Peeking over federation via MSC2444 (#1391)

* a very very WIP first cut of peeking via MSC2753.

doesn't yet compile or work.
needs to actually add the peeking block into the sync response.
checking in now before it gets any bigger, and to gather any initial feedback on the vague shape of it.

* make PeekingDeviceSet private

* add server_name param

* blind stab at adding a `peek` section to /sync

* make it build

* make it launch

* add peeking to getResponseWithPDUsForCompleteSync

* cancel any peeks when we join a room

* spell out how to runoutside of docker if you want speed

* fix SQL

* remove unnecessary txn for SelectPeeks

* fix s/join/peek/ cargocult fail

* HACK: Track goroutine IDs to determine when we write by the wrong thread

To use: set `DENDRITE_TRACE_SQL=1` then grep for `unsafe`

* Track partition offsets and only log unsafe for non-selects

* Put redactions in the writer goroutine

* Update filters on writer goroutine

* wrap peek storage in goid hack

* use exclusive writer, and MarkPeeksAsOld more efficiently

* don't log ascii in binary at sql trace...

* strip out empty roomd deltas

* re-add txn to SelectPeeks

* re-add accidentally deleted field

* reject peeks for non-worldreadable rooms

* move perform_peek

* fix package

* correctly refactor perform_peek

* WIP of implementing MSC2444

* typo

* Revert "Merge branch 'kegan/HACK-goid-sqlite-db-is-locked' into matthew/peeking"

This reverts commit 3cebd8dbfb, reversing
changes made to ed4b3a58a7.

* (almost) make it build

* clean up bad merge

* support SendEventWithState with optional event

* fix build & lint

* fix build & lint

* reinstate federated peeks in the roomserver (doh)

* fix sql thinko

* todo for authenticating state returned by /peek

* support returning current state from QueryStateAndAuthChain

* handle SS /peek

* reimplement SS /peek to prod the RS to tell the FS about the peek

* rename RemotePeeks as OutboundPeeks

* rename remote_peeks_table as outbound_peeks_table

* add perform_handle_remote_peek.go

* flesh out federation doc

* add inbound peeks table and hook it up

* rename ambiguous RemotePeek as InboundPeek

* rename FSAPI's PerformPeek as PerformOutboundPeek

* setup inbound peeks db correctly

* fix api.SendEventWithState with no event

* track latestevent on /peek

* go fmt

* document the peek send stream race better

* fix SendEventWithRewrite not to bail if handed a non-state event

* add fixme

* switch SS /peek to use SendEventWithRewrite

* fix comment

* use reverse topo ordering to find latest extrem

* support postgres for federated peeking

* go fmt

* back out bogus go.mod change

* Fix performOutboundPeekUsingServer

* Fix getAuthChain -> GetAuthChain

* Fix build issues

* Fix build again

* Fix getAuthChain -> GetAuthChain

* Don't repeat outbound peeks for the same room ID to the same servers

* Fix lint

* Don't omitempty to appease sytest

Co-authored-by: Kegan Dougal <kegan@matrix.org>
Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>

docs/peeking.md

@@ -1,19 +1,26 @@
 ## Peeking
 
-Peeking is implemented as per [MSC2753](https://github.com/matrix-org/matrix-doc/pull/2753).
+Local peeking is implemented as per [MSC2753](https://github.com/matrix-org/matrix-doc/pull/2753).
 
 Implementationwise, this means:
  * Users call `/peek` and `/unpeek` on the clientapi from a given device.
  * The clientapi delegates these via HTTP to the roomserver, which coordinates peeking in general for a given room
  * The roomserver writes an NewPeek event into the kafka log headed to the syncserver
- * The syncserver tracks the existence of the local peek in its DB, and then starts waking up the peeking devices for the room in question, putting it in the `peek` section of the /sync response.
+ * The syncserver tracks the existence of the local peek in the syncapi_peeks table in its DB, and then starts waking up the peeking devices for the room in question, putting it in the `peek` section of the /sync response.
 
-Questions (given this is [my](https://github.com/ara4n) first time hacking on Dendrite):
+Peeking over federation is implemented as per [MSC2444](https://github.com/matrix-org/matrix-doc/pull/2444).
- * The whole clientapi -> roomserver -> syncapi flow to initiate a peek seems very indirect.  Is there a reason not to just let syncapi itself host the implementation of `/peek`?
 
-In future, peeking over federation will be added as per [MSC2444](https://github.com/matrix-org/matrix-doc/pull/2444).
+For requests to peek our rooms ("inbound peeks"):
- * The `roomserver` will kick the `federationsender` much as it does for a federated `/join` in order to trigger a federated `/peek`
+ * Remote servers call `/peek` on federationapi
- * The `federationsender` tracks the existence of the remote peek in question
+   * The federationapi queries the federationsender to check if this is renewing an inbound peek or not.
+   * If not, it hits the PerformInboundPeek on the roomserver to ask it for the current state of the room.
+   * The roomserver atomically (in theory) adds a NewInboundPeek to its kafka stream to tell the federationserver to start peeking.
+   * The federationsender receives the event, tracks the inbound peek in the federationsender_inbound_peeks table, and starts sending events to the peeking server.
+   * The federationsender evicts stale inbound peeks which haven't been renewed.
+
+For peeking into other server's rooms ("outbound peeks"):
+ * The `roomserver` will kick the `federationsender` much as it does for a federated `/join` in order to trigger a federated outbound `/peek`
+ * The `federationsender` tracks the existence of the outbound peek in in its federationsender_outbound_peeks table.
  * The `federationsender` regularly renews the remote peek as long as there are still peeking devices syncing for it.
   * TBD: how do we tell if there are no devices currently syncing for a given peeked room?  The syncserver needs to tell the roomserver
     somehow who then needs to warn the federationsender.

federationapi/routing/peek.go

@@ -0,0 +1,102 @@
+// Copyright 2020 New Vector 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 routing
+
+import (
+	"net/http"
+
+	"github.com/matrix-org/dendrite/clientapi/jsonerror"
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/dendrite/setup/config"
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+)
+
+// Peek implements the SS /peek API, handling inbound peeks
+func Peek(
+	httpReq *http.Request,
+	request *gomatrixserverlib.FederationRequest,
+	cfg *config.FederationAPI,
+	rsAPI api.RoomserverInternalAPI,
+	roomID, peekID string,
+	remoteVersions []gomatrixserverlib.RoomVersion,
+) util.JSONResponse {
+	// TODO: check if we're just refreshing an existing peek by querying the federationsender
+
+	verReq := api.QueryRoomVersionForRoomRequest{RoomID: roomID}
+	verRes := api.QueryRoomVersionForRoomResponse{}
+	if err := rsAPI.QueryRoomVersionForRoom(httpReq.Context(), &verReq, &verRes); err != nil {
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: jsonerror.InternalServerError(),
+		}
+	}
+
+	// Check that the room that the peeking server is trying to peek is actually
+	// one of the room versions that they listed in their supported ?ver= in
+	// the peek URL.
+	remoteSupportsVersion := false
+	for _, v := range remoteVersions {
+		if v == verRes.RoomVersion {
+			remoteSupportsVersion = true
+			break
+		}
+	}
+	// If it isn't, stop trying to peek the room.
+	if !remoteSupportsVersion {
+		return util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.IncompatibleRoomVersion(verRes.RoomVersion),
+		}
+	}
+
+	// TODO: Check history visibility
+
+	// tell the peeking server to renew every hour
+	renewalInterval := int64(60 * 60 * 1000 * 1000)
+
+	var response api.PerformInboundPeekResponse
+	err := rsAPI.PerformInboundPeek(
+		httpReq.Context(),
+		&api.PerformInboundPeekRequest{
+			RoomID:          roomID,
+			PeekID:          peekID,
+			ServerName:      request.Origin(),
+			RenewalInterval: renewalInterval,
+		},
+		&response,
+	)
+	if err != nil {
+		resErr := util.ErrorResponse(err)
+		return resErr
+	}
+
+	if !response.RoomExists {
+		return util.JSONResponse{Code: http.StatusNotFound, JSON: nil}
+	}
+
+	respPeek := gomatrixserverlib.RespPeek{
+		StateEvents:     gomatrixserverlib.UnwrapEventHeaders(response.StateEvents),
+		AuthEvents:      gomatrixserverlib.UnwrapEventHeaders(response.AuthChainEvents),
+		RoomVersion:     response.RoomVersion,
+		LatestEvent:     response.LatestEvent.Unwrap(),
+		RenewalInterval: renewalInterval,
+	}
+
+	return util.JSONResponse{
+		Code: http.StatusOK,
+		JSON: respPeek,
+	}
+}

federationapi/routing/routing.go

@@ -229,7 +229,37 @@ func Setup(
 		},
 	)).Methods(http.MethodGet)
 
-	v1fedmux.Handle("/make_join/{roomID}/{eventID}", httputil.MakeFedAPI(
+	v1fedmux.Handle("/peek/{roomID}/{peekID}", httputil.MakeFedAPI(
+		"federation_peek", cfg.Matrix.ServerName, keys, wakeup,
+		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
+			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
+				return util.JSONResponse{
+					Code: http.StatusForbidden,
+					JSON: jsonerror.Forbidden("Forbidden by server ACLs"),
+				}
+			}
+			roomID := vars["roomID"]
+			peekID := vars["peekID"]
+			queryVars := httpReq.URL.Query()
+			remoteVersions := []gomatrixserverlib.RoomVersion{}
+			if vers, ok := queryVars["ver"]; ok {
+				// The remote side supplied a ?ver= so use that to build up the list
+				// of supported room versions
+				for _, v := range vers {
+					remoteVersions = append(remoteVersions, gomatrixserverlib.RoomVersion(v))
+				}
+			} else {
+				// The remote side didn't supply a ?ver= so just assume that they only
+				// support room version 1
+				remoteVersions = append(remoteVersions, gomatrixserverlib.RoomVersionV1)
+			}
+			return Peek(
+				httpReq, request, cfg, rsAPI, roomID, peekID, remoteVersions,
+			)
+		},
+	)).Methods(http.MethodPut, http.MethodDelete)
+
+	v1fedmux.Handle("/make_join/{roomID}/{userID}", httputil.MakeFedAPI(
 		"federation_make_join", cfg.Matrix.ServerName, keys, wakeup,
 		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest, vars map[string]string) util.JSONResponse {
 			if roomserverAPI.IsServerBannedFromRoom(httpReq.Context(), rsAPI, vars["roomID"], request.Origin()) {
@@ -239,11 +269,11 @@ func Setup(
 				}
 			}
 			roomID := vars["roomID"]
-			eventID := vars["eventID"]
+			userID := vars["userID"]
 			queryVars := httpReq.URL.Query()
 			remoteVersions := []gomatrixserverlib.RoomVersion{}
 			if vers, ok := queryVars["ver"]; ok {
-				// The remote side supplied a ?=ver so use that to build up the list
+				// The remote side supplied a ?ver= so use that to build up the list
 				// of supported room versions
 				for _, v := range vers {
 					remoteVersions = append(remoteVersions, gomatrixserverlib.RoomVersion(v))
@@ -255,7 +285,7 @@ func Setup(
 				remoteVersions = append(remoteVersions, gomatrixserverlib.RoomVersionV1)
 			}
 			return MakeJoin(
-				httpReq, request, cfg, rsAPI, roomID, eventID, remoteVersions,
+				httpReq, request, cfg, rsAPI, roomID, userID, remoteVersions,
 			)
 		},
 	)).Methods(http.MethodGet)

federationsender/api/api.go

@@ -62,6 +62,12 @@ type FederationSenderInternalAPI interface {
 		request *PerformJoinRequest,
 		response *PerformJoinResponse,
 	)
+	// Handle an instruction to peek a room on a remote server.
+	PerformOutboundPeek(
+		ctx context.Context,
+		request *PerformOutboundPeekRequest,
+		response *PerformOutboundPeekResponse,
+	) error
 	// Handle an instruction to make_leave & send_leave with a remote server.
 	PerformLeave(
 		ctx context.Context,
@@ -111,6 +117,16 @@ type PerformJoinResponse struct {
 	LastError *gomatrix.HTTPError
 }
 
+type PerformOutboundPeekRequest struct {
+	RoomID string `json:"room_id"`
+	// The sorted list of servers to try. Servers will be tried sequentially, after de-duplication.
+	ServerNames types.ServerNames `json:"server_names"`
+}
+
+type PerformOutboundPeekResponse struct {
+	LastError *gomatrix.HTTPError
+}
+
 type PerformLeaveRequest struct {
 	RoomID      string            `json:"room_id"`
 	UserID      string            `json:"user_id"`

federationsender/consumers/roomserver.go

@@ -111,6 +111,14 @@ func (s *OutputRoomEventConsumer) onMessage(msg *sarama.ConsumerMessage) error {
 			}
 			return nil
 		}
+	case api.OutputTypeNewInboundPeek:
+		if err := s.processInboundPeek(*output.NewInboundPeek); err != nil {
+			log.WithFields(log.Fields{
+				"event":      output.NewInboundPeek,
+				log.ErrorKey: err,
+			}).Panicf("roomserver output log: remote peek event failure")
+			return nil
+		}
 	default:
 		log.WithField("type", output.Type).Debug(
 			"roomserver output log: ignoring unknown output type",
@@ -121,6 +129,23 @@ func (s *OutputRoomEventConsumer) onMessage(msg *sarama.ConsumerMessage) error {
 	return nil
 }
 
+// processInboundPeek starts tracking a new federated inbound peek (replacing the existing one if any)
+// causing the federationsender to start sending messages to the peeking server
+func (s *OutputRoomEventConsumer) processInboundPeek(orp api.OutputNewInboundPeek) error {
+
+	// FIXME: there's a race here - we should start /sending new peeked events
+	// atomically after the orp.LatestEventID to ensure there are no gaps between
+	// the peek beginning and the send stream beginning.
+	//
+	// We probably need to track orp.LatestEventID on the inbound peek, but it's
+	// unclear how we then use that to prevent the race when we start the send
+	// stream.
+	//
+	// This is making the tests flakey.
+
+	return s.db.AddInboundPeek(context.TODO(), orp.ServerName, orp.RoomID, orp.PeekID, orp.RenewalInterval)
+}
+
 // processMessage updates the list of currently joined hosts in the room
 // and then sends the event to the hosts that were joined before the event.
 func (s *OutputRoomEventConsumer) processMessage(ore api.OutputNewRoomEvent) error {
@@ -164,6 +189,10 @@ func (s *OutputRoomEventConsumer) processMessage(ore api.OutputNewRoomEvent) err
 		return err
 	}
 
+	// TODO: do housekeeping to evict unrenewed peeking hosts
+
+	// TODO: implement query to let the fedapi check whether a given peek is live or not
+
 	// Send the event.
 	return s.queues.SendEvent(
 		ore.Event, gomatrixserverlib.ServerName(ore.SendAsServer), joinedHostsAtEvent,
@@ -171,7 +200,7 @@ func (s *OutputRoomEventConsumer) processMessage(ore api.OutputNewRoomEvent) err
 }
 
 // joinedHostsAtEvent works out a list of matrix servers that were joined to
-// the room at the event.
+// the room at the event (including peeking ones)
 // It is important to use the state at the event for sending messages because:
 //   1) We shouldn't send messages to servers that weren't in the room.
 //   2) If a server is kicked from the rooms it should still be told about the
@@ -222,6 +251,15 @@ func (s *OutputRoomEventConsumer) joinedHostsAtEvent(
 		joined[joinedHost.ServerName] = true
 	}
 
+	// handle peeking hosts
+	inboundPeeks, err := s.db.GetInboundPeeks(context.TODO(), ore.Event.Event.RoomID())
+	if err != nil {
+		return nil, err
+	}
+	for _, inboundPeek := range inboundPeeks {
+		joined[inboundPeek.ServerName] = true
+	}
+
 	var result []gomatrixserverlib.ServerName
 	for serverName, include := range joined {
 		if include {

federationsender/internal/perform.go

@@ -234,7 +234,7 @@ func (r *FederationSenderInternalAPI) performJoinUsingServer(
 		// Check that the send_join response was valid.
 		joinCtx := perform.JoinContext(r.federation, r.keyRing)
 		respState, err := joinCtx.CheckSendJoinResponse(
-			ctx, event, serverName, respMakeJoin, respSendJoin,
+			ctx, event, serverName, respSendJoin,
 		)
 		if err != nil {
 			logrus.WithFields(logrus.Fields{
@@ -266,6 +266,172 @@ func (r *FederationSenderInternalAPI) performJoinUsingServer(
 	return nil
 }
 
+// PerformOutboundPeekRequest implements api.FederationSenderInternalAPI
+func (r *FederationSenderInternalAPI) PerformOutboundPeek(
+	ctx context.Context,
+	request *api.PerformOutboundPeekRequest,
+	response *api.PerformOutboundPeekResponse,
+) error {
+	// Look up the supported room versions.
+	var supportedVersions []gomatrixserverlib.RoomVersion
+	for version := range version.SupportedRoomVersions() {
+		supportedVersions = append(supportedVersions, version)
+	}
+
+	// Deduplicate the server names we were provided but keep the ordering
+	// as this encodes useful information about which servers are most likely
+	// to respond.
+	seenSet := make(map[gomatrixserverlib.ServerName]bool)
+	var uniqueList []gomatrixserverlib.ServerName
+	for _, srv := range request.ServerNames {
+		if seenSet[srv] {
+			continue
+		}
+		seenSet[srv] = true
+		uniqueList = append(uniqueList, srv)
+	}
+	request.ServerNames = uniqueList
+
+	// See if there's an existing outbound peek for this room ID with
+	// one of the specified servers.
+	if peeks, err := r.db.GetOutboundPeeks(ctx, request.RoomID); err == nil {
+		for _, peek := range peeks {
+			if _, ok := seenSet[peek.ServerName]; ok {
+				return nil
+			}
+		}
+	}
+
+	// Try each server that we were provided until we land on one that
+	// successfully completes the peek
+	var lastErr error
+	for _, serverName := range request.ServerNames {
+		if err := r.performOutboundPeekUsingServer(
+			ctx,
+			request.RoomID,
+			serverName,
+			supportedVersions,
+		); err != nil {
+			logrus.WithError(err).WithFields(logrus.Fields{
+				"server_name": serverName,
+				"room_id":     request.RoomID,
+			}).Warnf("Failed to peek room through server")
+			lastErr = err
+			continue
+		}
+
+		// We're all good.
+		return nil
+	}
+
+	// If we reach here then we didn't complete a peek for some reason.
+	var httpErr gomatrix.HTTPError
+	if ok := errors.As(lastErr, &httpErr); ok {
+		httpErr.Message = string(httpErr.Contents)
+		// Clear the wrapped error, else serialising to JSON (in polylith mode) will fail
+		httpErr.WrappedError = nil
+		response.LastError = &httpErr
+	} else {
+		response.LastError = &gomatrix.HTTPError{
+			Code:         0,
+			WrappedError: nil,
+			Message:      lastErr.Error(),
+		}
+	}
+
+	logrus.Errorf(
+		"failed to peek room %q through %d server(s): last error %s",
+		request.RoomID, len(request.ServerNames), lastErr,
+	)
+
+	return lastErr
+}
+
+func (r *FederationSenderInternalAPI) performOutboundPeekUsingServer(
+	ctx context.Context,
+	roomID string,
+	serverName gomatrixserverlib.ServerName,
+	supportedVersions []gomatrixserverlib.RoomVersion,
+) error {
+	// create a unique ID for this peek.
+	// for now we just use the room ID again. In future, if we ever
+	// support concurrent peeks to the same room with different filters
+	// then we would need to disambiguate further.
+	peekID := roomID
+
+	// check whether we're peeking already to try to avoid needlessly
+	// re-peeking on the server. we don't need a transaction for this,
+	// given this is a nice-to-have.
+	outboundPeek, err := r.db.GetOutboundPeek(ctx, serverName, roomID, peekID)
+	if err != nil {
+		return err
+	}
+	renewing := false
+	if outboundPeek != nil {
+		nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
+		if nowMilli > outboundPeek.RenewedTimestamp+outboundPeek.RenewalInterval {
+			logrus.Infof("stale outbound peek to %s for %s already exists; renewing", serverName, roomID)
+			renewing = true
+		} else {
+			logrus.Infof("live outbound peek to %s for %s already exists", serverName, roomID)
+			return nil
+		}
+	}
+
+	// Try to perform an outbound /peek using the information supplied in the
+	// request.
+	respPeek, err := r.federation.Peek(
+		ctx,
+		serverName,
+		roomID,
+		peekID,
+		supportedVersions,
+	)
+	if err != nil {
+		r.statistics.ForServer(serverName).Failure()
+		return fmt.Errorf("r.federation.Peek: %w", err)
+	}
+	r.statistics.ForServer(serverName).Success()
+
+	// Work out if we support the room version that has been supplied in
+	// the peek response.
+	if respPeek.RoomVersion == "" {
+		respPeek.RoomVersion = gomatrixserverlib.RoomVersionV1
+	}
+	if _, err = respPeek.RoomVersion.EventFormat(); err != nil {
+		return fmt.Errorf("respPeek.RoomVersion.EventFormat: %w", err)
+	}
+
+	// TODO: authenticate the state returned (check its auth events etc)
+	// the equivalent of CheckSendJoinResponse()
+
+	// If we've got this far, the remote server is peeking.
+	if renewing {
+		if err = r.db.RenewOutboundPeek(ctx, serverName, roomID, peekID, respPeek.RenewalInterval); err != nil {
+			return err
+		}
+	} else {
+		if err = r.db.AddOutboundPeek(ctx, serverName, roomID, peekID, respPeek.RenewalInterval); err != nil {
+			return err
+		}
+	}
+
+	respState := respPeek.ToRespState()
+	// logrus.Warnf("got respPeek %#v", respPeek)
+	// Send the newly returned state to the roomserver to update our local view.
+	if err = roomserverAPI.SendEventWithState(
+		ctx, r.rsAPI,
+		roomserverAPI.KindNew,
+		&respState,
+		respPeek.LatestEvent.Headered(respPeek.RoomVersion),
+		nil,
+	); err != nil {
+		return fmt.Errorf("r.producer.SendEventWithState: %w", err)
+	}
+
+	return nil
+}
+
 // PerformLeaveRequest implements api.FederationSenderInternalAPI
 func (r *FederationSenderInternalAPI) PerformLeave(
 	ctx context.Context,

federationsender/internal/perform/join.go

@@ -1,3 +1,17 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// 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 perform
 
 import (
@@ -28,7 +42,6 @@ func (r joinContext) CheckSendJoinResponse(
 	ctx context.Context,
 	event *gomatrixserverlib.Event,
 	server gomatrixserverlib.ServerName,
-	respMakeJoin gomatrixserverlib.RespMakeJoin,
 	respSendJoin gomatrixserverlib.RespSendJoin,
 ) (*gomatrixserverlib.RespState, error) {
 	// A list of events that we have retried, if they were not included in

federationsender/inthttp/client.go

@@ -20,6 +20,7 @@ const (
 	FederationSenderPerformJoinRequestPath            = "/federationsender/performJoinRequest"
 	FederationSenderPerformLeaveRequestPath           = "/federationsender/performLeaveRequest"
 	FederationSenderPerformInviteRequestPath          = "/federationsender/performInviteRequest"
+	FederationSenderPerformOutboundPeekRequestPath    = "/federationsender/performOutboundPeekRequest"
 	FederationSenderPerformServersAlivePath           = "/federationsender/performServersAlive"
 	FederationSenderPerformBroadcastEDUPath           = "/federationsender/performBroadcastEDU"
 
@@ -76,6 +77,19 @@ func (h *httpFederationSenderInternalAPI) PerformInvite(
 	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
 }
 
+// Handle starting a peek on a remote server.
+func (h *httpFederationSenderInternalAPI) PerformOutboundPeek(
+	ctx context.Context,
+	request *api.PerformOutboundPeekRequest,
+	response *api.PerformOutboundPeekResponse,
+) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "PerformOutboundPeekRequest")
+	defer span.Finish()
+
+	apiURL := h.federationSenderURL + FederationSenderPerformOutboundPeekRequestPath
+	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+}
+
 func (h *httpFederationSenderInternalAPI) PerformServersAlive(
 	ctx context.Context,
 	request *api.PerformServersAliveRequest,

federationsender/storage/interface.go

@@ -51,7 +51,18 @@ type Database interface {
 	GetPendingPDUServerNames(ctx context.Context) ([]gomatrixserverlib.ServerName, error)
 	GetPendingEDUServerNames(ctx context.Context) ([]gomatrixserverlib.ServerName, error)
 
+	// these don't have contexts passed in as we want things to happen regardless of the request context
 	AddServerToBlacklist(serverName gomatrixserverlib.ServerName) error
 	RemoveServerFromBlacklist(serverName gomatrixserverlib.ServerName) error
 	IsServerBlacklisted(serverName gomatrixserverlib.ServerName) (bool, error)
+
+	AddOutboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) error
+	RenewOutboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) error
+	GetOutboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string) (*types.OutboundPeek, error)
+	GetOutboundPeeks(ctx context.Context, roomID string) ([]types.OutboundPeek, error)
+
+	AddInboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) error
+	RenewInboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) error
+	GetInboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string) (*types.InboundPeek, error)
+	GetInboundPeeks(ctx context.Context, roomID string) ([]types.InboundPeek, error)
 }

federationsender/storage/postgres/inbound_peeks_table.go

@@ -0,0 +1,176 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// 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 postgres
+
+import (
+	"context"
+	"database/sql"
+	"time"
+
+	"github.com/matrix-org/dendrite/federationsender/types"
+	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+const inboundPeeksSchema = `
+CREATE TABLE IF NOT EXISTS federationsender_inbound_peeks (
+	room_id TEXT NOT NULL,
+	server_name TEXT NOT NULL,
+	peek_id TEXT NOT NULL,
+    creation_ts BIGINT NOT NULL,
+    renewed_ts BIGINT NOT NULL,
+    renewal_interval BIGINT NOT NULL,
+	UNIQUE (room_id, server_name, peek_id)
+);
+`
+
+const insertInboundPeekSQL = "" +
+	"INSERT INTO federationsender_inbound_peeks (room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval) VALUES ($1, $2, $3, $4, $5, $6)"
+
+const selectInboundPeekSQL = "" +
+	"SELECT room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval FROM federationsender_inbound_peeks WHERE room_id = $1 and server_name = $2 and peek_id = $3"
+
+const selectInboundPeeksSQL = "" +
+	"SELECT room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval FROM federationsender_inbound_peeks WHERE room_id = $1"
+
+const renewInboundPeekSQL = "" +
+	"UPDATE federationsender_inbound_peeks SET renewed_ts=$1, renewal_interval=$2 WHERE room_id = $3 and server_name = $4 and peek_id = $5"
+
+const deleteInboundPeekSQL = "" +
+	"DELETE FROM federationsender_inbound_peeks WHERE room_id = $1 and server_name = $2"
+
+const deleteInboundPeeksSQL = "" +
+	"DELETE FROM federationsender_inbound_peeks WHERE room_id = $1"
+
+type inboundPeeksStatements struct {
+	db                     *sql.DB
+	insertInboundPeekStmt  *sql.Stmt
+	selectInboundPeekStmt  *sql.Stmt
+	selectInboundPeeksStmt *sql.Stmt
+	renewInboundPeekStmt   *sql.Stmt
+	deleteInboundPeekStmt  *sql.Stmt
+	deleteInboundPeeksStmt *sql.Stmt
+}
+
+func NewPostgresInboundPeeksTable(db *sql.DB) (s *inboundPeeksStatements, err error) {
+	s = &inboundPeeksStatements{
+		db: db,
+	}
+	_, err = db.Exec(inboundPeeksSchema)
+	if err != nil {
+		return
+	}
+
+	if s.insertInboundPeekStmt, err = db.Prepare(insertInboundPeekSQL); err != nil {
+		return
+	}
+	if s.selectInboundPeekStmt, err = db.Prepare(selectInboundPeekSQL); err != nil {
+		return
+	}
+	if s.selectInboundPeeksStmt, err = db.Prepare(selectInboundPeeksSQL); err != nil {
+		return
+	}
+	if s.renewInboundPeekStmt, err = db.Prepare(renewInboundPeekSQL); err != nil {
+		return
+	}
+	if s.deleteInboundPeeksStmt, err = db.Prepare(deleteInboundPeeksSQL); err != nil {
+		return
+	}
+	if s.deleteInboundPeekStmt, err = db.Prepare(deleteInboundPeekSQL); err != nil {
+		return
+	}
+	return
+}
+
+func (s *inboundPeeksStatements) InsertInboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64,
+) (err error) {
+	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
+	stmt := sqlutil.TxStmt(txn, s.insertInboundPeekStmt)
+	_, err = stmt.ExecContext(ctx, roomID, serverName, peekID, nowMilli, nowMilli, renewalInterval)
+	return
+}
+
+func (s *inboundPeeksStatements) RenewInboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64,
+) (err error) {
+	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
+	_, err = sqlutil.TxStmt(txn, s.renewInboundPeekStmt).ExecContext(ctx, nowMilli, renewalInterval, roomID, serverName, peekID)
+	return
+}
+
+func (s *inboundPeeksStatements) SelectInboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string,
+) (*types.InboundPeek, error) {
+	row := sqlutil.TxStmt(txn, s.selectInboundPeeksStmt).QueryRowContext(ctx, roomID)
+	inboundPeek := types.InboundPeek{}
+	err := row.Scan(
+		&inboundPeek.RoomID,
+		&inboundPeek.ServerName,
+		&inboundPeek.PeekID,
+		&inboundPeek.CreationTimestamp,
+		&inboundPeek.RenewedTimestamp,
+		&inboundPeek.RenewalInterval,
+	)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &inboundPeek, nil
+}
+
+func (s *inboundPeeksStatements) SelectInboundPeeks(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (inboundPeeks []types.InboundPeek, err error) {
+	rows, err := sqlutil.TxStmt(txn, s.selectInboundPeeksStmt).QueryContext(ctx, roomID)
+	if err != nil {
+		return
+	}
+	defer internal.CloseAndLogIfError(ctx, rows, "SelectInboundPeeks: rows.close() failed")
+
+	for rows.Next() {
+		inboundPeek := types.InboundPeek{}
+		if err = rows.Scan(
+			&inboundPeek.RoomID,
+			&inboundPeek.ServerName,
+			&inboundPeek.PeekID,
+			&inboundPeek.CreationTimestamp,
+			&inboundPeek.RenewedTimestamp,
+			&inboundPeek.RenewalInterval,
+		); err != nil {
+			return
+		}
+		inboundPeeks = append(inboundPeeks, inboundPeek)
+	}
+
+	return inboundPeeks, rows.Err()
+}
+
+func (s *inboundPeeksStatements) DeleteInboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteInboundPeekStmt).ExecContext(ctx, roomID, serverName, peekID)
+	return
+}
+
+func (s *inboundPeeksStatements) DeleteInboundPeeks(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteInboundPeeksStmt).ExecContext(ctx, roomID)
+	return
+}

federationsender/storage/postgres/outbound_peeks_table.go

@@ -0,0 +1,176 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// 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 postgres
+
+import (
+	"context"
+	"database/sql"
+	"time"
+
+	"github.com/matrix-org/dendrite/federationsender/types"
+	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+const outboundPeeksSchema = `
+CREATE TABLE IF NOT EXISTS federationsender_outbound_peeks (
+	room_id TEXT NOT NULL,
+	server_name TEXT NOT NULL,
+	peek_id TEXT NOT NULL,
+    creation_ts BIGINT NOT NULL,
+    renewed_ts BIGINT NOT NULL,
+    renewal_interval BIGINT NOT NULL,
+	UNIQUE (room_id, server_name, peek_id)
+);
+`
+
+const insertOutboundPeekSQL = "" +
+	"INSERT INTO federationsender_outbound_peeks (room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval) VALUES ($1, $2, $3, $4, $5, $6)"
+
+const selectOutboundPeekSQL = "" +
+	"SELECT room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval FROM federationsender_outbound_peeks WHERE room_id = $1 and server_name = $2 and peek_id = $3"
+
+const selectOutboundPeeksSQL = "" +
+	"SELECT room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval FROM federationsender_outbound_peeks WHERE room_id = $1"
+
+const renewOutboundPeekSQL = "" +
+	"UPDATE federationsender_outbound_peeks SET renewed_ts=$1, renewal_interval=$2 WHERE room_id = $3 and server_name = $4 and peek_id = $5"
+
+const deleteOutboundPeekSQL = "" +
+	"DELETE FROM federationsender_outbound_peeks WHERE room_id = $1 and server_name = $2"
+
+const deleteOutboundPeeksSQL = "" +
+	"DELETE FROM federationsender_outbound_peeks WHERE room_id = $1"
+
+type outboundPeeksStatements struct {
+	db                      *sql.DB
+	insertOutboundPeekStmt  *sql.Stmt
+	selectOutboundPeekStmt  *sql.Stmt
+	selectOutboundPeeksStmt *sql.Stmt
+	renewOutboundPeekStmt   *sql.Stmt
+	deleteOutboundPeekStmt  *sql.Stmt
+	deleteOutboundPeeksStmt *sql.Stmt
+}
+
+func NewPostgresOutboundPeeksTable(db *sql.DB) (s *outboundPeeksStatements, err error) {
+	s = &outboundPeeksStatements{
+		db: db,
+	}
+	_, err = db.Exec(outboundPeeksSchema)
+	if err != nil {
+		return
+	}
+
+	if s.insertOutboundPeekStmt, err = db.Prepare(insertOutboundPeekSQL); err != nil {
+		return
+	}
+	if s.selectOutboundPeekStmt, err = db.Prepare(selectOutboundPeekSQL); err != nil {
+		return
+	}
+	if s.selectOutboundPeeksStmt, err = db.Prepare(selectOutboundPeeksSQL); err != nil {
+		return
+	}
+	if s.renewOutboundPeekStmt, err = db.Prepare(renewOutboundPeekSQL); err != nil {
+		return
+	}
+	if s.deleteOutboundPeeksStmt, err = db.Prepare(deleteOutboundPeeksSQL); err != nil {
+		return
+	}
+	if s.deleteOutboundPeekStmt, err = db.Prepare(deleteOutboundPeekSQL); err != nil {
+		return
+	}
+	return
+}
+
+func (s *outboundPeeksStatements) InsertOutboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64,
+) (err error) {
+	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
+	stmt := sqlutil.TxStmt(txn, s.insertOutboundPeekStmt)
+	_, err = stmt.ExecContext(ctx, roomID, serverName, peekID, nowMilli, nowMilli, renewalInterval)
+	return
+}
+
+func (s *outboundPeeksStatements) RenewOutboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64,
+) (err error) {
+	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
+	_, err = sqlutil.TxStmt(txn, s.renewOutboundPeekStmt).ExecContext(ctx, nowMilli, renewalInterval, roomID, serverName, peekID)
+	return
+}
+
+func (s *outboundPeeksStatements) SelectOutboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string,
+) (*types.OutboundPeek, error) {
+	row := sqlutil.TxStmt(txn, s.selectOutboundPeeksStmt).QueryRowContext(ctx, roomID)
+	outboundPeek := types.OutboundPeek{}
+	err := row.Scan(
+		&outboundPeek.RoomID,
+		&outboundPeek.ServerName,
+		&outboundPeek.PeekID,
+		&outboundPeek.CreationTimestamp,
+		&outboundPeek.RenewedTimestamp,
+		&outboundPeek.RenewalInterval,
+	)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &outboundPeek, nil
+}
+
+func (s *outboundPeeksStatements) SelectOutboundPeeks(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (outboundPeeks []types.OutboundPeek, err error) {
+	rows, err := sqlutil.TxStmt(txn, s.selectOutboundPeeksStmt).QueryContext(ctx, roomID)
+	if err != nil {
+		return
+	}
+	defer internal.CloseAndLogIfError(ctx, rows, "SelectOutboundPeeks: rows.close() failed")
+
+	for rows.Next() {
+		outboundPeek := types.OutboundPeek{}
+		if err = rows.Scan(
+			&outboundPeek.RoomID,
+			&outboundPeek.ServerName,
+			&outboundPeek.PeekID,
+			&outboundPeek.CreationTimestamp,
+			&outboundPeek.RenewedTimestamp,
+			&outboundPeek.RenewalInterval,
+		); err != nil {
+			return
+		}
+		outboundPeeks = append(outboundPeeks, outboundPeek)
+	}
+
+	return outboundPeeks, rows.Err()
+}
+
+func (s *outboundPeeksStatements) DeleteOutboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteOutboundPeekStmt).ExecContext(ctx, roomID, serverName, peekID)
+	return
+}
+
+func (s *outboundPeeksStatements) DeleteOutboundPeeks(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteOutboundPeeksStmt).ExecContext(ctx, roomID)
+	return
+}

federationsender/storage/postgres/storage.go

@@ -64,6 +64,14 @@ func NewDatabase(dbProperties *config.DatabaseOptions, cache caching.FederationS
 	if err != nil {
 		return nil, err
 	}
+	inboundPeeks, err := NewPostgresInboundPeeksTable(d.db)
+	if err != nil {
+		return nil, err
+	}
+	outboundPeeks, err := NewPostgresOutboundPeeksTable(d.db)
+	if err != nil {
+		return nil, err
+	}
 	d.Database = shared.Database{
 		DB:                            d.db,
 		Cache:                         cache,
@@ -74,6 +82,8 @@ func NewDatabase(dbProperties *config.DatabaseOptions, cache caching.FederationS
 		FederationSenderQueueJSON:     queueJSON,
 		FederationSenderRooms:         rooms,
 		FederationSenderBlacklist:     blacklist,
+		FederationSenderInboundPeeks:  inboundPeeks,
+		FederationSenderOutboundPeeks: outboundPeeks,
 	}
 	if err = d.PartitionOffsetStatements.Prepare(d.db, d.writer, "federationsender"); err != nil {
 		return nil, err

federationsender/storage/shared/storage.go

@@ -36,6 +36,8 @@ type Database struct {
 	FederationSenderJoinedHosts   tables.FederationSenderJoinedHosts
 	FederationSenderRooms         tables.FederationSenderRooms
 	FederationSenderBlacklist     tables.FederationSenderBlacklist
+	FederationSenderOutboundPeeks tables.FederationSenderOutboundPeeks
+	FederationSenderInboundPeeks  tables.FederationSenderInboundPeeks
 }
 
 // An Receipt contains the NIDs of a call to GetNextTransactionPDUs/EDUs.
@@ -173,3 +175,43 @@ func (d *Database) RemoveServerFromBlacklist(serverName gomatrixserverlib.Server
 func (d *Database) IsServerBlacklisted(serverName gomatrixserverlib.ServerName) (bool, error) {
 	return d.FederationSenderBlacklist.SelectBlacklist(context.TODO(), nil, serverName)
 }
+
+func (d *Database) AddOutboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) error {
+	return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		return d.FederationSenderOutboundPeeks.InsertOutboundPeek(ctx, txn, serverName, roomID, peekID, renewalInterval)
+	})
+}
+
+func (d *Database) RenewOutboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) error {
+	return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		return d.FederationSenderOutboundPeeks.RenewOutboundPeek(ctx, txn, serverName, roomID, peekID, renewalInterval)
+	})
+}
+
+func (d *Database) GetOutboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string) (*types.OutboundPeek, error) {
+	return d.FederationSenderOutboundPeeks.SelectOutboundPeek(ctx, nil, serverName, roomID, peekID)
+}
+
+func (d *Database) GetOutboundPeeks(ctx context.Context, roomID string) ([]types.OutboundPeek, error) {
+	return d.FederationSenderOutboundPeeks.SelectOutboundPeeks(ctx, nil, roomID)
+}
+
+func (d *Database) AddInboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) error {
+	return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		return d.FederationSenderInboundPeeks.InsertInboundPeek(ctx, txn, serverName, roomID, peekID, renewalInterval)
+	})
+}
+
+func (d *Database) RenewInboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) error {
+	return d.Writer.Do(d.DB, nil, func(txn *sql.Tx) error {
+		return d.FederationSenderInboundPeeks.RenewInboundPeek(ctx, txn, serverName, roomID, peekID, renewalInterval)
+	})
+}
+
+func (d *Database) GetInboundPeek(ctx context.Context, serverName gomatrixserverlib.ServerName, roomID, peekID string) (*types.InboundPeek, error) {
+	return d.FederationSenderInboundPeeks.SelectInboundPeek(ctx, nil, serverName, roomID, peekID)
+}
+
+func (d *Database) GetInboundPeeks(ctx context.Context, roomID string) ([]types.InboundPeek, error) {
+	return d.FederationSenderInboundPeeks.SelectInboundPeeks(ctx, nil, roomID)
+}

federationsender/storage/sqlite3/inbound_peeks_table.go

@@ -0,0 +1,176 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// 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 sqlite3
+
+import (
+	"context"
+	"database/sql"
+	"time"
+
+	"github.com/matrix-org/dendrite/federationsender/types"
+	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+const inboundPeeksSchema = `
+CREATE TABLE IF NOT EXISTS federationsender_inbound_peeks (
+	room_id TEXT NOT NULL,
+	server_name TEXT NOT NULL,
+	peek_id TEXT NOT NULL,
+    creation_ts INTEGER NOT NULL,
+    renewed_ts INTEGER NOT NULL,
+    renewal_interval INTEGER NOT NULL,
+	UNIQUE (room_id, server_name, peek_id)
+);
+`
+
+const insertInboundPeekSQL = "" +
+	"INSERT INTO federationsender_inbound_peeks (room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval) VALUES ($1, $2, $3, $4, $5, $6)"
+
+const selectInboundPeekSQL = "" +
+	"SELECT room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval FROM federationsender_inbound_peeks WHERE room_id = $1 and server_name = $2 and peek_id = $3"
+
+const selectInboundPeeksSQL = "" +
+	"SELECT room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval FROM federationsender_inbound_peeks WHERE room_id = $1"
+
+const renewInboundPeekSQL = "" +
+	"UPDATE federationsender_inbound_peeks SET renewed_ts=$1, renewal_interval=$2 WHERE room_id = $3 and server_name = $4 and peek_id = $5"
+
+const deleteInboundPeekSQL = "" +
+	"DELETE FROM federationsender_inbound_peeks WHERE room_id = $1 and server_name = $2"
+
+const deleteInboundPeeksSQL = "" +
+	"DELETE FROM federationsender_inbound_peeks WHERE room_id = $1"
+
+type inboundPeeksStatements struct {
+	db                     *sql.DB
+	insertInboundPeekStmt  *sql.Stmt
+	selectInboundPeekStmt  *sql.Stmt
+	selectInboundPeeksStmt *sql.Stmt
+	renewInboundPeekStmt   *sql.Stmt
+	deleteInboundPeekStmt  *sql.Stmt
+	deleteInboundPeeksStmt *sql.Stmt
+}
+
+func NewSQLiteInboundPeeksTable(db *sql.DB) (s *inboundPeeksStatements, err error) {
+	s = &inboundPeeksStatements{
+		db: db,
+	}
+	_, err = db.Exec(inboundPeeksSchema)
+	if err != nil {
+		return
+	}
+
+	if s.insertInboundPeekStmt, err = db.Prepare(insertInboundPeekSQL); err != nil {
+		return
+	}
+	if s.selectInboundPeekStmt, err = db.Prepare(selectInboundPeekSQL); err != nil {
+		return
+	}
+	if s.selectInboundPeeksStmt, err = db.Prepare(selectInboundPeeksSQL); err != nil {
+		return
+	}
+	if s.renewInboundPeekStmt, err = db.Prepare(renewInboundPeekSQL); err != nil {
+		return
+	}
+	if s.deleteInboundPeeksStmt, err = db.Prepare(deleteInboundPeeksSQL); err != nil {
+		return
+	}
+	if s.deleteInboundPeekStmt, err = db.Prepare(deleteInboundPeekSQL); err != nil {
+		return
+	}
+	return
+}
+
+func (s *inboundPeeksStatements) InsertInboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64,
+) (err error) {
+	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
+	stmt := sqlutil.TxStmt(txn, s.insertInboundPeekStmt)
+	_, err = stmt.ExecContext(ctx, roomID, serverName, peekID, nowMilli, nowMilli, renewalInterval)
+	return
+}
+
+func (s *inboundPeeksStatements) RenewInboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64,
+) (err error) {
+	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
+	_, err = sqlutil.TxStmt(txn, s.renewInboundPeekStmt).ExecContext(ctx, nowMilli, renewalInterval, roomID, serverName, peekID)
+	return
+}
+
+func (s *inboundPeeksStatements) SelectInboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string,
+) (*types.InboundPeek, error) {
+	row := sqlutil.TxStmt(txn, s.selectInboundPeeksStmt).QueryRowContext(ctx, roomID)
+	inboundPeek := types.InboundPeek{}
+	err := row.Scan(
+		&inboundPeek.RoomID,
+		&inboundPeek.ServerName,
+		&inboundPeek.PeekID,
+		&inboundPeek.CreationTimestamp,
+		&inboundPeek.RenewedTimestamp,
+		&inboundPeek.RenewalInterval,
+	)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &inboundPeek, nil
+}
+
+func (s *inboundPeeksStatements) SelectInboundPeeks(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (inboundPeeks []types.InboundPeek, err error) {
+	rows, err := sqlutil.TxStmt(txn, s.selectInboundPeeksStmt).QueryContext(ctx, roomID)
+	if err != nil {
+		return
+	}
+	defer internal.CloseAndLogIfError(ctx, rows, "SelectInboundPeeks: rows.close() failed")
+
+	for rows.Next() {
+		inboundPeek := types.InboundPeek{}
+		if err = rows.Scan(
+			&inboundPeek.RoomID,
+			&inboundPeek.ServerName,
+			&inboundPeek.PeekID,
+			&inboundPeek.CreationTimestamp,
+			&inboundPeek.RenewedTimestamp,
+			&inboundPeek.RenewalInterval,
+		); err != nil {
+			return
+		}
+		inboundPeeks = append(inboundPeeks, inboundPeek)
+	}
+
+	return inboundPeeks, rows.Err()
+}
+
+func (s *inboundPeeksStatements) DeleteInboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteInboundPeekStmt).ExecContext(ctx, roomID, serverName, peekID)
+	return
+}
+
+func (s *inboundPeeksStatements) DeleteInboundPeeks(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteInboundPeeksStmt).ExecContext(ctx, roomID)
+	return
+}

federationsender/storage/sqlite3/outbound_peeks_table.go

@@ -0,0 +1,176 @@
+// Copyright 2020 The Matrix.org Foundation C.I.C.
+//
+// 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 sqlite3
+
+import (
+	"context"
+	"database/sql"
+	"time"
+
+	"github.com/matrix-org/dendrite/federationsender/types"
+	"github.com/matrix-org/dendrite/internal"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+const outboundPeeksSchema = `
+CREATE TABLE IF NOT EXISTS federationsender_outbound_peeks (
+	room_id TEXT NOT NULL,
+	server_name TEXT NOT NULL,
+	peek_id TEXT NOT NULL,
+    creation_ts INTEGER NOT NULL,
+    renewed_ts INTEGER NOT NULL,
+    renewal_interval INTEGER NOT NULL,
+	UNIQUE (room_id, server_name, peek_id)
+);
+`
+
+const insertOutboundPeekSQL = "" +
+	"INSERT INTO federationsender_outbound_peeks (room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval) VALUES ($1, $2, $3, $4, $5, $6)"
+
+const selectOutboundPeekSQL = "" +
+	"SELECT room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval FROM federationsender_outbound_peeks WHERE room_id = $1 and server_name = $2 and peek_id = $3"
+
+const selectOutboundPeeksSQL = "" +
+	"SELECT room_id, server_name, peek_id, creation_ts, renewed_ts, renewal_interval FROM federationsender_outbound_peeks WHERE room_id = $1"
+
+const renewOutboundPeekSQL = "" +
+	"UPDATE federationsender_outbound_peeks SET renewed_ts=$1, renewal_interval=$2 WHERE room_id = $3 and server_name = $4 and peek_id = $5"
+
+const deleteOutboundPeekSQL = "" +
+	"DELETE FROM federationsender_outbound_peeks WHERE room_id = $1 and server_name = $2"
+
+const deleteOutboundPeeksSQL = "" +
+	"DELETE FROM federationsender_outbound_peeks WHERE room_id = $1"
+
+type outboundPeeksStatements struct {
+	db                      *sql.DB
+	insertOutboundPeekStmt  *sql.Stmt
+	selectOutboundPeekStmt  *sql.Stmt
+	selectOutboundPeeksStmt *sql.Stmt
+	renewOutboundPeekStmt   *sql.Stmt
+	deleteOutboundPeekStmt  *sql.Stmt
+	deleteOutboundPeeksStmt *sql.Stmt
+}
+
+func NewSQLiteOutboundPeeksTable(db *sql.DB) (s *outboundPeeksStatements, err error) {
+	s = &outboundPeeksStatements{
+		db: db,
+	}
+	_, err = db.Exec(outboundPeeksSchema)
+	if err != nil {
+		return
+	}
+
+	if s.insertOutboundPeekStmt, err = db.Prepare(insertOutboundPeekSQL); err != nil {
+		return
+	}
+	if s.selectOutboundPeekStmt, err = db.Prepare(selectOutboundPeekSQL); err != nil {
+		return
+	}
+	if s.selectOutboundPeeksStmt, err = db.Prepare(selectOutboundPeeksSQL); err != nil {
+		return
+	}
+	if s.renewOutboundPeekStmt, err = db.Prepare(renewOutboundPeekSQL); err != nil {
+		return
+	}
+	if s.deleteOutboundPeeksStmt, err = db.Prepare(deleteOutboundPeeksSQL); err != nil {
+		return
+	}
+	if s.deleteOutboundPeekStmt, err = db.Prepare(deleteOutboundPeekSQL); err != nil {
+		return
+	}
+	return
+}
+
+func (s *outboundPeeksStatements) InsertOutboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64,
+) (err error) {
+	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
+	stmt := sqlutil.TxStmt(txn, s.insertOutboundPeekStmt)
+	_, err = stmt.ExecContext(ctx, roomID, serverName, peekID, nowMilli, nowMilli, renewalInterval)
+	return
+}
+
+func (s *outboundPeeksStatements) RenewOutboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64,
+) (err error) {
+	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
+	_, err = sqlutil.TxStmt(txn, s.renewOutboundPeekStmt).ExecContext(ctx, nowMilli, renewalInterval, roomID, serverName, peekID)
+	return
+}
+
+func (s *outboundPeeksStatements) SelectOutboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string,
+) (*types.OutboundPeek, error) {
+	row := sqlutil.TxStmt(txn, s.selectOutboundPeeksStmt).QueryRowContext(ctx, roomID)
+	outboundPeek := types.OutboundPeek{}
+	err := row.Scan(
+		&outboundPeek.RoomID,
+		&outboundPeek.ServerName,
+		&outboundPeek.PeekID,
+		&outboundPeek.CreationTimestamp,
+		&outboundPeek.RenewedTimestamp,
+		&outboundPeek.RenewalInterval,
+	)
+	if err == sql.ErrNoRows {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &outboundPeek, nil
+}
+
+func (s *outboundPeeksStatements) SelectOutboundPeeks(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (outboundPeeks []types.OutboundPeek, err error) {
+	rows, err := sqlutil.TxStmt(txn, s.selectOutboundPeeksStmt).QueryContext(ctx, roomID)
+	if err != nil {
+		return
+	}
+	defer internal.CloseAndLogIfError(ctx, rows, "SelectOutboundPeeks: rows.close() failed")
+
+	for rows.Next() {
+		outboundPeek := types.OutboundPeek{}
+		if err = rows.Scan(
+			&outboundPeek.RoomID,
+			&outboundPeek.ServerName,
+			&outboundPeek.PeekID,
+			&outboundPeek.CreationTimestamp,
+			&outboundPeek.RenewedTimestamp,
+			&outboundPeek.RenewalInterval,
+		); err != nil {
+			return
+		}
+		outboundPeeks = append(outboundPeeks, outboundPeek)
+	}
+
+	return outboundPeeks, rows.Err()
+}
+
+func (s *outboundPeeksStatements) DeleteOutboundPeek(
+	ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteOutboundPeekStmt).ExecContext(ctx, roomID, serverName, peekID)
+	return
+}
+
+func (s *outboundPeeksStatements) DeleteOutboundPeeks(
+	ctx context.Context, txn *sql.Tx, roomID string,
+) (err error) {
+	_, err = sqlutil.TxStmt(txn, s.deleteOutboundPeeksStmt).ExecContext(ctx, roomID)
+	return
+}

federationsender/storage/sqlite3/storage.go

@@ -66,6 +66,14 @@ func NewDatabase(dbProperties *config.DatabaseOptions, cache caching.FederationS
 	if err != nil {
 		return nil, err
 	}
+	outboundPeeks, err := NewSQLiteOutboundPeeksTable(d.db)
+	if err != nil {
+		return nil, err
+	}
+	inboundPeeks, err := NewSQLiteInboundPeeksTable(d.db)
+	if err != nil {
+		return nil, err
+	}
 	d.Database = shared.Database{
 		DB:                            d.db,
 		Cache:                         cache,
@@ -76,6 +84,8 @@ func NewDatabase(dbProperties *config.DatabaseOptions, cache caching.FederationS
 		FederationSenderQueueJSON:     queueJSON,
 		FederationSenderRooms:         rooms,
 		FederationSenderBlacklist:     blacklist,
+		FederationSenderOutboundPeeks: outboundPeeks,
+		FederationSenderInboundPeeks:  inboundPeeks,
 	}
 	if err = d.PartitionOffsetStatements.Prepare(d.db, d.writer, "federationsender"); err != nil {
 		return nil, err

federationsender/storage/tables/interface.go

@@ -67,3 +67,21 @@ type FederationSenderBlacklist interface {
 	SelectBlacklist(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName) (bool, error)
 	DeleteBlacklist(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName) error
 }
+
+type FederationSenderOutboundPeeks interface {
+	InsertOutboundPeek(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) (err error)
+	RenewOutboundPeek(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) (err error)
+	SelectOutboundPeek(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string) (outboundPeek *types.OutboundPeek, err error)
+	SelectOutboundPeeks(ctx context.Context, txn *sql.Tx, roomID string) (outboundPeeks []types.OutboundPeek, err error)
+	DeleteOutboundPeek(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string) (err error)
+	DeleteOutboundPeeks(ctx context.Context, txn *sql.Tx, roomID string) (err error)
+}
+
+type FederationSenderInboundPeeks interface {
+	InsertInboundPeek(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) (err error)
+	RenewInboundPeek(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string, renewalInterval int64) (err error)
+	SelectInboundPeek(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string) (inboundPeek *types.InboundPeek, err error)
+	SelectInboundPeeks(ctx context.Context, txn *sql.Tx, roomID string) (inboundPeeks []types.InboundPeek, err error)
+	DeleteInboundPeek(ctx context.Context, txn *sql.Tx, serverName gomatrixserverlib.ServerName, roomID, peekID string) (err error)
+	DeleteInboundPeeks(ctx context.Context, txn *sql.Tx, roomID string) (err error)
+}

federationsender/types/types.go

@@ -49,3 +49,23 @@ func (e EventIDMismatchError) Error() string {
 		e.DatabaseID, e.RoomServerID,
 	)
 }
+
+// tracks peeks we're performing on another server over federation
+type OutboundPeek struct {
+	PeekID            string
+	RoomID            string
+	ServerName        gomatrixserverlib.ServerName
+	CreationTimestamp int64
+	RenewedTimestamp  int64
+	RenewalInterval   int64
+}
+
+// tracks peeks other servers are performing on us over federation
+type InboundPeek struct {
+	PeekID            string
+	RoomID            string
+	ServerName        gomatrixserverlib.ServerName
+	CreationTimestamp int64
+	RenewedTimestamp  int64
+	RenewalInterval   int64
+}

go.mod

@@ -41,7 +41,7 @@ require (
 	go.uber.org/atomic v1.6.0
 	golang.org/x/crypto v0.0.0-20201221181555-eec23a3978ad
 	golang.org/x/net v0.0.0-20200528225125-3c3fba18258b
-	golang.org/x/sys v0.0.0-20210113181707-4bcb84eeeb78 // indirect
+	golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 // indirect
 	gopkg.in/h2non/bimg.v1 v1.1.4
 	gopkg.in/yaml.v2 v2.3.0
 )

go.sum

@@ -995,8 +995,8 @@ golang.org/x/sys v0.0.0-20200302150141-5c8b2ff67527/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200615200032-f1bc736245b1 h1:ogLJMz+qpzav7lGMh10LMvAkM/fAoGlaiiHYiFYdm80=
 golang.org/x/sys v0.0.0-20200615200032-f1bc736245b1/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210113181707-4bcb84eeeb78 h1:nVuTkr9L6Bq62qpUqKo/RnZCFfzDBL0bYo6w9OJUqZY=
+golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 h1:myAQVi0cGEoqQVR5POX+8RR2mrocKqNN1hmeMqhX27k=
-golang.org/x/sys v0.0.0-20210113181707-4bcb84eeeb78/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/term v0.0.0-20201117132131-f5c789dd3221/go.mod h1:Nr5EML6q2oocZ2LXRh80K7BxOlk5/8JxuGnuhpl+muw=
 golang.org/x/text v0.0.0-20170915032832-14c0d48ead0c/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

roomserver/api/api.go

@@ -56,6 +56,12 @@ type RoomserverInternalAPI interface {
 		res *PerformPublishResponse,
 	)
 
+	PerformInboundPeek(
+		ctx context.Context,
+		req *PerformInboundPeekRequest,
+		res *PerformInboundPeekResponse,
+	) error
+
 	QueryPublishedRooms(
 		ctx context.Context,
 		req *QueryPublishedRoomsRequest,

roomserver/api/api_trace.go

@@ -88,6 +88,16 @@ func (t *RoomserverInternalAPITrace) PerformPublish(
 	util.GetLogger(ctx).Infof("PerformPublish req=%+v res=%+v", js(req), js(res))
 }
 
+func (t *RoomserverInternalAPITrace) PerformInboundPeek(
+	ctx context.Context,
+	req *PerformInboundPeekRequest,
+	res *PerformInboundPeekResponse,
+) error {
+	err := t.Impl.PerformInboundPeek(ctx, req, res)
+	util.GetLogger(ctx).Infof("PerformInboundPeek req=%+v res=%+v", js(req), js(res))
+	return err
+}
+
 func (t *RoomserverInternalAPITrace) QueryPublishedRooms(
 	ctx context.Context,
 	req *QueryPublishedRoomsRequest,

roomserver/api/output.go

@@ -51,6 +51,8 @@ const (
 
 	// OutputTypeNewPeek indicates that the kafka event is an OutputNewPeek
 	OutputTypeNewPeek OutputType = "new_peek"
+	// OutputTypeNewInboundPeek indicates that the kafka event is an OutputNewInboundPeek
+	OutputTypeNewInboundPeek OutputType = "new_inbound_peek"
 	// OutputTypeRetirePeek indicates that the kafka event is an OutputRetirePeek
 	OutputTypeRetirePeek OutputType = "retire_peek"
 )
@@ -72,6 +74,8 @@ type OutputEvent struct {
 	RedactedEvent *OutputRedactedEvent `json:"redacted_event,omitempty"`
 	// The content of event with type OutputTypeNewPeek
 	NewPeek *OutputNewPeek `json:"new_peek,omitempty"`
+	// The content of event with type OutputTypeNewInboundPeek
+	NewInboundPeek *OutputNewInboundPeek `json:"new_inbound_peek,omitempty"`
 	// The content of event with type OutputTypeRetirePeek
 	RetirePeek *OutputRetirePeek `json:"retire_peek,omitempty"`
 }
@@ -245,6 +249,19 @@ type OutputNewPeek struct {
 	DeviceID string
 }
 
+// An OutputNewInboundPeek is written whenever a server starts peeking into a room
+type OutputNewInboundPeek struct {
+	RoomID string
+	PeekID string
+	// the event ID at which the peek begins (so we can avoid
+	// a race between tracking the state returned by /peek and emitting subsequent
+	// peeked events)
+	LatestEventID string
+	ServerName    gomatrixserverlib.ServerName
+	// how often we told the peeking server to renew the peek
+	RenewalInterval int64
+}
+
 // An OutputRetirePeek is written whenever a user stops peeking into a room.
 type OutputRetirePeek struct {
 	RoomID   string

roomserver/api/perform.go

@@ -172,6 +172,28 @@ type PerformPublishResponse struct {
 	Error *PerformError
 }
 
+type PerformInboundPeekRequest struct {
+	UserID          string                       `json:"user_id"`
+	RoomID          string                       `json:"room_id"`
+	PeekID          string                       `json:"peek_id"`
+	ServerName      gomatrixserverlib.ServerName `json:"server_name"`
+	RenewalInterval int64                        `json:"renewal_interval"`
+}
+
+type PerformInboundPeekResponse struct {
+	// Does the room exist on this roomserver?
+	// If the room doesn't exist this will be false and StateEvents will be empty.
+	RoomExists bool `json:"room_exists"`
+	// The room version of the room.
+	RoomVersion gomatrixserverlib.RoomVersion `json:"room_version"`
+	// The current state and auth chain events.
+	// The lists will be in an arbitrary order.
+	StateEvents     []*gomatrixserverlib.HeaderedEvent `json:"state_events"`
+	AuthChainEvents []*gomatrixserverlib.HeaderedEvent `json:"auth_chain_events"`
+	// The event at which this state was captured
+	LatestEvent *gomatrixserverlib.HeaderedEvent `json:"latest_event"`
+}
+
 // PerformForgetRequest is a request to PerformForget
 type PerformForgetRequest struct {
 	RoomID string `json:"room_id"`

roomserver/api/query.go

@@ -221,7 +221,7 @@ type QueryStateAndAuthChainRequest struct {
 	// The room ID to query the state in.
 	RoomID string `json:"room_id"`
 	// The list of prev events for the event. Used to calculate the state at
-	// the event
+	// the event.
 	PrevEventIDs []string `json:"prev_event_ids"`
 	// The list of auth events for the event. Used to calculate the auth chain
 	AuthEventIDs []string `json:"auth_event_ids"`

roomserver/api/wrapper.go

@@ -43,7 +43,7 @@ func SendEvents(
 
 // SendEventWithState writes an event with the specified kind to the roomserver
 // with the state at the event as KindOutlier before it. Will not send any event that is
-// marked as `true` in haveEventIDs
+// marked as `true` in haveEventIDs.
 func SendEventWithState(
 	ctx context.Context, rsAPI RoomserverInternalAPI, kind Kind,
 	state *gomatrixserverlib.RespState, event *gomatrixserverlib.HeaderedEvent,

roomserver/internal/api.go

@@ -24,6 +24,7 @@ type RoomserverInternalAPI struct {
 	*perform.Inviter
 	*perform.Joiner
 	*perform.Peeker
+	*perform.InboundPeeker
 	*perform.Unpeeker
 	*perform.Leaver
 	*perform.Publisher
@@ -97,6 +98,10 @@ func (r *RoomserverInternalAPI) SetFederationSenderAPI(fsAPI fsAPI.FederationSen
 		FSAPI:      r.fsAPI,
 		Inputer:    r.Inputer,
 	}
+	r.InboundPeeker = &perform.InboundPeeker{
+		DB:      r.DB,
+		Inputer: r.Inputer,
+	}
 	r.Unpeeker = &perform.Unpeeker{
 		ServerName: r.Cfg.Matrix.ServerName,
 		Cfg:        r.Cfg,

roomserver/internal/perform/perform_inbound_peek.go

@@ -0,0 +1,129 @@
+// Copyright 2020 New Vector 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 perform
+
+import (
+	"context"
+
+	"github.com/matrix-org/dendrite/roomserver/api"
+	"github.com/matrix-org/dendrite/roomserver/internal/helpers"
+	"github.com/matrix-org/dendrite/roomserver/internal/input"
+	"github.com/matrix-org/dendrite/roomserver/internal/query"
+	"github.com/matrix-org/dendrite/roomserver/state"
+	"github.com/matrix-org/dendrite/roomserver/storage"
+	"github.com/matrix-org/dendrite/roomserver/types"
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+)
+
+type InboundPeeker struct {
+	DB      storage.Database
+	Inputer *input.Inputer
+}
+
+// PerformInboundPeek handles peeking into matrix rooms, including over
+// federation by talking to the federationsender. called when a remote server
+// initiates a /peek over federation.
+//
+// It should atomically figure out the current state of the room (for the
+// response to /peek) while adding the new inbound peek to the kafka stream so the
+// fed sender can start sending peeked events without a race between the state
+// snapshot and the stream of peeked events.
+func (r *InboundPeeker) PerformInboundPeek(
+	ctx context.Context,
+	request *api.PerformInboundPeekRequest,
+	response *api.PerformInboundPeekResponse,
+) error {
+	info, err := r.DB.RoomInfo(ctx, request.RoomID)
+	if err != nil {
+		return err
+	}
+	if info == nil || info.IsStub {
+		return nil
+	}
+	response.RoomExists = true
+	response.RoomVersion = info.RoomVersion
+
+	var stateEvents []*gomatrixserverlib.Event
+
+	var currentStateSnapshotNID types.StateSnapshotNID
+	latestEventRefs, currentStateSnapshotNID, _, err :=
+		r.DB.LatestEventIDs(ctx, info.RoomNID)
+	if err != nil {
+		return err
+	}
+	latestEvents, err := r.DB.EventsFromIDs(ctx, []string{latestEventRefs[0].EventID})
+	if err != nil {
+		return err
+	}
+	var sortedLatestEvents []*gomatrixserverlib.Event
+	for _, ev := range latestEvents {
+		sortedLatestEvents = append(sortedLatestEvents, ev.Event)
+	}
+	sortedLatestEvents = gomatrixserverlib.ReverseTopologicalOrdering(
+		sortedLatestEvents,
+		gomatrixserverlib.TopologicalOrderByPrevEvents,
+	)
+	response.LatestEvent = sortedLatestEvents[0].Headered(info.RoomVersion)
+
+	// XXX: do we actually need to do a state resolution here?
+	roomState := state.NewStateResolution(r.DB, *info)
+
+	var stateEntries []types.StateEntry
+	stateEntries, err = roomState.LoadStateAtSnapshot(
+		ctx, currentStateSnapshotNID,
+	)
+	if err != nil {
+		return err
+	}
+	stateEvents, err = helpers.LoadStateEvents(ctx, r.DB, stateEntries)
+	if err != nil {
+		return err
+	}
+
+	// get the auth event IDs for the current state events
+	var authEventIDs []string
+	for _, se := range stateEvents {
+		authEventIDs = append(authEventIDs, se.AuthEventIDs()...)
+	}
+	authEventIDs = util.UniqueStrings(authEventIDs) // de-dupe
+
+	authEvents, err := query.GetAuthChain(ctx, r.DB.EventsFromIDs, authEventIDs)
+	if err != nil {
+		return err
+	}
+
+	for _, event := range stateEvents {
+		response.StateEvents = append(response.StateEvents, event.Headered(info.RoomVersion))
+	}
+
+	for _, event := range authEvents {
+		response.AuthChainEvents = append(response.AuthChainEvents, event.Headered(info.RoomVersion))
+	}
+
+	err = r.Inputer.WriteOutputEvents(request.RoomID, []api.OutputEvent{
+		{
+			Type: api.OutputTypeNewInboundPeek,
+			NewInboundPeek: &api.OutputNewInboundPeek{
+				RoomID:          request.RoomID,
+				PeekID:          request.PeekID,
+				LatestEventID:   latestEvents[0].EventID(),
+				ServerName:      request.ServerName,
+				RenewalInterval: request.RenewalInterval,
+			},
+		},
+	})
+	return err
+}

roomserver/internal/perform/perform_peek.go

@@ -151,11 +151,28 @@ func (r *Peeker) performPeekRoomByID(
 		}
 	}
 
+	// handle federated peeks
+	// FIXME: don't create an outbound peek if we already have one going.
+	if domain != r.Cfg.Matrix.ServerName {
 		// If the server name in the room ID isn't ours then it's a
 		// possible candidate for finding the room via federation. Add
 		// it to the list of servers to try.
-	if domain != r.Cfg.Matrix.ServerName {
 		req.ServerNames = append(req.ServerNames, domain)
+
+		// Try peeking by all of the supplied server names.
+		fedReq := fsAPI.PerformOutboundPeekRequest{
+			RoomID:      req.RoomIDOrAlias, // the room ID to try and peek
+			ServerNames: req.ServerNames,   // the servers to try peeking via
+		}
+		fedRes := fsAPI.PerformOutboundPeekResponse{}
+		_ = r.FSAPI.PerformOutboundPeek(ctx, &fedReq, &fedRes)
+		if fedRes.LastError != nil {
+			return "", &api.PerformError{
+				Code:       api.PerformErrRemote,
+				Msg:        fedRes.LastError.Message,
+				RemoteCode: fedRes.LastError.Code,
+			}
+		}
 	}
 
 	// If this room isn't world_readable, we reject.

roomserver/internal/query/query.go

@@ -107,7 +107,7 @@ func (r *Queryer) QueryStateAfterEvents(
 		}
 		authEventIDs = util.UniqueStrings(authEventIDs)
 
-		authEvents, err := getAuthChain(ctx, r.DB.EventsFromIDs, authEventIDs)
+		authEvents, err := GetAuthChain(ctx, r.DB.EventsFromIDs, authEventIDs)
 		if err != nil {
 			return fmt.Errorf("getAuthChain: %w", err)
 		}
@@ -447,10 +447,12 @@ func (r *Queryer) QueryStateAndAuthChain(
 	response.RoomExists = true
 	response.RoomVersion = info.RoomVersion
 
-	stateEvents, err := r.loadStateAtEventIDs(ctx, *info, request.PrevEventIDs)
+	var stateEvents []*gomatrixserverlib.Event
+	stateEvents, err = r.loadStateAtEventIDs(ctx, *info, request.PrevEventIDs)
 	if err != nil {
 		return err
 	}
+
 	response.PrevEventsExist = true
 
 	// add the auth event IDs for the current state events too
@@ -461,7 +463,7 @@ func (r *Queryer) QueryStateAndAuthChain(
 	}
 	authEventIDs = util.UniqueStrings(authEventIDs) // de-dupe
 
-	authEvents, err := getAuthChain(ctx, r.DB.EventsFromIDs, authEventIDs)
+	authEvents, err := GetAuthChain(ctx, r.DB.EventsFromIDs, authEventIDs)
 	if err != nil {
 		return err
 	}
@@ -510,11 +512,11 @@ func (r *Queryer) loadStateAtEventIDs(ctx context.Context, roomInfo types.RoomIn
 
 type eventsFromIDs func(context.Context, []string) ([]types.Event, error)
 
-// getAuthChain fetches the auth chain for the given auth events. An auth chain
+// GetAuthChain fetches the auth chain for the given auth events. An auth chain
 // is the list of all events that are referenced in the auth_events section, and
 // all their auth_events, recursively. The returned set of events contain the
 // given events. Will *not* error if we don't have all auth events.
-func getAuthChain(
+func GetAuthChain(
 	ctx context.Context, fn eventsFromIDs, authEventIDs []string,
 ) ([]*gomatrixserverlib.Event, error) {
 	// List of event IDs to fetch. On each pass, these events will be requested
@@ -718,7 +720,7 @@ func (r *Queryer) QueryServerBannedFromRoom(ctx context.Context, req *api.QueryS
 }
 
 func (r *Queryer) QueryAuthChain(ctx context.Context, req *api.QueryAuthChainRequest, res *api.QueryAuthChainResponse) error {
-	chain, err := getAuthChain(ctx, r.DB.EventsFromIDs, req.EventIDs)
+	chain, err := GetAuthChain(ctx, r.DB.EventsFromIDs, req.EventIDs)
 	if err != nil {
 		return err
 	}

roomserver/internal/query/query_test.go

@@ -106,7 +106,7 @@ func TestGetAuthChainSingle(t *testing.T) {
 		t.Fatalf("Failed to add events to db: %v", err)
 	}
 
-	result, err := getAuthChain(context.TODO(), db.EventsFromIDs, []string{"e"})
+	result, err := GetAuthChain(context.TODO(), db.EventsFromIDs, []string{"e"})
 	if err != nil {
 		t.Fatalf("getAuthChain failed: %v", err)
 	}
@@ -139,7 +139,7 @@ func TestGetAuthChainMultiple(t *testing.T) {
 		t.Fatalf("Failed to add events to db: %v", err)
 	}
 
-	result, err := getAuthChain(context.TODO(), db.EventsFromIDs, []string{"e", "f"})
+	result, err := GetAuthChain(context.TODO(), db.EventsFromIDs, []string{"e", "f"})
 	if err != nil {
 		t.Fatalf("getAuthChain failed: %v", err)
 	}

roomserver/inthttp/client.go

@@ -33,6 +33,7 @@ const (
 	RoomserverPerformLeavePath       = "/roomserver/performLeave"
 	RoomserverPerformBackfillPath    = "/roomserver/performBackfill"
 	RoomserverPerformPublishPath     = "/roomserver/performPublish"
+	RoomserverPerformInboundPeekPath = "/roomserver/performInboundPeek"
 	RoomserverPerformForgetPath      = "/roomserver/performForget"
 
 	// Query operations
@@ -216,6 +217,18 @@ func (h *httpRoomserverInternalAPI) PerformPeek(
 	}
 }
 
+func (h *httpRoomserverInternalAPI) PerformInboundPeek(
+	ctx context.Context,
+	request *api.PerformInboundPeekRequest,
+	response *api.PerformInboundPeekResponse,
+) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "PerformInboundPeek")
+	defer span.Finish()
+
+	apiURL := h.roomserverURL + RoomserverPerformInboundPeekPath
+	return httputil.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+}
+
 func (h *httpRoomserverInternalAPI) PerformUnpeek(
 	ctx context.Context,
 	request *api.PerformUnpeekRequest,

roomserver/inthttp/server.go

@@ -72,6 +72,19 @@ func AddRoutes(r api.RoomserverInternalAPI, internalAPIMux *mux.Router) {
 			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
 		}),
 	)
+	internalAPIMux.Handle(RoomserverPerformInboundPeekPath,
+		httputil.MakeInternalAPI("performInboundPeek", func(req *http.Request) util.JSONResponse {
+			var request api.PerformInboundPeekRequest
+			var response api.PerformInboundPeekResponse
+			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
+				return util.MessageResponse(http.StatusBadRequest, err.Error())
+			}
+			if err := r.PerformInboundPeek(req.Context(), &request, &response); err != nil {
+				return util.ErrorResponse(err)
+			}
+			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
+		}),
+	)
 	internalAPIMux.Handle(RoomserverPerformPeekPath,
 		httputil.MakeInternalAPI("performUnpeek", func(req *http.Request) util.JSONResponse {
 			var request api.PerformUnpeekRequest

syncapi/types/types.go

@@ -372,7 +372,7 @@ type Response struct {
 		Leave  map[string]LeaveResponse  `json:"leave"`
 	} `json:"rooms"`
 	ToDevice struct {
-		Events []gomatrixserverlib.SendToDeviceEvent `json:"events,omitempty"`
+		Events []gomatrixserverlib.SendToDeviceEvent `json:"events"`
 	} `json:"to_device"`
 	DeviceLists struct {
 		Changed []string `json:"changed,omitempty"`