Metrics improvements

- Label graphs by their duration, not update period
- Extend to 60 units so they are either 10 minutes or an hour of data
- Improvements to retention information
- Change javascript calculations, fixes #9 (I hope)

smtpd/listener.go

@@ -104,11 +104,12 @@ func metricsTicker(t *time.Ticker) {
 	}
 }
 
-// pushMetric adds the metric to the end of the list and returns a comma
-// separated string of the previous 50 entries
+// pushMetric adds the metric to the end of the list and returns a comma separated string of the
+// previous 61 entries.  We return 61 instead of 60 (an hour) because the chart on the client
+// tracks deltas between these values - there is nothing to compare the first value against.
 func pushMetric(history *list.List, ev expvar.Var) string {
 	history.PushBack(ev.String())
-	if history.Len() > 50 {
+	if history.Len() > 61 {
 		history.Remove(history.Front())
 	}
 	return JoinStringList(history)

smtpd/retention.go

@@ -13,6 +13,7 @@ var retentionScanCompleted time.Time
 var retentionScanCompletedMu sync.RWMutex
 
 var expRetentionDeletesTotal = new(expvar.Int)
+var expRetentionPeriod = new(expvar.Int)
 
 // History of certain stats
 var retentionDeletesHist = list.New()
@@ -22,6 +23,7 @@ var expRetentionDeletesHist = new(expvar.String)
 
 func StartRetentionScanner(ds DataStore) {
 	cfg := config.GetDataStoreConfig()
+	expRetentionPeriod.Set(int64(cfg.RetentionMinutes * 60))
 	if cfg.RetentionMinutes > 0 {
 		// Retention scanning enabled
 		log.Info("Retention configured for %v minutes", cfg.RetentionMinutes)
@@ -109,4 +111,5 @@ func init() {
 	rm.Set("SecondsSinceScanCompleted", expvar.Func(secondsSinceRetentionScanCompleted))
 	rm.Set("DeletesHist", expRetentionDeletesHist)
 	rm.Set("DeletesTotal", expRetentionDeletesTotal)
+	rm.Set("Period", expRetentionPeriod)
 }