Fix read tombstones: EOF

Due to an bug in TSM tombstone files, it was possible to create
empty tombstone files.  At startup, the TSM file would error out
and not load the TSM file.

Instead, treat it as an empty v1 file so the TSM file can load
correctly.

Fixes #6641

CHANGELOG.md

@@ -32,6 +32,7 @@
 - [#6406](https://github.com/influxdata/influxdb/issues/6406): Max index entries exceeded
 - [#6557](https://github.com/influxdata/influxdb/issues/6557): Overwriting points on large series can cause memory spikes during compactions
 - [#6611](https://github.com/influxdata/influxdb/issues/6611): Queries slow down hundreds times after overwriting points
+- [#6641](https://github.com/influxdata/influxdb/issues/6641): Fix read tombstones: EOF
 
 ## v0.13.0 [2016-05-12]
 

tsdb/engine/tsm1/tombstone.go

@@ -161,7 +161,10 @@ func (t *Tombstoner) readTombstone() ([]Tombstone, error) {
 		var b [4]byte
 		_, err := f.Read(b[:])
 		if err != nil {
-			return nil, err
+			// Might be a zero length file which should not exist, but
+			// an old bug allowed them to occur.  Treat it as an empty
+			// v1 tombstone file so we don't abort loading the TSM file.
+			return t.readTombstoneV1(f)
 		}
 
 		if _, err := f.Seek(0, os.SEEK_SET); err != nil {
@@ -171,7 +174,6 @@ func (t *Tombstoner) readTombstone() ([]Tombstone, error) {
 		if binary.BigEndian.Uint32(b[:]) == v2header {
 			return t.readTombstoneV2(f)
 		}
-
 		return t.readTombstoneV1(f)
 	}
 	return nil, nil

tsdb/engine/tsm1/tombstone_test.go

@@ -173,3 +173,31 @@ func TestTombstoner_ReadV1(t *testing.T) {
 		t.Fatalf("value mismatch: got %v, exp %v", got, exp)
 	}
 }
+
+func TestTombstoner_ReadEmptyV1(t *testing.T) {
+	dir := MustTempDir()
+	defer func() { os.RemoveAll(dir) }()
+
+	f := MustTempFile(dir)
+	f.Close()
+
+	if err := os.Rename(f.Name(), f.Name()+".tombstone"); err != nil {
+		t.Fatalf("rename tombstone failed: %v", err)
+	}
+
+	ts := &tsm1.Tombstoner{Path: f.Name()}
+
+	entries, err := ts.ReadAll()
+	if err != nil {
+		fatal(t, "ReadAll", err)
+	}
+
+	entries, err = ts.ReadAll()
+	if err != nil {
+		fatal(t, "ReadAll", err)
+	}
+
+	if got, exp := len(entries), 0; got != exp {
+		t.Fatalf("length mismatch: got %v, exp %v", got, exp)
+	}
+}