Close the retention blocks before deleting them.

Signed-off-by: Goutham Veeramachaneni <cs14btech11014@iith.ac.in>

db.go

@@ -277,16 +277,23 @@ func (db *DB) retentionCutoff() (bool, error) {
 	}
 
 	db.mtx.RLock()
-	defer db.mtx.RUnlock()
+	blocks := db.blocks[:]
+	db.mtx.RUnlock()
 
-	if len(db.blocks) == 0 {
+	if len(blocks) == 0 {
 		return false, nil
 	}
 
-	last := db.blocks[len(db.blocks)-1]
-	mint := last.Meta().MaxTime - int64(db.opts.RetentionDuration)
+	last := blocks[len(db.blocks)-1]
 
-	return retentionCutoff(db.dir, mint)
+	mint := last.Meta().MaxTime - int64(db.opts.RetentionDuration)
+	dirs, err := retentionCutoffDirs(db.dir, mint)
+	if err != nil {
+		return false, err
+	}
+
+	// This will close the dirs and then delete the dirs.
+	return len(dirs) > 0, db.reload(dirs...)
 }
 
 // Appender opens a new appender against the database.
@@ -388,40 +395,37 @@ func (db *DB) compact() (changes bool, err error) {
 	return changes, nil
 }
 
-// retentionCutoff deletes all directories of blocks in dir that are strictly
+// retentionCutoffDirs returns all directories of blocks in dir that are strictly
 // before mint.
-func retentionCutoff(dir string, mint int64) (bool, error) {
+func retentionCutoffDirs(dir string, mint int64) ([]string, error) {
 	df, err := fileutil.OpenDir(dir)
 	if err != nil {
-		return false, errors.Wrapf(err, "open directory")
+		return nil, errors.Wrapf(err, "open directory")
 	}
 	defer df.Close()
 
 	dirs, err := blockDirs(dir)
 	if err != nil {
-		return false, errors.Wrapf(err, "list block dirs %s", dir)
+		return nil, errors.Wrapf(err, "list block dirs %s", dir)
 	}
 
-	changes := false
+	delDirs := []string{}
 
 	for _, dir := range dirs {
 		meta, err := readMetaFile(dir)
 		if err != nil {
-			return changes, errors.Wrapf(err, "read block meta %s", dir)
+			return nil, errors.Wrapf(err, "read block meta %s", dir)
 		}
 		// The first block we encounter marks that we crossed the boundary
 		// of deletable blocks.
 		if meta.MaxTime >= mint {
 			break
 		}
-		changes = true
 
-		if err := os.RemoveAll(dir); err != nil {
-			return changes, err
-		}
+		delDirs = append(delDirs, dir)
 	}
 
-	return changes, fileutil.Fsync(df)
+	return delDirs, nil
 }
 
 func (db *DB) getBlock(id ulid.ULID) (*Block, bool) {

db_test.go

@@ -551,3 +551,60 @@ func TestWALFlushedOnDBClose(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, values, []string{"labelvalue"})
 }
+
+func TestDB_Retention(t *testing.T) {
+	tmpdir, _ := ioutil.TempDir("", "test")
+	defer os.RemoveAll(tmpdir)
+
+	db, err := Open(tmpdir, nil, nil, nil)
+	require.NoError(t, err)
+
+	lbls := labels.Labels{labels.Label{Name: "labelname", Value: "labelvalue"}}
+
+	app := db.Appender()
+	_, err = app.Add(lbls, 0, 1)
+	require.NoError(t, err)
+	require.NoError(t, app.Commit())
+
+	// create snapshot to make it create a block.
+	// TODO(gouthamve): Add a method to compact headblock.
+	snap, err := ioutil.TempDir("", "snap")
+	require.NoError(t, err)
+	require.NoError(t, db.Snapshot(snap))
+	require.NoError(t, db.Close())
+	defer os.RemoveAll(snap)
+
+	// reopen DB from snapshot
+	db, err = Open(snap, nil, nil, nil)
+	require.NoError(t, err)
+
+	Equals(t, 1, len(db.blocks))
+
+	app = db.Appender()
+	_, err = app.Add(lbls, 100, 1)
+	require.NoError(t, err)
+	require.NoError(t, app.Commit())
+
+	// Snapshot again to create another block.
+	snap, err = ioutil.TempDir("", "snap")
+	require.NoError(t, err)
+	require.NoError(t, db.Snapshot(snap))
+	require.NoError(t, db.Close())
+	defer os.RemoveAll(snap)
+
+	// reopen DB from snapshot
+	db, err = Open(snap, nil, nil, &Options{
+		RetentionDuration: 10,
+		BlockRanges:       []int64{50},
+	})
+	require.NoError(t, err)
+
+	Equals(t, 2, len(db.blocks))
+
+	// Now call rentention.
+	changes, err := db.retentionCutoff()
+	Ok(t, err)
+	Assert(t, changes, "there should be changes")
+	Equals(t, 1, len(db.blocks))
+	Equals(t, int64(100), db.blocks[0].meta.MaxTime) // To verify its the right block.
+}