rename WAL#Flush to WAL#FlushAndSync (#3345)

* rename WAL#Flush to WAL#FlushAndSync

- rename auto#Flush to auto#FlushAndSync
- cleanup WAL interface to not leak implementation details!
  * remove Group()
  * add WALReader interface and return it in SearchForEndHeight()
- add interface assertions

Refs #3337

* replace WALReader with io.ReadCloser

libs/autofile/cmd/logjack.go

@@ -70,7 +70,7 @@ func main() {
 	for {
 		n, err := os.Stdin.Read(buf)
 		group.Write(buf[:n])
-		group.Flush()
+		group.FlushAndSync()
 		if err != nil {
 			group.Stop()
 			if err == io.EOF {

libs/autofile/group.go

@@ -131,21 +131,23 @@ func GroupTotalSizeLimit(limit int64) func(*Group) {
 	}
 }
 
-// OnStart implements Service by starting the goroutine that checks file and
-// group limits.
+// OnStart implements cmn.Service by starting the goroutine that checks file
+// and group limits.
 func (g *Group) OnStart() error {
 	g.ticker = time.NewTicker(g.groupCheckDuration)
 	go g.processTicks()
 	return nil
 }
 
-// OnStop implements Service by stopping the goroutine described above.
+// OnStop implements cmn.Service by stopping the goroutine described above.
 // NOTE: g.Head must be closed separately using Close.
 func (g *Group) OnStop() {
 	g.ticker.Stop()
-	g.Flush() // flush any uncommitted data
+	g.FlushAndSync()
 }
 
+// Wait blocks until all internal goroutines are finished. Supposed to be
+// called after Stop.
 func (g *Group) Wait() {
 	// wait for processTicks routine to finish
 	<-g.doneProcessTicks
@@ -153,7 +155,7 @@ func (g *Group) Wait() {
 
 // Close closes the head file. The group must be stopped by this moment.
 func (g *Group) Close() {
-	g.Flush() // flush any uncommitted data
+	g.FlushAndSync()
 
 	g.mtx.Lock()
 	_ = g.Head.closeFile()
@@ -216,9 +218,9 @@ func (g *Group) Buffered() int {
 	return g.headBuf.Buffered()
 }
 
-// Flush writes any buffered data to the underlying file and commits the
-// current content of the file to stable storage.
-func (g *Group) Flush() error {
+// FlushAndSync writes any buffered data to the underlying file and commits the
+// current content of the file to stable storage (fsync).
+func (g *Group) FlushAndSync() error {
 	g.mtx.Lock()
 	defer g.mtx.Unlock()
 	err := g.headBuf.Flush()

libs/autofile/group_test.go

@@ -55,7 +55,7 @@ func TestCheckHeadSizeLimit(t *testing.T) {
 		err := g.WriteLine(cmn.RandStr(999))
 		require.NoError(t, err, "Error appending to head")
 	}
-	g.Flush()
+	g.FlushAndSync()
 	assertGroupInfo(t, g.ReadGroupInfo(), 0, 0, 999000, 999000)
 
 	// Even calling checkHeadSizeLimit manually won't rotate it.
@@ -65,7 +65,7 @@ func TestCheckHeadSizeLimit(t *testing.T) {
 	// Write 1000 more bytes.
 	err := g.WriteLine(cmn.RandStr(999))
 	require.NoError(t, err, "Error appending to head")
-	g.Flush()
+	g.FlushAndSync()
 
 	// Calling checkHeadSizeLimit this time rolls it.
 	g.checkHeadSizeLimit()
@@ -74,7 +74,7 @@ func TestCheckHeadSizeLimit(t *testing.T) {
 	// Write 1000 more bytes.
 	err = g.WriteLine(cmn.RandStr(999))
 	require.NoError(t, err, "Error appending to head")
-	g.Flush()
+	g.FlushAndSync()
 
 	// Calling checkHeadSizeLimit does nothing.
 	g.checkHeadSizeLimit()
@@ -85,7 +85,7 @@ func TestCheckHeadSizeLimit(t *testing.T) {
 		err = g.WriteLine(cmn.RandStr(999))
 		require.NoError(t, err, "Error appending to head")
 	}
-	g.Flush()
+	g.FlushAndSync()
 	assertGroupInfo(t, g.ReadGroupInfo(), 0, 1, 2000000, 1000000)
 
 	// Calling checkHeadSizeLimit rolls it again.
@@ -95,7 +95,7 @@ func TestCheckHeadSizeLimit(t *testing.T) {
 	// Write 1000 more bytes.
 	_, err = g.Head.Write([]byte(cmn.RandStr(999) + "\n"))
 	require.NoError(t, err, "Error appending to head")
-	g.Flush()
+	g.FlushAndSync()
 	assertGroupInfo(t, g.ReadGroupInfo(), 0, 2, 2001000, 1000)
 
 	// Calling checkHeadSizeLimit does nothing.
@@ -212,12 +212,12 @@ func TestRotateFile(t *testing.T) {
 	g.WriteLine("Line 1")
 	g.WriteLine("Line 2")
 	g.WriteLine("Line 3")
-	g.Flush()
+	g.FlushAndSync()
 	g.RotateFile()
 	g.WriteLine("Line 4")
 	g.WriteLine("Line 5")
 	g.WriteLine("Line 6")
-	g.Flush()
+	g.FlushAndSync()
 
 	// Read g.Head.Path+"000"
 	body1, err := ioutil.ReadFile(g.Head.Path + ".000")
@@ -244,13 +244,13 @@ func TestFindLast1(t *testing.T) {
 	g.WriteLine("Line 2")
 	g.WriteLine("# a")
 	g.WriteLine("Line 3")
-	g.Flush()
+	g.FlushAndSync()
 	g.RotateFile()
 	g.WriteLine("Line 4")
 	g.WriteLine("Line 5")
 	g.WriteLine("Line 6")
 	g.WriteLine("# b")
-	g.Flush()
+	g.FlushAndSync()
 
 	match, found, err := g.FindLast("#")
 	assert.NoError(t, err)
@@ -267,14 +267,14 @@ func TestFindLast2(t *testing.T) {
 	g.WriteLine("Line 1")
 	g.WriteLine("Line 2")
 	g.WriteLine("Line 3")
-	g.Flush()
+	g.FlushAndSync()
 	g.RotateFile()
 	g.WriteLine("# a")
 	g.WriteLine("Line 4")
 	g.WriteLine("Line 5")
 	g.WriteLine("# b")
 	g.WriteLine("Line 6")
-	g.Flush()
+	g.FlushAndSync()
 
 	match, found, err := g.FindLast("#")
 	assert.NoError(t, err)
@@ -293,12 +293,12 @@ func TestFindLast3(t *testing.T) {
 	g.WriteLine("Line 2")
 	g.WriteLine("# b")
 	g.WriteLine("Line 3")
-	g.Flush()
+	g.FlushAndSync()
 	g.RotateFile()
 	g.WriteLine("Line 4")
 	g.WriteLine("Line 5")
 	g.WriteLine("Line 6")
-	g.Flush()
+	g.FlushAndSync()
 
 	match, found, err := g.FindLast("#")
 	assert.NoError(t, err)
@@ -315,12 +315,12 @@ func TestFindLast4(t *testing.T) {
 	g.WriteLine("Line 1")
 	g.WriteLine("Line 2")
 	g.WriteLine("Line 3")
-	g.Flush()
+	g.FlushAndSync()
 	g.RotateFile()
 	g.WriteLine("Line 4")
 	g.WriteLine("Line 5")
 	g.WriteLine("Line 6")
-	g.Flush()
+	g.FlushAndSync()
 
 	match, found, err := g.FindLast("#")
 	assert.NoError(t, err)
@@ -336,7 +336,7 @@ func TestWrite(t *testing.T) {
 
 	written := []byte("Medusa")
 	g.Write(written)
-	g.Flush()
+	g.FlushAndSync()
 
 	read := make([]byte, len(written))
 	gr, err := g.NewReader(0)
@@ -357,11 +357,11 @@ func TestGroupReaderRead(t *testing.T) {
 
 	professor := []byte("Professor Monster")
 	g.Write(professor)
-	g.Flush()
+	g.FlushAndSync()
 	g.RotateFile()
 	frankenstein := []byte("Frankenstein's Monster")
 	g.Write(frankenstein)
-	g.Flush()
+	g.FlushAndSync()
 
 	totalWrittenLength := len(professor) + len(frankenstein)
 	read := make([]byte, totalWrittenLength)
@@ -386,12 +386,12 @@ func TestGroupReaderRead2(t *testing.T) {
 
 	professor := []byte("Professor Monster")
 	g.Write(professor)
-	g.Flush()
+	g.FlushAndSync()
 	g.RotateFile()
 	frankenstein := []byte("Frankenstein's Monster")
 	frankensteinPart := []byte("Frankenstein")
 	g.Write(frankensteinPart) // note writing only a part
-	g.Flush()
+	g.FlushAndSync()
 
 	totalLength := len(professor) + len(frankenstein)
 	read := make([]byte, totalLength)
@@ -427,7 +427,7 @@ func TestMaxIndex(t *testing.T) {
 	assert.Zero(t, g.MaxIndex(), "MaxIndex should be zero at the beginning")
 
 	g.WriteLine("Line 1")
-	g.Flush()
+	g.FlushAndSync()
 	g.RotateFile()
 
 	assert.Equal(t, 1, g.MaxIndex(), "MaxIndex should point to the last file")