Fix empty registry file on machine crash

CHANGELOG.asciidoc

@@ -44,6 +44,7 @@ https://github.com/elastic/beats/compare/v5.1.1...master[Check the HEAD diff]
 - Always use absolute path for event and registry. {pull}3328[3328]
 - Raise an exception in case there is a syntax error in one of the configuration files available under
   filebeat.config_dir. {pull}3573[3573]
+- Fix empty registry file on machine crash. {issue}3537[3537]
 
 *Heartbeat*
 

filebeat/registrar/registrar.go

@@ -298,7 +298,7 @@ func (r *Registrar) writeRegistry() error {
 	logp.Debug("registrar", "Write registry file: %s", r.registryFile)
 
 	tempfile := r.registryFile + ".new"
-	f, err := os.OpenFile(tempfile, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
+	f, err := os.OpenFile(tempfile, os.O_RDWR|os.O_CREATE|os.O_TRUNC|os.O_SYNC, 0600)
 	if err != nil {
 		logp.Err("Failed to create tempfile (%s) for writing: %s", tempfile, err)
 		return err

winlogbeat/checkpoint/file_unix.go

@@ -5,5 +5,5 @@ package checkpoint
 import "os"
 
 func create(path string) (*os.File, error) {
-	return os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
+	return os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC|os.O_SYNC, 0600)
 }