From fb5c5535fc2dc76d224478c9390a34845d3b07c3 Mon Sep 17 00:00:00 2001
From: Fabian Reinartz <fab.reinartz@gmail.com>
Date: Thu, 18 May 2017 16:31:02 +0200
Subject: [PATCH] Misc cleanup

---
 db.go       | 30 ++++++------------------------
 wal_test.go |  6 +-----
 2 files changed, 7 insertions(+), 29 deletions(-)

diff --git a/db.go b/db.go
index 56a13e268b..34d1e884bb 100644
--- a/db.go
+++ b/db.go
@@ -482,26 +482,6 @@ func (db *DB) Close() error {
 func (db *DB) Appender() Appender {
 	db.mtx.RLock()
 	return &dbAppender{db: db}
-
-	// 	// XXX(fabxc): turn off creating initial appender as it will happen on-demand
-	// 	// anyway. For now this, with combination of only having a single timestamp per batch,
-	// 	// prevents opening more than one appender and hitting an unresolved deadlock (#11).
-	// 	//
-
-	// 	// Only instantiate appender after returning the headmtx to avoid
-	// 	// questionable locking order.
-	// 	db.headmtx.RLock()
-	// 	app := db.appendable()
-	// 	db.headmtx.RUnlock()
-
-	// 	for _, b := range app {
-	// 		a.heads = append(a.heads, &metaAppender{
-	// 			meta: b.Meta(),
-	// 			app:  b.Appender(),
-	// 		})
-	// 	}
-
-	// 	return a
 }
 
 type dbAppender struct {
@@ -612,14 +592,16 @@ func rangeForTimestamp(t int64, width int64) (mint, maxt int64) {
 func (db *DB) ensureHead(t int64) error {
 	mint, maxt := rangeForTimestamp(t, int64(db.opts.MinBlockDuration))
 
-	// Initial case with an empty database. t is the first timestamp we ever received.
-	// Create an additional buffering block in front.
-	if len(db.blocks) == 0 {
+	last := db.blocks[len(db.blocks)-1].Meta()
+	// Create another block of buffer in front if the DB is initialized or retrieving
+	// new data after a long gap.
+	// This ensures we always have a full block width if append window.
+	if len(db.blocks) == 0 || last.MaxTime <= mint-int64(db.opts.MinBlockDuration) {
 		if _, err := db.createHeadBlock(mint-int64(db.opts.MinBlockDuration), mint); err != nil {
 			return err
 		}
 		// If the previous block reaches into our new window, make it smaller.
-	} else if mt := db.blocks[len(db.blocks)-1].Meta().MaxTime; mt > mint {
+	} else if mt := last.MaxTime; mt > mint {
 		mint = mt
 	}
 	if mint >= maxt {
diff --git a/wal_test.go b/wal_test.go
index cbd6c62477..c2988e7e04 100644
--- a/wal_test.go
+++ b/wal_test.go
@@ -320,17 +320,13 @@ func TestWALRestoreCorrupted(t *testing.T) {
 			require.Equal(t, 0, len(l))
 			require.Equal(t, []RefSample{{T: 1, V: 2}}, s)
 
-			// Truncation should happen transparently and now cause an error.
+			// Truncation should happen transparently and not cause an error.
 			require.False(t, r.Next())
 			require.Nil(t, r.Err())
 
 			require.NoError(t, w2.Log(nil, []RefSample{{T: 99, V: 100}}))
 			require.NoError(t, w2.Close())
 
-			files, err := fileutil.ReadDir(dir)
-			require.NoError(t, err)
-			require.Equal(t, 1, len(files))
-
 			// We should see the first valid entry and the new one, everything after
 			// is truncated.
 			w3, err := OpenSegmentWAL(dir, logger, 0)