Properly shut down crawler in case one prospector is misconfigured

If one prospector started to already send data and a second one was misconfigured, the beat paniced during shutdown. This is no prevented by properly shutting down the crawler also on error.

Closes #3917

CHANGELOG.asciidoc

@@ -61,6 +61,7 @@ https://github.com/elastic/beats/compare/v5.1.1...master[Check the HEAD diff]
 - Downgrade Elasticsearch per batch item failure log to debug level. {issue}3953[3953]
 - Allow log lines without a program name in the Syslog fileset. {pull}3944[3944]
 - Fix panic in JSON decoding code if the input line is "null". {pull}4042[4042]
+- Properly shut down crawler in case one prospector is misconfigured. {pull}4037[4037]
 
 *Heartbeat*
 - Add default ports in HTTP monitor. {pull}3924[3924]

filebeat/beater/filebeat.go

@@ -184,6 +184,7 @@ func (fb *Filebeat) Run(b *beat.Beat) error {
 
 	err = crawler.Start(registrar, config.ProspectorReload)
 	if err != nil {
+		crawler.Stop()
 		return err
 	}
 

filebeat/crawler/crawler.go

@@ -76,7 +76,7 @@ func (c *Crawler) startProspector(config *common.Config, states []file.State) er
 
 	err = p.LoadStates(states)
 	if err != nil {
-		return fmt.Errorf("error loading states for propsector %v: %v", p.ID(), err)
+		return fmt.Errorf("error loading states for prospector %v: %v", p.ID(), err)
 	}
 
 	c.prospectors[p.ID()] = p

filebeat/prospector/prospector.go

@@ -148,7 +148,7 @@ func (p *Prospector) Start() {
 				logp.Info("Prospector channel stopped")
 				return
 			case <-p.beatDone:
-				logp.Info("Prospector channel stopped")
+				logp.Info("Prospector channel stopped because beat is stopping.")
 				return
 			case event := <-p.harvesterChan:
 				// No stopping on error, because on error it is expected that beatDone is closed

filebeat/prospector/prospector_log.go

@@ -32,6 +32,10 @@ func NewLog(p *Prospector) (*Log, error) {
 		config:     p.config,
 	}
 
+	if len(p.config.Paths) == 0 {
+		return nil, fmt.Errorf("each prospector must have at least one path defined")
+	}
+
 	return prospectorer, nil
 }
 

filebeat/prospector/prospector_test.go

@@ -28,6 +28,7 @@ func TestProspectorFileExclude(t *testing.T) {
 
 	prospector := Prospector{
 		config: prospectorConfig{
+			Paths:        []string{"test.log"},
 			ExcludeFiles: []match.Matcher{match.MustCompile(`\.gz$`)},
 		},
 	}

filebeat/tests/system/config/filebeat.yml.j2

@@ -82,6 +82,9 @@ filebeat.prospectors:
     max_lines: {{ max_lines|default(500) }}
   {% endif %}
 {% endif %}
+{% if prospector_raw %}
+{{prospector_raw}}
+{% endif %}
 
 filebeat.spool_size:
 filebeat.shutdown_timeout: {{ shutdown_timeout|default(0) }}

filebeat/tests/system/test_shutdown.py

@@ -146,3 +146,27 @@ def nasa_logs(self):
         self.copy_files(["logs/nasa-50k.log"],
                         source_dir="../files",
                         target_dir="log")
+
+    def test_stopping_empty_path(self):
+        """
+        Test filebeat stops properly when 1 prospector has an invalid config.
+        """
+
+        prospector_raw = """
+- input_type: log
+  paths: []
+"""
+
+        self.render_config_template(
+            path=os.path.abspath(self.working_dir) + "/log/*",
+            prospector_raw=prospector_raw,
+        )
+        filebeat = self.start_beat()
+        time.sleep(2)
+
+        # Wait until first flush
+        self.wait_until(
+            lambda: self.log_contains_count("No paths were defined for prospector") >= 1,
+            max_timeout=5)
+
+        filebeat.check_wait(exit_code=1)