p2p/protocols: synchronize reporter run goroutine with db close

p2p/protocols/reporter.go

@@ -36,10 +36,13 @@ type AccountingMetrics struct {
 //for a graceful cleanup
 func (am *AccountingMetrics) Close() {
 	close(am.reporter.quit)
-	// save account metrics on close to avoid data loss
-	// when more metrics are measured between the last
-	// reporter run ticker tick and the close
-	am.reporter.save()
+	// wait for reporter loop to finish saving metrics
+	// before reporter database is closed
+	select {
+	case <-time.After(10 * time.Second):
+		log.Error("accounting metrics reporter timeout")
+	case <-am.reporter.done:
+	}
 	am.reporter.db.Close()
 }
 
@@ -50,6 +53,7 @@ type reporter struct {
 	interval time.Duration    //duration at which the reporter will persist metrics
 	db       *leveldb.DB      //the actual DB
 	quit     chan struct{}    //quit the reporter loop
+	done     chan struct{}    //signal that reporter loop is done
 }
 
 //NewMetricsDB creates a new LevelDB instance used to persist metrics defined
@@ -96,6 +100,7 @@ func NewAccountingMetrics(r metrics.Registry, d time.Duration, path string) *Acc
 		interval: d,
 		db:       db,
 		quit:     make(chan struct{}),
+		done:     make(chan struct{}),
 	}
 
 	//run the go routine
@@ -110,6 +115,9 @@ func NewAccountingMetrics(r metrics.Registry, d time.Duration, path string) *Acc
 
 //run is the goroutine which periodically sends the metrics to the configured LevelDB
 func (r *reporter) run() {
+	// signal that the reporter loop is done
+	defer close(r.done)
+
 	intervalTicker := time.NewTicker(r.interval)
 
 	for {
@@ -125,6 +133,9 @@ func (r *reporter) run() {
 			}
 		case <-r.quit:
 			//graceful shutdown
+			if err := r.save(); err != nil {
+				log.Error("unable to send metrics to LevelDB", "err", err)
+			}
 			return
 		}
 	}