filer: add conditional update preconditions (#8647)

* filer: add conditional update preconditions

* iceberg: tighten metadata CAS preconditions

weed/plugin/worker/iceberg/exec_test.go

@@ -24,6 +24,7 @@ import (
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials/insecure"
 	"google.golang.org/grpc/status"
+	"google.golang.org/protobuf/proto"
 )
 
 // ---------------------------------------------------------------------------
@@ -35,8 +36,9 @@ import (
 type fakeFilerServer struct {
 	filer_pb.UnimplementedSeaweedFilerServer
 
-	mu      sync.Mutex
-	entries map[string]map[string]*filer_pb.Entry // dir → name → entry
+	mu           sync.Mutex
+	entries      map[string]map[string]*filer_pb.Entry // dir → name → entry
+	beforeUpdate func(*fakeFilerServer, *filer_pb.UpdateEntryRequest) error
 
 	// Counters for assertions
 	createCalls int
@@ -138,9 +140,41 @@ func (f *fakeFilerServer) CreateEntry(_ context.Context, req *filer_pb.CreateEnt
 func (f *fakeFilerServer) UpdateEntry(_ context.Context, req *filer_pb.UpdateEntryRequest) (*filer_pb.UpdateEntryResponse, error) {
 	f.mu.Lock()
 	f.updateCalls++
+	beforeUpdate := f.beforeUpdate
+	f.beforeUpdate = nil
 	f.mu.Unlock()
 
-	f.putEntry(req.Directory, req.Entry.Name, req.Entry)
+	if beforeUpdate != nil {
+		if err := beforeUpdate(f, req); err != nil {
+			return nil, err
+		}
+	}
+
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	dirEntries, ok := f.entries[req.Directory]
+	if !ok {
+		return nil, status.Errorf(codes.NotFound, "entry not found: %s/%s", req.Directory, req.Entry.Name)
+	}
+	current := dirEntries[req.Entry.Name]
+	if current == nil {
+		return nil, status.Errorf(codes.NotFound, "entry not found: %s/%s", req.Directory, req.Entry.Name)
+	}
+	for key, expectedValue := range req.ExpectedExtended {
+		actualValue, ok := current.Extended[key]
+		if ok {
+			if !bytes.Equal(actualValue, expectedValue) {
+				return nil, status.Errorf(codes.FailedPrecondition, "extended attribute %q changed", key)
+			}
+			continue
+		}
+		if len(expectedValue) > 0 {
+			return nil, status.Errorf(codes.FailedPrecondition, "extended attribute %q changed", key)
+		}
+	}
+
+	dirEntries[req.Entry.Name] = req.Entry
 	return &filer_pb.UpdateEntryResponse{}, nil
 }
 
@@ -281,7 +315,8 @@ func populateTable(t *testing.T, fs *fakeFilerServer, setup tableSetup) table.Me
 		Name:        setup.TableName,
 		IsDirectory: true,
 		Extended: map[string][]byte{
-			s3tables.ExtendedKeyMetadata: xattr,
+			s3tables.ExtendedKeyMetadata:        xattr,
+			s3tables.ExtendedKeyMetadataVersion: metadataVersionXattr(metadataVersion),
 		},
 	})
 
@@ -1486,6 +1521,68 @@ func TestMetadataVersionCAS(t *testing.T) {
 	}
 }
 
+func TestMetadataVersionCASDetectsConcurrentUpdate(t *testing.T) {
+	fs, client := startFakeFiler(t)
+
+	now := time.Now().UnixMilli()
+	setup := tableSetup{
+		BucketName: "test-bucket",
+		Namespace:  "ns",
+		TableName:  "tbl",
+		Snapshots: []table.Snapshot{
+			{SnapshotID: 1, TimestampMs: now, ManifestList: "metadata/snap-1.avro"},
+		},
+	}
+	populateTable(t, fs, setup)
+
+	tableDir := path.Join(s3tables.TablesPath, setup.BucketName, setup.tablePath())
+	fs.beforeUpdate = func(f *fakeFilerServer, req *filer_pb.UpdateEntryRequest) error {
+		entry := f.getEntry(path.Dir(tableDir), path.Base(tableDir))
+		if entry == nil {
+			return fmt.Errorf("table entry not found before concurrent update")
+		}
+
+		updatedEntry := cloneEntryForTest(t, entry)
+		var internalMeta map[string]json.RawMessage
+		if err := json.Unmarshal(updatedEntry.Extended[s3tables.ExtendedKeyMetadata], &internalMeta); err != nil {
+			return fmt.Errorf("unmarshal xattr: %w", err)
+		}
+
+		versionJSON, err := json.Marshal(2)
+		if err != nil {
+			return fmt.Errorf("marshal version: %w", err)
+		}
+		internalMeta["metadataVersion"] = versionJSON
+
+		updatedXattr, err := json.Marshal(internalMeta)
+		if err != nil {
+			return fmt.Errorf("marshal xattr: %w", err)
+		}
+		updatedEntry.Extended[s3tables.ExtendedKeyMetadata] = updatedXattr
+		updatedEntry.Extended[s3tables.ExtendedKeyMetadataVersion] = metadataVersionXattr(2)
+		f.putEntry(path.Dir(tableDir), path.Base(tableDir), updatedEntry)
+		return nil
+	}
+
+	err := updateTableMetadataXattr(context.Background(), client, tableDir, 1, []byte(`{}`), "metadata/v2.metadata.json")
+	if err == nil {
+		t.Fatal("expected version conflict error")
+	}
+	if !strings.Contains(err.Error(), "metadata version conflict") {
+		t.Fatalf("expected metadata version conflict, got %q", err)
+	}
+}
+
+func cloneEntryForTest(t *testing.T, entry *filer_pb.Entry) *filer_pb.Entry {
+	t.Helper()
+
+	cloned, ok := proto.Clone(entry).(*filer_pb.Entry)
+	if !ok {
+		t.Fatal("clone entry: unexpected type")
+	}
+	return cloned
+}
+
 // ---------------------------------------------------------------------------
 // Avro manifest content patching for tests
 // ---------------------------------------------------------------------------