dendrite/roomserver/internal/input/input.go
Neil Alexander 98a5e410d7
Per-room consumers (#2293)
* Roomserver input refactoring — again!

* Ensure the actor runs again

* Preserve consumer after unsubscribe

* Another sprinkling of magic

* Rename `TopicFor` to `Prefixed`

* Recreate the stream if the config is bad

* Check streams too

* Prefix subjects, preserve inboxes

* Recreate if subjects wrong

* Remove stream subject

* Reconstruct properly

* Fix mutex unlock

* Comments

* Fix tests

* Don't drop events

* Review comments

* Separate `queueInputRoomEvents` function

* Re-jig control flow a bit
2022-03-23 10:20:18 +00:00

437 lines
15 KiB
Go

// Copyright 2017 Vector Creations Ltd
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package input contains the code processes new room events
package input
import (
"context"
"encoding/json"
"errors"
"fmt"
"sync"
"time"
"github.com/Arceliar/phony"
"github.com/getsentry/sentry-go"
fedapi "github.com/matrix-org/dendrite/federationapi/api"
"github.com/matrix-org/dendrite/roomserver/acls"
"github.com/matrix-org/dendrite/roomserver/api"
"github.com/matrix-org/dendrite/roomserver/internal/query"
"github.com/matrix-org/dendrite/roomserver/storage"
"github.com/matrix-org/dendrite/setup/config"
"github.com/matrix-org/dendrite/setup/jetstream"
"github.com/matrix-org/dendrite/setup/process"
"github.com/matrix-org/gomatrixserverlib"
"github.com/nats-io/nats.go"
"github.com/prometheus/client_golang/prometheus"
"github.com/sirupsen/logrus"
log "github.com/sirupsen/logrus"
"github.com/tidwall/gjson"
)
var keyContentFields = map[string]string{
"m.room.join_rules": "join_rule",
"m.room.history_visibility": "history_visibility",
"m.room.member": "membership",
}
// Inputer is responsible for consuming from the roomserver input
// streams and processing the events. All input events are queued
// into a single NATS stream and the order is preserved strictly.
// The `room_id` message header will contain the room ID which will
// be used to assign the pending event to a per-room worker.
//
// The input API maintains an ephemeral headers-only consumer. It
// will speed through the stream working out which room IDs are
// pending and create durable consumers for them. The durable
// consumer will then be used for each room worker goroutine to
// fetch events one by one and process them. Each room having a
// durable consumer of its own means there is no head-of-line
// blocking between rooms. Filtering ensures that each durable
// consumer only receives events for the room it is interested in.
//
// The ephemeral consumer closely tracks the newest events. The
// per-room durable consumers will only progress through the stream
// as events are processed.
//
// A BC * -> positions of each consumer (* = ephemeral)
// ⌄ ⌄⌄ ⌄
// ABAABCAABCAA -> newest (letter = subject for each message)
//
// In this example, A is still processing an event but has two
// pending events to process afterwards. Both B and C are caught
// up, so they will do nothing until a new event comes in for B
// or C.
type Inputer struct {
Cfg *config.RoomServer
ProcessContext *process.ProcessContext
DB storage.Database
NATSClient *nats.Conn
JetStream nats.JetStreamContext
Durable nats.SubOpt
ServerName gomatrixserverlib.ServerName
FSAPI fedapi.FederationInternalAPI
KeyRing gomatrixserverlib.JSONVerifier
ACLs *acls.ServerACLs
InputRoomEventTopic string
OutputRoomEventTopic string
workers sync.Map // room ID -> *worker
Queryer *query.Queryer
}
type worker struct {
phony.Inbox
sync.Mutex
r *Inputer
roomID string
subscription *nats.Subscription
}
func (r *Inputer) startWorkerForRoom(roomID string) {
v, loaded := r.workers.LoadOrStore(roomID, &worker{
r: r,
roomID: roomID,
})
w := v.(*worker)
w.Lock()
defer w.Unlock()
if !loaded || w.subscription == nil {
consumer := r.Cfg.Matrix.JetStream.Prefixed("RoomInput" + jetstream.Tokenise(w.roomID))
subject := r.Cfg.Matrix.JetStream.Prefixed(jetstream.InputRoomEventSubj(w.roomID))
// Create the consumer. We do this as a specific step rather than
// letting PullSubscribe create it for us because we need the consumer
// to outlive the subscription. If we do it this way, we can Bind in the
// next step, and when we Unsubscribe, the consumer continues to live. If
// we leave PullSubscribe to create the durable consumer, Unsubscribe will
// delete it because it thinks it "owns" it, which in turn breaks the
// interest-based retention storage policy.
// If the durable consumer already exists, this is effectively a no-op.
// Another interesting tid-bit here: the ACK policy is set to "all" so that
// if we acknowledge a message, we also acknowledge everything that comes
// before it. This is necessary because otherwise our consumer will never
// acknowledge things we filtered out for other subjects and therefore they
// will linger around forever.
if _, err := w.r.JetStream.AddConsumer(
r.Cfg.Matrix.JetStream.Prefixed(jetstream.InputRoomEvent),
&nats.ConsumerConfig{
Durable: consumer,
AckPolicy: nats.AckAllPolicy,
DeliverPolicy: nats.DeliverAllPolicy,
FilterSubject: subject,
AckWait: MaximumMissingProcessingTime + (time.Second * 10),
},
); err != nil {
logrus.WithError(err).Errorf("Failed to create consumer for room %q", w.roomID)
return
}
// Bind to our durable consumer. We want to receive all messages waiting
// for this subject and we want to manually acknowledge them, so that we
// can ensure they are only cleaned up when we are done processing them.
sub, err := w.r.JetStream.PullSubscribe(
subject, consumer,
nats.ManualAck(),
nats.DeliverAll(),
nats.AckWait(MaximumMissingProcessingTime+(time.Second*10)),
nats.Bind(r.InputRoomEventTopic, consumer),
)
if err != nil {
logrus.WithError(err).Errorf("Failed to subscribe to stream for room %q", w.roomID)
return
}
// Go and start pulling messages off the queue.
w.subscription = sub
w.Act(nil, w._next)
}
}
// Start creates an ephemeral non-durable consumer on the roomserver
// input topic. It is configured to deliver us headers only because we
// don't actually care about the contents of the message at this point,
// we only care about the `room_id` field. Once a message arrives, we
// will look to see if we have a worker for that room which has its
// own consumer. If we don't, we'll start one.
func (r *Inputer) Start() error {
_, err := r.JetStream.Subscribe(
"", // This is blank because we specified it in BindStream.
func(m *nats.Msg) {
roomID := m.Header.Get(jetstream.RoomID)
r.startWorkerForRoom(roomID)
_ = m.Ack()
},
nats.HeadersOnly(),
nats.DeliverAll(),
nats.AckAll(),
nats.BindStream(r.InputRoomEventTopic),
)
return err
}
// _next is called by the worker for the room. It must only be called
// by the actor embedded into the worker.
func (w *worker) _next() {
// Look up what the next event is that's waiting to be processed.
ctx, cancel := context.WithTimeout(w.r.ProcessContext.Context(), time.Minute)
defer cancel()
msgs, err := w.subscription.Fetch(1, nats.Context(ctx))
switch err {
case nil:
// Make sure that once we're done here, we queue up another call
// to _next in the inbox.
defer w.Act(nil, w._next)
// If no error was reported, but we didn't get exactly one message,
// then skip over this and try again on the next iteration.
if len(msgs) != 1 {
return
}
case context.DeadlineExceeded:
// The context exceeded, so we've been waiting for more than a
// minute for activity in this room. At this point we will shut
// down the subscriber to free up resources. It'll get started
// again if new activity happens.
if err = w.subscription.Unsubscribe(); err != nil {
logrus.WithError(err).Errorf("Failed to unsubscribe to stream for room %q", w.roomID)
}
w.Lock()
w.subscription = nil
w.Unlock()
return
default:
// Something went wrong while trying to fetch the next event
// from the queue. In which case, we'll shut down the subscriber
// and wait to be notified about new room activity again. Maybe
// the problem will be corrected by then.
logrus.WithError(err).Errorf("Failed to get next stream message for room %q", w.roomID)
if err = w.subscription.Unsubscribe(); err != nil {
logrus.WithError(err).Errorf("Failed to unsubscribe to stream for room %q", w.roomID)
}
w.Lock()
w.subscription = nil
w.Unlock()
return
}
// Try to unmarshal the input room event. If the JSON unmarshalling
// fails then we'll terminate the message — this notifies NATS that
// we are done with the message and never want to see it again.
msg := msgs[0]
var inputRoomEvent api.InputRoomEvent
if err = json.Unmarshal(msg.Data, &inputRoomEvent); err != nil {
_ = msg.Term()
return
}
roomserverInputBackpressure.With(prometheus.Labels{"room_id": w.roomID}).Inc()
defer roomserverInputBackpressure.With(prometheus.Labels{"room_id": w.roomID}).Dec()
// Process the room event. If something goes wrong then we'll tell
// NATS to terminate the message. We'll store the error result as
// a string, because we might want to return that to the caller if
// it was a synchronous request.
var errString string
if err = w.r.processRoomEvent(w.r.ProcessContext.Context(), &inputRoomEvent); err != nil {
if !errors.Is(err, context.DeadlineExceeded) && !errors.Is(err, context.Canceled) {
sentry.CaptureException(err)
}
logrus.WithError(err).WithFields(logrus.Fields{
"room_id": w.roomID,
"event_id": inputRoomEvent.Event.EventID(),
"type": inputRoomEvent.Event.Type(),
}).Warn("Roomserver failed to process async event")
_ = msg.Term()
errString = err.Error()
} else {
_ = msg.Ack()
}
// If it was a synchronous input request then the "sync" field
// will be present in the message. That means that someone is
// waiting for a response. The temporary inbox name is present in
// that field, so send back the error string (if any). If there
// was no error then we'll return a blank message, which means
// that everything was OK.
if replyTo := msg.Header.Get("sync"); replyTo != "" {
if err = w.r.NATSClient.Publish(replyTo, []byte(errString)); err != nil {
logrus.WithError(err).WithFields(logrus.Fields{
"room_id": w.roomID,
"event_id": inputRoomEvent.Event.EventID(),
"type": inputRoomEvent.Event.Type(),
}).Warn("Roomserver failed to respond for sync event")
}
}
}
// queueInputRoomEvents queues events into the roomserver input
// stream in NATS.
func (r *Inputer) queueInputRoomEvents(
ctx context.Context,
request *api.InputRoomEventsRequest,
) (replySub *nats.Subscription, err error) {
// If the request is synchronous then we need to create a
// temporary inbox to wait for responses on, and then create
// a subscription to it. If it's asynchronous then we won't
// bother, so these values will remain empty.
var replyTo string
if !request.Asynchronous {
replyTo = nats.NewInbox()
replySub, err = r.NATSClient.SubscribeSync(replyTo)
if err != nil {
return nil, fmt.Errorf("r.NATSClient.SubscribeSync: %w", err)
}
if replySub == nil {
// This shouldn't ever happen, but it doesn't hurt to check
// because we can potentially avoid a nil pointer panic later
// if it did for some reason.
return nil, fmt.Errorf("expected a subscription to the temporary inbox")
}
}
// For each event, marshal the input room event and then
// send it into the input queue.
for _, e := range request.InputRoomEvents {
roomID := e.Event.RoomID()
subj := r.Cfg.Matrix.JetStream.Prefixed(jetstream.InputRoomEventSubj(roomID))
msg := &nats.Msg{
Subject: subj,
Header: nats.Header{},
}
msg.Header.Set("room_id", roomID)
if replyTo != "" {
msg.Header.Set("sync", replyTo)
}
msg.Data, err = json.Marshal(e)
if err != nil {
return nil, fmt.Errorf("json.Marshal: %w", err)
}
if _, err = r.JetStream.PublishMsg(msg, nats.Context(ctx)); err != nil {
logrus.WithError(err).WithFields(logrus.Fields{
"room_id": roomID,
"event_id": e.Event.EventID(),
"subj": subj,
}).Error("Roomserver failed to queue async event")
return nil, fmt.Errorf("r.JetStream.PublishMsg: %w", err)
}
}
return
}
// InputRoomEvents implements api.RoomserverInternalAPI
func (r *Inputer) InputRoomEvents(
ctx context.Context,
request *api.InputRoomEventsRequest,
response *api.InputRoomEventsResponse,
) {
// Queue up the event into the roomserver.
replySub, err := r.queueInputRoomEvents(ctx, request)
if err != nil {
response.ErrMsg = err.Error()
return
}
// If we aren't waiting for synchronous responses then we can
// give up here, there is nothing further to do.
if replySub == nil {
return
}
// Otherwise, we'll want to sit and wait for the responses
// from the roomserver. There will be one response for every
// input we submitted. The last error value we receive will
// be the one returned as the error string.
defer replySub.Drain() // nolint:errcheck
for i := 0; i < len(request.InputRoomEvents); i++ {
msg, err := replySub.NextMsgWithContext(ctx)
if err != nil {
response.ErrMsg = err.Error()
return
}
if len(msg.Data) > 0 {
response.ErrMsg = string(msg.Data)
}
}
}
// WriteOutputEvents implements OutputRoomEventWriter
func (r *Inputer) WriteOutputEvents(roomID string, updates []api.OutputEvent) error {
var err error
for _, update := range updates {
msg := &nats.Msg{
Subject: r.OutputRoomEventTopic,
Header: nats.Header{},
}
msg.Header.Set(jetstream.RoomID, roomID)
msg.Data, err = json.Marshal(update)
if err != nil {
return err
}
logger := log.WithFields(log.Fields{
"room_id": roomID,
"type": update.Type,
})
if update.NewRoomEvent != nil {
eventType := update.NewRoomEvent.Event.Type()
logger = logger.WithFields(log.Fields{
"event_type": eventType,
"event_id": update.NewRoomEvent.Event.EventID(),
"adds_state": len(update.NewRoomEvent.AddsStateEventIDs),
"removes_state": len(update.NewRoomEvent.RemovesStateEventIDs),
"send_as_server": update.NewRoomEvent.SendAsServer,
"sender": update.NewRoomEvent.Event.Sender(),
})
if update.NewRoomEvent.Event.StateKey() != nil {
logger = logger.WithField("state_key", *update.NewRoomEvent.Event.StateKey())
}
contentKey := keyContentFields[eventType]
if contentKey != "" {
value := gjson.GetBytes(update.NewRoomEvent.Event.Content(), contentKey)
if value.Exists() {
logger = logger.WithField("content_value", value.String())
}
}
if eventType == "m.room.server_acl" && update.NewRoomEvent.Event.StateKeyEquals("") {
ev := update.NewRoomEvent.Event.Unwrap()
defer r.ACLs.OnServerACLUpdate(ev)
}
}
logger.Tracef("Producing to topic '%s'", r.OutputRoomEventTopic)
if _, err := r.JetStream.PublishMsg(msg); err != nil {
logger.WithError(err).Errorf("Failed to produce to topic '%s': %s", r.OutputRoomEventTopic, err)
return err
}
}
return nil
}
func init() {
prometheus.MustRegister(roomserverInputBackpressure)
}
var roomserverInputBackpressure = prometheus.NewGaugeVec(
prometheus.GaugeOpts{
Namespace: "dendrite",
Subsystem: "roomserver",
Name: "input_backpressure",
Help: "How many events are queued for input for a given room",
},
[]string{"room_id"},
)