Move db writes to a separate goroutine.

main/datalog.go

@@ -30,7 +30,7 @@ type StratuxTimestamp struct {
 	id                   int64
 	Time_type_preference int // 0 = stratuxClock, 1 = gpsClock, 2 = gpsClock extrapolated via stratuxClock.
 	StratuxClock_value   time.Time
-	GPSClock_value       time.Time
+	GPSClock_value       time.Time // The value of this is either from the GPS or extrapolated from the GPS via stratuxClock if pref is 1 or 2. It is time.Time{} if 0.
 	PreferredTime_value  time.Time
 }
 
@@ -66,6 +66,7 @@ func checkTimestamp() bool {
 				// Re-set the preferred timestamp type to '2' (extrapolated time).
 				ts.Time_type_preference = 2
 				ts.PreferredTime_value = extrapolatedGPSTimestamp
+				ts.GPSClock_value = extrapolatedGPSTimestamp
 			}
 		}
 
@@ -267,7 +268,30 @@ type DataLogRow struct {
 var dataLogChan chan DataLogRow
 var shutdownDataLog chan bool
 
-func dataLogWriter() {
+var dataLogWriteChan chan DataLogRow
+
+func dataLogWriter(db *sql.DB) {
+	dataLogWriteChan = make(chan DataLogRow, 10240)
+	// The write queue. As data comes in via dataLogChan, it is timestamped and stored.
+	//  When writeTicker comes up, the queue is emptied.
+	writeTicker := time.NewTicker(5 * time.Second)
+	rowsQueuedForWrite := make([]DataLogRow, 0)
+	for {
+		select {
+		case r := <-dataLogWriteChan:
+			// Accept timestamped row.
+			rowsQueuedForWrite = append(rowsQueuedForWrite, r)
+		case <-writeTicker.C:
+			// Write the buffered rows. This will block occasionally.
+			for _, r := range rowsQueuedForWrite {
+				insertData(r.data, r.tbl, db, r.ts_num)
+			}
+			rowsQueuedForWrite = make([]DataLogRow, 0) // Zero the queue.
+		}
+	}
+}
+
+func dataLog() {
 	dataLogChan = make(chan DataLogRow, 10240)
 	shutdownDataLog = make(chan bool)
 	dataLogTimestamps = make(map[int64]StratuxTimestamp, 0)
@@ -286,6 +310,8 @@ func dataLogWriter() {
 	}
 	defer db.Close()
 
+	go dataLogWriter(db)
+
 	// Do we need to create the database?
 	if createDatabase {
 		makeTable(StratuxTimestamp{}, "timestamp", db)
@@ -297,27 +323,16 @@ func dataLogWriter() {
 		makeTable(Dump1090TermMessage{}, "dump1090_terminal", db)
 	}
 
-	// The write queue. As data comes in via dataLogChan, it is timestamped and stored.
-	//  When writeTicker comes up, the queue is emptied.
-	rowsQueuedForWrite := make([]DataLogRow, 0)
-	writeTicker := time.NewTicker(5 * time.Second)
-
 	for {
 		select {
-		//FIXME: measure latency from here to end of block. Messages may need to be timestamped *before* executing everything here.
 		case r := <-dataLogChan:
-
+			// When data is input, the first step is to timestamp it.
 			// Check if our time bucket has expired or has never been entered.
 			checkTimestamp()
 			// Mark the row with the current timestamp ID, in case it gets entered later.
 			r.ts_num = dataLogCurTimestamp
 			// Queue it for the scheduled write.
-			rowsQueuedForWrite = append(rowsQueuedForWrite, r)
-		case <-writeTicker.C:
-			for _, r := range rowsQueuedForWrite {
-				insertData(r.data, r.tbl, db, r.ts_num)
-			}
-			rowsQueuedForWrite = make([]DataLogRow, 0) // Zero the queue.
+			dataLogWriteChan <- r
 		case <-shutdownDataLog: // Received a message on the channel (anything). Graceful shutdown (defer statement).
 			return
 		}
@@ -375,5 +390,5 @@ func logDump1090TermMessage(m Dump1090TermMessage) {
 }
 
 func initDataLog() {
-	go dataLogWriter()
+	go dataLog()
 }