update

pkg/actor/simple_grain_pool_test.go

@@ -45,7 +45,7 @@ func newMockHost(name string) *mockHost {
 	return &mockHost{name: name, healthy: true}
 }
 
-func (m *mockHost) AnnounceExpiry(ids []uint64) {
+func (m *mockHost) AnnounceExpiry(ids []uint64, _ []int64) {
 	m.mu.Lock()
 	m.expiry = append(m.expiry, ids...)
 	m.mu.Unlock()
@@ -84,7 +84,7 @@ func (m *mockHost) Ping() bool { return m.healthy }
 
 func (m *mockHost) IsHealthy() bool { return m.healthy }
 
-func (m *mockHost) AnnounceOwnership(_ string, ids []uint64) {
+func (m *mockHost) AnnounceOwnership(_ string, ids []uint64, _ []int64) {
 	m.mu.Lock()
 	m.ownership = append(m.ownership, ids...)
 	m.mu.Unlock()
@@ -247,11 +247,19 @@ func TestSimpleGrainPoolHandleOwnershipChange(t *testing.T) {
 	host := newMockHost("peer-d")
 	pool := newTestPool(t, func(string) (Host[testState], error) { return host, nil })
 
+	// First-spawn-wins arbitration: a remote broadcast wins only when its
+	// lastChange stamp is strictly earlier than the local grain's stamp
+	// (or the local grain is absent). Capture the local spawn time once
+	// and pass a stamp 1ns earlier to the remote so the test continues to
+	// assert "external owner takes over given an earlier remote spawn"
+	// under the new arbitration rule.
+	spawnTime := time.Now()
 	pool.localMu.Lock()
-	pool.grains[7] = &testGrain{id: 7, accessed: time.Now()}
+	pool.grains[7] = &testGrain{id: 7, accessed: spawnTime}
 	pool.localMu.Unlock()
 
-	if err := pool.HandleOwnershipChange(host.name, []uint64{7}); err != nil {
+	remoteStamp := spawnTime.UnixNano() - 1
+	if err := pool.HandleOwnershipChange(host.name, []uint64{7}, []int64{remoteStamp}); err != nil {
 		t.Fatal(err)
 	}
 
@@ -268,6 +276,121 @@ func TestSimpleGrainPoolHandleOwnershipChange(t *testing.T) {
 	}
 }
 
+// TestSimpleGrainPoolHandleOwnershipChangeArbitration verifies the
+// first-spawn-wins arbitration rules for HandleOwnershipChange:
+//
+//   - Remote with earlier lastChange than local  → accept remote.
+//   - Remote with later lastChange than local   → keep local.
+//   - Equal lastChange                           → lower hostname wins.
+//   - Remote stamp == -1 (legacy path)           → accept remote (pre-arbitration).
+//   - Local grain absent                        → accept remote.
+func TestSimpleGrainPoolHandleOwnershipChangeArbitration(t *testing.T) {
+	host := newMockHost("peer-arbitrate")
+	// Each table case constructs a fresh pool inside t.Run — we don't
+	// share state across cases because per-case hostname differs
+	// (hostname is the tie-break oracle on equal lastChange stamps).
+
+	now := time.Now().UnixNano()
+
+	cases := []struct {
+		name          string
+		name_local    string // pool hostname for ordering check
+		id            uint64
+		localStamp    int64  // UnixNano of the local grain; -1 = no local grain
+		remoteStamp   int64  // UnixNano stamped on the broadcast
+		expectLocal   bool   // true → local grain still resident
+		expectRemote  bool   // true → remoteOwners[id] = host
+	}{
+		{
+			name:        "remote older stamp wins",
+			name_local:  "zzz", // pool above "peer-arbitrate" lex
+			id:          10,
+			localStamp:  now + 100,
+			remoteStamp: now,
+			expectLocal: false,
+			expectRemote: true,
+		},
+		{
+			name:        "local earlier stamp keeps",
+			name_local:  "aaa", // pool below "peer-arbitrate" lex but stamp decides
+			id:          11,
+			localStamp:  now,
+			remoteStamp: now + 100,
+			expectLocal: true,
+			expectRemote: false,
+		},
+		{
+			name:        "equal stamp + lower local hostname keeps",
+			name_local:  "a-peer", // below host
+			id:          12,
+			localStamp:  now,
+			remoteStamp: now,
+			expectLocal: true,
+			expectRemote: false,
+		},
+		{
+			name:        "equal stamp + higher local hostname defers",
+			name_local:  "zzz-peer", // above host
+			id:          13,
+			localStamp:  now,
+			remoteStamp: now,
+			expectLocal: false,
+			expectRemote: true,
+		},
+		{
+			name:        "legacy (no remote stamp) accepts remote",
+			name_local:  "zzz", // we'd otherwise keep local
+			id:          14,
+			localStamp:  now + 100,
+			remoteStamp: -1,
+			expectLocal: false,
+			expectRemote: true,
+		},
+		{
+			name:        "no local grain accepts remote",
+			name_local:  "aaa",
+			id:          15,
+			localStamp:  -1,
+			remoteStamp: now,
+			expectLocal: false,
+			expectRemote: true,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			// Fresh pool per case so hostname differences don't leak.
+			p := newTestPool(t, func(string) (Host[testState], error) { return host, nil })
+			p.hostname = tc.name_local
+
+			p.localMu.Lock()
+			if tc.localStamp != -1 {
+				p.grains[tc.id] = &testGrain{id: tc.id, accessed: time.Unix(0, tc.localStamp)}
+			}
+			p.localMu.Unlock()
+
+			if err := p.HandleOwnershipChange(host.name, []uint64{tc.id}, []int64{tc.remoteStamp}); err != nil {
+				t.Fatal(err)
+			}
+
+			p.localMu.RLock()
+			_, hasLocal := p.grains[tc.id]
+			p.localMu.RUnlock()
+			if hasLocal != tc.expectLocal {
+				t.Fatalf("local grain presence = %v, want %v", hasLocal, tc.expectLocal)
+			}
+
+			owner, ok := p.OwnerHost(tc.id)
+			if ok != tc.expectRemote {
+				t.Fatalf("OwnerHost ok = %v, want %v", ok, tc.expectRemote)
+			}
+			if tc.expectRemote && (owner == nil || owner.Name() != host.name) {
+				t.Fatalf("Owner = %v, want host %q", owner, host.name)
+			}
+		})
+	}
+}
+
 func TestSimpleGrainPoolPurgeEvictsStaleGrains(t *testing.T) {
 	pool := newTestPool(t, func(string) (Host[testState], error) {
 		return nil, fmt.Errorf("no remotes")