Live: make maximum WebSocket message size configurable (#99770)

Co-authored-by: Chris Marchbanks <chris.marchbanks@grafana.com>

pkg/services/live/live.go

@@ -269,12 +269,14 @@ func ProvideService(plugCtxProvider *plugincontext.Provider, cfg *setting.Cfg, r
 	originGlobs, _ := setting.GetAllowedOriginGlobs(originPatterns) // error already checked on config load.
 	checkOrigin := getCheckOriginFunc(appURL, originPatterns, originGlobs)
 
+	wsCfg := centrifuge.WebsocketConfig{
+		ReadBufferSize:   1024,
+		WriteBufferSize:  1024,
+		CheckOrigin:      checkOrigin,
+		MessageSizeLimit: cfg.LiveMessageSizeLimit,
+	}
 	// Use a pure websocket transport.
-	wsHandler := centrifuge.NewWebsocketHandler(node, centrifuge.WebsocketConfig{
-		ReadBufferSize:  1024,
-		WriteBufferSize: 1024,
-		CheckOrigin:     checkOrigin,
-	})
+	wsHandler := centrifuge.NewWebsocketHandler(node, wsCfg)
 
 	pushWSHandler := pushws.NewHandler(g.ManagedStreamRunner, pushws.Config{
 		ReadBufferSize:  1024,

pkg/setting/setting.go

@@ -435,6 +435,9 @@ type Cfg struct {
 	// LiveAllowedOrigins is a set of origins accepted by Live. If not provided
 	// then Live uses AppURL as the only allowed origin.
 	LiveAllowedOrigins []string
+	// LiveMessageSizeLimit is the maximum size in bytes of Websocket messages
+	// from clients. Defaults to 64KB.
+	LiveMessageSizeLimit int
 
 	// Grafana.com URL, used for OAuth redirect.
 	GrafanaComURL string
@@ -1974,6 +1977,10 @@ func (cfg *Cfg) readLiveSettings(iniFile *ini.File) error {
 	if cfg.LiveMaxConnections < -1 {
 		return fmt.Errorf("unexpected value %d for [live] max_connections", cfg.LiveMaxConnections)
 	}
+	cfg.LiveMessageSizeLimit = section.Key("message_size_limit").MustInt(65536)
+	if cfg.LiveMessageSizeLimit < -1 {
+		return fmt.Errorf("unexpected value %d for [live] message_size_limit", cfg.LiveMaxConnections)
+	}
 	cfg.LiveHAEngine = section.Key("ha_engine").MustString("")
 	switch cfg.LiveHAEngine {
 	case "", "redis":