Avoid infinite loop in Kubernetes watcher

In case of unmarshalling errors the Watcher was ending up in a infinite loop,
this code ignores those errors and only restarts the watcher in case of
EOF.

CHANGELOG.asciidoc

@@ -30,6 +30,8 @@ https://github.com/elastic/beats/compare/v6.2.0...6.2[Check the HEAD diff]
 
 *Affecting all Beats*
 
+- Fix infinite loop when event unmarshal fails in Kubernetes pod watcher. {pull}6353[6353]
+
 *Auditbeat*
 
 *Filebeat*

libbeat/common/kubernetes/watcher.go

@@ -3,6 +3,7 @@ package kubernetes
 import (
 	"context"
 	"errors"
+	"io"
 	"sync"
 	"time"
 
@@ -144,8 +145,16 @@ func (p *podWatcher) watch() {
 			_, apiPod, err := watcher.Next()
 			if err != nil {
 				logp.Err("kubernetes: Watching API error %v", err)
-				watcher.Close()
-				break
+
+				// In case of EOF, stop watching and restart the process
+				if err == io.EOF || err == io.ErrUnexpectedEOF {
+					watcher.Close()
+					time.Sleep(time.Second)
+					break
+				}
+
+				// Otherwise, this is probably an unknown event (unmarshal error), ignore it
+				continue
 			}
 
 			// Update last resource version