use unique p2p preflight idempotency keys

loadtest/im-pressure/httpapi.go

@@ -216,11 +216,12 @@ type p2pResponse struct {
 
 func (a *apiClient) ensureP2P(ctx context.Context, source, target AccountRecord) (*p2pResponse, error) {
 	var result p2pResponse
-	// EnsureP2P is itself idempotent and must execute on every preflight so it
-	// can repair subscriptions and refresh a loaded topic. A stable HTTP
-	// idempotency key would replay an old response and skip that repair.
+	// EnsureP2P must execute on every preflight so it can repair subscriptions
+	// and refresh a loaded topic. Use a fresh key instead of replaying an old
+	// successful response from a previous load-test run.
+	idempotencyKey := fmt.Sprintf("loadtest-p2p-%d-%s-%04d", time.Now().UnixNano(), source.Machine, source.Index)
 	err := a.do(ctx, http.MethodPost, "/v1/im/conversations/p2p", source.Token,
-		"",
+		idempotencyKey,
 		map[string]any{"peer_user_id": target.UserID}, &result)
 	return &result, err
 }