leveldb: add write delay statistic

leveldb/db.go

@@ -51,6 +51,8 @@ type DB struct {
 
 	// Stats.
 	aliveSnaps, aliveIters int32
+	cWriteDelayN           int32 // The cumulative number of write delays
+	cWriteDelay            int64 // The cumulative duration of write delays
 
 	// Write.
 	batchPool    sync.Pool
@@ -904,6 +906,8 @@ func (db *DB) GetSnapshot() (*Snapshot, error) {
 //		Returns the number of files at level 'n'.
 //	leveldb.stats
 //		Returns statistics of the underlying DB.
+//	leveldb.writedelay
+//		Returns cumulative write delay caused by compaction.
 //	leveldb.sstables
 //		Returns sstables list for each level.
 //	leveldb.blockpool
@@ -955,6 +959,9 @@ func (db *DB) GetProperty(name string) (value string, err error) {
 				level, len(tables), float64(tables.size())/1048576.0, duration.Seconds(),
 				float64(read)/1048576.0, float64(write)/1048576.0)
 		}
+	case p == "writedelay":
+		writeDelayN, writeDelay := atomic.LoadInt32(&db.cWriteDelayN), atomic.LoadInt64(&db.cWriteDelay)
+		value = fmt.Sprintf("DelayN:%d Delay(sec):%.5f", writeDelayN, float64(writeDelay)/1000000000.0)
 	case p == "sstables":
 		for level, tables := range v.levels {
 			value += fmt.Sprintf("--- level %d ---\n", level)

leveldb/db_write.go

@@ -12,6 +12,7 @@ import (
 	"github.com/syndtr/goleveldb/leveldb/memdb"
 	"github.com/syndtr/goleveldb/leveldb/opt"
 	"github.com/syndtr/goleveldb/leveldb/util"
+	"sync/atomic"
 )
 
 func (db *DB) writeJournal(batches []*Batch, seq uint64, sync bool) error {
@@ -117,6 +118,8 @@ func (db *DB) flush(n int) (mdb *memDB, mdbFree int, err error) {
 		db.writeDelayN++
 	} else if db.writeDelayN > 0 {
 		db.logf("db@write was delayed N·%d T·%v", db.writeDelayN, db.writeDelay)
+		atomic.AddInt32(&db.cWriteDelayN, int32(db.writeDelayN))
+		atomic.AddInt64(&db.cWriteDelay, db.writeDelay.Nanoseconds())
 		db.writeDelay = 0
 		db.writeDelayN = 0
 	}

manualtest/dbstress/main.go

@@ -425,9 +425,9 @@ func main() {
 			alivesnaps, _ := db.GetProperty("leveldb.alivesnaps")
 			aliveiters, _ := db.GetProperty("leveldb.aliveiters")
 			blockpool, _ := db.GetProperty("leveldb.blockpool")
-			log.Printf("> BlockCache=%s OpenedTables=%s AliveSnaps=%s AliveIter=%s BlockPool=%q",
-				cachedblock, openedtables, alivesnaps, aliveiters, blockpool)
-
+			writeDelay, _ := db.GetProperty("leveldb.writedelay")
+			log.Printf("> BlockCache=%s OpenedTables=%s AliveSnaps=%s AliveIter=%s BlockPool=%q WriteDelay=%q",
+				cachedblock, openedtables, alivesnaps, aliveiters, blockpool, writeDelay)
 			log.Print("------------------------")
 		}
 	}()