WIP Third Party Protocol Definition Lookup

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

@@ -27,6 +27,7 @@ import (
 	"github.com/matrix-org/dendrite/clientapi/auth/storage/accounts"
 	"github.com/matrix-org/gomatrixserverlib"
 
+	"github.com/matrix-org/dendrite/appservice/types"
 	commonHTTP "github.com/matrix-org/dendrite/common/http"
 	opentracing "github.com/opentracing/opentracing-go"
 )
@@ -65,6 +66,29 @@ type UserIDExistsResponse struct {
 	UserIDExists bool `json:"exists"`
 }
 
+// GetProtocolDefinitionRequest is a request to the appservice component asking
+// for the definition of a single third party protocol
+type GetProtocolDefinitionRequest struct {
+	ProtocolID string `json:"protocol_definition"`
+}
+
+// GetProtocolDefinitionResponse is a response providing a protocol definition
+// for the given protocol ID
+type GetProtocolDefinitionResponse struct {
+	ProtocolDefinition string `json:"protocol_definition"`
+}
+
+// GetAllProtocolDefinitionsRequest is a request to the appservice component
+// asking for what third party protocols are known and their definitions
+type GetAllProtocolDefinitionsRequest struct {
+}
+
+// GetAllProtocolDefinitionsResponse is a response containing all known third
+// party IDs and their definitions
+type GetAllProtocolDefinitionsResponse struct {
+	Protocols types.ThirdPartyProtocols `json:"protocols"`
+}
+
 // AppServiceQueryAPI is used to query user and room alias data from application
 // services
 type AppServiceQueryAPI interface {
@@ -80,10 +104,28 @@ type AppServiceQueryAPI interface {
 		req *UserIDExistsRequest,
 		resp *UserIDExistsResponse,
 	) error
+	// Get the definition of a given single third party protocol
+	GetProtocolDefinition(
+		ctx context.Context,
+		req *GetProtocolDefinitionRequest,
+		response *GetProtocolDefinitionResponse,
+	) error
+	// Get the definition of all known third party protocols
+	GetAllProtocolDefinitions(
+		ctx context.Context,
+		req *GetAllProtocolDefinitionsRequest,
+		response *GetAllProtocolDefinitionsResponse,
+	) error
 }
 
-// AppServiceRoomAliasExistsPath is the HTTP path for the RoomAliasExists API
-const AppServiceRoomAliasExistsPath = "/api/appservice/RoomAliasExists"
+// RoomAliasExistsPath is the HTTP path for the RoomAliasExists API
+const RoomAliasExistsPath = "/api/appservice/RoomAliasExists"
+
+// GetProtocolDefinitionPath is the HTTP path for the GetProtocolDefinition API
+const GetProtocolDefinitionPath = "/api/appservice/GetProtocolDefinition"
+
+// GetAllProtocolDefinitionsPath is the HTTP path for the GetAllProtocolDefinitions API
+const GetAllProtocolDefinitionsPath = "/api/appservice/GetAllProtocolDefinitions"
 
 // AppServiceUserIDExistsPath is the HTTP path for the UserIDExists API
 const AppServiceUserIDExistsPath = "/api/appservice/UserIDExists"
@@ -117,7 +159,33 @@ func (h *httpAppServiceQueryAPI) RoomAliasExists(
 	span, ctx := opentracing.StartSpanFromContext(ctx, "appserviceRoomAliasExists")
 	defer span.Finish()
 
-	apiURL := h.appserviceURL + AppServiceRoomAliasExistsPath
+	apiURL := h.appserviceURL + RoomAliasExistsPath
+	return commonHTTP.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+}
+
+// GetProtocolDefinition implements AppServiceQueryAPI
+func (h *httpAppServiceQueryAPI) GetProtocolDefinition(
+	ctx context.Context,
+	request *GetProtocolDefinitionRequest,
+	response *GetProtocolDefinitionResponse,
+) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "appserviceGetProtocolDefinition")
+	defer span.Finish()
+
+	apiURL := h.appserviceURL + GetProtocolDefinitionPath
+	return commonHTTP.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
+}
+
+// GetAllProtocolDefinitions implements AppServiceQueryAPI
+func (h *httpAppServiceQueryAPI) GetAllProtocolDefinitions(
+	ctx context.Context,
+	request *GetAllProtocolDefinitionsRequest,
+	response *GetAllProtocolDefinitionsResponse,
+) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "appserviceGetAllProtocolDefinitions")
+	defer span.Finish()
+
+	apiURL := h.appserviceURL + GetAllProtocolDefinitionsPath
 	return commonHTTP.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
 }
 

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

@@ -18,7 +18,6 @@ import (
 	"context"
 	"net/http"
 	"sync"
-	"time"
 
 	appserviceAPI "github.com/matrix-org/dendrite/appservice/api"
 	"github.com/matrix-org/dendrite/appservice/consumers"
@@ -34,7 +33,7 @@ import (
 	"github.com/matrix-org/dendrite/common/transactions"
 	roomserverAPI "github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/gomatrixserverlib"
-	"github.com/sirupsen/logrus"
+	log "github.com/sirupsen/logrus"
 )
 
 // SetupAppServiceAPIComponent sets up and registers HTTP handlers for the AppServices
@@ -51,7 +50,7 @@ func SetupAppServiceAPIComponent(
 	// Create a connection to the appservice postgres DB
 	appserviceDB, err := storage.NewDatabase(string(base.Cfg.Database.AppService))
 	if err != nil {
-		logrus.WithError(err).Panicf("failed to connect to appservice db")
+		log.WithError(err).Panicf("failed to connect to appservice db")
 	}
 
 	// Wrap application services in a type that relates the application service and
@@ -68,7 +67,7 @@ func SetupAppServiceAPIComponent(
 
 		// Create bot account for this AS if it doesn't already exist
 		if err = generateAppServiceAccount(accountsDB, deviceDB, appservice); err != nil {
-			logrus.WithFields(logrus.Fields{
+			log.WithFields(log.Fields{
 				"appservice": appservice.ID,
 			}).WithError(err).Panicf("failed to generate bot account for appservice")
 		}
@@ -77,10 +76,8 @@ func SetupAppServiceAPIComponent(
 	// 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: &http.Client{
-			Timeout: time.Second * 30,
-		},
 		Cfg: base.Cfg,
+		Db:  appserviceDB,
 	}
 
 	appserviceQueryAPI.SetupHTTP(http.DefaultServeMux)
@@ -90,13 +87,11 @@ func SetupAppServiceAPIComponent(
 		roomserverQueryAPI, roomserverAliasAPI, workerStates,
 	)
 	if err := consumer.Start(); err != nil {
-		logrus.WithError(err).Panicf("failed to start appservice roomserver consumer")
+		log.WithError(err).Panicf("failed to start app service roomserver consumer")
 	}
 
-	// Create application service transaction workers
-	if err := workers.SetupTransactionWorkers(appserviceDB, workerStates); err != nil {
-		logrus.WithError(err).Panicf("failed to start app service transaction workers")
-	}
+	// Create application service transaction and third party workers
+	setupWorkers(appserviceDB, workerStates)
 
 	// Set up HTTP Endpoints
 	routing.Setup(
@@ -130,3 +125,29 @@ func generateAppServiceAccount(
 	_, err = deviceDB.CreateDevice(ctx, as.SenderLocalpart, nil, as.ASToken, &as.SenderLocalpart)
 	return err
 }
+
+// setupWorkers creates worker goroutines that each interface with a connected
+// application service.
+func setupWorkers(
+	appserviceDB *storage.Database,
+	workerStates []types.ApplicationServiceWorkerState,
+) {
+	// Clear all old protocol definitions on startup
+	appserviceDB.ClearProtocolDefinitions(context.TODO())
+
+	// Create a worker that handles transmitting events to a single homeserver
+	for _, workerState := range workerStates {
+		log.WithFields(log.Fields{
+			"appservice": workerState.AppService.ID,
+		}).Info("starting application service")
+
+		// Don't create a worker if this AS doesn't want to receive events
+		if workerState.AppService.URL != "" {
+			// Worker to handle sending event transactions
+			go workers.TransactionWorker(appserviceDB, workerState)
+
+			// Worker to handle retreiving information about third parties
+			go workers.ThirdPartyWorker(appserviceDB, workerState.AppService)
+		}
+	}
+}

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

@@ -24,6 +24,7 @@ import (
 	"time"
 
 	"github.com/matrix-org/dendrite/appservice/api"
+	"github.com/matrix-org/dendrite/appservice/storage"
 	"github.com/matrix-org/dendrite/common"
 	"github.com/matrix-org/dendrite/common/config"
 	"github.com/matrix-org/util"
@@ -38,6 +39,45 @@ const userIDExistsPath = "/users/"
 type AppServiceQueryAPI struct {
 	HTTPClient *http.Client
 	Cfg        *config.Dendrite
+	Db         *storage.Database
+}
+
+// GetProtocolDefinition queries the database for the protocol definition of a
+// protocol with given ID
+func (a *AppServiceQueryAPI) GetProtocolDefinition(
+	ctx context.Context,
+	request *api.GetProtocolDefinitionRequest,
+	response *api.GetProtocolDefinitionResponse,
+) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "ApplicationServiceGetProtocolDefinition")
+	defer span.Finish()
+
+	protocolDefinition, err := a.Db.GetProtocolDefinition(ctx, request.ProtocolID)
+	if err != nil {
+		return err
+	}
+
+	response.ProtocolDefinition = protocolDefinition
+	return nil
+}
+
+// GetAllProtocolDefinitions queries the database for all known protocol
+// definitions and their IDs
+func (a *AppServiceQueryAPI) GetAllProtocolDefinitions(
+	ctx context.Context,
+	request *api.GetAllProtocolDefinitionsRequest,
+	response *api.GetAllProtocolDefinitionsResponse,
+) error {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "ApplicationServiceGetAllProtocolDefinitions")
+	defer span.Finish()
+
+	protocolDefinitions, err := a.Db.GetAllProtocolDefinitions(ctx)
+	if err != nil {
+		return err
+	}
+
+	response.Protocols = protocolDefinitions
+	return nil
 }
 
 // RoomAliasExists performs a request to '/room/{roomAlias}' on all known
@@ -184,7 +224,7 @@ func makeHTTPClient() *http.Client {
 // handles and muxes incoming api requests the to internal AppServiceQueryAPI.
 func (a *AppServiceQueryAPI) SetupHTTP(servMux *http.ServeMux) {
 	servMux.Handle(
-		api.AppServiceRoomAliasExistsPath,
+		api.RoomAliasExistsPath,
 		common.MakeInternalAPI("appserviceRoomAliasExists", func(req *http.Request) util.JSONResponse {
 			var request api.RoomAliasExistsRequest
 			var response api.RoomAliasExistsResponse
@@ -211,4 +251,32 @@ func (a *AppServiceQueryAPI) SetupHTTP(servMux *http.ServeMux) {
 			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
 		}),
 	)
+	servMux.Handle(
+		api.GetProtocolDefinitionPath,
+		common.MakeInternalAPI("appserviceGetProtocolDefinition", func(req *http.Request) util.JSONResponse {
+			var request api.GetProtocolDefinitionRequest
+			var response api.GetProtocolDefinitionResponse
+			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
+				return util.ErrorResponse(err)
+			}
+			if err := a.GetProtocolDefinition(req.Context(), &request, &response); err != nil {
+				return util.ErrorResponse(err)
+			}
+			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
+		}),
+	)
+	servMux.Handle(
+		api.GetAllProtocolDefinitionsPath,
+		common.MakeInternalAPI("appserviceGetAllProtocolDefinitions", func(req *http.Request) util.JSONResponse {
+			var request api.GetAllProtocolDefinitionsRequest
+			var response api.GetAllProtocolDefinitionsResponse
+			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
+				return util.ErrorResponse(err)
+			}
+			if err := a.GetAllProtocolDefinitions(req.Context(), &request, &response); err != nil {
+				return util.ErrorResponse(err)
+			}
+			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
+		}),
+	)
 }

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

@@ -20,14 +20,16 @@ import (
 
 	// Import postgres database driver
 	_ "github.com/lib/pq"
+	"github.com/matrix-org/dendrite/appservice/types"
 	"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
+	events     eventsStatements
+	txnID      txnStatements
+	thirdparty thirdPartyStatements
+	db         *sql.DB
 }
 
 // NewDatabase opens a new database
@@ -48,6 +50,10 @@ func (d *Database) prepare() error {
 		return err
 	}
 
+	if err := d.thirdparty.prepare(d.db); err != nil {
+		return err
+	}
+
 	return d.txnID.prepare(d.db)
 }
 
@@ -108,3 +114,36 @@ func (d *Database) GetLatestTxnID(
 ) (int, error) {
 	return d.txnID.selectTxnID(ctx)
 }
+
+// GetProtocolDefinition retreives a JSON-encoded protocol definition given a
+// protocol ID
+func (d *Database) GetProtocolDefinition(
+	ctx context.Context,
+	protocolID string,
+) (string, error) {
+	return d.thirdparty.selectProtocolDefinition(ctx, protocolID)
+}
+
+// GetAllProtocolDefinitions retrieves a map of all known third party protocols
+func (d *Database) GetAllProtocolDefinitions(
+	ctx context.Context,
+) (types.ThirdPartyProtocols, error) {
+	return d.thirdparty.selectAllProtocolDefinitions(ctx)
+}
+
+// StoreProtocolDefinition stores a protocol and its definition
+func (d *Database) StoreProtocolDefinition(
+	ctx context.Context,
+	protocolID, protocolDefinition string,
+) error {
+	return d.thirdparty.insertProtocolDefinition(ctx, protocolID, protocolDefinition)
+}
+
+// ClearProtocolDefinition clears all protocol definition entries in the
+// database. This is done on each startup to wipe old protocol definitions from
+// previous application services.
+func (d *Database) ClearProtocolDefinitions(
+	ctx context.Context,
+) error {
+	return d.thirdparty.clearProtocolDefinitions(ctx)
+}

src/github.com/matrix-org/dendrite/appservice/storage/third_party_table.go

@@ -0,0 +1,151 @@
+// Copyright 2018 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 storage
+
+import (
+	"context"
+	"database/sql"
+
+	"github.com/matrix-org/dendrite/appservice/types"
+	"github.com/matrix-org/gomatrixserverlib"
+	log "github.com/sirupsen/logrus"
+)
+
+const thirdPartySchema = `
+-- Stores protocol definitions for clients to later request
+CREATE TABLE IF NOT EXISTS appservice_third_party_protocol_def (
+	-- The ID of the procotol
+	protocol_id TEXT NOT NULL PRIMARY KEY,
+	-- The JSON-encoded protocol definition
+	protocol_definition TEXT NOT NULL,
+	UNIQUE(protocol_id)
+);
+
+CREATE INDEX IF NOT EXISTS appservice_third_party_protocol_def_id
+ON appservice_third_party_protocol_def(protocol_id);
+`
+
+const selectProtocolDefinitionSQL = "" +
+	"SELECT protocol_definition FROM appservice_third_party_protocol_def " +
+	"WHERE protocol_id = $1"
+
+const selectAllProtocolDefinitionsSQL = "" +
+	"SELECT protocol_id, protocol_definition FROM appservice_third_party_protocol_def"
+
+const insertProtocolDefinitionSQL = "" +
+	"INSERT INTO appservice_third_party_protocol_def(protocol_id, protocol_definition) " +
+	"VALUES ($1, $2)"
+
+const clearProtocolDefinitionsSQL = "" +
+	"TRUNCATE appservice_third_party_protocol_def"
+
+type thirdPartyStatements struct {
+	selectProtocolDefinitionStmt     *sql.Stmt
+	selectAllProtocolDefinitionsStmt *sql.Stmt
+	insertProtocolDefinitionStmt     *sql.Stmt
+	clearProtocolDefinitionsStmt     *sql.Stmt
+}
+
+func (s *thirdPartyStatements) prepare(db *sql.DB) (err error) {
+	_, err = db.Exec(thirdPartySchema)
+	if err != nil {
+		return
+	}
+
+	if s.selectProtocolDefinitionStmt, err = db.Prepare(selectProtocolDefinitionSQL); err != nil {
+		return
+	}
+
+	if s.selectAllProtocolDefinitionsStmt, err = db.Prepare(selectAllProtocolDefinitionsSQL); err != nil {
+		return
+	}
+
+	if s.insertProtocolDefinitionStmt, err = db.Prepare(insertProtocolDefinitionSQL); err != nil {
+		return
+	}
+
+	if s.clearProtocolDefinitionsStmt, err = db.Prepare(clearProtocolDefinitionsSQL); err != nil {
+		return
+	}
+
+	return
+}
+
+// selectProtocolDefinition returns a single protocol definition for a given ID.
+// Returns an empty string if the ID was not found.
+func (s *thirdPartyStatements) selectProtocolDefinition(
+	ctx context.Context,
+	protocolID string,
+) (protocolDefinition string, err error) {
+	err = s.selectProtocolDefinitionStmt.QueryRowContext(
+		ctx, protocolID,
+	).Scan(&protocolDefinition)
+
+	if err != nil && err != sql.ErrNoRows {
+		return "", err
+	}
+
+	return
+}
+
+// selectAllProtocolDefinitions returns all protcol IDs and definitions in the
+// database. Returns an empty map if no definitions were found.
+func (s *thirdPartyStatements) selectAllProtocolDefinitions(
+	ctx context.Context,
+) (protocols types.ThirdPartyProtocols, err error) {
+	protocolDefinitionRows, err := s.selectAllProtocolDefinitionsStmt.QueryContext(ctx)
+	if err != nil && err != sql.ErrNoRows {
+		return
+	}
+	defer func() {
+		err = protocolDefinitionRows.Close()
+		if err != nil {
+			log.WithError(err).Fatalf("unable to close protocol definitions")
+		}
+	}()
+
+	for protocolDefinitionRows.Next() {
+		var protocolID, protocolDefinition string
+		if err = protocolDefinitionRows.Scan(&protocolID, &protocolDefinition); err != nil {
+			return nil, err
+		}
+
+		protocols[protocolID] = gomatrixserverlib.RawJSON(protocolDefinition)
+	}
+
+	return protocols, nil
+}
+
+// insertProtocolDefinition inserts a protocol ID along with its definition in
+// order for clients to later retreive it from the client-server API.
+func (s *thirdPartyStatements) insertProtocolDefinition(
+	ctx context.Context,
+	protocolID, protocolDefinition string,
+) (err error) {
+	_, err = s.insertProtocolDefinitionStmt.ExecContext(
+		ctx,
+		protocolID,
+		protocolDefinition,
+	)
+	return
+}
+
+// clearProtocolDefinitions removes all protocol definitions from the database.
+func (s *thirdPartyStatements) clearProtocolDefinitions(
+	ctx context.Context,
+) (err error) {
+	_, err = s.clearProtocolDefinitionsStmt.ExecContext(ctx)
+	return
+}

src/github.com/matrix-org/dendrite/appservice/types/third_party.go

@@ -0,0 +1,23 @@
+// Copyright 2018 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 types
+
+import (
+	"github.com/matrix-org/gomatrixserverlib"
+)
+
+// ThirdPartyProtocols is a map of all third party protocols supported by
+// connected application services.
+type ThirdPartyProtocols map[string]gomatrixserverlib.RawJSON

src/github.com/matrix-org/dendrite/appservice/workers/third_party.go

@@ -0,0 +1,151 @@
+// 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 (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"io/ioutil"
+	"math"
+	"net/http"
+	"time"
+
+	"github.com/matrix-org/dendrite/appservice/storage"
+	"github.com/matrix-org/dendrite/common/config"
+	log "github.com/sirupsen/logrus"
+)
+
+const (
+	// Timeout for requests to an application service to complete
+	requestTimeout = time.Second * 300
+)
+
+const protocolPath = "/_matrix/app/unstable/thirdparty/protocol/"
+
+// ThirdPartyWorker interfaces with a given application service on third party
+// network related information.
+// At the moment it simply asks for information on protocols that an application
+// service supports, then exits.
+func ThirdPartyWorker(
+	db *storage.Database,
+	appservice config.ApplicationService,
+) {
+	ctx := context.Background()
+
+	// Grab the HTTP client for sending requests to app services
+	client := &http.Client{
+		Timeout: requestTimeout,
+		// TODO: Verify certificates
+		Transport: &http.Transport{
+			TLSClientConfig: &tls.Config{
+				InsecureSkipVerify: true, // nolint: gas
+			},
+		},
+	}
+
+	backoffCount := 0
+
+	// Retrieve protocol information from the application service
+	for i := 0; i < len(appservice.Protocols); i++ {
+		protocolID := appservice.Protocols[i]
+		protocolDefinition, err := retreiveProtocolInformation(
+			ctx, client, appservice, protocolID,
+		)
+		if err != nil {
+			log.WithFields(log.Fields{
+				"appservice":       appservice.ID,
+				"backoff_exponent": backoffCount,
+			}).WithError(err).Warn("error contacting appservice thirdparty endpoints")
+
+			// Backoff before contacting again
+			backoff(&backoffCount)
+
+			// Try this protocol again
+			i--
+			continue
+		}
+
+		// Cache protocol definition for clients to request later
+		storeProtocolDefinition(ctx, db, appservice, protocolID, protocolDefinition)
+	}
+}
+
+// backoff for the request amount of 2^number seconds
+// We want to support a few different use cases. Application services that don't
+// implement these endpoints and thus will always return an error. Application
+// services that are not currently up when Dendrite starts. Application services
+// that are broken for a while but will come back online later.
+// We can support all of these without being too resource intensive with
+// exponential backoff.
+func backoff(exponent *int) {
+	// Calculate how long to backoff for
+	backoffDuration := time.Duration(math.Pow(2, float64(*exponent)))
+	backoffSeconds := time.Second * backoffDuration
+
+	if *exponent < 6 {
+		*exponent++
+	}
+
+	// Backoff
+	time.Sleep(backoffSeconds)
+}
+
+// retreiveProtocolInformation contacts an application service and asks for
+// information about a given protocol.
+func retreiveProtocolInformation(
+	ctx context.Context,
+	httpClient *http.Client,
+	appservice config.ApplicationService,
+	protocol string,
+) (string, error) {
+	// Create a request to the application service
+	requestURL := appservice.URL + protocolPath + protocol
+	req, err := http.NewRequest(http.MethodGet, requestURL, nil)
+	if err != nil {
+		return "", err
+	}
+
+	// Perform the request
+	resp, err := httpClient.Do(req.WithContext(ctx))
+	if err != nil {
+		return "", err
+	}
+
+	// Check that the request was successful
+	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)
+	}
+
+	// Read the response body
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return "", err
+	}
+
+	return string(body), nil
+}
+
+// storeProtocolDefinition stores a protocol definition along with the protocol
+// ID in the database
+func storeProtocolDefinition(
+	ctx context.Context,
+	db *storage.Database,
+	appservice config.ApplicationService,
+	protocolID, protocolDefinition string,
+) error {
+	return db.StoreProtocolDefinition(ctx, protocolID, protocolDefinition)
+}

src/github.com/matrix-org/dendrite/appservice/workers/transaction_scheduler.go

@@ -19,7 +19,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"math"
 	"net/http"
 	"time"
 
@@ -30,38 +29,19 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
-var (
+const (
 	// Maximum size of events sent in each transaction.
 	transactionBatchSize = 50
 	// Timeout for sending a single transaction to an application service.
 	transactionTimeout = time.Second * 60
 )
 
-// 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
+// TransactionWorker is a goroutine that sends any queued events to the application service
+// it is given. Each worker handles 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(
-	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(appserviceDB, workerState)
-		}
-	}
-	return nil
-}
-
-// worker is a goroutine that sends any queued events to the application service
-// it is given.
-func worker(db *storage.Database, ws types.ApplicationServiceWorkerState) {
-	log.WithFields(log.Fields{
-		"appservice": ws.AppService.ID,
-	}).Info("starting application service")
+func TransactionWorker(db *storage.Database, ws types.ApplicationServiceWorkerState) {
 	ctx := context.Background()
 
 	// Create a HTTP client for sending requests to app services
@@ -100,8 +80,13 @@ func worker(db *storage.Database, ws types.ApplicationServiceWorkerState) {
 		// 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,
+				"backoff_exponent": ws.Backoff,
+			}).WithError(err).Warnf("unable to send transactions successfully, backing off")
+
 			// Backoff
-			backoff(&ws, err)
+			backoff(&ws.Backoff)
 			continue
 		}
 
@@ -125,26 +110,6 @@ func worker(db *storage.Database, ws types.ApplicationServiceWorkerState) {
 	}
 }
 
-// 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(

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

@@ -388,6 +388,20 @@ func Setup(
 		}),
 	).Methods(http.MethodPut, http.MethodOptions)
 
+	// Third party lookups
+	r0mux.Handle("/thirdparty/protocol/{protocolID}",
+		common.MakeExternalAPI("get_protocols", func(req *http.Request) util.JSONResponse {
+			vars := mux.Vars(req)
+			return GetThirdPartyProtocol(req, asAPI, vars["protocolID"])
+		}),
+	).Methods(http.MethodGet, http.MethodOptions)
+
+	r0mux.Handle("/thirdparty/protocols",
+		common.MakeExternalAPI("get_protocols", func(req *http.Request) util.JSONResponse {
+			return GetThirdPartyProtocols(req, asAPI)
+		}),
+	).Methods(http.MethodGet, http.MethodOptions)
+
 	// Stub implementations for sytest
 	r0mux.Handle("/events",
 		common.MakeExternalAPI("events", func(req *http.Request) util.JSONResponse {

src/github.com/matrix-org/dendrite/clientapi/routing/third_party.go

@@ -0,0 +1,74 @@
+// 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 routing
+
+import (
+	"encoding/json"
+	"net/http"
+
+	appserviceAPI "github.com/matrix-org/dendrite/appservice/api"
+	"github.com/matrix-org/dendrite/clientapi/httputil"
+	"github.com/matrix-org/util"
+)
+
+// GetThirdPartyProtocol returns the protocol definition of a single, given
+// protocol ID
+func GetThirdPartyProtocol(
+	req *http.Request,
+	asAPI appserviceAPI.AppServiceQueryAPI,
+	protocolID string,
+) util.JSONResponse {
+	// Retrieve a single protocol definition from the appservice component
+	queryReq := appserviceAPI.GetProtocolDefinitionRequest{
+		ProtocolID: protocolID,
+	}
+	var queryRes appserviceAPI.GetProtocolDefinitionResponse
+	if err := asAPI.GetProtocolDefinition(req.Context(), &queryReq, &queryRes); err != nil {
+		return httputil.LogThenError(req, err)
+	}
+
+	return util.JSONResponse{
+		Code: http.StatusOK,
+		JSON: queryRes.ProtocolDefinition,
+	}
+}
+
+// GetThirdPartyProtocols returns all known third party protocols provided by
+// application services connected to this homeserver
+func GetThirdPartyProtocols(
+	req *http.Request,
+	asAPI appserviceAPI.AppServiceQueryAPI,
+) util.JSONResponse {
+	// Retrieve all known protocols from appservice component
+	queryReq := appserviceAPI.GetAllProtocolDefinitionsRequest{}
+	var queryRes appserviceAPI.GetAllProtocolDefinitionsResponse
+	if err := asAPI.GetAllProtocolDefinitions(req.Context(), &queryReq, &queryRes); err != nil {
+		return httputil.LogThenError(req, err)
+	}
+
+	// TODO: Check what we get if no protocols defined by anyone
+
+	// Marshal protocols to JSON
+	protocolJSON, err := json.Marshal(queryRes.Protocols)
+	if err != nil {
+		return httputil.LogThenError(req, err)
+	}
+
+	// Return protocol IDs along with definitions
+	return util.JSONResponse{
+		Code: http.StatusOK,
+		JSON: protocolJSON,
+	}
+}

src/github.com/matrix-org/dendrite/common/config/appservice.go

@@ -221,6 +221,7 @@ func appendExclusiveNamespaceRegexs(
 func checkErrors(config *Dendrite) (err error) {
 	var idMap = make(map[string]bool)
 	var tokenMap = make(map[string]bool)
+	var protocolMap = make(map[string]bool)
 
 	// Compile regexp object for checking groupIDs
 	groupIDRegexp := regexp.MustCompile(`\+.*:.*`)
@@ -238,39 +239,56 @@ func checkErrors(config *Dendrite) (err error) {
 
 		// Check if the url has trailing /'s. If so, remove them
 		appservice.URL = strings.TrimRight(appservice.URL, "/")
-
-		// Check if we've already seen this ID. No two application services
-		// can have the same ID or token.
-		if idMap[appservice.ID] {
-			return configErrors([]string{fmt.Sprintf(
-				"Application service ID %s must be unique", appservice.ID,
-			)})
+		if err = duplicationCheck(appservice, &idMap, &tokenMap, &protocolMap); err != nil {
+			return err
 		}
-		// Check if we've already seen this token
-		if tokenMap[appservice.ASToken] {
-			return configErrors([]string{fmt.Sprintf(
-				"Application service Token %s must be unique", appservice.ASToken,
-			)})
-		}
-
-		// Add the id/token to their respective maps if we haven't already
-		// seen them.
-		idMap[appservice.ID] = true
-		tokenMap[appservice.ASToken] = true
 
 		// TODO: Remove once rate_limited is implemented
 		if appservice.RateLimited {
-			log.Warn("WARNING: Application service option rate_limited is currently unimplemented")
-		}
-		// TODO: Remove once protocols is implemented
-		if len(appservice.Protocols) > 0 {
-			log.Warn("WARNING: Application service option protocols is currently unimplemented")
+			log.Warn("WARNING: Application service option 'rate_limited' is currently unimplemented")
 		}
 	}
 
 	return setupRegexps(config)
 }
 
+// duplicationCheck returns an error if any application service configuration
+// entries that are supposed to be unique appear than once.
+func duplicationCheck(appservice ApplicationService, idMap, tokenMap, protocolMap *map[string]bool) error {
+	// Check if we've already seen this ID. No two application services
+	// can have the same ID or token.
+	if (*idMap)[appservice.ID] {
+		return configErrors([]string{fmt.Sprintf(
+			"Application service ID '%s' must be unique", appservice.ID,
+		)})
+	}
+	// Check if we've already seen this token
+	if (*tokenMap)[appservice.ASToken] {
+		return configErrors([]string{fmt.Sprintf(
+			"Application service token '%s' must be unique", appservice.ASToken,
+		)})
+	}
+
+	// Add the id/token to their respective maps if we haven't already
+	// seen them.
+	(*idMap)[appservice.ID] = true
+	(*tokenMap)[appservice.ASToken] = true
+
+	// Check if any application services are already handling this protocol
+	for _, protocol := range appservice.Protocols {
+		if (*protocolMap)[protocol] {
+			return configErrors([]string{fmt.Sprintf(
+				"Application service protocol '%s' must be unique", protocol,
+			)})
+		}
+
+		// Add the protocol to the map of seen protocols
+		(*protocolMap)[protocol] = true
+	}
+
+	return nil
+}
+
 // validateNamespace returns nil or an error based on whether a given
 // application service namespace is valid. A namespace is valid if it has the
 // required fields, and its regex is correct.
@@ -290,12 +308,12 @@ func validateNamespace(
 	// Check if GroupID for the users namespace is in the correct format
 	if key == "users" && namespace.GroupID != "" {
 		// TODO: Remove once group_id is implemented
-		log.Warn("WARNING: Application service option group_id is currently unimplemented")
+		log.Warn("WARNING: Application service option 'group_id' is currently unimplemented")
 
 		correctFormat := groupIDRegexp.MatchString(namespace.GroupID)
 		if !correctFormat {
 			return configErrors([]string{fmt.Sprintf(
-				"Invalid user group_id field for application service %s.",
+				"Invalid user 'group_id' field for application service %s.",
 				appservice.ID,
 			)})
 		}