fix (multitenant collector): Use consistent report timestamp

Previously the code called `time.Now()` in two different places so the
timestamps didn't match. Now we use the timestamp of the report itself.

Add the collector's local time to the report if it didn't have one.

app/collector.go

@@ -348,6 +348,7 @@ func replay(a Adder, timestamps []time.Time, reports []report.Report) {
 	due := time.Now()
 	for {
 		for i, r := range reports {
+			r.TS = due
 			a.Add(nil, r, nil)
 			due = due.Add(delays[i])
 			delay := due.Sub(time.Now())

app/multitenant/aws_collector.go

@@ -538,7 +538,7 @@ func (c *awsCollector) Add(ctx context.Context, rep report.Report, buf []byte) e
 	}
 
 	// first, put the report on s3
-	rowKey, colKey := calculateDynamoKeys(userid, time.Now())
+	rowKey, colKey := calculateDynamoKeys(userid, rep.TS)
 	reportKey, err := calculateReportKey(rowKey, colKey)
 	if err != nil {
 		return err

app/multitenant/billing_emitter.go

@@ -59,7 +59,7 @@ func (e *BillingEmitter) Add(ctx context.Context, rep report.Report, buf []byte)
 		// proceeding.
 		return err
 	}
-	rowKey, colKey := calculateDynamoKeys(userID, now)
+	rowKey, colKey := calculateDynamoKeys(userID, rep.TS)
 
 	interval := e.reportInterval(rep)
 	// Cache the last-known value of interval for this user, and use

app/router.go

@@ -148,6 +148,10 @@ func RegisterReportPostHandler(a Adder, router *mux.Router) {
 			buf, _ = rpt.WriteBinary()
 		}
 
+		// If it didn't come in with a timestamp, give it one now
+		if rpt.TS.IsZero() {
+			rpt.TS = time.Now().UTC()
+		}
 		if err := a.Add(ctx, *rpt, buf.Bytes()); err != nil {
 			log.Errorf("Error Adding report: %v", err)
 			respondWith(w, http.StatusInternalServerError, err)