Refactor appservices component (#2687)

This PR refactors the app services component. It makes the following changes:

* Each appservice now gets its own NATS JetStream consumer
* The appservice database is now removed entirely, since we just use JetStream as a data source instead
* The entire component is now much simpler and we deleted lots of lines of code 💅

The result is that it should be much lighter and hopefully much more performant.

15 files changed, 207 insertions, 1469 deletions

diff --git a/appservice/README.md b/appservice/README.md
deleted file mode 100644
index d7555744..00000000
--- a/appservice/README.md
+++ /dev/null
@@ -1,10 +0,0 @@
-# Application Service
-
-This component interfaces with external [Application
-Services](https://matrix.org/docs/spec/application_service/unstable.html).
-This includes any HTTP endpoints that application services call, as well as talking
-to any HTTP endpoints that application services provide themselves.
-
-## Consumers
-
-This component consumes and filters events from the Roomserver Kafka stream, passing on any necessary events to subscribing application services.
\ No newline at end of file
diff --git a/appservice/appservice.go b/appservice/appservice.go
index 8fe1b2fc..9000adb1 100644
--- a/appservice/appservice.go
+++ b/appservice/appservice.go
@@ -18,7 +18,6 @@ import (
 	"context"
 	"crypto/tls"
 	"net/http"
-	"sync"
 	"time"
 
 	"github.com/gorilla/mux"
@@ -28,9 +27,6 @@ import (
 	"github.com/matrix-org/dendrite/appservice/consumers"
 	"github.com/matrix-org/dendrite/appservice/inthttp"
 	"github.com/matrix-org/dendrite/appservice/query"
-	"github.com/matrix-org/dendrite/appservice/storage"
-	"github.com/matrix-org/dendrite/appservice/types"
-	"github.com/matrix-org/dendrite/appservice/workers"
 	roomserverAPI "github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/setup/base"
 	"github.com/matrix-org/dendrite/setup/config"
@@ -59,57 +55,40 @@ func NewInternalAPI(
 			Proxy: http.ProxyFromEnvironment,
 		},
 	}
-	js, _ := base.NATS.Prepare(base.ProcessContext, &base.Cfg.Global.JetStream)
+	// Create appserivce query API with an HTTP client that will be used for all
+	// outbound and inbound requests (inbound only for the internal API)
+	appserviceQueryAPI := &query.AppServiceQueryAPI{
+		HTTPClient: client,
+		Cfg:        &base.Cfg.AppServiceAPI,
+	}
 
-	// Create a connection to the appservice postgres DB
-	appserviceDB, err := storage.NewDatabase(base, &base.Cfg.AppServiceAPI.Database)
-	if err != nil {
-		logrus.WithError(err).Panicf("failed to connect to appservice db")
+	if len(base.Cfg.Derived.ApplicationServices) == 0 {
+		return appserviceQueryAPI
 	}
 
 	// Wrap application services in a type that relates the application service and
 	// a sync.Cond object that can be used to notify workers when there are new
 	// events to be sent out.
-	workerStates := make([]types.ApplicationServiceWorkerState, len(base.Cfg.Derived.ApplicationServices))
-	for i, appservice := range base.Cfg.Derived.ApplicationServices {
-		m := sync.Mutex{}
-		ws := types.ApplicationServiceWorkerState{
-			AppService: appservice,
-			Cond:       sync.NewCond(&m),
-		}
-		workerStates[i] = ws
-
+	for _, appservice := range base.Cfg.Derived.ApplicationServices {
 		// Create bot account for this AS if it doesn't already exist
-		if err = generateAppServiceAccount(userAPI, appservice); err != nil {
+		if err := generateAppServiceAccount(userAPI, appservice); err != nil {
 			logrus.WithFields(logrus.Fields{
 				"appservice": appservice.ID,
 			}).WithError(err).Panicf("failed to generate bot account for appservice")
 		}
 	}
 
-	// Create appserivce query API with an HTTP client that will be used for all
-	// outbound and inbound requests (inbound only for the internal API)
-	appserviceQueryAPI := &query.AppServiceQueryAPI{
-		HTTPClient: client,
-		Cfg:        base.Cfg,
-	}
-
 	// Only consume if we actually have ASes to track, else we'll just chew cycles needlessly.
 	// We can't add ASes at runtime so this is safe to do.
-	if len(workerStates) > 0 {
-		consumer := consumers.NewOutputRoomEventConsumer(
-			base.ProcessContext, base.Cfg, js, appserviceDB,
-			rsAPI, workerStates,
-		)
-		if err := consumer.Start(); err != nil {
-			logrus.WithError(err).Panicf("failed to start appservice roomserver consumer")
-		}
+	js, _ := base.NATS.Prepare(base.ProcessContext, &base.Cfg.Global.JetStream)
+	consumer := consumers.NewOutputRoomEventConsumer(
+		base.ProcessContext, &base.Cfg.AppServiceAPI,
+		client, js, rsAPI,
+	)
+	if err := consumer.Start(); err != nil {
+		logrus.WithError(err).Panicf("failed to start appservice roomserver consumer")
 	}
 
-	// Create application service transaction workers
-	if err := workers.SetupTransactionWorkers(client, appserviceDB, workerStates); err != nil {
-		logrus.WithError(err).Panicf("failed to start app service transaction workers")
-	}
 	return appserviceQueryAPI
 }
 
diff --git a/appservice/consumers/roomserver.go b/appservice/consumers/roomserver.go
index 21b52bc3..a30944e7 100644
--- a/appservice/consumers/roomserver.go
+++ b/appservice/consumers/roomserver.go
@@ -15,14 +15,18 @@
 package consumers
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
+	"fmt"
+	"math"
+	"net/http"
+	"net/url"
+	"time"
 
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/nats-io/nats.go"
 
-	"github.com/matrix-org/dendrite/appservice/storage"
-	"github.com/matrix-org/dendrite/appservice/types"
 	"github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/setup/config"
 	"github.com/matrix-org/dendrite/setup/jetstream"
@@ -33,178 +37,192 @@ import (
 
 // OutputRoomEventConsumer consumes events that originated in the room server.
 type OutputRoomEventConsumer struct {
-	ctx          context.Context
-	jetstream    nats.JetStreamContext
-	durable      string
-	topic        string
-	asDB         storage.Database
-	rsAPI        api.AppserviceRoomserverAPI
-	serverName   string
-	workerStates []types.ApplicationServiceWorkerState
+	ctx       context.Context
+	cfg       *config.AppServiceAPI
+	client    *http.Client
+	jetstream nats.JetStreamContext
+	topic     string
+	rsAPI     api.AppserviceRoomserverAPI
+}
+
+type appserviceState struct {
+	*config.ApplicationService
+	backoff int
 }
 
 // NewOutputRoomEventConsumer creates a new OutputRoomEventConsumer. Call
 // Start() to begin consuming from room servers.
 func NewOutputRoomEventConsumer(
 	process *process.ProcessContext,
-	cfg *config.Dendrite,
+	cfg *config.AppServiceAPI,
+	client *http.Client,
 	js nats.JetStreamContext,
-	appserviceDB storage.Database,
 	rsAPI api.AppserviceRoomserverAPI,
-	workerStates []types.ApplicationServiceWorkerState,
 ) *OutputRoomEventConsumer {
 	return &OutputRoomEventConsumer{
-		ctx:          process.Context(),
-		jetstream:    js,
-		durable:      cfg.Global.JetStream.Durable("AppserviceRoomserverConsumer"),
-		topic:        cfg.Global.JetStream.Prefixed(jetstream.OutputRoomEvent),
-		asDB:         appserviceDB,
-		rsAPI:        rsAPI,
-		serverName:   string(cfg.Global.ServerName),
-		workerStates: workerStates,
+		ctx:       process.Context(),
+		cfg:       cfg,
+		client:    client,
+		jetstream: js,
+		topic:     cfg.Matrix.JetStream.Prefixed(jetstream.OutputRoomEvent),
+		rsAPI:     rsAPI,
 	}
 }
 
 // Start consuming from room servers
 func (s *OutputRoomEventConsumer) Start() error {
-	return jetstream.JetStreamConsumer(
-		s.ctx, s.jetstream, s.topic, s.durable, 1,
-		s.onMessage, nats.DeliverAll(), nats.ManualAck(),
-	)
+	for _, as := range s.cfg.Derived.ApplicationServices {
+		appsvc := as
+		state := &appserviceState{
+			ApplicationService: &appsvc,
+		}
+		token := jetstream.Tokenise(as.ID)
+		if err := jetstream.JetStreamConsumer(
+			s.ctx, s.jetstream, s.topic,
+			s.cfg.Matrix.JetStream.Durable("Appservice_"+token),
+			50, // maximum number of events to send in a single transaction
+			func(ctx context.Context, msgs []*nats.Msg) bool {
+				return s.onMessage(ctx, state, msgs)
+			},
+			nats.DeliverNew(), nats.ManualAck(),
+		); err != nil {
+			return fmt.Errorf("failed to create %q consumer: %w", token, err)
+		}
+	}
+	return nil
 }
 
 // onMessage is called when the appservice component receives a new event from
 // the room server output log.
-func (s *OutputRoomEventConsumer) onMessage(ctx context.Context, msgs []*nats.Msg) bool {
-	msg := msgs[0] // Guaranteed to exist if onMessage is called
-	// Parse out the event JSON
-	var output api.OutputEvent
-	if err := json.Unmarshal(msg.Data, &output); err != nil {
-		// If the message was invalid, log it and move on to the next message in the stream
-		log.WithError(err).Errorf("roomserver output log: message parse failure")
-		return true
-	}
-
-	log.WithFields(log.Fields{
-		"type": output.Type,
-	}).Debug("Got a message in OutputRoomEventConsumer")
-
-	events := []*gomatrixserverlib.HeaderedEvent{}
-	if output.Type == api.OutputTypeNewRoomEvent && output.NewRoomEvent != nil {
-		newEventID := output.NewRoomEvent.Event.EventID()
-		events = append(events, output.NewRoomEvent.Event)
-		if len(output.NewRoomEvent.AddsStateEventIDs) > 0 {
-			eventsReq := &api.QueryEventsByIDRequest{
-				EventIDs: make([]string, 0, len(output.NewRoomEvent.AddsStateEventIDs)),
+func (s *OutputRoomEventConsumer) onMessage(
+	ctx context.Context, state *appserviceState, msgs []*nats.Msg,
+) bool {
+	log.WithField("appservice", state.ID).Tracef("Appservice worker received %d message(s) from roomserver", len(msgs))
+	events := make([]*gomatrixserverlib.HeaderedEvent, 0, len(msgs))
+	for _, msg := range msgs {
+		// Parse out the event JSON
+		var output api.OutputEvent
+		if err := json.Unmarshal(msg.Data, &output); err != nil {
+			// If the message was invalid, log it and move on to the next message in the stream
+			log.WithField("appservice", state.ID).WithError(err).Errorf("Appservice failed to parse message, ignoring")
+			continue
+		}
+		switch output.Type {
+		case api.OutputTypeNewRoomEvent:
+			if output.NewRoomEvent == nil || !s.appserviceIsInterestedInEvent(ctx, output.NewRoomEvent.Event, state.ApplicationService) {
+				continue
 			}
-			eventsRes := &api.QueryEventsByIDResponse{}
-			for _, eventID := range output.NewRoomEvent.AddsStateEventIDs {
-				if eventID != newEventID {
-					eventsReq.EventIDs = append(eventsReq.EventIDs, eventID)
+			events = append(events, output.NewRoomEvent.Event)
+			if len(output.NewRoomEvent.AddsStateEventIDs) > 0 {
+				newEventID := output.NewRoomEvent.Event.EventID()
+				eventsReq := &api.QueryEventsByIDRequest{
+					EventIDs: make([]string, 0, len(output.NewRoomEvent.AddsStateEventIDs)),
 				}
-			}
-			if len(eventsReq.EventIDs) > 0 {
-				if err := s.rsAPI.QueryEventsByID(s.ctx, eventsReq, eventsRes); err != nil {
-					log.WithError(err).Errorf("s.rsAPI.QueryEventsByID failed")
-					return false
+				eventsRes := &api.QueryEventsByIDResponse{}
+				for _, eventID := range output.NewRoomEvent.AddsStateEventIDs {
+					if eventID != newEventID {
+						eventsReq.EventIDs = append(eventsReq.EventIDs, eventID)
+					}
+				}
+				if len(eventsReq.EventIDs) > 0 {
+					if err := s.rsAPI.QueryEventsByID(s.ctx, eventsReq, eventsRes); err != nil {
+						log.WithError(err).Errorf("s.rsAPI.QueryEventsByID failed")
+						return false
+					}
+					events = append(events, eventsRes.Events...)
 				}
-				events = append(events, eventsRes.Events...)
 			}
+
+		case api.OutputTypeNewInviteEvent:
+			if output.NewInviteEvent == nil {
+				continue
+			}
+			events = append(events, output.NewInviteEvent.Event)
+
+		default:
+			continue
 		}
-	} else if output.Type == api.OutputTypeNewInviteEvent && output.NewInviteEvent != nil {
-		events = append(events, output.NewInviteEvent.Event)
-	} else {
-		log.WithFields(log.Fields{
-			"type": output.Type,
-		}).Debug("appservice OutputRoomEventConsumer ignoring event", string(msg.Data))
-		return true
 	}
 
-	// Send event to any relevant application services
-	if err := s.filterRoomserverEvents(context.TODO(), events); err != nil {
-		log.WithError(err).Errorf("roomserver output log: filter error")
+	// If there are no events selected for sending then we should
+	// ack the messages so that we don't get sent them again in the
+	// future.
+	if len(events) == 0 {
 		return true
 	}
 
-	return true
+	// Send event to any relevant application services. If we hit
+	// an error here, return false, so that we negatively ack.
+	log.WithField("appservice", state.ID).Debugf("Appservice worker sending %d events(s) from roomserver", len(events))
+	return s.sendEvents(ctx, state, events) == nil
 }
 
-// filterRoomserverEvents takes in events and decides whether any of them need
-// to be passed on to an external application service. It does this by checking
-// each namespace of each registered application service, and if there is a
-// match, adds the event to the queue for events to be sent to a particular
-// application service.
-func (s *OutputRoomEventConsumer) filterRoomserverEvents(
-	ctx context.Context,
+// sendEvents passes events to the appservice by using the transactions
+// endpoint. It will block for the backoff period if necessary.
+func (s *OutputRoomEventConsumer) sendEvents(
+	ctx context.Context, state *appserviceState,
 	events []*gomatrixserverlib.HeaderedEvent,
 ) error {
-	for _, ws := range s.workerStates {
-		for _, event := range events {
-			// Check if this event is interesting to this application service
-			if s.appserviceIsInterestedInEvent(ctx, event, ws.AppService) {
-				// Queue this event to be sent off to the application service
-				if err := s.asDB.StoreEvent(ctx, ws.AppService.ID, event); err != nil {
-					log.WithError(err).Warn("failed to insert incoming event into appservices database")
-					return err
-				} else {
-					// Tell our worker to send out new messages by updating remaining message
-					// count and waking them up with a broadcast
-					ws.NotifyNewEvents()
-				}
-			}
-		}
+	// Create the transaction body.
+	transaction, err := json.Marshal(
+		gomatrixserverlib.ApplicationServiceTransaction{
+			Events: gomatrixserverlib.HeaderedToClientEvents(events, gomatrixserverlib.FormatAll),
+		},
+	)
+	if err != nil {
+		return err
 	}
 
-	return nil
-}
+	// TODO: We should probably be more intelligent and pick something not
+	// in the control of the event. A NATS timestamp header or something maybe.
+	txnID := events[0].Event.OriginServerTS()
 
-// appserviceJoinedAtEvent returns a boolean depending on whether a given
-// appservice has membership at the time a given event was created.
-func (s *OutputRoomEventConsumer) appserviceJoinedAtEvent(ctx context.Context, event *gomatrixserverlib.HeaderedEvent, appservice config.ApplicationService) bool {
-	// TODO: This is only checking the current room state, not the state at
-	// the event in question. Pretty sure this is what Synapse does too, but
-	// until we have a lighter way of checking the state before the event that
-	// doesn't involve state res, then this is probably OK.
-	membershipReq := &api.QueryMembershipsForRoomRequest{
-		RoomID:     event.RoomID(),
-		JoinedOnly: true,
+	// Send the transaction to the appservice.
+	// https://matrix.org/docs/spec/application_service/r0.1.2#put-matrix-app-v1-transactions-txnid
+	address := fmt.Sprintf("%s/transactions/%d?access_token=%s", state.URL, txnID, url.QueryEscape(state.HSToken))
+	req, err := http.NewRequestWithContext(ctx, "PUT", address, bytes.NewBuffer(transaction))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("Content-Type", "application/json")
+	resp, err := s.client.Do(req)
+	if err != nil {
+		return state.backoffAndPause(err)
 	}
-	membershipRes := &api.QueryMembershipsForRoomResponse{}
 
-	// XXX: This could potentially race if the state for the event is not known yet
-	// e.g. the event came over federation but we do not have the full state persisted.
-	if err := s.rsAPI.QueryMembershipsForRoom(ctx, membershipReq, membershipRes); err == nil {
-		for _, ev := range membershipRes.JoinEvents {
-			var membership gomatrixserverlib.MemberContent
-			if err = json.Unmarshal(ev.Content, &membership); err != nil || ev.StateKey == nil {
-				continue
-			}
-			if appservice.IsInterestedInUserID(*ev.StateKey) {
-				return true
-			}
-		}
-	} else {
-		log.WithFields(log.Fields{
-			"room_id": event.RoomID(),
-		}).WithError(err).Errorf("Unable to get membership for room")
+	// If the response was fine then we can clear any backoffs in place and
+	// report that everything was OK. Otherwise, back off for a while.
+	switch resp.StatusCode {
+	case http.StatusOK:
+		state.backoff = 0
+	default:
+		return state.backoffAndPause(fmt.Errorf("received HTTP status code %d from appservice", resp.StatusCode))
 	}
-	return false
+	return nil
+}
+
+// backoff pauses the calling goroutine for a 2^some backoff exponent seconds
+func (s *appserviceState) backoffAndPause(err error) error {
+	if s.backoff < 6 {
+		s.backoff++
+	}
+	duration := time.Second * time.Duration(math.Pow(2, float64(s.backoff)))
+	log.WithField("appservice", s.ID).WithError(err).Errorf("Unable to send transaction to appservice, backing off for %s", duration.String())
+	time.Sleep(duration)
+	return err
 }
 
 // appserviceIsInterestedInEvent returns a boolean depending on whether a given
 // event falls within one of a given application service's namespaces.
 //
 // TODO: This should be cached, see https://github.com/matrix-org/dendrite/issues/1682
-func (s *OutputRoomEventConsumer) appserviceIsInterestedInEvent(ctx context.Context, event *gomatrixserverlib.HeaderedEvent, appservice config.ApplicationService) bool {
-	// No reason to queue events if they'll never be sent to the application
-	// service
-	if appservice.URL == "" {
+func (s *OutputRoomEventConsumer) appserviceIsInterestedInEvent(ctx context.Context, event *gomatrixserverlib.HeaderedEvent, appservice *config.ApplicationService) bool {
+	switch {
+	case appservice.URL == "":
 		return false
-	}
-
-	// Check Room ID and Sender of the event
-	if appservice.IsInterestedInUserID(event.Sender()) ||
-		appservice.IsInterestedInRoomID(event.RoomID()) {
+	case appservice.IsInterestedInUserID(event.Sender()):
+		return true
+	case appservice.IsInterestedInRoomID(event.RoomID()):
 		return true
 	}
 
@@ -225,10 +243,52 @@ func (s *OutputRoomEventConsumer) appserviceIsInterestedInEvent(ctx context.Cont
 		}
 	} else {
 		log.WithFields(log.Fields{
-			"room_id": event.RoomID(),
+			"appservice": appservice.ID,
+			"room_id":    event.RoomID(),
 		}).WithError(err).Errorf("Unable to get aliases for room")
 	}
 
 	// Check if any of the members in the room match the appservice
 	return s.appserviceJoinedAtEvent(ctx, event, appservice)
 }
+
+// appserviceJoinedAtEvent returns a boolean depending on whether a given
+// appservice has membership at the time a given event was created.
+func (s *OutputRoomEventConsumer) appserviceJoinedAtEvent(ctx context.Context, event *gomatrixserverlib.HeaderedEvent, appservice *config.ApplicationService) bool {
+	// TODO: This is only checking the current room state, not the state at
+	// the event in question. Pretty sure this is what Synapse does too, but
+	// until we have a lighter way of checking the state before the event that
+	// doesn't involve state res, then this is probably OK.
+	membershipReq := &api.QueryMembershipsForRoomRequest{
+		RoomID:     event.RoomID(),
+		JoinedOnly: true,
+	}
+	membershipRes := &api.QueryMembershipsForRoomResponse{}
+
+	// XXX: This could potentially race if the state for the event is not known yet
+	// e.g. the event came over federation but we do not have the full state persisted.
+	if err := s.rsAPI.QueryMembershipsForRoom(ctx, membershipReq, membershipRes); err == nil {
+		for _, ev := range membershipRes.JoinEvents {
+			switch {
+			case ev.StateKey == nil:
+				continue
+			case ev.Type != gomatrixserverlib.MRoomMember:
+				continue
+			}
+			var membership gomatrixserverlib.MemberContent
+			err = json.Unmarshal(ev.Content, &membership)
+			switch {
+			case err != nil:
+				continue
+			case membership.Membership == gomatrixserverlib.Join:
+				return true
+			}
+		}
+	} else {
+		log.WithFields(log.Fields{
+			"appservice": appservice.ID,
+			"room_id":    event.RoomID(),
+		}).WithError(err).Errorf("Unable to get membership for room")
+	}
+	return false
+}
diff --git a/appservice/query/query.go b/appservice/query/query.go
index dacd3caa..53b34cb1 100644
--- a/appservice/query/query.go
+++ b/appservice/query/query.go
@@ -33,7 +33,7 @@ const userIDExistsPath = "/users/"
 // AppServiceQueryAPI is an implementation of api.AppServiceQueryAPI
 type AppServiceQueryAPI struct {
 	HTTPClient *http.Client
-	Cfg        *config.Dendrite
+	Cfg        *config.AppServiceAPI
 }
 
 // RoomAliasExists performs a request to '/room/{roomAlias}' on all known
diff --git a/appservice/storage/interface.go b/appservice/storage/interface.go
deleted file mode 100644
index 25d35af6..00000000
--- a/appservice/storage/interface.go
+++ /dev/null
@@ -1,30 +0,0 @@
-// 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 storage
-
-import (
-	"context"
-
-	"github.com/matrix-org/gomatrixserverlib"
-)
-
-type Database interface {
-	StoreEvent(ctx context.Context, appServiceID string, event *gomatrixserverlib.HeaderedEvent) error
-	GetEventsWithAppServiceID(ctx context.Context, appServiceID string, limit int) (int, int, []gomatrixserverlib.HeaderedEvent, bool, error)
-	CountEventsWithAppServiceID(ctx context.Context, appServiceID string) (int, error)
-	UpdateTxnIDForEvents(ctx context.Context, appserviceID string, maxID, txnID int) error
-	RemoveEventsBeforeAndIncludingID(ctx context.Context, appserviceID string, eventTableID int) error
-	GetLatestTxnID(ctx context.Context) (int, error)
-}
diff --git a/appservice/storage/postgres/appservice_events_table.go b/appservice/storage/postgres/appservice_events_table.go
deleted file mode 100644
index a95be6b8..00000000
--- a/appservice/storage/postgres/appservice_events_table.go
+++ /dev/null
@@ -1,256 +0,0 @@
-// Copyright 2018 New Vector Ltd
-// Copyright 2019-2020 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"
-	"encoding/json"
-	"time"
-
-	"github.com/matrix-org/gomatrixserverlib"
-	log "github.com/sirupsen/logrus"
-)
-
-const appserviceEventsSchema = `
--- Stores events to be sent to application services
-CREATE TABLE IF NOT EXISTS appservice_events (
-	-- An auto-incrementing id unique to each event in the table
-	id BIGSERIAL NOT NULL PRIMARY KEY,
-	-- The ID of the application service the event will be sent to
-	as_id TEXT NOT NULL,
-	-- JSON representation of the event
-	headered_event_json TEXT NOT NULL,
-	-- The ID of the transaction that this event is a part of
-	txn_id BIGINT NOT NULL
-);
-
-CREATE INDEX IF NOT EXISTS appservice_events_as_id ON appservice_events(as_id);
-`
-
-const selectEventsByApplicationServiceIDSQL = "" +
-	"SELECT id, headered_event_json, txn_id " +
-	"FROM appservice_events WHERE as_id = $1 ORDER BY txn_id DESC, id ASC"
-
-const countEventsByApplicationServiceIDSQL = "" +
-	"SELECT COUNT(id) FROM appservice_events WHERE as_id = $1"
-
-const insertEventSQL = "" +
-	"INSERT INTO appservice_events(as_id, headered_event_json, txn_id) " +
-	"VALUES ($1, $2, $3)"
-
-const updateTxnIDForEventsSQL = "" +
-	"UPDATE appservice_events SET txn_id = $1 WHERE as_id = $2 AND id <= $3"
-
-const deleteEventsBeforeAndIncludingIDSQL = "" +
-	"DELETE FROM appservice_events WHERE as_id = $1 AND id <= $2"
-
-const (
-	// A transaction ID number that no transaction should ever have. Used for
-	// checking again the default value.
-	invalidTxnID = -2
-)
-
-type eventsStatements struct {
-	selectEventsByApplicationServiceIDStmt *sql.Stmt
-	countEventsByApplicationServiceIDStmt  *sql.Stmt
-	insertEventStmt                        *sql.Stmt
-	updateTxnIDForEventsStmt               *sql.Stmt
-	deleteEventsBeforeAndIncludingIDStmt   *sql.Stmt
-}
-
-func (s *eventsStatements) prepare(db *sql.DB) (err error) {
-	_, err = db.Exec(appserviceEventsSchema)
-	if err != nil {
-		return
-	}
-
-	if s.selectEventsByApplicationServiceIDStmt, err = db.Prepare(selectEventsByApplicationServiceIDSQL); err != nil {
-		return
-	}
-	if s.countEventsByApplicationServiceIDStmt, err = db.Prepare(countEventsByApplicationServiceIDSQL); err != nil {
-		return
-	}
-	if s.insertEventStmt, err = db.Prepare(insertEventSQL); err != nil {
-		return
-	}
-	if s.updateTxnIDForEventsStmt, err = db.Prepare(updateTxnIDForEventsSQL); err != nil {
-		return
-	}
-	if s.deleteEventsBeforeAndIncludingIDStmt, err = db.Prepare(deleteEventsBeforeAndIncludingIDSQL); err != nil {
-		return
-	}
-
-	return
-}
-
-// selectEventsByApplicationServiceID takes in an application service ID and
-// returns a slice of events that need to be sent to that application service,
-// as well as an int later used to remove these same events from the database
-// once successfully sent to an application service.
-func (s *eventsStatements) selectEventsByApplicationServiceID(
-	ctx context.Context,
-	applicationServiceID string,
-	limit int,
-) (
-	txnID, maxID int,
-	events []gomatrixserverlib.HeaderedEvent,
-	eventsRemaining bool,
-	err error,
-) {
-	defer func() {
-		if err != nil {
-			log.WithFields(log.Fields{
-				"appservice": applicationServiceID,
-			}).WithError(err).Fatalf("appservice unable to select new events to send")
-		}
-	}()
-	// Retrieve events from the database. Unsuccessfully sent events first
-	eventRows, err := s.selectEventsByApplicationServiceIDStmt.QueryContext(ctx, applicationServiceID)
-	if err != nil {
-		return
-	}
-	defer checkNamedErr(eventRows.Close, &err)
-	events, maxID, txnID, eventsRemaining, err = retrieveEvents(eventRows, limit)
-	if err != nil {
-		return
-	}
-
-	return
-}
-
-// checkNamedErr calls fn and overwrite err if it was nil and fn returned non-nil
-func checkNamedErr(fn func() error, err *error) {
-	if e := fn(); e != nil && *err == nil {
-		*err = e
-	}
-}
-
-func retrieveEvents(eventRows *sql.Rows, limit int) (events []gomatrixserverlib.HeaderedEvent, maxID, txnID int, eventsRemaining bool, err error) {
-	// Get current time for use in calculating event age
-	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
-
-	// Iterate through each row and store event contents
-	// If txn_id changes dramatically, we've switched from collecting old events to
-	// new ones. Send back those events first.
-	lastTxnID := invalidTxnID
-	for eventsProcessed := 0; eventRows.Next(); {
-		var event gomatrixserverlib.HeaderedEvent
-		var eventJSON []byte
-		var id int
-		err = eventRows.Scan(
-			&id,
-			&eventJSON,
-			&txnID,
-		)
-		if err != nil {
-			return nil, 0, 0, false, err
-		}
-
-		// Unmarshal eventJSON
-		if err = json.Unmarshal(eventJSON, &event); err != nil {
-			return nil, 0, 0, false, err
-		}
-
-		// If txnID has changed on this event from the previous event, then we've
-		// reached the end of a transaction's events. Return only those events.
-		if lastTxnID > invalidTxnID && lastTxnID != txnID {
-			return events, maxID, lastTxnID, true, nil
-		}
-		lastTxnID = txnID
-
-		// Limit events that aren't part of an old transaction
-		if txnID == -1 {
-			// Return if we've hit the limit
-			if eventsProcessed++; eventsProcessed > limit {
-				return events, maxID, lastTxnID, true, nil
-			}
-		}
-
-		if id > maxID {
-			maxID = id
-		}
-
-		// Portion of the event that is unsigned due to rapid change
-		// TODO: Consider removing age as not many app services use it
-		if err = event.SetUnsignedField("age", nowMilli-int64(event.OriginServerTS())); err != nil {
-			return nil, 0, 0, false, err
-		}
-
-		events = append(events, event)
-	}
-
-	return
-}
-
-// countEventsByApplicationServiceID inserts an event mapped to its corresponding application service
-// IDs into the db.
-func (s *eventsStatements) countEventsByApplicationServiceID(
-	ctx context.Context,
-	appServiceID string,
-) (int, error) {
-	var count int
-	err := s.countEventsByApplicationServiceIDStmt.QueryRowContext(ctx, appServiceID).Scan(&count)
-	if err != nil && err != sql.ErrNoRows {
-		return 0, err
-	}
-
-	return count, nil
-}
-
-// insertEvent inserts an event mapped to its corresponding application service
-// IDs into the db.
-func (s *eventsStatements) insertEvent(
-	ctx context.Context,
-	appServiceID string,
-	event *gomatrixserverlib.HeaderedEvent,
-) (err error) {
-	// Convert event to JSON before inserting
-	eventJSON, err := json.Marshal(event)
-	if err != nil {
-		return err
-	}
-
-	_, err = s.insertEventStmt.ExecContext(
-		ctx,
-		appServiceID,
-		eventJSON,
-		-1, // No transaction ID yet
-	)
-	return
-}
-
-// updateTxnIDForEvents sets the transactionID for a collection of events. Done
-// before sending them to an AppService. Referenced before sending to make sure
-// we aren't constructing multiple transactions with the same events.
-func (s *eventsStatements) updateTxnIDForEvents(
-	ctx context.Context,
-	appserviceID string,
-	maxID, txnID int,
-) (err error) {
-	_, err = s.updateTxnIDForEventsStmt.ExecContext(ctx, txnID, appserviceID, maxID)
-	return
-}
-
-// deleteEventsBeforeAndIncludingID removes events matching given IDs from the database.
-func (s *eventsStatements) deleteEventsBeforeAndIncludingID(
-	ctx context.Context,
-	appserviceID string,
-	eventTableID int,
-) (err error) {
-	_, err = s.deleteEventsBeforeAndIncludingIDStmt.ExecContext(ctx, appserviceID, eventTableID)
-	return
-}
diff --git a/appservice/storage/postgres/storage.go b/appservice/storage/postgres/storage.go
deleted file mode 100644
index a4c04b2c..00000000
--- a/appservice/storage/postgres/storage.go
+++ /dev/null
@@ -1,115 +0,0 @@
-// Copyright 2018 New Vector Ltd
-// Copyright 2019-2020 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"
-
-	// Import postgres database driver
-	_ "github.com/lib/pq"
-	"github.com/matrix-org/dendrite/internal/sqlutil"
-	"github.com/matrix-org/dendrite/setup/base"
-	"github.com/matrix-org/dendrite/setup/config"
-	"github.com/matrix-org/gomatrixserverlib"
-)
-
-// Database stores events intended to be later sent to application services
-type Database struct {
-	events eventsStatements
-	txnID  txnStatements
-	db     *sql.DB
-	writer sqlutil.Writer
-}
-
-// NewDatabase opens a new database
-func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions) (*Database, error) {
-	var result Database
-	var err error
-	if result.db, result.writer, err = base.DatabaseConnection(dbProperties, sqlutil.NewDummyWriter()); err != nil {
-		return nil, err
-	}
-	if err = result.prepare(); err != nil {
-		return nil, err
-	}
-	return &result, nil
-}
-
-func (d *Database) prepare() error {
-	if err := d.events.prepare(d.db); err != nil {
-		return err
-	}
-
-	return d.txnID.prepare(d.db)
-}
-
-// StoreEvent takes in a gomatrixserverlib.HeaderedEvent and stores it in the database
-// for a transaction worker to pull and later send to an application service.
-func (d *Database) StoreEvent(
-	ctx context.Context,
-	appServiceID string,
-	event *gomatrixserverlib.HeaderedEvent,
-) error {
-	return d.events.insertEvent(ctx, appServiceID, event)
-}
-
-// GetEventsWithAppServiceID returns a slice of events and their IDs intended to
-// be sent to an application service given its ID.
-func (d *Database) GetEventsWithAppServiceID(
-	ctx context.Context,
-	appServiceID string,
-	limit int,
-) (int, int, []gomatrixserverlib.HeaderedEvent, bool, error) {
-	return d.events.selectEventsByApplicationServiceID(ctx, appServiceID, limit)
-}
-
-// CountEventsWithAppServiceID returns the number of events destined for an
-// application service given its ID.
-func (d *Database) CountEventsWithAppServiceID(
-	ctx context.Context,
-	appServiceID string,
-) (int, error) {
-	return d.events.countEventsByApplicationServiceID(ctx, appServiceID)
-}
-
-// UpdateTxnIDForEvents takes in an application service ID and a
-// and stores them in the DB, unless the pair already exists, in
-// which case it updates them.
-func (d *Database) UpdateTxnIDForEvents(
-	ctx context.Context,
-	appserviceID string,
-	maxID, txnID int,
-) error {
-	return d.events.updateTxnIDForEvents(ctx, appserviceID, maxID, txnID)
-}
-
-// RemoveEventsBeforeAndIncludingID removes all events from the database that
-// are less than or equal to a given maximum ID. IDs here are implemented as a
-// serial, thus this should always delete events in chronological order.
-func (d *Database) RemoveEventsBeforeAndIncludingID(
-	ctx context.Context,
-	appserviceID string,
-	eventTableID int,
-) error {
-	return d.events.deleteEventsBeforeAndIncludingID(ctx, appserviceID, eventTableID)
-}
-
-// GetLatestTxnID returns the latest available transaction id
-func (d *Database) GetLatestTxnID(
-	ctx context.Context,
-) (int, error) {
-	return d.txnID.selectTxnID(ctx)
-}
diff --git a/appservice/storage/postgres/txn_id_counter_table.go b/appservice/storage/postgres/txn_id_counter_table.go
deleted file mode 100644
index a96a0e36..00000000
--- a/appservice/storage/postgres/txn_id_counter_table.go
+++ /dev/null
@@ -1,53 +0,0 @@
-// Copyright 2018 New Vector Ltd
-// Copyright 2019-2020 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"
-)
-
-const txnIDSchema = `
--- Keeps a count of the current transaction ID
-CREATE SEQUENCE IF NOT EXISTS txn_id_counter START 1;
-`
-
-const selectTxnIDSQL = "SELECT nextval('txn_id_counter')"
-
-type txnStatements struct {
-	selectTxnIDStmt *sql.Stmt
-}
-
-func (s *txnStatements) prepare(db *sql.DB) (err error) {
-	_, err = db.Exec(txnIDSchema)
-	if err != nil {
-		return
-	}
-
-	if s.selectTxnIDStmt, err = db.Prepare(selectTxnIDSQL); err != nil {
-		return
-	}
-
-	return
-}
-
-// selectTxnID selects the latest ascending transaction ID
-func (s *txnStatements) selectTxnID(
-	ctx context.Context,
-) (txnID int, err error) {
-	err = s.selectTxnIDStmt.QueryRowContext(ctx).Scan(&txnID)
-	return
-}
diff --git a/appservice/storage/sqlite3/appservice_events_table.go b/appservice/storage/sqlite3/appservice_events_table.go
deleted file mode 100644
index 34b4859e..00000000
--- a/appservice/storage/sqlite3/appservice_events_table.go
+++ /dev/null
@@ -1,267 +0,0 @@
-// Copyright 2018 New Vector Ltd
-// Copyright 2019-2020 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"
-	"encoding/json"
-	"time"
-
-	"github.com/matrix-org/dendrite/internal/sqlutil"
-	"github.com/matrix-org/gomatrixserverlib"
-	log "github.com/sirupsen/logrus"
-)
-
-const appserviceEventsSchema = `
--- Stores events to be sent to application services
-CREATE TABLE IF NOT EXISTS appservice_events (
-	-- An auto-incrementing id unique to each event in the table
-	id INTEGER PRIMARY KEY AUTOINCREMENT,
-	-- The ID of the application service the event will be sent to
-	as_id TEXT NOT NULL,
-	-- JSON representation of the event
-	headered_event_json TEXT NOT NULL,
-	-- The ID of the transaction that this event is a part of
-	txn_id INTEGER NOT NULL
-);
-
-CREATE INDEX IF NOT EXISTS appservice_events_as_id ON appservice_events(as_id);
-`
-
-const selectEventsByApplicationServiceIDSQL = "" +
-	"SELECT id, headered_event_json, txn_id " +
-	"FROM appservice_events WHERE as_id = $1 ORDER BY txn_id DESC, id ASC"
-
-const countEventsByApplicationServiceIDSQL = "" +
-	"SELECT COUNT(id) FROM appservice_events WHERE as_id = $1"
-
-const insertEventSQL = "" +
-	"INSERT INTO appservice_events(as_id, headered_event_json, txn_id) " +
-	"VALUES ($1, $2, $3)"
-
-const updateTxnIDForEventsSQL = "" +
-	"UPDATE appservice_events SET txn_id = $1 WHERE as_id = $2 AND id <= $3"
-
-const deleteEventsBeforeAndIncludingIDSQL = "" +
-	"DELETE FROM appservice_events WHERE as_id = $1 AND id <= $2"
-
-const (
-	// A transaction ID number that no transaction should ever have. Used for
-	// checking again the default value.
-	invalidTxnID = -2
-)
-
-type eventsStatements struct {
-	db                                     *sql.DB
-	writer                                 sqlutil.Writer
-	selectEventsByApplicationServiceIDStmt *sql.Stmt
-	countEventsByApplicationServiceIDStmt  *sql.Stmt
-	insertEventStmt                        *sql.Stmt
-	updateTxnIDForEventsStmt               *sql.Stmt
-	deleteEventsBeforeAndIncludingIDStmt   *sql.Stmt
-}
-
-func (s *eventsStatements) prepare(db *sql.DB, writer sqlutil.Writer) (err error) {
-	s.db = db
-	s.writer = writer
-	_, err = db.Exec(appserviceEventsSchema)
-	if err != nil {
-		return
-	}
-
-	if s.selectEventsByApplicationServiceIDStmt, err = db.Prepare(selectEventsByApplicationServiceIDSQL); err != nil {
-		return
-	}
-	if s.countEventsByApplicationServiceIDStmt, err = db.Prepare(countEventsByApplicationServiceIDSQL); err != nil {
-		return
-	}
-	if s.insertEventStmt, err = db.Prepare(insertEventSQL); err != nil {
-		return
-	}
-	if s.updateTxnIDForEventsStmt, err = db.Prepare(updateTxnIDForEventsSQL); err != nil {
-		return
-	}
-	if s.deleteEventsBeforeAndIncludingIDStmt, err = db.Prepare(deleteEventsBeforeAndIncludingIDSQL); err != nil {
-		return
-	}
-
-	return
-}
-
-// selectEventsByApplicationServiceID takes in an application service ID and
-// returns a slice of events that need to be sent to that application service,
-// as well as an int later used to remove these same events from the database
-// once successfully sent to an application service.
-func (s *eventsStatements) selectEventsByApplicationServiceID(
-	ctx context.Context,
-	applicationServiceID string,
-	limit int,
-) (
-	txnID, maxID int,
-	events []gomatrixserverlib.HeaderedEvent,
-	eventsRemaining bool,
-	err error,
-) {
-	defer func() {
-		if err != nil {
-			log.WithFields(log.Fields{
-				"appservice": applicationServiceID,
-			}).WithError(err).Fatalf("appservice unable to select new events to send")
-		}
-	}()
-	// Retrieve events from the database. Unsuccessfully sent events first
-	eventRows, err := s.selectEventsByApplicationServiceIDStmt.QueryContext(ctx, applicationServiceID)
-	if err != nil {
-		return
-	}
-	defer checkNamedErr(eventRows.Close, &err)
-	events, maxID, txnID, eventsRemaining, err = retrieveEvents(eventRows, limit)
-	if err != nil {
-		return
-	}
-
-	return
-}
-
-// checkNamedErr calls fn and overwrite err if it was nil and fn returned non-nil
-func checkNamedErr(fn func() error, err *error) {
-	if e := fn(); e != nil && *err == nil {
-		*err = e
-	}
-}
-
-func retrieveEvents(eventRows *sql.Rows, limit int) (events []gomatrixserverlib.HeaderedEvent, maxID, txnID int, eventsRemaining bool, err error) {
-	// Get current time for use in calculating event age
-	nowMilli := time.Now().UnixNano() / int64(time.Millisecond)
-
-	// Iterate through each row and store event contents
-	// If txn_id changes dramatically, we've switched from collecting old events to
-	// new ones. Send back those events first.
-	lastTxnID := invalidTxnID
-	for eventsProcessed := 0; eventRows.Next(); {
-		var event gomatrixserverlib.HeaderedEvent
-		var eventJSON []byte
-		var id int
-		err = eventRows.Scan(
-			&id,
-			&eventJSON,
-			&txnID,
-		)
-		if err != nil {
-			return nil, 0, 0, false, err
-		}
-
-		// Unmarshal eventJSON
-		if err = json.Unmarshal(eventJSON, &event); err != nil {
-			return nil, 0, 0, false, err
-		}
-
-		// If txnID has changed on this event from the previous event, then we've
-		// reached the end of a transaction's events. Return only those events.
-		if lastTxnID > invalidTxnID && lastTxnID != txnID {
-			return events, maxID, lastTxnID, true, nil
-		}
-		lastTxnID = txnID
-
-		// Limit events that aren't part of an old transaction
-		if txnID == -1 {
-			// Return if we've hit the limit
-			if eventsProcessed++; eventsProcessed > limit {
-				return events, maxID, lastTxnID, true, nil
-			}
-		}
-
-		if id > maxID {
-			maxID = id
-		}
-
-		// Portion of the event that is unsigned due to rapid change
-		// TODO: Consider removing age as not many app services use it
-		if err = event.SetUnsignedField("age", nowMilli-int64(event.OriginServerTS())); err != nil {
-			return nil, 0, 0, false, err
-		}
-
-		events = append(events, event)
-	}
-
-	return
-}
-
-// countEventsByApplicationServiceID inserts an event mapped to its corresponding application service
-// IDs into the db.
-func (s *eventsStatements) countEventsByApplicationServiceID(
-	ctx context.Context,
-	appServiceID string,
-) (int, error) {
-	var count int
-	err := s.countEventsByApplicationServiceIDStmt.QueryRowContext(ctx, appServiceID).Scan(&count)
-	if err != nil && err != sql.ErrNoRows {
-		return 0, err
-	}
-
-	return count, nil
-}
-
-// insertEvent inserts an event mapped to its corresponding application service
-// IDs into the db.
-func (s *eventsStatements) insertEvent(
-	ctx context.Context,
-	appServiceID string,
-	event *gomatrixserverlib.HeaderedEvent,
-) (err error) {
-	// Convert event to JSON before inserting
-	eventJSON, err := json.Marshal(event)
-	if err != nil {
-		return err
-	}
-
-	return s.writer.Do(s.db, nil, func(txn *sql.Tx) error {
-		_, err := s.insertEventStmt.ExecContext(
-			ctx,
-			appServiceID,
-			eventJSON,
-			-1, // No transaction ID yet
-		)
-		return err
-	})
-}
-
-// updateTxnIDForEvents sets the transactionID for a collection of events. Done
-// before sending them to an AppService. Referenced before sending to make sure
-// we aren't constructing multiple transactions with the same events.
-func (s *eventsStatements) updateTxnIDForEvents(
-	ctx context.Context,
-	appserviceID string,
-	maxID, txnID int,
-) (err error) {
-	return s.writer.Do(s.db, nil, func(txn *sql.Tx) error {
-		_, err := s.updateTxnIDForEventsStmt.ExecContext(ctx, txnID, appserviceID, maxID)
-		return err
-	})
-}
-
-// deleteEventsBeforeAndIncludingID removes events matching given IDs from the database.
-func (s *eventsStatements) deleteEventsBeforeAndIncludingID(
-	ctx context.Context,
-	appserviceID string,
-	eventTableID int,
-) (err error) {
-	return s.writer.Do(s.db, nil, func(txn *sql.Tx) error {
-		_, err := s.deleteEventsBeforeAndIncludingIDStmt.ExecContext(ctx, appserviceID, eventTableID)
-		return err
-	})
-}
diff --git a/appservice/storage/sqlite3/storage.go b/appservice/storage/sqlite3/storage.go
deleted file mode 100644
index ad62b362..00000000
--- a/appservice/storage/sqlite3/storage.go
+++ /dev/null
@@ -1,114 +0,0 @@
-// Copyright 2018 New Vector Ltd
-// Copyright 2019-2020 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"
-
-	// Import SQLite database driver
-	"github.com/matrix-org/dendrite/internal/sqlutil"
-	"github.com/matrix-org/dendrite/setup/base"
-	"github.com/matrix-org/dendrite/setup/config"
-	"github.com/matrix-org/gomatrixserverlib"
-)
-
-// Database stores events intended to be later sent to application services
-type Database struct {
-	events eventsStatements
-	txnID  txnStatements
-	db     *sql.DB
-	writer sqlutil.Writer
-}
-
-// NewDatabase opens a new database
-func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions) (*Database, error) {
-	var result Database
-	var err error
-	if result.db, result.writer, err = base.DatabaseConnection(dbProperties, sqlutil.NewExclusiveWriter()); err != nil {
-		return nil, err
-	}
-	if err = result.prepare(); err != nil {
-		return nil, err
-	}
-	return &result, nil
-}
-
-func (d *Database) prepare() error {
-	if err := d.events.prepare(d.db, d.writer); err != nil {
-		return err
-	}
-
-	return d.txnID.prepare(d.db, d.writer)
-}
-
-// StoreEvent takes in a gomatrixserverlib.HeaderedEvent and stores it in the database
-// for a transaction worker to pull and later send to an application service.
-func (d *Database) StoreEvent(
-	ctx context.Context,
-	appServiceID string,
-	event *gomatrixserverlib.HeaderedEvent,
-) error {
-	return d.events.insertEvent(ctx, appServiceID, event)
-}
-
-// GetEventsWithAppServiceID returns a slice of events and their IDs intended to
-// be sent to an application service given its ID.
-func (d *Database) GetEventsWithAppServiceID(
-	ctx context.Context,
-	appServiceID string,
-	limit int,
-) (int, int, []gomatrixserverlib.HeaderedEvent, bool, error) {
-	return d.events.selectEventsByApplicationServiceID(ctx, appServiceID, limit)
-}
-
-// CountEventsWithAppServiceID returns the number of events destined for an
-// application service given its ID.
-func (d *Database) CountEventsWithAppServiceID(
-	ctx context.Context,
-	appServiceID string,
-) (int, error) {
-	return d.events.countEventsByApplicationServiceID(ctx, appServiceID)
-}
-
-// UpdateTxnIDForEvents takes in an application service ID and a
-// and stores them in the DB, unless the pair already exists, in
-// which case it updates them.
-func (d *Database) UpdateTxnIDForEvents(
-	ctx context.Context,
-	appserviceID string,
-	maxID, txnID int,
-) error {
-	return d.events.updateTxnIDForEvents(ctx, appserviceID, maxID, txnID)
-}
-
-// RemoveEventsBeforeAndIncludingID removes all events from the database that
-// are less than or equal to a given maximum ID. IDs here are implemented as a
-// serial, thus this should always delete events in chronological order.
-func (d *Database) RemoveEventsBeforeAndIncludingID(
-	ctx context.Context,
-	appserviceID string,
-	eventTableID int,
-) error {
-	return d.events.deleteEventsBeforeAndIncludingID(ctx, appserviceID, eventTableID)
-}
-
-// GetLatestTxnID returns the latest available transaction id
-func (d *Database) GetLatestTxnID(
-	ctx context.Context,
-) (int, error) {
-	return d.txnID.selectTxnID(ctx)
-}
diff --git a/appservice/storage/sqlite3/txn_id_counter_table.go b/appservice/storage/sqlite3/txn_id_counter_table.go
deleted file mode 100644
index f2e902f9..00000000
--- a/appservice/storage/sqlite3/txn_id_counter_table.go
+++ /dev/null
@@ -1,82 +0,0 @@
-// Copyright 2018 New Vector Ltd
-// Copyright 2019-2020 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"
-
-	"github.com/matrix-org/dendrite/internal/sqlutil"
-)
-
-const txnIDSchema = `
--- Keeps a count of the current transaction ID
-CREATE TABLE IF NOT EXISTS appservice_counters (
-  name TEXT PRIMARY KEY NOT NULL,
-  last_id INTEGER DEFAULT 1
-);
-INSERT OR IGNORE INTO appservice_counters (name, last_id) VALUES('txn_id', 1);
-`
-
-const selectTxnIDSQL = `
-  SELECT last_id FROM appservice_counters WHERE name='txn_id'
-`
-
-const updateTxnIDSQL = `
-  UPDATE appservice_counters SET last_id=last_id+1 WHERE name='txn_id'
-`
-
-type txnStatements struct {
-	db              *sql.DB
-	writer          sqlutil.Writer
-	selectTxnIDStmt *sql.Stmt
-	updateTxnIDStmt *sql.Stmt
-}
-
-func (s *txnStatements) prepare(db *sql.DB, writer sqlutil.Writer) (err error) {
-	s.db = db
-	s.writer = writer
-	_, err = db.Exec(txnIDSchema)
-	if err != nil {
-		return
-	}
-
-	if s.selectTxnIDStmt, err = db.Prepare(selectTxnIDSQL); err != nil {
-		return
-	}
-
-	if s.updateTxnIDStmt, err = db.Prepare(updateTxnIDSQL); err != nil {
-		return
-	}
-
-	return
-}
-
-// selectTxnID selects the latest ascending transaction ID
-func (s *txnStatements) selectTxnID(
-	ctx context.Context,
-) (txnID int, err error) {
-	err = s.writer.Do(s.db, nil, func(txn *sql.Tx) error {
-		err := s.selectTxnIDStmt.QueryRowContext(ctx).Scan(&txnID)
-		if err != nil {
-			return err
-		}
-
-		_, err = s.updateTxnIDStmt.ExecContext(ctx)
-		return err
-	})
-	return
-}
diff --git a/appservice/storage/storage.go b/appservice/storage/storage.go
deleted file mode 100644
index 89d5e0cc..00000000
--- a/appservice/storage/storage.go
+++ /dev/null
@@ -1,40 +0,0 @@
-// 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.
-
-//go:build !wasm
-// +build !wasm
-
-package storage
-
-import (
-	"fmt"
-
-	"github.com/matrix-org/dendrite/appservice/storage/postgres"
-	"github.com/matrix-org/dendrite/appservice/storage/sqlite3"
-	"github.com/matrix-org/dendrite/setup/base"
-	"github.com/matrix-org/dendrite/setup/config"
-)
-
-// NewDatabase opens a new Postgres or Sqlite database (based on dataSourceName scheme)
-// and sets DB connection parameters
-func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions) (Database, error) {
-	switch {
-	case dbProperties.ConnectionString.IsSQLite():
-		return sqlite3.NewDatabase(base, dbProperties)
-	case dbProperties.ConnectionString.IsPostgres():
-		return postgres.NewDatabase(base, dbProperties)
-	default:
-		return nil, fmt.Errorf("unexpected database type")
-	}
-}
diff --git a/appservice/storage/storage_wasm.go b/appservice/storage/storage_wasm.go
deleted file mode 100644
index 23025459..00000000
--- a/appservice/storage/storage_wasm.go
+++ /dev/null
@@ -1,34 +0,0 @@
-// 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 storage
-
-import (
-	"fmt"
-
-	"github.com/matrix-org/dendrite/appservice/storage/sqlite3"
-	"github.com/matrix-org/dendrite/setup/base"
-	"github.com/matrix-org/dendrite/setup/config"
-)
-
-func NewDatabase(base *base.BaseDendrite, dbProperties *config.DatabaseOptions) (Database, error) {
-	switch {
-	case dbProperties.ConnectionString.IsSQLite():
-		return sqlite3.NewDatabase(base, dbProperties)
-	case dbProperties.ConnectionString.IsPostgres():
-		return nil, fmt.Errorf("can't use Postgres implementation")
-	default:
-		return nil, fmt.Errorf("unexpected database type")
-	}
-}
diff --git a/appservice/types/types.go b/appservice/types/types.go
deleted file mode 100644
index 098face6..00000000
--- a/appservice/types/types.go
+++ /dev/null
@@ -1,64 +0,0 @@
-// 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 types
-
-import (
-	"sync"
-
-	"github.com/matrix-org/dendrite/setup/config"
-)
-
-const (
-	// AppServiceDeviceID is the AS dummy device ID
-	AppServiceDeviceID = "AS_Device"
-)
-
-// ApplicationServiceWorkerState is a type that couples an application service,
-// a lockable condition as well as some other state variables, allowing the
-// roomserver to notify appservice workers when there are events ready to send
-// externally to application services.
-type ApplicationServiceWorkerState struct {
-	AppService config.ApplicationService
-	Cond       *sync.Cond
-	// Events ready to be sent
-	EventsReady bool
-	// Backoff exponent (2^x secs). Max 6, aka 64s.
-	Backoff int
-}
-
-// NotifyNewEvents wakes up all waiting goroutines, notifying that events remain
-// in the event queue for this application service worker.
-func (a *ApplicationServiceWorkerState) NotifyNewEvents() {
-	a.Cond.L.Lock()
-	a.EventsReady = true
-	a.Cond.Broadcast()
-	a.Cond.L.Unlock()
-}
-
-// FinishEventProcessing marks all events of this worker as being sent to the
-// application service.
-func (a *ApplicationServiceWorkerState) FinishEventProcessing() {
-	a.Cond.L.Lock()
-	a.EventsReady = false
-	a.Cond.L.Unlock()
-}
-
-// WaitForNewEvents causes the calling goroutine to wait on the worker state's
-// condition for a broadcast or similar wakeup, if there are no events ready.
-func (a *ApplicationServiceWorkerState) WaitForNewEvents() {
-	a.Cond.L.Lock()
-	if !a.EventsReady {
-		a.Cond.Wait()
-	}
-	a.Cond.L.Unlock()
-}
diff --git a/appservice/workers/transaction_scheduler.go b/appservice/workers/transaction_scheduler.go
deleted file mode 100644
index 4dab00bd..00000000
--- a/appservice/workers/transaction_scheduler.go
+++ /dev/null
@@ -1,236 +0,0 @@
-// Copyright 2018 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 workers
-
-import (
-	"bytes"
-	"context"
-	"encoding/json"
-	"fmt"
-	"math"
-	"net/http"
-	"net/url"
-	"time"
-
-	"github.com/matrix-org/dendrite/appservice/storage"
-	"github.com/matrix-org/dendrite/appservice/types"
-	"github.com/matrix-org/dendrite/setup/config"
-	"github.com/matrix-org/gomatrixserverlib"
-	log "github.com/sirupsen/logrus"
-)
-
-var (
-	// Maximum size of events sent in each transaction.
-	transactionBatchSize = 50
-)
-
-// SetupTransactionWorkers spawns a separate goroutine for each application
-// service. Each of these "workers" handle taking all events intended for their
-// app service, batch them up into a single transaction (up to a max transaction
-// size), then send that off to the AS's /transactions/{txnID} endpoint. It also
-// handles exponentially backing off in case the AS isn't currently available.
-func SetupTransactionWorkers(
-	client *http.Client,
-	appserviceDB storage.Database,
-	workerStates []types.ApplicationServiceWorkerState,
-) error {
-	// Create a worker that handles transmitting events to a single homeserver
-	for _, workerState := range workerStates {
-		// Don't create a worker if this AS doesn't want to receive events
-		if workerState.AppService.URL != "" {
-			go worker(client, appserviceDB, workerState)
-		}
-	}
-	return nil
-}
-
-// worker is a goroutine that sends any queued events to the application service
-// it is given.
-func worker(client *http.Client, db storage.Database, ws types.ApplicationServiceWorkerState) {
-	log.WithFields(log.Fields{
-		"appservice": ws.AppService.ID,
-	}).Info("Starting application service")
-	ctx := context.Background()
-
-	// Initial check for any leftover events to send from last time
-	eventCount, err := db.CountEventsWithAppServiceID(ctx, ws.AppService.ID)
-	if err != nil {
-		log.WithFields(log.Fields{
-			"appservice": ws.AppService.ID,
-		}).WithError(err).Fatal("appservice worker unable to read queued events from DB")
-		return
-	}
-	if eventCount > 0 {
-		ws.NotifyNewEvents()
-	}
-
-	// Loop forever and keep waiting for more events to send
-	for {
-		// Wait for more events if we've sent all the events in the database
-		ws.WaitForNewEvents()
-
-		// Batch events up into a transaction
-		transactionJSON, txnID, maxEventID, eventsRemaining, err := createTransaction(ctx, db, ws.AppService.ID)
-		if err != nil {
-			log.WithFields(log.Fields{
-				"appservice": ws.AppService.ID,
-			}).WithError(err).Fatal("appservice worker unable to create transaction")
-
-			return
-		}
-
-		// Send the events off to the application service
-		// Backoff if the application service does not respond
-		err = send(client, ws.AppService, txnID, transactionJSON)
-		if err != nil {
-			log.WithFields(log.Fields{
-				"appservice": ws.AppService.ID,
-			}).WithError(err).Error("unable to send event")
-			// Backoff
-			backoff(&ws, err)
-			continue
-		}
-
-		// We sent successfully, hooray!
-		ws.Backoff = 0
-
-		// Transactions have a maximum event size, so there may still be some events
-		// left over to send. Keep sending until none are left
-		if !eventsRemaining {
-			ws.FinishEventProcessing()
-		}
-
-		// Remove sent events from the DB
-		err = db.RemoveEventsBeforeAndIncludingID(ctx, ws.AppService.ID, maxEventID)
-		if err != nil {
-			log.WithFields(log.Fields{
-				"appservice": ws.AppService.ID,
-			}).WithError(err).Fatal("unable to remove appservice events from the database")
-			return
-		}
-	}
-}
-
-// backoff pauses the calling goroutine for a 2^some backoff exponent seconds
-func backoff(ws *types.ApplicationServiceWorkerState, err error) {
-	// Calculate how long to backoff for
-	backoffDuration := time.Duration(math.Pow(2, float64(ws.Backoff)))
-	backoffSeconds := time.Second * backoffDuration
-
-	log.WithFields(log.Fields{
-		"appservice": ws.AppService.ID,
-	}).WithError(err).Warnf("unable to send transactions successfully, backing off for %ds",
-		backoffDuration)
-
-	ws.Backoff++
-	if ws.Backoff > 6 {
-		ws.Backoff = 6
-	}
-
-	// Backoff
-	time.Sleep(backoffSeconds)
-}
-
-// createTransaction takes in a slice of AS events, stores them in an AS
-// transaction, and JSON-encodes the results.
-func createTransaction(
-	ctx context.Context,
-	db storage.Database,
-	appserviceID string,
-) (
-	transactionJSON []byte,
-	txnID, maxID int,
-	eventsRemaining bool,
-	err error,
-) {
-	// Retrieve the latest events from the DB (will return old events if they weren't successfully sent)
-	txnID, maxID, events, eventsRemaining, err := db.GetEventsWithAppServiceID(ctx, appserviceID, transactionBatchSize)
-	if err != nil {
-		log.WithFields(log.Fields{
-			"appservice": appserviceID,
-		}).WithError(err).Fatalf("appservice worker unable to read queued events from DB")
-
-		return
-	}
-
-	// Check if these events do not already have a transaction ID
-	if txnID == -1 {
-		// If not, grab next available ID from the DB
-		txnID, err = db.GetLatestTxnID(ctx)
-		if err != nil {
-			return nil, 0, 0, false, err
-		}
-
-		// Mark new events with current transactionID
-		if err = db.UpdateTxnIDForEvents(ctx, appserviceID, maxID, txnID); err != nil {
-			return nil, 0, 0, false, err
-		}
-	}
-
-	var ev []*gomatrixserverlib.HeaderedEvent
-	for i := range events {
-		ev = append(ev, &events[i])
-	}
-
-	// Create a transaction and store the events inside
-	transaction := gomatrixserverlib.ApplicationServiceTransaction{
-		Events: gomatrixserverlib.HeaderedToClientEvents(ev, gomatrixserverlib.FormatAll),
-	}
-
-	transactionJSON, err = json.Marshal(transaction)
-	if err != nil {
-		return
-	}
-
-	return
-}
-
-// send sends events to an application service. Returns an error if an OK was not
-// received back from the application service or the request timed out.
-func send(
-	client *http.Client,
-	appservice config.ApplicationService,
-	txnID int,
-	transaction []byte,
-) (err error) {
-	// PUT a transaction to our AS
-	// https://matrix.org/docs/spec/application_service/r0.1.2#put-matrix-app-v1-transactions-txnid
-	address := fmt.Sprintf("%s/transactions/%d?access_token=%s", appservice.URL, txnID, url.QueryEscape(appservice.HSToken))
-	req, err := http.NewRequest("PUT", address, bytes.NewBuffer(transaction))
-	if err != nil {
-		return err
-	}
-	req.Header.Set("Content-Type", "application/json")
-	resp, err := client.Do(req)
-	if err != nil {
-		return err
-	}
-	defer checkNamedErr(resp.Body.Close, &err)
-
-	// Check the AS received the events correctly
-	if resp.StatusCode != http.StatusOK {
-		// TODO: Handle non-200 error codes from application services
-		return fmt.Errorf("non-OK status code %d returned from AS", resp.StatusCode)
-	}
-
-	return nil
-}
-
-// checkNamedErr calls fn and overwrite err if it was nil and fn returned non-nil
-func checkNamedErr(fn func() error, err *error) {
-	if e := fn(); e != nil && *err == nil {
-		*err = e
-	}
-}