fix: keep load test websocket sessions alive

loadtest/im-pressure/agent.go

@@ -141,6 +141,9 @@ func runAgent(ctx context.Context, cfg *Config, manifest *Manifest, machine, coo
 	if err != nil {
 		return err
 	}
+	if alive := run.aliveConnections(); alive != len(run.clients) {
+		return fmt.Errorf("connections alive after coordinator wait=%d expected=%d", alive, len(run.clients))
+	}
 	if !runIDPattern.MatchString(start.RunID) || !validScenario(start.Scenario) {
 		return fmt.Errorf("invalid coordinator start: %+v", start)
 	}
@@ -586,6 +589,16 @@ func (r *agentRun) acceptedCopy() []AcceptedMessage {
 	return out
 }
 
+func (r *agentRun) aliveConnections() int {
+	alive := 0
+	for _, client := range r.clients {
+		if client.alive() {
+			alive++
+		}
+	}
+	return alive
+}
+
 func (r *agentRun) drainDuration() (time.Duration, error) {
 	if r.scenario == "p2p" {
 		return configDuration(r.cfg.DrainP2P)