 +24,9 @@ import (
 //      7 <----- latest
 //
 func updateLatestEvents(
-	db RoomEventDatabase, roomNID types.RoomNID, stateAtEvent types.StateAtEvent, event gomatrixserverlib.Event,
+	db RoomEventDatabase, ow OutputRoomEventWriter, roomNID types.RoomNID, stateAtEvent types.StateAtEvent, event gomatrixserverlib.Event,
 ) (err error) {
-	oldLatest, updater, err := db.GetLatestEventsForUpdate(roomNID)
+	updater, err := db.GetLatestEventsForUpdate(roomNID)
 	if err != nil {
 		return
 	}
@@ -42,22 +44,81 @@ func updateLatestEvents(
 		}
 	}()
 
-	err = doUpdateLatestEvents(updater, oldLatest, roomNID, stateAtEvent, event)
+	err = doUpdateLatestEvents(db, updater, ow, roomNID, stateAtEvent, event)
 	return
 }
 
 func doUpdateLatestEvents(
-	updater types.RoomRecentEventsUpdater, oldLatest []types.StateAtEventAndReference, roomNID types.RoomNID, stateAtEvent types.StateAtEvent, event gomatrixserverlib.Event,
+	db RoomEventDatabase, updater types.RoomRecentEventsUpdater, ow OutputRoomEventWriter, roomNID types.RoomNID, stateAtEvent types.StateAtEvent, event gomatrixserverlib.Event,
 ) error {
 	var err error
 	var prevEvents []gomatrixserverlib.EventReference
 	prevEvents = event.PrevEvents()
+	oldLatest := updater.LatestEvents()
+	lastEventIDSent := updater.LastEventIDSent()
+	oldStateNID := updater.CurrentStateSnapshotNID()
+
+	if hasBeenSent, err := updater.HasEventBeenSent(stateAtEvent.EventNID); err != nil {
+		return err
+	} else if hasBeenSent {
+		// Already sent this event so we can stop processing
+		return nil
+	}
 
 	if err = updater.StorePreviousEvents(stateAtEvent.EventNID, prevEvents); err != nil {
 		return err
 	}
 
-	// Check if this event references any of the latest events in the room.
+	eventReference := event.EventReference()
+	// Check if this event is already referenced by another event in the room.
+	var alreadyReferenced bool
+	if alreadyReferenced, err = updater.IsReferenced(eventReference); err != nil {
+		return err
+	}
+
+	newLatest := calculateLatest(oldLatest, alreadyReferenced, prevEvents, types.StateAtEventAndReference{
+		EventReference: eventReference,
+		StateAtEvent:   stateAtEvent,
+	})
+
+	latestStateAtEvents := make([]types.StateAtEvent, len(newLatest))
+	for i := range newLatest {
+		latestStateAtEvents[i] = newLatest[i].StateAtEvent
+	}
+	newStateNID, err := calculateAndStoreStateAfterEvents(db, roomNID, latestStateAtEvents)
+	if err != nil {
+		return err
+	}
+
+	removed, added, err := differenceBetweeenStateSnapshots(db, oldStateNID, newStateNID)
+	if err != nil {
+		return err
+	}
+
+	// Send the event to the output logs.
+	// We do this inside the database transaction to ensure that we only mark an event as sent if we sent it.
+	// (n.b. this means that it's possible that the same event will be sent twice if the transaction fails but
+	//  the write to the output log succeeds)
+	// TODO: This assumes that writing the event to the output log is synchronous. It should be possible to
+	// send the event asynchronously but we would need to ensure that 1) the events are written to the log in
+	// the correct order, 2) that pending writes are resent across restarts. In order to avoid writing all the
+	// necessary bookkeeping we'll keep the event sending synchronous for now.
+	if err = writeEvent(db, ow, lastEventIDSent, event, newLatest, removed, added); err != nil {
+		return err
+	}
+
+	if err = updater.SetLatestEvents(roomNID, newLatest, stateAtEvent.EventNID, newStateNID); err != nil {
+		return err
+	}
+
+	if err = updater.MarkEventAsSent(stateAtEvent.EventNID); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func calculateLatest(oldLatest []types.StateAtEventAndReference, alreadyReferenced bool, prevEvents []gomatrixserverlib.EventReference, newEvent types.StateAtEventAndReference) []types.StateAtEventAndReference {
 	var alreadyInLatest bool
 	var newLatest []types.StateAtEventAndReference
 	for _, l := range oldLatest {
@@ -71,7 +132,7 @@ func doUpdateLatestEvents(
 				break
 			}
 		}
-		if l.EventNID == stateAtEvent.EventNID {
+		if l.EventNID == newEvent.EventNID {
 			alreadyInLatest = true
 		}
 		if keep {
@@ -80,26 +141,51 @@ func doUpdateLatestEvents(
 		}
 	}
 
-	eventReference := event.EventReference()
-	// Check if this event is already referenced by another event in the room.
-	var alreadyReferenced bool
-	if alreadyReferenced, err = updater.IsReferenced(eventReference); err != nil {
-		return err
-	}
-
 	if !alreadyReferenced && !alreadyInLatest {
 		// This event is not referenced by any of the events in the room
 		// and the event is not already in the latest events.
 		// Add it to the latest events
-		newLatest = append(newLatest, types.StateAtEventAndReference{
-			StateAtEvent:   stateAtEvent,
-			EventReference: eventReference,
-		})
+		newLatest = append(newLatest, newEvent)
 	}
 
-	if err = updater.SetLatestEvents(roomNID, newLatest); err != nil {
+	return newLatest
+}
+
+func writeEvent(
+	db RoomEventDatabase, ow OutputRoomEventWriter, lastEventIDSent string,
+	event gomatrixserverlib.Event, latest []types.StateAtEventAndReference,
+	removed, added []types.StateEntry,
+) error {
+
+	latestEventIDs := make([]string, len(latest))
+	for i := range latest {
+		latestEventIDs[i] = latest[i].EventID
+	}
+
+	ore := api.OutputRoomEvent{
+		Event:           event.JSON(),
+		LastSentEventID: lastEventIDSent,
+		LatestEventIDs:  latestEventIDs,
+	}
+
+	var stateEventNIDs []types.EventNID
+	for _, entry := range added {
+		stateEventNIDs = append(stateEventNIDs, entry.EventNID)
+	}
+	for _, entry := range removed {
+		stateEventNIDs = append(stateEventNIDs, entry.EventNID)
+	}
+	eventIDMap, err := db.EventIDs(stateEventNIDs)
+	if err != nil {
 		return err
 	}
+	for _, entry := range added {
+		ore.AddsStateEventIDs = append(ore.AddsStateEventIDs, eventIDMap[entry.EventNID])
+	}
+	for _, entry := range removed {
+		ore.RemovesStateEventIDs = append(ore.RemovesStateEventIDs, eventIDMap[entry.EventNID])
+	}
 
-	return nil
+	// TODO: Fill out VisibilityStateIDs
+	return ow.WriteOutputRoomEvent(ore)
 }

src/github.com/matrix-org/dendrite/roomserver/input/state.go

@@ -9,8 +9,8 @@ import (
 
 // calculateAndStoreState calculates a snapshot of the state of a room before an event.
 // Stores the snapshot of the state in the database.
-// Returns a numeric ID for that snapshot.
-func calculateAndStoreState(
+// Returns a numeric ID for the snapshot of the state before the event.
+func calculateAndStoreStateBeforeEvent(
 	db RoomEventDatabase, event gomatrixserverlib.Event, roomNID types.RoomNID,
 ) (types.StateSnapshotNID, error) {
 	// Load the state at the prev events.
@@ -25,6 +25,13 @@ func calculateAndStoreState(
 		return 0, err
 	}
 
+	// The state before this event will be the state after the events that came before it.
+	return calculateAndStoreStateAfterEvents(db, roomNID, prevStates)
+}
+
+// calculateAndStoreStateAfterEvents finds the room state after the given events.
+// Stores the resulting state in the database and returns a numeric ID for that snapshot.
+func calculateAndStoreStateAfterEvents(db RoomEventDatabase, roomNID types.RoomNID, prevStates []types.StateAtEvent) (types.StateSnapshotNID, error) {
 	if len(prevStates) == 0 {
 		// 2) There weren't any prev_events for this event so the state is
 		// empty.
@@ -55,9 +62,9 @@ func calculateAndStoreState(
 			)
 		}
 		// If there are too many deltas then we need to calculate the full state
-		// So fall through to calculateAndStoreStateMany
+		// So fall through to calculateAndStoreStateAfterManyEvents
 	}
-	return calculateAndStoreStateMany(db, roomNID, prevStates)
+	return calculateAndStoreStateAfterManyEvents(db, roomNID, prevStates)
 }
 
 // maxStateBlockNIDs is the maximum number of state data blocks to use to encode a snapshot of room state.
@@ -67,10 +74,10 @@ func calculateAndStoreState(
 // TODO: Tune this to get the right balance between size and lookup performance.
 const maxStateBlockNIDs = 64
 
-// calculateAndStoreStateMany calculates the state of the room before an event
-// using the states at each of the event's prev events.
+// calculateAndStoreStateAfterManyEvents finds the room state after the given events.
+// This handles the slow path of calculateAndStoreStateAfterEvents for when there is more than one event.
 // Stores the resulting state and returns a numeric ID for the snapshot.
-func calculateAndStoreStateMany(db RoomEventDatabase, roomNID types.RoomNID, prevStates []types.StateAtEvent) (types.StateSnapshotNID, error) {
+func calculateAndStoreStateAfterManyEvents(db RoomEventDatabase, roomNID types.RoomNID, prevStates []types.StateAtEvent) (types.StateSnapshotNID, error) {
 	// Conflict resolution.
 	// First stage: load the state after each of the prev events.
 	combined, err := loadCombinedStateAfterEvents(db, prevStates)
@@ -107,6 +114,98 @@ func calculateAndStoreStateMany(db RoomEventDatabase, roomNID types.RoomNID, pre
 	return db.AddState(roomNID, nil, state)
 }
 
+// differenceBetweeenStateSnapshots works out which state entries have been added and removed between two snapshots.
+func differenceBetweeenStateSnapshots(db RoomEventDatabase, oldStateNID, newStateNID types.StateSnapshotNID) (
+	removed, added []types.StateEntry, err error,
+) {
+	if oldStateNID == newStateNID {
+		// If the snapshot NIDs are the same then nothing has changed
+		return nil, nil, nil
+	}
+
+	var oldEntries []types.StateEntry
+	var newEntries []types.StateEntry
+	if oldStateNID != 0 {
+		oldEntries, err = loadStateAtSnapshot(db, oldStateNID)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+	if newStateNID != 0 {
+		newEntries, err = loadStateAtSnapshot(db, newStateNID)
+		if err != nil {
+			return nil, nil, err
+		}
+	}
+
+	var oldI int
+	var newI int
+	for {
+		switch {
+		case oldI == len(oldEntries):
+			// We've reached the end of the old entries.
+			// The rest of the new list must have been newly added.
+			added = append(added, newEntries[newI:]...)
+			return
+		case newI == len(newEntries):
+			// We've reached the end of the new entries.
+			// The rest of the old list must be have been removed.
+			removed = append(removed, oldEntries[oldI:]...)
+			return
+		case oldEntries[oldI] == newEntries[newI]:
+			// The entry is in both lists so skip over it.
+			oldI++
+			newI++
+		case oldEntries[oldI].LessThan(newEntries[newI]):
+			// The lists are sorted so the old entry being less than the new entry means that it only appears in the old list.
+			removed = append(removed, oldEntries[oldI])
+			oldI++
+		default:
+			// Reaching the default case implies that the new entry is less than the old entry.
+			// Since the lists are sorted this means that it only appears in the new list.
+			added = append(added, newEntries[newI])
+			newI++
+		}
+	}
+}
+
+// loadStateAtSnapshot loads the full state of a room at a particular snapshot.
+// This is typically the state before an event or the current state of a room.
+// Returns a sorted list of state entries or an error if there was a problem talking to the database.
+func loadStateAtSnapshot(db RoomEventDatabase, stateNID types.StateSnapshotNID) ([]types.StateEntry, error) {
+	stateBlockNIDLists, err := db.StateBlockNIDs([]types.StateSnapshotNID{stateNID})
+	if err != nil {
+		return nil, err
+	}
+	stateBlockNIDList := stateBlockNIDLists[0]
+
+	stateEntryLists, err := db.StateEntries(stateBlockNIDList.StateBlockNIDs)
+	if err != nil {
+		return nil, err
+	}
+	stateEntriesMap := stateEntryListMap(stateEntryLists)
+
+	// Combined all the state entries for this snapshot.
+	// The order of state block NIDs in the list tells us the order to combine them in.
+	var fullState []types.StateEntry
+	for _, stateBlockNID := range stateBlockNIDList.StateBlockNIDs {
+		entries, ok := stateEntriesMap.lookup(stateBlockNID)
+		if !ok {
+			// This should only get hit if the database is corrupt.
+			// It should be impossible for an event to reference a NID that doesn't exist
+			panic(fmt.Errorf("Corrupt DB: Missing state block numeric ID %d", stateBlockNID))
+		}
+		fullState = append(fullState, entries...)
+	}
+
+	// Stable sort so that the most recent entry for each state key stays
+	// remains later in the list than the older entries for the same state key.
+	sort.Stable(stateEntryByStateKeySorter(fullState))
+	// Unique returns the last entry and hence the most recent entry for each state key.
+	fullState = fullState[:unique(stateEntryByStateKeySorter(fullState))]
+	return fullState, nil
+}
+
 // loadCombinedStateAfterEvents loads a snapshot of the state after each of the events
 // and combines those snapshots together into a single list.
 func loadCombinedStateAfterEvents(db RoomEventDatabase, prevStates []types.StateAtEvent) ([]types.StateEntry, error) {
@@ -146,18 +245,18 @@ func loadCombinedStateAfterEvents(db RoomEventDatabase, prevStates []types.State
 		if !ok {
 			// This should only get hit if the database is corrupt.
 			// It should be impossible for an event to reference a NID that doesn't exist
-			panic(fmt.Errorf("Corrupt DB: Missing state numeric ID %d", prevState.BeforeStateSnapshotNID))
+			panic(fmt.Errorf("Corrupt DB: Missing state snapshot numeric ID %d", prevState.BeforeStateSnapshotNID))
 		}
 
 		// Combined all the state entries for this snapshot.
-		// The order of state data NIDs in the list tells us the order to combine them in.
+		// The order of state block NIDs in the list tells us the order to combine them in.
 		var fullState []types.StateEntry
 		for _, stateBlockNID := range stateBlockNIDs {
 			entries, ok := stateEntriesMap.lookup(stateBlockNID)
 			if !ok {
 				// This should only get hit if the database is corrupt.
 				// It should be impossible for an event to reference a NID that doesn't exist
-				panic(fmt.Errorf("Corrupt DB: Missing state numeric ID %d", prevState.BeforeStateSnapshotNID))
+				panic(fmt.Errorf("Corrupt DB: Missing state block numeric ID %d", stateBlockNID))
 			}
 			fullState = append(fullState, entries...)
 		}

src/github.com/matrix-org/dendrite/roomserver/query/query.go

@@ -0,0 +1,68 @@
+package query
+
+import (
+	"encoding/json"
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/dendrite/roomserver/types"
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+	"github.com/prometheus/client_golang/prometheus"
+	"net/http"
+)
+
+// RoomserverQueryAPIDatabase has the storage APIs needed to implement the query API.
+type RoomserverQueryAPIDatabase interface {
+	// Lookup the numeric ID for the room.
+	// Returns 0 if the room doesn't exists.
+	// Returns an error if there was a problem talking to the database.
+	RoomNID(roomID string) (types.RoomNID, error)
+	// Lookup event references for the latest events in the room.
+	// Returns an error if there was a problem talking to the database.
+	LatestEventIDs(roomNID types.RoomNID) ([]gomatrixserverlib.EventReference, error)
+}
+
+// RoomserverQueryAPI is an implementation of RoomserverQueryAPI
+type RoomserverQueryAPI struct {
+	DB RoomserverQueryAPIDatabase
+}
+
+// QueryLatestEventsAndState implements api.RoomserverQueryAPI
+func (r *RoomserverQueryAPI) QueryLatestEventsAndState(
+	request *api.QueryLatestEventsAndStateRequest,
+	response *api.QueryLatestEventsAndStateResponse,
+) (err error) {
+	response.QueryLatestEventsAndStateRequest = *request
+	roomNID, err := r.DB.RoomNID(request.RoomID)
+	if err != nil {
+		return err
+	}
+	if roomNID == 0 {
+		return nil
+	}
+	response.RoomExists = true
+	response.LatestEvents, err = r.DB.LatestEventIDs(roomNID)
+	// TODO: look up the current state.
+	return err
+}
+
+// SetupHTTP adds the RoomserverQueryAPI handlers to the http.ServeMux.
+func (r *RoomserverQueryAPI) SetupHTTP(servMux *http.ServeMux) {
+	servMux.Handle(
+		api.RoomserverQueryLatestEventsAndStatePath,
+		makeAPI("query_latest_events_and_state", func(req *http.Request) util.JSONResponse {
+			var request api.QueryLatestEventsAndStateRequest
+			var response api.QueryLatestEventsAndStateResponse
+			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
+				return util.ErrorResponse(err)
+			}
+			if err := r.QueryLatestEventsAndState(&request, &response); err != nil {
+				return util.ErrorResponse(err)
+			}
+			return util.JSONResponse{Code: 200, JSON: &response}
+		}),
+	)
+}
+
+func makeAPI(metric string, apiFunc func(req *http.Request) util.JSONResponse) http.Handler {
+	return prometheus.InstrumentHandler(metric, util.MakeJSONAPI(util.NewJSONRequestHandler(apiFunc)))
+}

src/github.com/matrix-org/dendrite/roomserver/roomserver-integration-tests/main.go

@@ -0,0 +1,382 @@
+package main
+
+import (
+	"fmt"
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/gomatrixserverlib"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+var (
+	// Path to where kafka is installed.
+	kafkaDir = defaulting(os.Getenv("KAFKA_DIR"), "kafka")
+	// The URI the kafka zookeeper is listening on.
+	zookeeperURI = defaulting(os.Getenv("ZOOKEEPER_URI"), "localhost:2181")
+	// The URI the kafka server is listening on.
+	kafkaURI = defaulting(os.Getenv("KAFKA_URIS"), "localhost:9092")
+	// The address the roomserver should listen on.
+	roomserverAddr = defaulting(os.Getenv("ROOMSERVER_URI"), "localhost:9876")
+	// How long to wait for the roomserver to write the expected output messages.
+	// This needs to be high enough to account for the time it takes to create
+	// the postgres database tables which can take a while on travis.
+	timeoutString = defaulting(os.Getenv("TIMEOUT"), "60s")
+	// The name of maintenance database to connect to in order to create the test database.
+	postgresDatabase = defaulting(os.Getenv("POSTGRES_DATABASE"), "postgres")
+	// The name of the test database to create.
+	testDatabaseName = defaulting(os.Getenv("DATABASE_NAME"), "roomserver_test")
+	// The postgres connection config for connecting to the test database.
+	testDatabase = defaulting(os.Getenv("DATABASE"), fmt.Sprintf("dbname=%s binary_parameters=yes", testDatabaseName))
+)
+
+func defaulting(value, defaultValue string) string {
+	if value == "" {
+		value = defaultValue
+	}
+	return value
+}
+
+var timeout time.Duration
+
+func init() {
+	var err error
+	timeout, err = time.ParseDuration(timeoutString)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func createDatabase(database string) error {
+	cmd := exec.Command("psql", postgresDatabase)
+	cmd.Stdin = strings.NewReader(
+		fmt.Sprintf("DROP DATABASE IF EXISTS %s; CREATE DATABASE %s;", database, database),
+	)
+	// Send stdout and stderr to our stderr so that we see error messages from
+	// the psql process
+	cmd.Stdout = os.Stderr
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+func createTopic(topic string) error {
+	cmd := exec.Command(
+		filepath.Join(kafkaDir, "bin", "kafka-topics.sh"),
+		"--create",
+		"--zookeeper", zookeeperURI,
+		"--replication-factor", "1",
+		"--partitions", "1",
+		"--topic", topic,
+	)
+	// Send stdout and stderr to our stderr so that we see error messages from
+	// the kafka process.
+	cmd.Stdout = os.Stderr
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+func writeToTopic(topic string, data []string) error {
+	cmd := exec.Command(
+		filepath.Join(kafkaDir, "bin", "kafka-console-producer.sh"),
+		"--broker-list", kafkaURI,
+		"--topic", topic,
+	)
+	// Send stdout and stderr to our stderr so that we see error messages from
+	// the kafka process.
+	cmd.Stdout = os.Stderr
+	cmd.Stderr = os.Stderr
+	cmd.Stdin = strings.NewReader(strings.Join(data, "\n"))
+	return cmd.Run()
+}
+
+// runAndReadFromTopic runs a command and waits for a number of messages to be
+// written to a kafka topic. It returns if the command exits, the number of
+// messages is reached or after a timeout. It kills the command before it returns.
+// It returns a list of the messages read from the command on success or an error
+// on failure.
+func runAndReadFromTopic(runCmd *exec.Cmd, topic string, count int, checkQueryAPI func()) ([]string, error) {
+	type result struct {
+		// data holds all of stdout on success.
+		data []byte
+		// err is set on failure.
+		err error
+	}
+	done := make(chan result)
+	readCmd := exec.Command(
+		filepath.Join(kafkaDir, "bin", "kafka-console-consumer.sh"),
+		"--bootstrap-server", kafkaURI,
+		"--topic", topic,
+		"--from-beginning",
+		"--max-messages", fmt.Sprintf("%d", count),
+	)
+	// Send stderr to our stderr so the user can see any error messages.
+	readCmd.Stderr = os.Stderr
+	// Run the command, read the messages and wait for a timeout in parallel.
+	go func() {
+		// Read all of stdout.
+		defer func() {
+			if err := recover(); err != nil {
+				if errv, ok := err.(error); ok {
+					done <- result{nil, errv}
+				} else {
+					panic(err)
+				}
+			}
+		}()
+		data, err := readCmd.Output()
+		checkQueryAPI()
+		done <- result{data, err}
+	}()
+	go func() {
+		err := runCmd.Run()
+		done <- result{nil, err}
+	}()
+	go func() {
+		time.Sleep(timeout)
+		done <- result{nil, fmt.Errorf("Timeout reading %d messages from topic %q", count, topic)}
+	}()
+	// Wait for one of the tasks to finsh.
+	r := <-done
+
+	// Kill both processes. We don't check if the processes are running and
+	// we ignore failures since we are just trying to clean up before returning.
+	runCmd.Process.Kill()
+	readCmd.Process.Kill()
+
+	if r.err != nil {
+		return nil, r.err
+	}
+
+	// The kafka console consumer writes a newline character after each message.
+	// So we split on newline characters
+	lines := strings.Split(string(r.data), "\n")
+	if len(lines) > 0 {
+		// Remove the blank line at the end of the data.
+		lines = lines[:len(lines)-1]
+	}
+	return lines, nil
+}
+
+func deleteTopic(topic string) error {
+	cmd := exec.Command(
+		filepath.Join(kafkaDir, "bin", "kafka-topics.sh"),
+		"--delete",
+		"--if-exists",
+		"--zookeeper", zookeeperURI,
+		"--topic", topic,
+	)
+	cmd.Stderr = os.Stderr
+	cmd.Stdout = os.Stderr
+	return cmd.Run()
+}
+
+// testRoomserver is used to run integration tests against a single roomserver.
+// It creates new kafka topics for the input and output of the roomserver.
+// It writes the input messages to the input kafka topic, formatting each message
+// as canonical JSON so that it fits on a single line.
+// It then runs the roomserver and waits for a number of messages to be written
+// to the output topic.
+// Once those messages have been written it runs the checkQueries function passing
+// a api.RoomserverQueryAPI client. The caller can use this function to check the
+// behaviour of the query API.
+func testRoomserver(input []string, wantOutput []string, checkQueries func(api.RoomserverQueryAPI)) {
+	const (
+		inputTopic  = "roomserverInput"
+		outputTopic = "roomserverOutput"
+	)
+	deleteTopic(inputTopic)
+	if err := createTopic(inputTopic); err != nil {
+		panic(err)
+	}
+	deleteTopic(outputTopic)
+	if err := createTopic(outputTopic); err != nil {
+		panic(err)
+	}
+
+	if err := writeToTopic(inputTopic, canonicalJSONInput(input)); err != nil {
+		panic(err)
+	}
+
+	if err := createDatabase(testDatabaseName); err != nil {
+		panic(err)
+	}
+
+	cmd := exec.Command(filepath.Join(filepath.Dir(os.Args[0]), "roomserver"))
+
+	// Append the roomserver config to the existing environment.
+	// We append to the environment rather than replacing so that any additional
+	// postgres and golang environment variables such as PGHOST are passed to
+	// the roomserver process.
+	cmd.Env = append(
+		os.Environ(),
+		fmt.Sprintf("DATABASE=%s", testDatabase),
+		fmt.Sprintf("KAFKA_URIS=%s", kafkaURI),
+		fmt.Sprintf("TOPIC_INPUT_ROOM_EVENT=%s", inputTopic),
+		fmt.Sprintf("TOPIC_OUTPUT_ROOM_EVENT=%s", outputTopic),
+		fmt.Sprintf("BIND_ADDRESS=%s", roomserverAddr),
+	)
+	cmd.Stderr = os.Stderr
+
+	gotOutput, err := runAndReadFromTopic(cmd, outputTopic, len(wantOutput), func() {
+		queryAPI := api.NewRoomserverQueryAPIHTTP("http://"+roomserverAddr, nil)
+		checkQueries(queryAPI)
+	})
+	if err != nil {
+		panic(err)
+	}
+
+	if len(wantOutput) != len(gotOutput) {
+		panic(fmt.Errorf("Wanted %d lines of output got %d lines", len(wantOutput), len(gotOutput)))
+	}
+
+	for i := range wantOutput {
+		if !equalJSON(wantOutput[i], gotOutput[i]) {
+			panic(fmt.Errorf("Wanted %q at index %d got %q", wantOutput[i], i, gotOutput[i]))
+		}
+	}
+}
+
+func canonicalJSONInput(jsonData []string) []string {
+	for i := range jsonData {
+		jsonBytes, err := gomatrixserverlib.CanonicalJSON([]byte(jsonData[i]))
+		if err != nil {
+			panic(err)
+		}
+		jsonData[i] = string(jsonBytes)
+	}
+	return jsonData
+}
+
+func equalJSON(a, b string) bool {
+	canonicalA, err := gomatrixserverlib.CanonicalJSON([]byte(a))
+	if err != nil {
+		panic(err)
+	}
+	canonicalB, err := gomatrixserverlib.CanonicalJSON([]byte(b))
+	if err != nil {
+		panic(err)
+	}
+	return string(canonicalA) == string(canonicalB)
+}
+
+func main() {
+	fmt.Println("==TESTING==", os.Args[0])
+
+	input := []string{
+		`{
+			"AuthEventIDs": [],
+			"Kind": 1,
+			"Event": {
+				"origin": "matrix.org",
+				"signatures": {
+					"matrix.org": {
+						"ed25519:auto": "3kXGwNtdj+zqEXlI8PWLiB76xtrQ7SxcvPuXAEVCTo+QPoBoUvLi1RkHs6O5mDz7UzIowK5bi1seAN4vOh0OBA"
+					}
+				},
+				"origin_server_ts": 1463671337837,
+				"sender": "@richvdh:matrix.org",
+				"event_id": "$1463671337126266wrSBX:matrix.org",
+				"prev_events": [],
+				"state_key": "",
+				"content": {"creator": "@richvdh:matrix.org"},
+				"depth": 1,
+				"prev_state": [],
+				"room_id": "!HCXfdvrfksxuYnIFiJ:matrix.org",
+				"auth_events": [],
+				"hashes": {"sha256": "Q05VLC8nztN2tguy+KnHxxhitI95wK9NelnsDaXRqeo"},
+				"type": "m.room.create"}
+		}`, `{
+			"AuthEventIDs": ["$1463671337126266wrSBX:matrix.org"],
+			"Kind": 2,
+			"StateEventIDs": ["$1463671337126266wrSBX:matrix.org"],
+			"Event": {
+				"origin": "matrix.org",
+				"signatures": {
+					"matrix.org": {
+						"ed25519:auto": "a2b3xXYVPPFeG1sHCU3hmZnAaKqZFgzGZozijRGblG5Y//ewRPAn1A2mCrI2UM5I+0zqr70cNpHgF8bmNFu4BA"
+					}
+				},
+				"origin_server_ts": 1463671339844,
+				"sender": "@richvdh:matrix.org",
+				"event_id": "$1463671339126270PnVwC:matrix.org",
+				"prev_events": [[
+					"$1463671337126266wrSBX:matrix.org", {"sha256": "h/VS07u8KlMwT3Ee8JhpkC7sa1WUs0Srgs+l3iBv6c0"}
+				]],
+				"membership": "join",
+				"state_key": "@richvdh:matrix.org",
+				"content": {
+					"membership": "join",
+					"avatar_url": "mxc://matrix.org/ZafPzsxMJtLaSaJXloBEKiws",
+					"displayname": "richvdh"
+				},
+				"depth": 2,
+				"prev_state": [],
+				"room_id": "!HCXfdvrfksxuYnIFiJ:matrix.org",
+				"auth_events": [[
+					"$1463671337126266wrSBX:matrix.org", {"sha256": "h/VS07u8KlMwT3Ee8JhpkC7sa1WUs0Srgs+l3iBv6c0"}
+				]],
+				"hashes": {"sha256": "t9t3sZV1Eu0P9Jyrs7pge6UTa1zuTbRdVxeUHnrQVH0"},
+				"type": "m.room.member"},
+			"HasState": true
+		}`,
+	}
+
+	want := []string{
+		`{
+			"Event":{
+				"auth_events":[[
+					"$1463671337126266wrSBX:matrix.org",{"sha256":"h/VS07u8KlMwT3Ee8JhpkC7sa1WUs0Srgs+l3iBv6c0"}
+				]],
+				"content":{
+					"avatar_url":"mxc://matrix.org/ZafPzsxMJtLaSaJXloBEKiws",
+					"displayname":"richvdh",
+					"membership":"join"
+				},
+				"depth": 2,
+				"event_id": "$1463671339126270PnVwC:matrix.org",
+				"hashes": {"sha256":"t9t3sZV1Eu0P9Jyrs7pge6UTa1zuTbRdVxeUHnrQVH0"},
+				"membership": "join",
+				"origin": "matrix.org",
+				"origin_server_ts": 1463671339844,
+				"prev_events": [[
+					"$1463671337126266wrSBX:matrix.org",{"sha256":"h/VS07u8KlMwT3Ee8JhpkC7sa1WUs0Srgs+l3iBv6c0"}
+				]],
+				"prev_state":[],
+				"room_id":"!HCXfdvrfksxuYnIFiJ:matrix.org",
+				"sender":"@richvdh:matrix.org",
+				"signatures":{
+					"matrix.org":{
+						"ed25519:auto":"a2b3xXYVPPFeG1sHCU3hmZnAaKqZFgzGZozijRGblG5Y//ewRPAn1A2mCrI2UM5I+0zqr70cNpHgF8bmNFu4BA"
+					}
+				},
+				"state_key":"@richvdh:matrix.org",
+				"type":"m.room.member"
+			},
+			"VisibilityEventIDs":null,
+			"LatestEventIDs":["$1463671339126270PnVwC:matrix.org"],
+			"AddsStateEventIDs":["$1463671337126266wrSBX:matrix.org", "$1463671339126270PnVwC:matrix.org"],
+			"RemovesStateEventIDs":null,
+			"LastSentEventID":""
+		}`,
+	}
+
+	testRoomserver(input, want, func(q api.RoomserverQueryAPI) {
+		var response api.QueryLatestEventsAndStateResponse
+		if err := q.QueryLatestEventsAndState(
+			&api.QueryLatestEventsAndStateRequest{RoomID: "!HCXfdvrfksxuYnIFiJ:matrix.org"},
+			&response,
+		); err != nil {
+			panic(err)
+		}
+		if !response.RoomExists {
+			panic(fmt.Errorf(`Wanted room "!HCXfdvrfksxuYnIFiJ:matrix.org" to exist`))
+		}
+		if len(response.LatestEvents) != 1 || response.LatestEvents[0].EventID != "$1463671339126270PnVwC:matrix.org" {
+			panic(fmt.Errorf(`Wanted "$1463671339126270PnVwC:matrix.org" to be the latest event got %#v`, response.LatestEvents))
+		}
+	})
+
+	fmt.Println("==PASSED==", os.Args[0])
+}

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

@@ -3,16 +3,20 @@ package main
 import (
 	"fmt"
 	"github.com/matrix-org/dendrite/roomserver/input"
+	"github.com/matrix-org/dendrite/roomserver/query"
 	"github.com/matrix-org/dendrite/roomserver/storage"
 	sarama "gopkg.in/Shopify/sarama.v1"
+	"net/http"
 	"os"
 	"strings"
 )
 
 var (
-	database       = os.Getenv("DATABASE")
-	kafkaURIs      = strings.Split(os.Getenv("KAFKA_URIS"), ",")
-	roomEventTopic = os.Getenv("TOPIC_ROOM_EVENT")
+	database             = os.Getenv("DATABASE")
+	kafkaURIs            = strings.Split(os.Getenv("KAFKA_URIS"), ",")
+	inputRoomEventTopic  = os.Getenv("TOPIC_INPUT_ROOM_EVENT")
+	outputRoomEventTopic = os.Getenv("TOPIC_OUTPUT_ROOM_EVENT")
+	bindAddr             = os.Getenv("BIND_ADDRESS")
 )
 
 func main() {
@@ -26,19 +30,31 @@ func main() {
 		panic(err)
 	}
 
+	kafkaProducer, err := sarama.NewSyncProducer(kafkaURIs, nil)
+	if err != nil {
+		panic(err)
+	}
+
 	consumer := input.Consumer{
-		Consumer:       kafkaConsumer,
-		DB:             db,
-		RoomEventTopic: roomEventTopic,
+		Consumer:             kafkaConsumer,
+		DB:                   db,
+		Producer:             kafkaProducer,
+		InputRoomEventTopic:  inputRoomEventTopic,
+		OutputRoomEventTopic: outputRoomEventTopic,
 	}
 
 	if err = consumer.Start(); err != nil {
 		panic(err)
 	}
 
+	queryAPI := query.RoomserverQueryAPI{
+		DB: db,
+	}
+
+	queryAPI.SetupHTTP(http.DefaultServeMux)
+
 	fmt.Println("Started roomserver")
 
-	// Wait forever.
 	// TODO: Implement clean shutdown.
-	select {}
+	http.ListenAndServe(bindAddr, nil)
 }

src/github.com/matrix-org/dendrite/roomserver/storage/event_json_table.go

@@ -2,7 +2,6 @@ package storage
 
 import (
 	"database/sql"
-	"github.com/lib/pq"
 	"github.com/matrix-org/dendrite/roomserver/types"
 )
 
@@ -45,13 +44,10 @@ func (s *eventJSONStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertEventJSONStmt, err = db.Prepare(insertEventJSONSQL); err != nil {
-		return
-	}
-	if s.bulkSelectEventJSONStmt, err = db.Prepare(bulkSelectEventJSONSQL); err != nil {
-		return
-	}
-	return
+	return statementList{
+		{&s.insertEventJSONStmt, insertEventJSONSQL},
+		{&s.bulkSelectEventJSONStmt, bulkSelectEventJSONSQL},
+	}.prepare(db)
 }
 
 func (s *eventJSONStatements) insertEventJSON(eventNID types.EventNID, eventJSON []byte) error {
@@ -65,11 +61,7 @@ type eventJSONPair struct {
 }
 
 func (s *eventJSONStatements) bulkSelectEventJSON(eventNIDs []types.EventNID) ([]eventJSONPair, error) {
-	nids := make([]int64, len(eventNIDs))
-	for i := range eventNIDs {
-		nids[i] = int64(eventNIDs[i])
-	}
-	rows, err := s.bulkSelectEventJSONStmt.Query(pq.Int64Array(nids))
+	rows, err := s.bulkSelectEventJSONStmt.Query(eventNIDsAsArray(eventNIDs))
 	if err != nil {
 		return nil, err
 	}

src/github.com/matrix-org/dendrite/roomserver/storage/event_state_keys_table.go

@@ -53,16 +53,11 @@ func (s *eventStateKeyStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertEventStateKeyNIDStmt, err = db.Prepare(insertEventStateKeyNIDSQL); err != nil {
-		return
-	}
-	if s.selectEventStateKeyNIDStmt, err = db.Prepare(selectEventStateKeyNIDSQL); err != nil {
-		return
-	}
-	if s.bulkSelectEventStateKeyNIDStmt, err = db.Prepare(bulkSelectEventStateKeyNIDSQL); err != nil {
-		return
-	}
-	return
+	return statementList{
+		{&s.insertEventStateKeyNIDStmt, insertEventStateKeyNIDSQL},
+		{&s.selectEventStateKeyNIDStmt, selectEventStateKeyNIDSQL},
+		{&s.bulkSelectEventStateKeyNIDStmt, bulkSelectEventStateKeyNIDSQL},
+	}.prepare(db)
 }
 
 func (s *eventStateKeyStatements) insertEventStateKeyNID(eventStateKey string) (types.EventStateKeyNID, error) {

src/github.com/matrix-org/dendrite/roomserver/storage/event_types_table.go

@@ -76,13 +76,11 @@ func (s *eventTypeStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertEventTypeNIDStmt, err = db.Prepare(insertEventTypeNIDSQL); err != nil {
-		return
-	}
-	if s.selectEventTypeNIDStmt, err = db.Prepare(selectEventTypeNIDSQL); err != nil {
-		return
-	}
-	return
+
+	return statementList{
+		{&s.insertEventTypeNIDStmt, insertEventTypeNIDSQL},
+		{&s.selectEventTypeNIDStmt, selectEventTypeNIDSQL},
+	}.prepare(db)
 }
 
 func (s *eventTypeStatements) insertEventTypeNID(eventType string) (types.EventTypeNID, error) {

src/github.com/matrix-org/dendrite/roomserver/storage/events_table.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"github.com/lib/pq"
 	"github.com/matrix-org/dendrite/roomserver/types"
+	"github.com/matrix-org/gomatrixserverlib"
 )
 
 const eventsSchema = `
@@ -23,6 +24,8 @@ CREATE TABLE IF NOT EXISTS events (
     -- Local numeric ID for the state_key of the event
     -- This is 0 if the event is not a state event.
     event_state_key_nid BIGINT NOT NULL,
+    -- Whether the event has been written to the output log.
+    sent_to_output BOOLEAN NOT NULL DEFAULT FALSE,
     -- Local numeric ID for the state at the event.
     -- This is 0 if we don't know the state at the event.
     -- If the state is not 0 then this event is part of the contiguous
@@ -68,17 +71,37 @@ const bulkSelectStateAtEventByIDSQL = "" +
 const updateEventStateSQL = "" +
 	"UPDATE events SET state_snapshot_nid = $2 WHERE event_nid = $1"
 
+const selectEventSentToOutputSQL = "" +
+	"SELECT sent_to_output FROM events WHERE event_nid = $1"
+
+const updateEventSentToOutputSQL = "" +
+	"UPDATE events SET sent_to_output = TRUE WHERE event_nid = $1"
+
+const selectEventIDSQL = "" +
+	"SELECT event_id FROM events WHERE event_nid = $1"
+
 const bulkSelectStateAtEventAndReferenceSQL = "" +
 	"SELECT event_type_nid, event_state_key_nid, event_nid, state_snapshot_nid, event_id, reference_sha256" +
 	" FROM events WHERE event_nid = ANY($1)"
 
+const bulkSelectEventReferenceSQL = "" +
+	"SELECT event_id, reference_sha256 FROM events WHERE event_nid = ANY($1)"
+
+const bulkSelectEventIDSQL = "" +
+	"SELECT event_nid, event_id FROM events WHERE event_nid = ANY($1)"
+
 type eventStatements struct {
 	insertEventStmt                        *sql.Stmt
 	selectEventStmt                        *sql.Stmt
 	bulkSelectStateEventByIDStmt           *sql.Stmt
 	bulkSelectStateAtEventByIDStmt         *sql.Stmt
 	updateEventStateStmt                   *sql.Stmt
+	selectEventSentToOutputStmt            *sql.Stmt
+	updateEventSentToOutputStmt            *sql.Stmt
+	selectEventIDStmt                      *sql.Stmt
 	bulkSelectStateAtEventAndReferenceStmt *sql.Stmt
+	bulkSelectEventReferenceStmt           *sql.Stmt
+	bulkSelectEventIDStmt                  *sql.Stmt
 }
 
 func (s *eventStatements) prepare(db *sql.DB) (err error) {
@@ -86,25 +109,20 @@ func (s *eventStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertEventStmt, err = db.Prepare(insertEventSQL); err != nil {
-		return
-	}
-	if s.selectEventStmt, err = db.Prepare(selectEventSQL); err != nil {
-		return
-	}
-	if s.bulkSelectStateEventByIDStmt, err = db.Prepare(bulkSelectStateEventByIDSQL); err != nil {
-		return
-	}
-	if s.bulkSelectStateAtEventByIDStmt, err = db.Prepare(bulkSelectStateAtEventByIDSQL); err != nil {
-		return
-	}
-	if s.updateEventStateStmt, err = db.Prepare(updateEventStateSQL); err != nil {
-		return
-	}
-	if s.bulkSelectStateAtEventAndReferenceStmt, err = db.Prepare(bulkSelectStateAtEventAndReferenceSQL); err != nil {
-		return
-	}
-	return
+
+	return statementList{
+		{&s.insertEventStmt, insertEventSQL},
+		{&s.selectEventStmt, selectEventSQL},
+		{&s.bulkSelectStateEventByIDStmt, bulkSelectStateEventByIDSQL},
+		{&s.bulkSelectStateAtEventByIDStmt, bulkSelectStateAtEventByIDSQL},
+		{&s.updateEventStateStmt, updateEventStateSQL},
+		{&s.updateEventSentToOutputStmt, updateEventSentToOutputSQL},
+		{&s.selectEventSentToOutputStmt, selectEventSentToOutputSQL},
+		{&s.selectEventIDStmt, selectEventIDSQL},
+		{&s.bulkSelectStateAtEventAndReferenceStmt, bulkSelectStateAtEventAndReferenceSQL},
+		{&s.bulkSelectEventReferenceStmt, bulkSelectEventReferenceSQL},
+		{&s.bulkSelectEventIDStmt, bulkSelectEventIDSQL},
+	}.prepare(db)
 }
 
 func (s *eventStatements) insertEvent(
@@ -113,15 +131,11 @@ func (s *eventStatements) insertEvent(
 	referenceSHA256 []byte,
 	authEventNIDs []types.EventNID,
 ) (types.EventNID, types.StateSnapshotNID, error) {
-	nids := make([]int64, len(authEventNIDs))
-	for i := range authEventNIDs {
-		nids[i] = int64(authEventNIDs[i])
-	}
 	var eventNID int64
 	var stateNID int64
 	err := s.insertEventStmt.QueryRow(
 		int64(roomNID), int64(eventTypeNID), int64(eventStateKeyNID), eventID, referenceSHA256,
-		pq.Int64Array(nids),
+		eventNIDsAsArray(authEventNIDs),
 	).Scan(&eventNID, &stateNID)
 	return types.EventNID(eventNID), types.StateSnapshotNID(stateNID), err
 }
@@ -199,12 +213,23 @@ func (s *eventStatements) updateEventState(eventNID types.EventNID, stateNID typ
 	return err
 }
 
+func (s *eventStatements) selectEventSentToOutput(txn *sql.Tx, eventNID types.EventNID) (sentToOutput bool, err error) {
+	err = txn.Stmt(s.selectEventSentToOutputStmt).QueryRow(int64(eventNID)).Scan(&sentToOutput)
+	return
+}
+
+func (s *eventStatements) updateEventSentToOutput(txn *sql.Tx, eventNID types.EventNID) error {
+	_, err := txn.Stmt(s.updateEventSentToOutputStmt).Exec(int64(eventNID))
+	return err
+}
+
+func (s *eventStatements) selectEventID(txn *sql.Tx, eventNID types.EventNID) (eventID string, err error) {
+	err = txn.Stmt(s.selectEventIDStmt).QueryRow(int64(eventNID)).Scan(&eventID)
+	return
+}
+
 func (s *eventStatements) bulkSelectStateAtEventAndReference(txn *sql.Tx, eventNIDs []types.EventNID) ([]types.StateAtEventAndReference, error) {
-	nids := make([]int64, len(eventNIDs))
-	for i := range eventNIDs {
-		nids[i] = int64(eventNIDs[i])
-	}
-	rows, err := txn.Stmt(s.bulkSelectStateAtEventAndReferenceStmt).Query(pq.Int64Array(nids))
+	rows, err := txn.Stmt(s.bulkSelectStateAtEventAndReferenceStmt).Query(eventNIDsAsArray(eventNIDs))
 	if err != nil {
 		return nil, err
 	}
@@ -238,3 +263,54 @@ func (s *eventStatements) bulkSelectStateAtEventAndReference(txn *sql.Tx, eventN
 	}
 	return results, nil
 }
+
+func (s *eventStatements) bulkSelectEventReference(eventNIDs []types.EventNID) ([]gomatrixserverlib.EventReference, error) {
+	rows, err := s.bulkSelectEventReferenceStmt.Query(eventNIDsAsArray(eventNIDs))
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	results := make([]gomatrixserverlib.EventReference, len(eventNIDs))
+	i := 0
+	for ; rows.Next(); i++ {
+		result := &results[i]
+		if err = rows.Scan(&result.EventID, &result.EventSHA256); err != nil {
+			return nil, err
+		}
+	}
+	if i != len(eventNIDs) {
+		return nil, fmt.Errorf("storage: event NIDs missing from the database (%d != %d)", i, len(eventNIDs))
+	}
+	return results, nil
+}
+
+// bulkSelectEventID returns a map from numeric event ID to string event ID.
+func (s *eventStatements) bulkSelectEventID(eventNIDs []types.EventNID) (map[types.EventNID]string, error) {
+	rows, err := s.bulkSelectEventIDStmt.Query(eventNIDsAsArray(eventNIDs))
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	results := make(map[types.EventNID]string, len(eventNIDs))
+	i := 0
+	for ; rows.Next(); i++ {
+		var eventNID int64
+		var eventID string
+		if err = rows.Scan(&eventNID, &eventID); err != nil {
+			return nil, err
+		}
+		results[types.EventNID(eventNID)] = eventID
+	}
+	if i != len(eventNIDs) {
+		return nil, fmt.Errorf("storage: event NIDs missing from the database (%d != %d)", i, len(eventNIDs))
+	}
+	return results, nil
+}
+
+func eventNIDsAsArray(eventNIDs []types.EventNID) pq.Int64Array {
+	nids := make([]int64, len(eventNIDs))
+	for i := range eventNIDs {
+		nids[i] = int64(eventNIDs[i])
+	}
+	return nids
+}

src/github.com/matrix-org/dendrite/roomserver/storage/partition_offset_table.go

@@ -36,13 +36,11 @@ func (s *partitionOffsetStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.selectPartitionOffsetsStmt, err = db.Prepare(selectPartitionOffsetsSQL); err != nil {
-		return
-	}
-	if s.upsertPartitionOffsetStmt, err = db.Prepare(upsertPartitionOffsetsSQL); err != nil {
-		return
-	}
-	return
+
+	return statementList{
+		{&s.selectPartitionOffsetsStmt, selectPartitionOffsetsSQL},
+		{&s.upsertPartitionOffsetStmt, upsertPartitionOffsetsSQL},
+	}.prepare(db)
 }
 
 func (s *partitionOffsetStatements) selectPartitionOffsets(topic string) ([]types.PartitionOffset, error) {

src/github.com/matrix-org/dendrite/roomserver/storage/prepare.go

@@ -0,0 +1,21 @@
+package storage
+
+import (
+	"database/sql"
+)
+
+// a statementList is a list of SQL statements to prepare and a pointer to where to store the resulting prepared statement.
+type statementList []struct {
+	statement **sql.Stmt
+	sql       string
+}
+
+// prepare the SQL for each statement in the list and assign the result to the prepared statement.
+func (s statementList) prepare(db *sql.DB) (err error) {
+	for _, statement := range s {
+		if *statement.statement, err = db.Prepare(statement.sql); err != nil {
+			return
+		}
+	}
+	return
+}

src/github.com/matrix-org/dendrite/roomserver/storage/previous_events_table.go

@@ -50,13 +50,11 @@ func (s *previousEventStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertPreviousEventStmt, err = db.Prepare(insertPreviousEventSQL); err != nil {
-		return
-	}
-	if s.selectPreviousEventExistsStmt, err = db.Prepare(selectPreviousEventExistsSQL); err != nil {
-		return
-	}
-	return
+
+	return statementList{
+		{&s.insertPreviousEventStmt, insertPreviousEventSQL},
+		{&s.selectPreviousEventExistsStmt, selectPreviousEventExistsSQL},
+	}.prepare(db)
 }
 
 func (s *previousEventStatements) insertPreviousEvent(txn *sql.Tx, previousEventID string, previousEventReferenceSHA256 []byte, eventNID types.EventNID) error {

src/github.com/matrix-org/dendrite/roomserver/storage/rooms_table.go

@@ -16,7 +16,12 @@ CREATE TABLE IF NOT EXISTS rooms (
     -- The most recent events in the room that aren't referenced by another event.
     -- This list may empty if the server hasn't joined the room yet.
     -- (The server will be in that state while it stores the events for the initial state of the room)
-    latest_event_nids BIGINT[] NOT NULL DEFAULT '{}'::BIGINT[]
+    latest_event_nids BIGINT[] NOT NULL DEFAULT '{}'::BIGINT[],
+    -- The last event written to the output log for this room.
+    last_event_sent_nid BIGINT NOT NULL DEFAULT 0,
+    -- The state of the room after the current set of latest events.
+    -- This will be 0 if there are no latest events in the room.
+    state_snapshot_nid BIGINT NOT NULL DEFAULT 0
 );
 `
 
@@ -30,16 +35,20 @@ const selectRoomNIDSQL = "" +
 	"SELECT room_nid FROM rooms WHERE room_id = $1"
 
 const selectLatestEventNIDsSQL = "" +
-	"SELECT latest_event_nids FROM rooms WHERE room_nid = $1 FOR UPDATE"
+	"SELECT latest_event_nids FROM rooms WHERE room_nid = $1"
+
+const selectLatestEventNIDsForUpdateSQL = "" +
+	"SELECT latest_event_nids, last_event_sent_nid, state_snapshot_nid FROM rooms WHERE room_nid = $1 FOR UPDATE"
 
 const updateLatestEventNIDsSQL = "" +
-	"UPDATE rooms SET latest_event_nids = $2 WHERE room_nid = $1"
+	"UPDATE rooms SET latest_event_nids = $2, last_event_sent_nid = $3, state_snapshot_nid = $4 WHERE room_nid = $1"
 
 type roomStatements struct {
-	insertRoomNIDStmt         *sql.Stmt
-	selectRoomNIDStmt         *sql.Stmt
-	selectLatestEventNIDsStmt *sql.Stmt
-	updateLatestEventNIDsStmt *sql.Stmt
+	insertRoomNIDStmt                  *sql.Stmt
+	selectRoomNIDStmt                  *sql.Stmt
+	selectLatestEventNIDsStmt          *sql.Stmt
+	selectLatestEventNIDsForUpdateStmt *sql.Stmt
+	updateLatestEventNIDsStmt          *sql.Stmt
 }
 
 func (s *roomStatements) prepare(db *sql.DB) (err error) {
@@ -47,19 +56,13 @@ func (s *roomStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertRoomNIDStmt, err = db.Prepare(insertRoomNIDSQL); err != nil {
-		return
-	}
-	if s.selectRoomNIDStmt, err = db.Prepare(selectRoomNIDSQL); err != nil {
-		return
-	}
-	if s.selectLatestEventNIDsStmt, err = db.Prepare(selectLatestEventNIDsSQL); err != nil {
-		return
-	}
-	if s.updateLatestEventNIDsStmt, err = db.Prepare(updateLatestEventNIDsSQL); err != nil {
-		return
-	}
-	return
+	return statementList{
+		{&s.insertRoomNIDStmt, insertRoomNIDSQL},
+		{&s.selectRoomNIDStmt, selectRoomNIDSQL},
+		{&s.selectLatestEventNIDsStmt, selectLatestEventNIDsSQL},
+		{&s.selectLatestEventNIDsForUpdateStmt, selectLatestEventNIDsForUpdateSQL},
+		{&s.updateLatestEventNIDsStmt, updateLatestEventNIDsSQL},
+	}.prepare(db)
 }
 
 func (s *roomStatements) insertRoomNID(roomID string) (types.RoomNID, error) {
@@ -74,9 +77,9 @@ func (s *roomStatements) selectRoomNID(roomID string) (types.RoomNID, error) {
 	return types.RoomNID(roomNID), err
 }
 
-func (s *roomStatements) selectLatestEventsNIDsForUpdate(txn *sql.Tx, roomNID types.RoomNID) ([]types.EventNID, error) {
+func (s *roomStatements) selectLatestEventNIDs(roomNID types.RoomNID) ([]types.EventNID, error) {
 	var nids pq.Int64Array
-	err := txn.Stmt(s.selectLatestEventNIDsStmt).QueryRow(int64(roomNID)).Scan(&nids)
+	err := s.selectLatestEventNIDsStmt.QueryRow(int64(roomNID)).Scan(&nids)
 	if err != nil {
 		return nil, err
 	}
@@ -87,11 +90,29 @@ func (s *roomStatements) selectLatestEventsNIDsForUpdate(txn *sql.Tx, roomNID ty
 	return eventNIDs, nil
 }
 
-func (s *roomStatements) updateLatestEventNIDs(txn *sql.Tx, roomNID types.RoomNID, eventNIDs []types.EventNID) error {
-	nids := make([]int64, len(eventNIDs))
-	for i := range eventNIDs {
-		nids[i] = int64(eventNIDs[i])
+func (s *roomStatements) selectLatestEventsNIDsForUpdate(txn *sql.Tx, roomNID types.RoomNID) (
+	[]types.EventNID, types.EventNID, types.StateSnapshotNID, error,
+) {
+	var nids pq.Int64Array
+	var lastEventSentNID int64
+	var stateSnapshotNID int64
+	err := txn.Stmt(s.selectLatestEventNIDsForUpdateStmt).QueryRow(int64(roomNID)).Scan(&nids, &lastEventSentNID, &stateSnapshotNID)
+	if err != nil {
+		return nil, 0, 0, err
 	}
-	_, err := txn.Stmt(s.updateLatestEventNIDsStmt).Exec(roomNID, pq.Int64Array(nids))
+	eventNIDs := make([]types.EventNID, len(nids))
+	for i := range nids {
+		eventNIDs[i] = types.EventNID(nids[i])
+	}
+	return eventNIDs, types.EventNID(lastEventSentNID), types.StateSnapshotNID(stateSnapshotNID), nil
+}
+
+func (s *roomStatements) updateLatestEventNIDs(
+	txn *sql.Tx, roomNID types.RoomNID, eventNIDs []types.EventNID, lastEventSentNID types.EventNID,
+	stateSnapshotNID types.StateSnapshotNID,
+) error {
+	_, err := txn.Stmt(s.updateLatestEventNIDsStmt).Exec(
+		roomNID, eventNIDsAsArray(eventNIDs), int64(lastEventSentNID), int64(stateSnapshotNID),
+	)
 	return err
 }

src/github.com/matrix-org/dendrite/roomserver/storage/state_block_table.go

@@ -57,16 +57,12 @@ func (s *stateBlockStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertStateDataStmt, err = db.Prepare(insertStateDataSQL); err != nil {
-		return
-	}
-	if s.selectNextStateBlockNIDStmt, err = db.Prepare(selectNextStateBlockNIDSQL); err != nil {
-		return
-	}
-	if s.bulkSelectStateDataEntriesStmt, err = db.Prepare(bulkSelectStateDataEntriesSQL); err != nil {
-		return
-	}
-	return
+
+	return statementList{
+		{&s.insertStateDataStmt, insertStateDataSQL},
+		{&s.selectNextStateBlockNIDStmt, selectNextStateBlockNIDSQL},
+		{&s.bulkSelectStateDataEntriesStmt, bulkSelectStateDataEntriesSQL},
+	}.prepare(db)
 }
 
 func (s *stateBlockStatements) bulkInsertStateData(stateBlockNID types.StateBlockNID, entries []types.StateEntry) error {

src/github.com/matrix-org/dendrite/roomserver/storage/state_snapshot_table.go

@@ -52,13 +52,11 @@ func (s *stateSnapshotStatements) prepare(db *sql.DB) (err error) {
 	if err != nil {
 		return
 	}
-	if s.insertStateStmt, err = db.Prepare(insertStateSQL); err != nil {
-		return
-	}
-	if s.bulkSelectStateBlockNIDsStmt, err = db.Prepare(bulkSelectStateBlockNIDsSQL); err != nil {
-		return
-	}
-	return
+
+	return statementList{
+		{&s.insertStateStmt, insertStateSQL},
+		{&s.bulkSelectStateBlockNIDsStmt, bulkSelectStateBlockNIDsSQL},
+	}.prepare(db)
 }
 
 func (s *stateSnapshotStatements) insertState(roomNID types.RoomNID, stateBlockNIDs []types.StateBlockNID) (stateNID types.StateSnapshotNID, err error) {

src/github.com/matrix-org/dendrite/roomserver/storage/storage.go

@@ -205,30 +205,62 @@ func (d *Database) StateEntries(stateBlockNIDs []types.StateBlockNID) ([]types.S
 	return d.statements.bulkSelectStateDataEntries(stateBlockNIDs)
 }
 
+// EventIDs implements input.RoomEventDatabase
+func (d *Database) EventIDs(eventNIDs []types.EventNID) (map[types.EventNID]string, error) {
+	return d.statements.bulkSelectEventID(eventNIDs)
+}
+
 // GetLatestEventsForUpdate implements input.EventDatabase
-func (d *Database) GetLatestEventsForUpdate(roomNID types.RoomNID) ([]types.StateAtEventAndReference, types.RoomRecentEventsUpdater, error) {
+func (d *Database) GetLatestEventsForUpdate(roomNID types.RoomNID) (types.RoomRecentEventsUpdater, error) {
 	txn, err := d.db.Begin()
 	if err != nil {
-		return nil, nil, err
+		return nil, err
 	}
-	eventNIDs, err := d.statements.selectLatestEventsNIDsForUpdate(txn, roomNID)
+	eventNIDs, lastEventNIDSent, currentStateSnapshotNID, err := d.statements.selectLatestEventsNIDsForUpdate(txn, roomNID)
 	if err != nil {
 		txn.Rollback()
-		return nil, nil, err
+		return nil, err
 	}
 	stateAndRefs, err := d.statements.bulkSelectStateAtEventAndReference(txn, eventNIDs)
 	if err != nil {
 		txn.Rollback()
-		return nil, nil, err
+		return nil, err
 	}
-	return stateAndRefs, &roomRecentEventsUpdater{txn, d}, nil
+	var lastEventIDSent string
+	if lastEventNIDSent != 0 {
+		lastEventIDSent, err = d.statements.selectEventID(txn, lastEventNIDSent)
+		if err != nil {
+			txn.Rollback()
+			return nil, err
+		}
+	}
+	return &roomRecentEventsUpdater{txn, d, stateAndRefs, lastEventIDSent, currentStateSnapshotNID}, nil
 }
 
 type roomRecentEventsUpdater struct {
-	txn *sql.Tx
-	d   *Database
+	txn                     *sql.Tx
+	d                       *Database
+	latestEvents            []types.StateAtEventAndReference
+	lastEventIDSent         string
+	currentStateSnapshotNID types.StateSnapshotNID
 }
 
+// LatestEvents implements types.RoomRecentEventsUpdater
+func (u *roomRecentEventsUpdater) LatestEvents() []types.StateAtEventAndReference {
+	return u.latestEvents
+}
+
+// LastEventIDSent implements types.RoomRecentEventsUpdater
+func (u *roomRecentEventsUpdater) LastEventIDSent() string {
+	return u.lastEventIDSent
+}
+
+// CurrentStateSnapshotNID implements types.RoomRecentEventsUpdater
+func (u *roomRecentEventsUpdater) CurrentStateSnapshotNID() types.StateSnapshotNID {
+	return u.currentStateSnapshotNID
+}
+
+// StorePreviousEvents implements types.RoomRecentEventsUpdater
 func (u *roomRecentEventsUpdater) StorePreviousEvents(eventNID types.EventNID, previousEventReferences []gomatrixserverlib.EventReference) error {
 	for _, ref := range previousEventReferences {
 		if err := u.d.statements.insertPreviousEvent(u.txn, ref.EventID, ref.EventSHA256, eventNID); err != nil {
@@ -238,6 +270,7 @@ func (u *roomRecentEventsUpdater) StorePreviousEvents(eventNID types.EventNID, p
 	return nil
 }
 
+// IsReferenced implements types.RoomRecentEventsUpdater
 func (u *roomRecentEventsUpdater) IsReferenced(eventReference gomatrixserverlib.EventReference) (bool, error) {
 	err := u.d.statements.selectPreviousEventExists(u.txn, eventReference.EventID, eventReference.EventSHA256)
 	if err == nil {
@@ -249,18 +282,52 @@ func (u *roomRecentEventsUpdater) IsReferenced(eventReference gomatrixserverlib.
 	return false, err
 }
 
-func (u *roomRecentEventsUpdater) SetLatestEvents(roomNID types.RoomNID, latest []types.StateAtEventAndReference) error {
+// SetLatestEvents implements types.RoomRecentEventsUpdater
+func (u *roomRecentEventsUpdater) SetLatestEvents(
+	roomNID types.RoomNID, latest []types.StateAtEventAndReference, lastEventNIDSent types.EventNID,
+	currentStateSnapshotNID types.StateSnapshotNID,
+) error {
 	eventNIDs := make([]types.EventNID, len(latest))
 	for i := range latest {
 		eventNIDs[i] = latest[i].EventNID
 	}
-	return u.d.statements.updateLatestEventNIDs(u.txn, roomNID, eventNIDs)
+	return u.d.statements.updateLatestEventNIDs(u.txn, roomNID, eventNIDs, lastEventNIDSent, currentStateSnapshotNID)
 }
 
+// HasEventBeenSent implements types.RoomRecentEventsUpdater
+func (u *roomRecentEventsUpdater) HasEventBeenSent(eventNID types.EventNID) (bool, error) {
+	return u.d.statements.selectEventSentToOutput(u.txn, eventNID)
+}
+
+// MarkEventAsSent implements types.RoomRecentEventsUpdater
+func (u *roomRecentEventsUpdater) MarkEventAsSent(eventNID types.EventNID) error {
+	return u.d.statements.updateEventSentToOutput(u.txn, eventNID)
+}
+
+// Commit implements types.RoomRecentEventsUpdater
 func (u *roomRecentEventsUpdater) Commit() error {
 	return u.txn.Commit()
 }
 
+// Rollback implements types.RoomRecentEventsUpdater
 func (u *roomRecentEventsUpdater) Rollback() error {
 	return u.txn.Rollback()
 }
+
+// RoomNID implements query.RoomserverQueryAPIDB
+func (d *Database) RoomNID(roomID string) (types.RoomNID, error) {
+	roomNID, err := d.statements.selectRoomNID(roomID)
+	if err == sql.ErrNoRows {
+		return 0, nil
+	}
+	return roomNID, err
+}
+
+// LatestEventIDs implements query.RoomserverQueryAPIDB
+func (d *Database) LatestEventIDs(roomNID types.RoomNID) ([]gomatrixserverlib.EventReference, error) {
+	eventNIDs, err := d.statements.selectLatestEventNIDs(roomNID)
+	if err != nil {
+		return nil, err
+	}
+	return d.statements.bulkSelectEventReference(eventNIDs)
+}

src/github.com/matrix-org/dendrite/roomserver/types/types.go

@@ -133,6 +133,12 @@ type StateEntryList struct {
 // (On postgresql this wraps a database transaction that holds a "FOR UPDATE"
 //  lock on the row holding the latest events for the room.)
 type RoomRecentEventsUpdater interface {
+	// The latest event IDs and state in the room.
+	LatestEvents() []StateAtEventAndReference
+	// The event ID of the latest event written to the output log in the room.
+	LastEventIDSent() string
+	// The current state of the room.
+	CurrentStateSnapshotNID() StateSnapshotNID
 	// Store the previous events referenced by an event.
 	// This adds the event NID to an entry in the database for each of the previous events.
 	// If there isn't an entry for one of previous events then an entry is created.
@@ -143,7 +149,14 @@ type RoomRecentEventsUpdater interface {
 	IsReferenced(eventReference gomatrixserverlib.EventReference) (bool, error)
 	// Set the list of latest events for the room.
 	// This replaces the current list stored in the database with the given list
-	SetLatestEvents(roomNID RoomNID, latest []StateAtEventAndReference) error
+	SetLatestEvents(
+		roomNID RoomNID, latest []StateAtEventAndReference, lastEventNIDSent EventNID,
+		currentStateSnapshotNID StateSnapshotNID,
+	) error
+	// Check if the event has already be written to the output logs.
+	HasEventBeenSent(eventNID EventNID) (bool, error)
+	// Mark the event as having been sent to the output logs.
+	MarkEventAsSent(eventNID EventNID) error
 	// Commit the transaction
 	Commit() error
 	// Rollback the transaction.

travis-install-kafka.sh

@@ -0,0 +1,22 @@
+# /bin/bash
+
+set -eu
+
+# The mirror to download kafka from is picked from the list of mirrors at
+# https://www.apache.org/dyn/closer.cgi?path=/kafka/0.10.2.0/kafka_2.11-0.10.2.0.tgz
+# TODO: Check the signature since we are downloading over HTTP.
+MIRROR=http://mirror.ox.ac.uk/sites/rsync.apache.org/kafka/0.10.2.0/kafka_2.11-0.10.2.0.tgz
+
+# Only download the kafka if it isn't already downloaded.
+test -f kafka.tgz || wget $MIRROR -O kafka.tgz
+# Unpack the kafka over the top of any existing installation
+mkdir -p kafka && tar xzf kafka.tgz -C kafka --strip-components 1
+# Start the zookeeper running in the background.
+# By default the zookeeper listens on localhost:2181
+kafka/bin/zookeeper-server-start.sh -daemon kafka/config/zookeeper.properties
+# Enable topic deletion so that the integration tests can create a fresh topic
+# for each test run.
+echo "delete.topic.enable=true" >> kafka/config/server.properties
+# Start the kafka server running in the background.
+# By default the kafka listens on localhost:9092
+kafka/bin/kafka-server-start.sh -daemon kafka/config/server.properties

travis-test.sh

@@ -0,0 +1,13 @@
+#! /bin/bash
+
+set -eu
+
+# Check that the servers build
+gb build github.com/matrix-org/dendrite/roomserver/roomserver
+gb build github.com/matrix-org/dendrite/roomserver/roomserver-integration-tests
+
+# Run the pre commit hooks
+./hooks/pre-commit
+
+# Run the integration tests
+bin/roomserver-integration-tests

vendor/manifest

@@ -98,7 +98,7 @@
 		{
 			"importpath": "github.com/matrix-org/util",
 			"repository": "https://github.com/matrix-org/util",
-			"revision": "ccef6dc7c24a7c896d96b433a9107b7c47ecf828",
+			"revision": "28bd7491c8aafbf346ca23821664f0f9911ef52b",
 			"branch": "master"
 		},
 		{
@@ -206,4 +206,4 @@
 			"branch": "master"
 		}
 	]
-}
+}

vendor/src/github.com/matrix-org/util/context.go

@@ -25,11 +25,13 @@ func GetRequestID(ctx context.Context) string {
 // ctxValueLogger is the key to extract the logrus Logger.
 const ctxValueLogger = contextKeys("logger")
 
-// GetLogger retrieves the logrus logger from the supplied context. Returns nil if there is no logger.
+// GetLogger retrieves the logrus logger from the supplied context. Always returns a logger,
+// even if there wasn't one originally supplied.
 func GetLogger(ctx context.Context) *log.Entry {
 	l := ctx.Value(ctxValueLogger)
 	if l == nil {
-		return nil
+		// Always return a logger so callers don't need to constantly nil check.
+		return log.WithField("context", "missing")
 	}
 	return l.(*log.Entry)
 }

vendor/src/github.com/matrix-org/util/json.go

@@ -58,6 +58,21 @@ type JSONRequestHandler interface {
 	OnIncomingRequest(req *http.Request) JSONResponse
 }
 
+// jsonRequestHandlerWrapper is a wrapper to allow in-line functions to conform to util.JSONRequestHandler
+type jsonRequestHandlerWrapper struct {
+	function func(req *http.Request) JSONResponse
+}
+
+// OnIncomingRequest implements util.JSONRequestHandler
+func (r *jsonRequestHandlerWrapper) OnIncomingRequest(req *http.Request) JSONResponse {
+	return r.function(req)
+}
+
+// NewJSONRequestHandler converts the given OnIncomingRequest function into a JSONRequestHandler
+func NewJSONRequestHandler(f func(req *http.Request) JSONResponse) JSONRequestHandler {
+	return &jsonRequestHandlerWrapper{f}
+}
+
 // Protect panicking HTTP requests from taking down the entire process, and log them using
 // the correct logger, returning a 500 with a JSON response rather than abruptly closing the
 // connection. The http.Request MUST have a ctxValueLogger.

vendor/src/github.com/matrix-org/util/json_test.go

@@ -164,8 +164,8 @@ func TestGetLogger(t *testing.T) {
 
 	noLoggerInReq, _ := http.NewRequest("GET", "http://example.com/foo", nil)
 	ctxLogger = GetLogger(noLoggerInReq.Context())
-	if ctxLogger != nil {
-		t.Errorf("TestGetLogger wanted nil logger, got '%v'", ctxLogger)
+	if ctxLogger == nil {
+		t.Errorf("TestGetLogger wanted logger, got nil")
 	}
 }