Add API for querying events by ID. (#127)

* Add API for querying events by ID.

* Fix tense

* Start implementing federation ingress

* More stuff

* Hook up federation event receiving

* Fix comments

* Comment on the order of the arrays

src/github.com/matrix-org/dendrite/cmd/dendrite-federation-api-server/main.go

@@ -18,11 +18,14 @@ import (
 	"encoding/base64"
 	"net/http"
 	"os"
+	"strings"
 	"time"
 
+	"github.com/matrix-org/dendrite/clientapi/producers"
 	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/federationapi/config"
 	"github.com/matrix-org/dendrite/federationapi/routing"
+	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/gomatrixserverlib"
 
 	log "github.com/Sirupsen/logrus"
@@ -41,6 +44,9 @@ var (
 	//     python -c 'print raw_input()[19:].replace(":","").decode("hex").encode("base64").rstrip("=\n")'
 	//
 	tlsFingerprint       = os.Getenv("TLS_FINGERPRINT")
+	kafkaURIs            = strings.Split(os.Getenv("KAFKA_URIS"), ",")
+	roomserverURL        = os.Getenv("ROOMSERVER_URL")
+	roomserverInputTopic = os.Getenv("TOPIC_INPUT_ROOM_EVENT")
 )
 
 func main() {
@@ -57,6 +63,18 @@ func main() {
 		log.Panic("No TLS_FINGERPRINT environment variable found.")
 	}
 
+	if len(kafkaURIs) == 0 {
+		// the kafka default is :9092
+		kafkaURIs = []string{"localhost:9092"}
+	}
+
+	if roomserverURL == "" {
+		log.Panic("No ROOMSERVER_URL environment variable found.")
+	}
+
+	if roomserverInputTopic == "" {
+		log.Panic("No TOPIC_INPUT_ROOM_EVENT environment variable found. This should match the roomserver input topic.")
+	}
 	cfg := config.FederationAPI{
 		ServerName: serverName,
 		// TODO: make the validity period configurable.
@@ -75,6 +93,37 @@ func main() {
 	}
 	cfg.TLSFingerPrints = []gomatrixserverlib.TLSFingerprint{{fingerprintSHA256}}
 
-	routing.Setup(http.DefaultServeMux, cfg)
+	federation := gomatrixserverlib.NewFederationClient(cfg.ServerName, cfg.KeyID, cfg.PrivateKey)
+
+	keyRing := gomatrixserverlib.KeyRing{
+		KeyFetchers: []gomatrixserverlib.KeyFetcher{
+			// TODO: Use perspective key fetchers for production.
+			&gomatrixserverlib.DirectKeyFetcher{federation.Client},
+		},
+		KeyDatabase: &dummyKeyDatabase{},
+	}
+	queryAPI := api.NewRoomserverQueryAPIHTTP(roomserverURL, nil)
+
+	roomserverProducer, err := producers.NewRoomserverProducer(kafkaURIs, roomserverInputTopic)
+	if err != nil {
+		log.Panicf("Failed to setup kafka producers(%s): %s", kafkaURIs, err)
+	}
+
+	routing.Setup(http.DefaultServeMux, cfg, queryAPI, roomserverProducer, keyRing)
 	log.Fatal(http.ListenAndServe(bindAddr, nil))
 }
+
+// TODO: Implement a proper key database.
+type dummyKeyDatabase struct{}
+
+func (d *dummyKeyDatabase) FetchKeys(
+	requests map[gomatrixserverlib.PublicKeyRequest]gomatrixserverlib.Timestamp,
+) (map[gomatrixserverlib.PublicKeyRequest]gomatrixserverlib.ServerKeys, error) {
+	return nil, nil
+}
+
+func (d *dummyKeyDatabase) StoreKeys(
+	map[gomatrixserverlib.PublicKeyRequest]gomatrixserverlib.ServerKeys,
+) error {
+	return nil
+}

src/github.com/matrix-org/dendrite/cmd/federation-api-proxy/main.go

@@ -0,0 +1,124 @@
+// Copyright 2017 Vector Creations Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	log "github.com/Sirupsen/logrus"
+	"net/http"
+	"net/http/httputil"
+	"net/url"
+	"os"
+	"strings"
+	"time"
+)
+
+const usage = `Usage: %s
+
+Create a single endpoint URL which remote matrix servers can be pointed at.
+
+The server-server API in Dendrite is split across multiple processes
+which listen on multiple ports. You cannot point a Matrix server at
+any of those ports, as there will be unimplemented functionality.
+In addition, all server-server API processes start with the additional
+path prefix '/api', which Matrix servers will be unaware of.
+
+This tool will proxy requests for all server-server URLs and forward
+them to their respective process. It will also add the '/api' path
+prefix to incoming requests.
+
+THIS TOOL IS FOR TESTING AND NOT INTENDED FOR PRODUCTION USE.
+
+Arguments:
+
+`
+
+var (
+	federationAPIURL = flag.String("federation-api-url", "", "The base URL of the listening 'dendrite-federation-api-server' process. E.g. 'http://localhost:4200'")
+	bindAddress      = flag.String("bind-address", ":8448", "The listening port for the proxy.")
+	certFile         = flag.String("tls-cert", "server.crt", "The X509 certificate to use for TLS")
+	keyFile          = flag.String("tls-key", "server.key", "The PEM private key to use for TLS")
+)
+
+func makeProxy(targetURL string) (*httputil.ReverseProxy, error) {
+	if !strings.HasSuffix(targetURL, "/") {
+		targetURL += "/"
+	}
+	// Check that we can parse the URL.
+	_, err := url.Parse(targetURL)
+	if err != nil {
+		return nil, err
+	}
+	return &httputil.ReverseProxy{
+		Director: func(req *http.Request) {
+			// URL.Path() removes the % escaping from the path.
+			// The % encoding will be added back when the url is encoded
+			// when the request is forwarded.
+			// This means that we will lose any unessecary escaping from the URL.
+			// Pratically this means that any distinction between '%2F' and '/'
+			// in the URL will be lost by the time it reaches the target.
+			path := req.URL.Path
+			path = "api" + path
+			log.WithFields(log.Fields{
+				"path":   path,
+				"url":    targetURL,
+				"method": req.Method,
+			}).Print("proxying request")
+			newURL, err := url.Parse(targetURL + path)
+			if err != nil {
+				// We already checked that we can parse the URL
+				// So this shouldn't ever get hit.
+				panic(err)
+			}
+			// Copy the query parameters from the request.
+			newURL.RawQuery = req.URL.RawQuery
+			req.URL = newURL
+		},
+	}, nil
+}
+
+func main() {
+	flag.Usage = func() {
+		fmt.Fprintf(os.Stderr, usage, os.Args[0])
+		flag.PrintDefaults()
+	}
+
+	flag.Parse()
+
+	if *federationAPIURL == "" {
+		flag.Usage()
+		fmt.Fprintln(os.Stderr, "no --federation-api-url specified.")
+		os.Exit(1)
+	}
+
+	federationProxy, err := makeProxy(*federationAPIURL)
+	if err != nil {
+		panic(err)
+	}
+
+	http.Handle("/", federationProxy)
+
+	srv := &http.Server{
+		Addr:         *bindAddress,
+		ReadTimeout:  1 * time.Minute, // how long we wait for the client to send the entire request (after connection accept)
+		WriteTimeout: 5 * time.Minute, // how long the proxy has to write the full response
+	}
+
+	fmt.Println("Proxying requests to:")
+	fmt.Println("  /*                       => ", *federationAPIURL+"/api/*")
+	fmt.Println("Listening on ", *bindAddress)
+	panic(srv.ListenAndServeTLS(*certFile, *keyFile))
+}

src/github.com/matrix-org/dendrite/federationapi/routing/routing.go

@@ -16,21 +16,34 @@ package routing
 
 import (
 	"github.com/gorilla/mux"
+	"github.com/matrix-org/dendrite/clientapi/producers"
 	"github.com/matrix-org/dendrite/federationapi/config"
 	"github.com/matrix-org/dendrite/federationapi/readers"
+	"github.com/matrix-org/dendrite/federationapi/writers"
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/matrix-org/util"
 	"github.com/prometheus/client_golang/prometheus"
 	"net/http"
+	"time"
 )
 
 const (
 	pathPrefixV2Keys       = "/_matrix/key/v2"
+	pathPrefixV1Federation = "/_matrix/federation/v1"
 )
 
 // Setup registers HTTP handlers with the given ServeMux.
-func Setup(servMux *http.ServeMux, cfg config.FederationAPI) {
+func Setup(
+	servMux *http.ServeMux,
+	cfg config.FederationAPI,
+	query api.RoomserverQueryAPI,
+	producer *producers.RoomserverProducer,
+	keys gomatrixserverlib.KeyRing,
+) {
 	apiMux := mux.NewRouter()
 	v2keysmux := apiMux.PathPrefix(pathPrefixV2Keys).Subrouter()
+	v1fedmux := apiMux.PathPrefix(pathPrefixV1Federation).Subrouter()
 
 	localKeys := makeAPI("localkeys", func(req *http.Request) util.JSONResponse {
 		return readers.LocalKeys(req, cfg)
@@ -43,6 +56,17 @@ func Setup(servMux *http.ServeMux, cfg config.FederationAPI) {
 	v2keysmux.Handle("/server/{keyID}", localKeys)
 	v2keysmux.Handle("/server/", localKeys)
 
+	v1fedmux.Handle("/send/{txnID}/", makeAPI("send",
+		func(req *http.Request) util.JSONResponse {
+			vars := mux.Vars(req)
+			return writers.Send(
+				req, gomatrixserverlib.TransactionID(vars["txnID"]),
+				time.Now(),
+				cfg, query, producer, keys,
+			)
+		},
+	))
+
 	servMux.Handle("/metrics", prometheus.Handler())
 	servMux.Handle("/api/", http.StripPrefix("/api", apiMux))
 }

src/github.com/matrix-org/dendrite/federationapi/writers/send.go

@@ -0,0 +1,182 @@
+package writers
+
+import (
+	"encoding/json"
+	"fmt"
+	"github.com/matrix-org/dendrite/clientapi/httputil"
+	"github.com/matrix-org/dendrite/clientapi/jsonerror"
+	"github.com/matrix-org/dendrite/clientapi/producers"
+	"github.com/matrix-org/dendrite/federationapi/config"
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+	"net/http"
+	"time"
+)
+
+// Send implements /_matrix/federation/v1/send/{txnID}
+func Send(
+	req *http.Request,
+	txnID gomatrixserverlib.TransactionID,
+	now time.Time,
+	cfg config.FederationAPI,
+	query api.RoomserverQueryAPI,
+	producer *producers.RoomserverProducer,
+	keys gomatrixserverlib.KeyRing,
+) util.JSONResponse {
+	request, errResp := gomatrixserverlib.VerifyHTTPRequest(req, now, cfg.ServerName, keys)
+	if request == nil {
+		return errResp
+	}
+
+	var content gomatrixserverlib.Transaction
+	if err := json.Unmarshal(request.Content(), &content); err != nil {
+		return util.JSONResponse{
+			Code: 400,
+			JSON: jsonerror.BadJSON("The request body could not be decoded into valid JSON. " + err.Error()),
+		}
+	}
+
+	content.Origin = request.Origin()
+	content.TransactionID = txnID
+	content.Destination = cfg.ServerName
+
+	resp, err := processTransaction(content, query, producer, keys)
+	if err != nil {
+		return httputil.LogThenError(req, err)
+	}
+
+	return util.JSONResponse{
+		Code: 200,
+		JSON: resp,
+	}
+}
+
+func processTransaction(
+	t gomatrixserverlib.Transaction,
+	query api.RoomserverQueryAPI,
+	producer *producers.RoomserverProducer,
+	keys gomatrixserverlib.KeyRing,
+) (*gomatrixserverlib.RespSend, error) {
+	// Check the event signatures
+	if err := gomatrixserverlib.VerifyEventSignatures(t.PDUs, keys); err != nil {
+		return nil, err
+	}
+
+	// Process the events.
+	results := map[string]gomatrixserverlib.PDUResult{}
+	for _, e := range t.PDUs {
+		err := processEvent(e, query, producer)
+		if err != nil {
+			// If the error is due to the event itself being bad then we skip
+			// it and move onto the next event. We report an error so that the
+			// sender knows that we have skipped processing it.
+			//
+			// However if the event is due to a temporary failure in our server
+			// such as a database being unavailable then we should bail, and
+			// hope that the sender will retry when we are feeling better.
+			//
+			// It is uncertain what we should do if an event fails because
+			// we failed to fetch more information from the sending server.
+			// For example if a request to /state fails.
+			// If we skip the event then we risk missing the event until we
+			// receive another event referencing it.
+			// If we bail and stop processing then we risk wedging incoming
+			// transactions from that server forever.
+			switch err.(type) {
+			case unknownRoomError:
+			case *gomatrixserverlib.NotAllowed:
+			default:
+				// Any other error should be the result of a temporary error in
+				// our server so we should bail processing the transaction entirely.
+				return nil, err
+			}
+			results[e.EventID()] = gomatrixserverlib.PDUResult{err.Error()}
+		} else {
+			results[e.EventID()] = gomatrixserverlib.PDUResult{}
+		}
+	}
+
+	// TODO: Process the EDUs.
+
+	return &gomatrixserverlib.RespSend{PDUs: results}, nil
+}
+
+type unknownRoomError string
+
+func (e unknownRoomError) Error() string { return fmt.Sprintf("unknown room %q", e) }
+
+func processEvent(
+	e gomatrixserverlib.Event,
+	query api.RoomserverQueryAPI,
+	producer *producers.RoomserverProducer,
+) error {
+	refs := e.PrevEvents()
+	prevEventIDs := make([]string, len(refs))
+	for i := range refs {
+		prevEventIDs[i] = refs[i].EventID
+	}
+
+	// Fetch the state needed to authenticate the event.
+	needed := gomatrixserverlib.StateNeededForAuth([]gomatrixserverlib.Event{e})
+	stateReq := api.QueryStateAfterEventsRequest{
+		RoomID:       e.RoomID(),
+		PrevEventIDs: prevEventIDs,
+		StateToFetch: needed.Tuples(),
+	}
+	var stateResp api.QueryStateAfterEventsResponse
+	if err := query.QueryStateAfterEvents(&stateReq, &stateResp); err != nil {
+		return err
+	}
+
+	if !stateResp.RoomExists {
+		// TODO: When synapse receives a message for a room it is not in it
+		// asked the remote server for the state of the room so that it can
+		// check if the remote server knows of a join "m.room.member" event
+		// that this server is unaware of.
+		// However generally speaking we should reject events for rooms we
+		// aren't a member of.
+		return unknownRoomError(e.RoomID())
+	}
+
+	if !stateResp.PrevEventsExist {
+		// We are missing the previous events for this events.
+		// This means that there is a gap in our view of the history of the
+		// room. There two ways that we can handle such a gap:
+		//   1) We can fill in the gap using /get_missing_events
+		//   2) We can leave the gap and request the state of the room at
+		//      this event from the remote server using either /state_ids
+		//      or /state.
+		// Synapse will attempt to do 1 and if that fails or if the gap is
+		// too large then it will attempt 2.
+		// Synapse will use /state_ids if possible since ususally the state
+		// is largely unchanged and it is more efficient to fetch a list of
+		// event ids and then use /event to fetch the individual events.
+		// However not all version of synapse support /state_ids so you may
+		// need to fallback to /state.
+		// TODO: Attempt to fill in the gap using /get_missing_events
+		// TODO: Attempt to fetch the state using /state_ids and /events
+		// TODO: Attempt to fetch the state using /state
+		panic(fmt.Errorf("Receiving events with missing prev_events is no implemented"))
+	}
+
+	// Check that the event is allowed by the state at the event.
+	authUsingState := gomatrixserverlib.NewAuthEvents(nil)
+	for i := range stateResp.StateEvents {
+		authUsingState.AddEvent(&stateResp.StateEvents[i])
+	}
+	err := gomatrixserverlib.Allowed(e, &authUsingState)
+	if err != nil {
+		return err
+	}
+
+	// TODO: Check that the roomserver has a copy of all of the auth_events.
+	// TODO: Check that the event is allowed by its auth_events.
+
+	// pass the event to the roomserver
+	if err := producer.SendEvents([]gomatrixserverlib.Event{e}); err != nil {
+		return err
+	}
+
+	return nil
+}

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

@@ -41,6 +41,7 @@ type QueryLatestEventsAndStateResponse struct {
 	// The latest events in the room.
 	LatestEvents []gomatrixserverlib.EventReference
 	// The state events requested.
+	// This list will be in an arbitrary order.
 	StateEvents []gomatrixserverlib.Event
 }
 
@@ -65,9 +66,30 @@ type QueryStateAfterEventsResponse struct {
 	// If some of previous events do not exist this will be false and StateEvents will be empty.
 	PrevEventsExist bool
 	// The state events requested.
+	// This list will be in an arbitrary order.
 	StateEvents []gomatrixserverlib.Event
 }
 
+// QueryEventsByIDRequest is a request to QueryEventsByID
+type QueryEventsByIDRequest struct {
+	// The event IDs to look up.
+	EventIDs []string
+}
+
+// QueryEventsByIDResponse is a response to QueryEventsByID
+type QueryEventsByIDResponse struct {
+	// Copy of the request for debugging.
+	QueryEventsByIDRequest
+	// A list of events with the requested IDs.
+	// If the roomserver does not have a copy of a requested event
+	// then it will omit that event from the list.
+	// If the roomserver thinks it has a copy of the event, but
+	// fails to read it from the database then it will fail
+	// the entire request.
+	// This list will be in an arbitrary order.
+	Events []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.
@@ -81,6 +103,12 @@ type RoomserverQueryAPI interface {
 		request *QueryStateAfterEventsRequest,
 		response *QueryStateAfterEventsResponse,
 	) error
+
+	// Query a list of events by event ID.
+	QueryEventsByID(
+		request *QueryEventsByIDRequest,
+		response *QueryEventsByIDResponse,
+	) error
 }
 
 // RoomserverQueryLatestEventsAndStatePath is the HTTP path for the QueryLatestEventsAndState API.
@@ -89,6 +117,9 @@ const RoomserverQueryLatestEventsAndStatePath = "/api/roomserver/QueryLatestEven
 // RoomserverQueryStateAfterEventsPath is the HTTP path for the QueryStateAfterEvents API.
 const RoomserverQueryStateAfterEventsPath = "/api/roomserver/QueryStateAfterEvents"
 
+// RoomserverQueryEventsByIDPath is the HTTP path for the QueryEventsByID API.
+const RoomserverQueryEventsByIDPath = "/api/roomserver/QueryEventsByID"
+
 // 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 {
@@ -121,6 +152,15 @@ func (h *httpRoomserverQueryAPI) QueryStateAfterEvents(
 	return postJSON(h.httpClient, apiURL, request, response)
 }
 
+// QueryEventsByID implements RoomserverQueryAPI
+func (h *httpRoomserverQueryAPI) QueryEventsByID(
+	request *QueryEventsByIDRequest,
+	response *QueryEventsByIDResponse,
+) error {
+	apiURL := h.roomserverURL + RoomserverQueryEventsByIDPath
+	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 {

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

@@ -35,6 +35,9 @@ type RoomserverQueryAPIDatabase interface {
 	// Lookup event references for the latest events in the room and the current state snapshot.
 	// Returns an error if there was a problem talking to the database.
 	LatestEventIDs(roomNID types.RoomNID) ([]gomatrixserverlib.EventReference, types.StateSnapshotNID, error)
+	// Lookup the numeric IDs for a list of events.
+	// Returns an error if there was a problem talking to the database.
+	EventNIDs(eventIDs []string) (map[string]types.EventNID, error)
 }
 
 // RoomserverQueryAPI is an implementation of RoomserverQueryAPI
@@ -46,7 +49,7 @@ type RoomserverQueryAPI struct {
 func (r *RoomserverQueryAPI) QueryLatestEventsAndState(
 	request *api.QueryLatestEventsAndStateRequest,
 	response *api.QueryLatestEventsAndStateResponse,
-) (err error) {
+) error {
 	response.QueryLatestEventsAndStateRequest = *request
 	roomNID, err := r.DB.RoomNID(request.RoomID)
 	if err != nil {
@@ -81,7 +84,7 @@ func (r *RoomserverQueryAPI) QueryLatestEventsAndState(
 func (r *RoomserverQueryAPI) QueryStateAfterEvents(
 	request *api.QueryStateAfterEventsRequest,
 	response *api.QueryStateAfterEventsResponse,
-) (err error) {
+) error {
 	response.QueryStateAfterEventsRequest = *request
 	roomNID, err := r.DB.RoomNID(request.RoomID)
 	if err != nil {
@@ -115,12 +118,41 @@ func (r *RoomserverQueryAPI) QueryStateAfterEvents(
 	return nil
 }
 
+// QueryEventsByID implements api.RoomserverQueryAPI
+func (r *RoomserverQueryAPI) QueryEventsByID(
+	request *api.QueryEventsByIDRequest,
+	response *api.QueryEventsByIDResponse,
+) error {
+	response.QueryEventsByIDRequest = *request
+
+	eventNIDMap, err := r.DB.EventNIDs(request.EventIDs)
+	if err != nil {
+		return err
+	}
+
+	var eventNIDs []types.EventNID
+	for _, nid := range eventNIDMap {
+		eventNIDs = append(eventNIDs, nid)
+	}
+
+	events, err := r.loadEvents(eventNIDs)
+	if err != nil {
+		return err
+	}
+
+	response.Events = events
+	return nil
+}
+
 func (r *RoomserverQueryAPI) loadStateEvents(stateEntries []types.StateEntry) ([]gomatrixserverlib.Event, error) {
 	eventNIDs := make([]types.EventNID, len(stateEntries))
 	for i := range stateEntries {
 		eventNIDs[i] = stateEntries[i].EventNID
 	}
+	return r.loadEvents(eventNIDs)
+}
 
+func (r *RoomserverQueryAPI) loadEvents(eventNIDs []types.EventNID) ([]gomatrixserverlib.Event, error) {
 	stateEvents, err := r.DB.Events(eventNIDs)
 	if err != nil {
 		return nil, err
@@ -163,4 +195,18 @@ func (r *RoomserverQueryAPI) SetupHTTP(servMux *http.ServeMux) {
 			return util.JSONResponse{Code: 200, JSON: &response}
 		}),
 	)
+	servMux.Handle(
+		api.RoomserverQueryEventsByIDPath,
+		common.MakeAPI("query_events_by_id", func(req *http.Request) util.JSONResponse {
+			var request api.QueryEventsByIDRequest
+			var response api.QueryEventsByIDResponse
+			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
+				return util.ErrorResponse(err)
+			}
+			if err := r.QueryEventsByID(&request, &response); err != nil {
+				return util.ErrorResponse(err)
+			}
+			return util.JSONResponse{Code: 200, JSON: &response}
+		}),
+	)
 }

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

@@ -104,6 +104,9 @@ const bulkSelectEventReferenceSQL = "" +
 const bulkSelectEventIDSQL = "" +
 	"SELECT event_nid, event_id FROM events WHERE event_nid = ANY($1)"
 
+const bulkSelectEventNIDSQL = "" +
+	"SELECT event_id, event_nid FROM events WHERE event_id = ANY($1)"
+
 type eventStatements struct {
 	insertEventStmt                        *sql.Stmt
 	selectEventStmt                        *sql.Stmt
@@ -116,6 +119,7 @@ type eventStatements struct {
 	bulkSelectStateAtEventAndReferenceStmt *sql.Stmt
 	bulkSelectEventReferenceStmt           *sql.Stmt
 	bulkSelectEventIDStmt                  *sql.Stmt
+	bulkSelectEventNIDStmt                 *sql.Stmt
 }
 
 func (s *eventStatements) prepare(db *sql.DB) (err error) {
@@ -136,6 +140,7 @@ func (s *eventStatements) prepare(db *sql.DB) (err error) {
 		{&s.bulkSelectStateAtEventAndReferenceStmt, bulkSelectStateAtEventAndReferenceSQL},
 		{&s.bulkSelectEventReferenceStmt, bulkSelectEventReferenceSQL},
 		{&s.bulkSelectEventIDStmt, bulkSelectEventIDSQL},
+		{&s.bulkSelectEventNIDStmt, bulkSelectEventNIDSQL},
 	}.prepare(db)
 }
 
@@ -321,6 +326,26 @@ func (s *eventStatements) bulkSelectEventID(eventNIDs []types.EventNID) (map[typ
 	return results, nil
 }
 
+// bulkSelectEventNIDs returns a map from string event ID to numeric event ID.
+// If an event ID is not in the database then it is omitted from the map.
+func (s *eventStatements) bulkSelectEventNID(eventIDs []string) (map[string]types.EventNID, error) {
+	rows, err := s.bulkSelectEventNIDStmt.Query(pq.StringArray(eventIDs))
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	results := make(map[string]types.EventNID, len(eventIDs))
+	for rows.Next() {
+		var eventID string
+		var eventNID int64
+		if err = rows.Scan(&eventID, &eventNID); err != nil {
+			return nil, err
+		}
+		results[eventID] = types.EventNID(eventNID)
+	}
+	return results, nil
+}
+
 func eventNIDsAsArray(eventNIDs []types.EventNID) pq.Int64Array {
 	nids := make([]int64, len(eventNIDs))
 	for i := range eventNIDs {

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

@@ -170,6 +170,11 @@ func (d *Database) EventStateKeyNIDs(eventStateKeys []string) (map[string]types.
 	return d.statements.bulkSelectEventStateKeyNID(eventStateKeys)
 }
 
+// EventNIDs implements query.RoomQueryDatabase
+func (d *Database) EventNIDs(eventIDs []string) (map[string]types.EventNID, error) {
+	return d.statements.bulkSelectEventNID(eventIDs)
+}
+
 // Events implements input.EventDatabase
 func (d *Database) Events(eventNIDs []types.EventNID) ([]types.Event, error) {
 	eventJSONs, err := d.statements.bulkSelectEventJSON(eventNIDs)