Read the router's ask ids without taking a second stop of the key lister for a failure (issue 1336)

cmd/mesh-controller/catch_up.go

@@ -14,6 +14,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/nats-io/nats.go"
 	"github.com/nats-io/nats.go/jetstream"
 
 	"git.novox.be/novox/mesh-sdk/go/asks"
@@ -267,6 +268,11 @@ var routerAskIDs = func(ctx context.Context, inv catalogueReader, asker string)
 	if err != nil {
 		return nil, err
 	}
+	return askIDsOf(ctx, kv, asker)
+}
+
+// askIDsOf are the ids of the asks an asker has in the router's bucket.
+func askIDsOf(ctx context.Context, kv jetstream.KeyValue, asker string) ([]string, error) {
 	lister, err := kv.ListKeysFiltered(ctx, asker+".>")
 	if err != nil {
 		return nil, err
@@ -275,7 +281,9 @@ var routerAskIDs = func(ctx context.Context, inv catalogueReader, asker string)
 	for key := range lister.Keys() {
 		ids = append(ids, strings.TrimPrefix(key, asker+"."))
 	}
-	if err := lister.Stop(); err != nil {
+	// The lister stops its own watch when it has sent the last key, so a stop of ours finds it stopped: nats answers that with
+	// "invalid subscription", which is no failure of the read (issue 1336). Any other error stays one.
+	if err := lister.Stop(); err != nil && !errors.Is(err, nats.ErrBadSubscription) {
 		return nil, err
 	}
 	return ids, nil

cmd/mesh-controller/router_ids_integration_test.go

@@ -0,0 +1,52 @@
+//go:build integration
+
+package main
+
+import (
+	"context"
+	"slices"
+	"testing"
+
+	"github.com/nats-io/nats.go"
+	"github.com/nats-io/nats.go/jetstream"
+
+	"github.com/novox/mesh-controller/internal/testbus"
+)
+
+// Issue 1336: the catch-up lists the ids of an asker's asks in the router's bucket. The key lister stops its own watch when the last
+// key is read, and a second stop answers "nats: invalid subscription"; read as a failure, it made every warrant unreadable on novox
+// (2026-10-20, 110 gaps named, none planned).
+func TestTheAskIDsOfAnAskerAreReadFromTheRoutersBucketWithoutAFalseFailure(t *testing.T) {
+	conn, err := nats.Connect(testbus.URL(t))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(conn.Close)
+	js, err := jetstream.New(conn)
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx := t.Context()
+	kv, err := js.CreateKeyValue(ctx, jetstream.KeyValueConfig{Bucket: "router_asks_test"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = js.DeleteKeyValue(context.Background(), "router_asks_test") })
+	for _, key := range []string{"mesh-delivery.merge-378-b9104454f9a5-1", "mesh-delivery.merge-377-aaaaaaaaaaaa-1",
+		"mesh-delivery-teller.merge-feat_r4b_sdk_users-ba59b03220f8-989afe0a3bcf", "keycloak.something"} {
+		if _, err := kv.Put(ctx, key, []byte(`{}`)); err != nil {
+			t.Fatal(err)
+		}
+	}
+	got, err := askIDsOf(ctx, kv, "mesh-delivery")
+	if err != nil {
+		t.Fatalf("the ids of an asker's asks could not be read: %v", err)
+	}
+	slices.Sort(got)
+	if want := []string{"merge-377-aaaaaaaaaaaa-1", "merge-378-b9104454f9a5-1"}; !slices.Equal(got, want) {
+		t.Fatalf("read %v, want %v: the teller's and another module's asks are not mesh-delivery's", got, want)
+	}
+	if none, err := askIDsOf(ctx, kv, "nobody"); err != nil || len(none) != 0 {
+		t.Fatalf("an asker with no asks read as %v, %v", none, err)
+	}
+}