Reduce database size

...and it's not a breaking change!
fix #36

Benchmark: using config/heavy-load.yml
From 14MB to 8MB → 40% of size reduction!

app/daemon.go

@@ -187,7 +187,7 @@ func MatchesManager() {
 			matchesManagerHandleFlush(fo)
 		case pft = <-matchesC:
 
-			entry := LogEntry{pft.t, pft.p, pft.f.stream.name, pft.f.name, false}
+			entry := LogEntry{pft.t, pft.p, pft.f.stream.name, pft.f.name, 0, false}
 
 			entry.Exec = matchesManagerHandleMatch(pft)
 

app/persist.go

@@ -43,16 +43,18 @@ func DatabaseManager(c *Conf) {
 }
 
 func (c *Conf) manageLogs(logDB *WriteDB, flushDB *WriteDB) {
-	var cpt int
+	cpt := 0
+	writeSF2int := make(map[SF]int)
+	writeCpt := 1
 	for {
 		select {
 		case entry := <-flushToDatabaseC:
 			flushDB.enc.Encode(entry)
 		case entry := <-logsC:
-			logDB.enc.Encode(entry)
+			encodeOrFatal(logDB.enc, entry, writeSF2int, &writeCpt)
 			cpt++
 			// let's say 100 000 entries ~ 10 MB
-			if cpt == 100_000 {
+			if cpt == 500_000 {
 				cpt = 0
 				logger.Printf(logger.INFO, "Rotating database...")
 				logDB.file.Close()
@@ -111,6 +113,12 @@ func (c *Conf) RotateDB(startup bool) (*WriteDB, *WriteDB) {
 }
 
 func rotateDB(c *Conf, logDec *gob.Decoder, flushDec *gob.Decoder, logEnc *gob.Encoder, startup bool) {
+	// This mapping is a space optimization feature
+	// It permits to compress stream+filter to a small number (which is a byte in gob)
+	// We do this only for matches, not for flushes
+	readSF2int := make(map[int]SF)
+	writeSF2int := make(map[SF]int)
+	writeCounter := 1
 	// This extra code is made to warn only one time for each non-existant filter
 	discardedEntries := make(map[SF]int)
 	malformedEntries := 0
@@ -170,7 +178,26 @@ func rotateDB(c *Conf, logDec *gob.Decoder, flushDec *gob.Decoder, logEnc *gob.E
 			continue
 		}
 
-		// retrieve related filter
+		// retrieve related stream & filter
+		if entry.Stream == "" && entry.Filter == "" {
+			if entry.SF != 0 {
+				sf, ok := readSF2int[entry.SF]
+				if ok {
+					entry.Stream = sf.s
+					entry.Filter = sf.f
+				} else {
+					discardedEntries[SF{"", ""}]++
+					continue
+				}
+			} else {
+				discardedEntries[SF{"", ""}]++
+				continue
+			}
+			// Only one of Stream, Filter is non-empty
+			// } else if entry.Stream == "" || entry.Filter == "" {
+			// discardedEntries[SF{"", ""}]++
+			// continue
+		} else {
 			if stream := c.Streams[entry.Stream]; stream != nil {
 				filter = stream.Filters[entry.Filter]
 			}
@@ -178,6 +205,10 @@ func rotateDB(c *Conf, logDec *gob.Decoder, flushDec *gob.Decoder, logEnc *gob.E
 				discardedEntries[SF{entry.Stream, entry.Filter}]++
 				continue
 			}
+			if entry.SF != 0 {
+				readSF2int[entry.SF] = SF{entry.Stream, entry.Filter}
+			}
+		}
 
 		// check if it hasn't been flushed
 		lastGlobalFlush := flushes[PSF{entry.Pattern, "", ""}].Unix()
@@ -193,7 +224,7 @@ func rotateDB(c *Conf, logDec *gob.Decoder, flushDec *gob.Decoder, logEnc *gob.E
 				startupMatchesC <- PFT{entry.Pattern, filter, entry.T}
 			}
 
-			encodeOrFatal(logEnc, entry)
+			encodeOrFatal(logEnc, entry, writeSF2int, &writeCounter)
 		}
 
 		// replay executions
@@ -203,12 +234,22 @@ func rotateDB(c *Conf, logDec *gob.Decoder, flushDec *gob.Decoder, logEnc *gob.E
 				filter.sendActions(entry.Pattern, entry.T)
 			}
 
-			encodeOrFatal(logEnc, entry)
+			encodeOrFatal(logEnc, entry, writeSF2int, &writeCounter)
 		}
 	}
 }
 
-func encodeOrFatal(enc *gob.Encoder, entry LogEntry) {
+func encodeOrFatal(enc *gob.Encoder, entry LogEntry, writeSF2int map[SF]int, writeCounter *int) {
+	sf, ok := writeSF2int[SF{entry.Stream, entry.Filter}]
+	if ok {
+		entry.SF = sf
+		entry.Stream = ""
+		entry.Filter = ""
+	} else {
+		entry.SF = *writeCounter
+		writeSF2int[SF{entry.Stream, entry.Filter}] = *writeCounter
+		*writeCounter++
+	}
 	err := enc.Encode(entry)
 	if err != nil {
 		logger.Fatalln("Failed to write to new DB:", err)

app/pipe.go

@@ -99,7 +99,7 @@ func SocketManager(streams map[string]*Stream) {
 			case Show:
 				response.ClientStatus = genClientStatus(actions, matches, &actionsLock, &matchesLock)
 			case Flush:
-				le := LogEntry{time.Now(), request.Pattern, "", "", false}
+				le := LogEntry{time.Now(), request.Pattern, "", "", 0, false}
 				matchesC := FlushMatchOrder{request.Pattern, make(chan MatchesMap)}
 				actionsC := FlushActionOrder{request.Pattern, make(chan ActionsMap)}
 				flushToMatchesC <- matchesC

app/types.go

@@ -64,6 +64,7 @@ type LogEntry struct {
 	T              time.Time
 	Pattern        string
 	Stream, Filter string
+	SF             int
 	Exec           bool
 }