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

3 files changed, 42 insertions, 7 deletions

diff --git a/setup/config/config_jetstream.go b/setup/config/config_jetstream.go
index 9271cd8b..b6a93d39 100644
--- a/setup/config/config_jetstream.go
+++ b/setup/config/config_jetstream.go
@@ -19,12 +19,12 @@ type JetStream struct {
 	InMemory bool `yaml:"in_memory"`
 }
 
-func (c *JetStream) TopicFor(name string) string {
+func (c *JetStream) Prefixed(name string) string {
 	return fmt.Sprintf("%s%s", c.TopicPrefix, name)
 }
 
 func (c *JetStream) Durable(name string) string {
-	return c.TopicFor(name)
+	return c.Prefixed(name)
 }
 
 func (c *JetStream) Defaults(generate bool) {
diff --git a/setup/jetstream/nats.go b/setup/jetstream/nats.go
index 43cc0331..748c191b 100644
--- a/setup/jetstream/nats.go
+++ b/setup/jetstream/nats.go
@@ -1,6 +1,7 @@
 package jetstream
 
 import (
+	"reflect"
 	"strings"
 	"sync"
 	"time"
@@ -75,14 +76,35 @@ func setupNATS(cfg *config.JetStream, nc *natsclient.Conn) (natsclient.JetStream
 	}
 
 	for _, stream := range streams { // streams are defined in streams.go
-		name := cfg.TopicFor(stream.Name)
+		name := cfg.Prefixed(stream.Name)
 		info, err := s.StreamInfo(name)
 		if err != nil && err != natsclient.ErrStreamNotFound {
 			logrus.WithError(err).Fatal("Unable to get stream info")
 		}
+		subjects := stream.Subjects
+		if len(subjects) == 0 {
+			// By default we want each stream to listen for the subjects
+			// that are either an exact match for the stream name, or where
+			// the first part of the subject is the stream name. ">" is a
+			// wildcard in NATS for one or more subject tokens. In the case
+			// that the stream is called "Foo", this will match any message
+			// with the subject "Foo", "Foo.Bar" or "Foo.Bar.Baz" etc.
+			subjects = []string{name, name + ".>"}
+		}
+		if info != nil {
+			switch {
+			case !reflect.DeepEqual(info.Config.Subjects, subjects):
+				fallthrough
+			case info.Config.Retention != stream.Retention:
+				fallthrough
+			case info.Config.Storage != stream.Storage:
+				if err = s.DeleteStream(name); err != nil {
+					logrus.WithError(err).Fatal("Unable to delete stream")
+				}
+				info = nil
+			}
+		}
 		if info == nil {
-			stream.Subjects = []string{name}
-
 			// If we're trying to keep everything in memory (e.g. unit tests)
 			// then overwrite the storage policy.
 			if cfg.InMemory {
@@ -93,8 +115,9 @@ func setupNATS(cfg *config.JetStream, nc *natsclient.Conn) (natsclient.JetStream
 			// array, otherwise we end up with namespaces on namespaces.
 			namespaced := *stream
 			namespaced.Name = name
+			namespaced.Subjects = subjects
 			if _, err = s.AddStream(&namespaced); err != nil {
-				logrus.WithError(err).WithField("stream", name).Fatal("Unable to add stream")
+				logrus.WithError(err).WithField("stream", name).WithField("subjects", subjects).Fatal("Unable to add stream")
 			}
 		}
 	}
diff --git a/setup/jetstream/streams.go b/setup/jetstream/streams.go
index aa3e95cb..aa979924 100644
--- a/setup/jetstream/streams.go
+++ b/setup/jetstream/streams.go
@@ -1,6 +1,8 @@
 package jetstream
 
 import (
+	"fmt"
+	"regexp"
 	"time"
 
 	"github.com/nats-io/nats.go"
@@ -24,10 +26,20 @@ var (
 	OutputReadUpdate        = "OutputReadUpdate"
 )
 
+var safeCharacters = regexp.MustCompile("[^A-Za-z0-9$]+")
+
+func Tokenise(str string) string {
+	return safeCharacters.ReplaceAllString(str, "_")
+}
+
+func InputRoomEventSubj(roomID string) string {
+	return fmt.Sprintf("%s.%s", InputRoomEvent, Tokenise(roomID))
+}
+
 var streams = []*nats.StreamConfig{
 	{
 		Name:      InputRoomEvent,
-		Retention: nats.WorkQueuePolicy,
+		Retention: nats.InterestPolicy,
 		Storage:   nats.FileStorage,
 	},
 	{