Try to sane default on jetstream base path

cmd/generate-config/main.go

@@ -1,8 +1,6 @@
 package main
 
 import (
-	"crypto/rand"
-	"encoding/hex"
 	"flag"
 	"fmt"
 
@@ -72,9 +70,6 @@ func main() {
 		// don't hit matrix.org when running tests!!!
 		cfg.SigningKeyServer.KeyPerspectives = config.KeyPerspectives{}
 		cfg.UserAPI.BCryptCost = bcrypt.MinCost
-		var id [8]byte
-		_, _ = rand.Read(id[:])
-		cfg.Global.JetStream.StoragePath = config.Path(hex.EncodeToString(id[:]))
 	}
 
 	j, err := yaml.Marshal(cfg)

setup/config/config.go

@@ -329,6 +329,7 @@ func (c *Dendrite) Verify(configErrs *ConfigErrors, isMonolith bool) {
 }
 
 func (c *Dendrite) Wiring() {
+	c.Global.JetStream.Matrix = &c.Global
 	c.ClientAPI.Matrix = &c.Global
 	c.EDUServer.Matrix = &c.Global
 	c.FederationAPI.Matrix = &c.Global

setup/config/config_jetstream.go

@@ -1,8 +1,14 @@
 package config
 
-import "fmt"
+import (
+	"fmt"
+	"log"
+	"regexp"
+)
 
 type JetStream struct {
+	Matrix *Global `yaml:"-"`
+
 	// Persistent directory to store JetStream streams in.
 	StoragePath Path `yaml:"storage_path"`
 	// A list of NATS addresses to connect to. If none are specified, an
@@ -22,7 +28,11 @@ func (c *JetStream) TopicFor(name string) string {
 func (c *JetStream) Defaults() {
 	c.Addresses = []string{}
 	c.TopicPrefix = "Dendrite"
-	c.StoragePath = Path("./")
+	reg, err := regexp.Compile(`[^a-zA-Z0-9\.]+`)
+	if err != nil {
+		log.Fatal(err)
+	}
+	c.StoragePath = Path("./" + reg.ReplaceAllString(string(c.Matrix.ServerName), ""))
 }
 
 func (c *JetStream) Verify(configErrs *ConfigErrors, isMonolith bool) {