ethdb/leveldb : use close(quit) to quit meter routine

ethdb/leveldb/leveldb.go

@@ -145,14 +145,8 @@ func (db *Database) Close() error {
 	db.quitLock.Lock()
 	defer db.quitLock.Unlock()
 
-	if db.quitChan != nil {
-		errc := make(chan error)
-		db.quitChan <- errc
-		if err := <-errc; err != nil {
-			db.log.Error("Metrics collection failed", "err", err)
-		}
-		db.quitChan = nil
-	}
+	close(db.quitChan)
+
 	db.wg.Wait()
 	return db.db.Close()
 }
@@ -249,19 +243,15 @@ func (db *Database) meter(refresh time.Duration) {
 		delaystats      [2]int64
 		lastWritePaused time.Time
 	)
-
-	var (
-		errc chan error
-		merr error
-	)
+	timer := time.NewTimer(refresh)
+	defer timer.Stop()
 
 	// Iterate ad infinitum and collect the stats
-	for i := 1; errc == nil && merr == nil; i++ {
+	for i := 1; ; i++ {
 		// Retrieve the database stats
 		stats, err := db.db.GetProperty("leveldb.stats")
 		if err != nil {
 			db.log.Error("Failed to read database stats", "err", err)
-			merr = err
 			continue
 		}
 		// Find the compaction table, skip the header
@@ -271,7 +261,6 @@ func (db *Database) meter(refresh time.Duration) {
 		}
 		if len(lines) <= 3 {
 			db.log.Error("Compaction leveldbTable not found")
-			merr = errors.New("compaction leveldbTable not found")
 			continue
 		}
 		lines = lines[3:]
@@ -289,7 +278,6 @@ func (db *Database) meter(refresh time.Duration) {
 				value, err := strconv.ParseFloat(strings.TrimSpace(counter), 64)
 				if err != nil {
 					db.log.Error("Compaction entry parsing failed", "err", err)
-					merr = err
 					continue
 				}
 				compactions[i%2][idx] += value
@@ -312,7 +300,6 @@ func (db *Database) meter(refresh time.Duration) {
 		writedelay, err := db.db.GetProperty("leveldb.writedelay")
 		if err != nil {
 			db.log.Error("Failed to read database write delay statistic", "err", err)
-			merr = err
 			continue
 		}
 		var (
@@ -323,13 +310,11 @@ func (db *Database) meter(refresh time.Duration) {
 		)
 		if n, err := fmt.Sscanf(writedelay, "DelayN:%d Delay:%s Paused:%t", &delayN, &delayDuration, &paused); n != 3 || err != nil {
 			db.log.Error("Write delay statistic not found")
-			merr = err
 			continue
 		}
 		duration, err = time.ParseDuration(delayDuration)
 		if err != nil {
 			db.log.Error("Failed to parse delay duration", "err", err)
-			merr = err
 			continue
 		}
 		if db.writeDelayNMeter != nil {
@@ -351,24 +336,20 @@ func (db *Database) meter(refresh time.Duration) {
 		ioStats, err := db.db.GetProperty("leveldb.iostats")
 		if err != nil {
 			db.log.Error("Failed to read database iostats", "err", err)
-			merr = err
 			continue
 		}
 		var nRead, nWrite float64
 		parts := strings.Split(ioStats, " ")
 		if len(parts) < 2 {
 			db.log.Error("Bad syntax of ioStats", "ioStats", ioStats)
-			merr = fmt.Errorf("bad syntax of ioStats %s", ioStats)
 			continue
 		}
 		if n, err := fmt.Sscanf(parts[0], "Read(MB):%f", &nRead); n != 1 || err != nil {
 			db.log.Error("Bad syntax of read entry", "entry", parts[0])
-			merr = err
 			continue
 		}
 		if n, err := fmt.Sscanf(parts[1], "Write(MB):%f", &nWrite); n != 1 || err != nil {
 			db.log.Error("Bad syntax of write entry", "entry", parts[1])
-			merr = err
 			continue
 		}
 		if db.diskReadMeter != nil {
@@ -382,7 +363,6 @@ func (db *Database) meter(refresh time.Duration) {
 		compCount, err := db.db.GetProperty("leveldb.compcount")
 		if err != nil {
 			db.log.Error("Failed to read database iostats", "err", err)
-			merr = err
 			continue
 		}
 
@@ -394,7 +374,6 @@ func (db *Database) meter(refresh time.Duration) {
 		)
 		if n, err := fmt.Sscanf(compCount, "MemComp:%d Level0Comp:%d NonLevel0Comp:%d SeekComp:%d", &memComp, &level0Comp, &nonLevel0Comp, &seekComp); n != 4 || err != nil {
 			db.log.Error("Compaction count statistic not found")
-			merr = err
 			continue
 		}
 		db.memCompGauge.Update(int64(memComp))
@@ -404,17 +383,14 @@ func (db *Database) meter(refresh time.Duration) {
 
 		// Sleep a bit, then repeat the stats collection
 		select {
-		case errc = <-db.quitChan:
+		case <-db.quitChan:
+			return
 			// Quit requesting, stop hammering the database
-		case <-time.After(refresh):
+		case <-timer.C:
+			timer.Reset(refresh)
 			// Timeout, gather a new set of stats
 		}
 	}
-
-	if errc == nil {
-		errc = <-db.quitChan
-	}
-	errc <- merr
 }
 
 // batch is a write-only leveldb batch that commits changes to its host database