When an tile is rendered the writing to disk can be done in background

concurrently to the rendering of the next tile.

cmd/mtwebmapper/tilesupdater.go

@@ -213,9 +213,9 @@ func (tu *tileUpdater) doUpdates() {
 			btc := common.NewBaseTileCreator(
 				client, tu.colors, tu.bg,
 				tu.yMin, tu.yMax,
-				tu.transparent, baseDir, bth.Update)
+				tu.transparent, baseDir)
 			done.Add(1)
-			go tu.updateBaseTiles(jobs, btc, &done)
+			go tu.updateBaseTiles(jobs, btc, &done, bth.Update)
 		}
 
 		for i := range changes {
@@ -338,19 +338,42 @@ func (tu *tileUpdater) updatePyramidTile(scratch, resized *image.RGBA, level int
 
 func (tu *tileUpdater) updateBaseTiles(
 	jobs chan *xzc,
-	btc *common.BaseTileCreator, done *sync.WaitGroup) {
+	btc *common.BaseTileCreator,
+	done *sync.WaitGroup,
+	update common.BaseTileUpdateFunc) {
+
+	type jobWriter struct {
+		job *xzc
+		wFn func() (bool, error)
+	}
+
+	jWs := make(chan jobWriter)
+
+	go func() {
+		for jw := range jWs {
+			updated, err := jw.wFn()
+			if err != nil {
+				log.Printf("WARN: writing tile failed: %v.\n", err)
+			}
+			if !updated {
+				jw.job.canceled = true
+			}
+		}
+	}()
+
+	defer func() {
+		close(jWs)
+		btc.Close()
+		done.Done()
+	}()
 
-	defer btc.Close()
-	defer done.Done()
 	for job := range jobs {
 		xz := job.dequantize()
-		//log.Printf("%d/%d %d/%d", x, z, job.X, job.Z)
-		updated, err := btc.CreateTile(xz.X-1, xz.Z-1, int(job.X), int(job.Z))
-		if err != nil {
-			log.Printf("WARN: create tile failed: %s\n", err)
-		}
-		if !updated {
+		if err := btc.RenderArea(xz.X-1, xz.Z-1); err != nil {
+			log.Printf("WARN: rendering tile failed: %v.\n", err)
 			job.canceled = true
+			continue
 		}
+		jWs <- jobWriter{job, btc.WriteFunc(int(job.X), int(job.Z), update)}
 	}
 }