Sample logging for no broadcasts (#61)

In production occasionally a node will have an issue
and this can generate a LOT of logs. Sampling should
reduce the volume but still make it pretty obvious that
something is wrong.

Author: relistan

services_delegate.go

@@ -2,12 +2,13 @@ package main
 
 import (
 	"encoding/json"
+	"math/rand"
 	"time"
 
 	"github.com/Nitro/memberlist"
 	"github.com/Nitro/sidecar/catalog"
 	"github.com/Nitro/sidecar/service"
-	"github.com/armon/go-metrics"
+	metrics "github.com/armon/go-metrics"
 	"github.com/pquerna/ffjson/ffjson"
 	log "github.com/sirupsen/logrus"
 )
@@ -200,7 +201,11 @@ func (d *servicesDelegate) packPacket(broadcasts [][]byte, limit int, overhead i
 		// Don't warn on startup... it's fairly normal
 		gracePeriod := time.Now().UTC().Add(0 - (5 * time.Second))
 		if d.StartedAt.Before(gracePeriod) {
-			log.Warnf("All messages were too long to fit! No broadcasts!")
+			// Sample this so that we don't go apeshit logging when there is something
+			// a bit blocked up. We'll log 1/50th of the time.
+			if rand.Intn(50) == 1 {
+				log.Warnf("All messages were too long to fit! No broadcasts!")
+			}
 		}
 
 		// There could be a scenario here where one hugely long broadcast could