Reduce filebeat verbosity at INFO level

Part of elastic#1931. Replaces two of the "periodic" Infos with Debugs + expvars.

filebeat/prospector/prospector.go

@@ -129,7 +129,7 @@ func (p *Prospector) Run() {
 			logp.Info("Prospector ticker stopped")
 			return
 		case <-time.After(p.config.ScanFrequency):
-			logp.Info("Run prospector")
+			logp.Debug("prospector", "Run prospector")
 			p.prospectorer.Run()
 		}
 	}

filebeat/publish/publish.go

@@ -1,6 +1,7 @@
 package publish
 
 import (
+	"expvar"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -61,6 +62,10 @@ const (
 	batchCanceled
 )
 
+var (
+	eventsSent = expvar.NewInt("publish.events")
+)
+
 func New(
 	async bool,
 	in, out chan []*input.FileEvent,
@@ -108,7 +113,8 @@ func (p *syncLogPublisher) Start() {
 			}
 
 			p.client.PublishEvents(pubEvents, publisher.Sync, publisher.Guaranteed)
-			logp.Info("Events sent: %d", len(events))
+			logp.Debug("publish", "Events sent: %d", len(events))
+			eventsSent.Add(int64(len(events)))
 
 			// Tell the registrar that we've successfully sent these events
 			select {

filebeat/registrar/registrar.go

@@ -2,6 +2,7 @@ package registrar
 
 import (
 	"encoding/json"
+	"expvar"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -24,6 +25,10 @@ type Registrar struct {
 	wg           sync.WaitGroup
 }
 
+var (
+	statesUpdated = expvar.NewInt("registrar.state_updates")
+)
+
 func New(registryFile string) (*Registrar, error) {
 
 	r := &Registrar{
@@ -234,7 +239,8 @@ func (r *Registrar) writeRegistry() error {
 	// Directly close file because of windows
 	f.Close()
 
-	logp.Info("Registry file updated. %d states written.", len(states))
+	logp.Debug("registrar", "Registry file updated. %d states written.", len(states))
+	statesUpdated.Add(int64(len(states)))
 
 	return file.SafeFileRotate(r.registryFile, tempfile)
 }