index: add a test to trigger fd leak on corrupted index (#576)

The test is designed to fail for windows when the function leaves open files.

CHANGELOG.md

@@ -4,7 +4,8 @@
  - [REMOVED] `FromData` is considered unused so was removed.
  - [FEATURE] Added option WALSegmentSize -1 to disable the WAL.
  - [BUGFIX] Fsync the meta file to persist it on disk to avoid data loss in case of a host crash.
- - [BUGFIX] Fix fd and vm_area leak on error path in chunks.NewDirReader
+ - [BUGFIX] Fix fd and vm_area leak on error path in chunks.NewDirReader.
+ - [BUGFIX] Fix fd and vm_area leak on error path in index.NewFileReader.
 
 ## 0.6.1
   - [BUGFIX] Update `last` after appending a non-overlapping chunk in `chunks.MergeOverlappingChunks`. [#539](https://github.com/prometheus/tsdb/pull/539)

index/index.go

@@ -29,6 +29,7 @@ import (
 	"github.com/pkg/errors"
 	"github.com/prometheus/tsdb/chunks"
 	"github.com/prometheus/tsdb/encoding"
+	tsdb_errors "github.com/prometheus/tsdb/errors"
 	"github.com/prometheus/tsdb/fileutil"
 	"github.com/prometheus/tsdb/labels"
 )
@@ -625,7 +626,15 @@ func NewFileReader(path string) (*Reader, error) {
 	if err != nil {
 		return nil, err
 	}
-	return newReader(realByteSlice(f.Bytes()), f)
+	r, err := newReader(realByteSlice(f.Bytes()), f)
+	if err != nil {
+		var merr tsdb_errors.MultiError
+		merr.Add(err)
+		merr.Add(f.Close())
+		return nil, merr
+	}
+
+	return r, nil
 }
 
 func newReader(b ByteSlice, c io.Closer) (*Reader, error) {

index/index_test.go

@@ -412,3 +412,18 @@ func TestReaderWithInvalidBuffer(t *testing.T) {
 	_, err := NewReader(b)
 	testutil.NotOk(t, err)
 }
+
+// TestNewFileReaderErrorNoOpenFiles ensures that in case of an error no file remains open.
+func TestNewFileReaderErrorNoOpenFiles(t *testing.T) {
+	dir := testutil.NewTemporaryDirectory("block", t)
+
+	idxName := filepath.Join(dir.Path(), "index")
+	err := ioutil.WriteFile(idxName, []byte("corrupted contents"), 0644)
+	testutil.Ok(t, err)
+
+	_, err = NewFileReader(idxName)
+	testutil.NotOk(t, err)
+
+	// dir.Close will fail on Win if idxName fd is not closed on error path.
+	dir.Close()
+}