Add a new component: currentstateserver (#1171)

* Add a new component: currentstateserver

- Add a skeleton for it, with databases and a single query method.
- Add integration tests for it.
- Add listen/address fields in the config (breaking as this will force people to specify this to validate)

Not currently hooked up to anything yet.

* Unbreak config tests

* Add current_state to sample config

* comments

currentstateserver/currentstateserver.go

@@ -0,0 +1,51 @@
+// 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 currentstateserver
+
+import (
+	"github.com/Shopify/sarama"
+	"github.com/gorilla/mux"
+	"github.com/matrix-org/dendrite/currentstateserver/api"
+	"github.com/matrix-org/dendrite/currentstateserver/consumers"
+	"github.com/matrix-org/dendrite/currentstateserver/internal"
+	"github.com/matrix-org/dendrite/currentstateserver/inthttp"
+	"github.com/matrix-org/dendrite/currentstateserver/storage"
+	"github.com/matrix-org/dendrite/internal/config"
+	"github.com/sirupsen/logrus"
+)
+
+// AddInternalRoutes registers HTTP handlers for the internal API. Invokes functions
+// on the given input API.
+func AddInternalRoutes(router *mux.Router, intAPI api.CurrentStateInternalAPI) {
+	inthttp.AddRoutes(router, intAPI)
+}
+
+// NewInternalAPI returns a concrete implementation of the internal API. Callers
+// can call functions directly on the returned API or via an HTTP interface using AddInternalRoutes.
+func NewInternalAPI(cfg *config.Dendrite, consumer sarama.Consumer) api.CurrentStateInternalAPI {
+	csDB, err := storage.NewDatabase(string(cfg.Database.CurrentState), cfg.DbProperties())
+	if err != nil {
+		logrus.WithError(err).Panicf("failed to open database")
+	}
+	roomConsumer := consumers.NewOutputRoomEventConsumer(
+		string(cfg.Kafka.Topics.OutputRoomEvent), consumer, csDB,
+	)
+	if err = roomConsumer.Start(); err != nil {
+		logrus.WithError(err).Panicf("failed to start room server consumer")
+	}
+	return &internal.CurrentStateInternalAPI{
+		DB: csDB,
+	}
+}