Fix async publisher sending empty events (elastic#2455)

CHANGELOG.asciidoc

@@ -57,6 +57,7 @@ https://github.com/elastic/beats/compare/v5.0.0-alpha5...master[Check the HEAD d
 
 *Filebeat*
 - Fix processor failure in Filebeat when using regex, contain, or equals with the message field. {issue}2178[2178]
+- Fix async publisher sending empty events {pull}2455[2455]
 
 *Winlogbeat*
 - Fix corrupt registry file that occurs on power loss by disabling file write caching. {issue}2313[2313]

filebeat/input/event.go

@@ -48,6 +48,12 @@ func (f *Event) ToMapStr() common.MapStr {
 	return event
 }
 
+// HasData returns true if the event itself contains data
+// Events without data are only state updates
+func (e *Event) HasData() bool {
+	return e.Bytes > 0
+}
+
 // mergeJSONFields writes the JSON fields in the event map,
 // respecting the KeysUnderRoot and OverwriteKeys configuration options.
 // If MessageKey is defined, the Text value from the event always

filebeat/publish/publish.go

@@ -111,7 +111,7 @@ func (p *syncLogPublisher) Start() {
 			pubEvents := make([]common.MapStr, 0, len(events))
 			for _, event := range events {
 				// Only send event with bytes read. 0 Bytes means state update only
-				if event.Bytes > 0 {
+				if event.HasData() {
 					pubEvents = append(pubEvents, event.ToMapStr())
 				}
 			}
@@ -172,9 +172,12 @@ func (p *asyncLogPublisher) Start() {
 			case <-p.done:
 				return
 			case events := <-p.in:
-				pubEvents := make([]common.MapStr, len(events))
-				for i, event := range events {
-					pubEvents[i] = event.ToMapStr()
+
+				pubEvents := make([]common.MapStr, 0, len(events))
+				for _, event := range events {
+					if event.HasData() {
+						pubEvents = append(pubEvents, event.ToMapStr())
+					}
 				}
 
 				batch := &eventsBatch{
@@ -185,6 +188,7 @@ func (p *asyncLogPublisher) Start() {
 					publisher.Signal(batch), publisher.Guaranteed)
 
 				p.active.append(batch)
+
 			case <-ticker.C:
 			}
 

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

@@ -74,6 +74,7 @@ filebeat.idle_timeout: 0.1s
 {% if not skip_registry_config %}
 filebeat.registry_file: {{ beat.working_dir + '/' }}{{ registryFile|default("registry")}}
 {%endif%}
+filebeat.publish_async: {{publish_async}}
 
 
 #================================ General =====================================

filebeat/tests/system/test_publisher.py

@@ -0,0 +1,60 @@
+from filebeat import BaseTest
+
+import os
+import platform
+import time
+import shutil
+import json
+from nose.plugins.skip import Skip, SkipTest
+
+
+# Additional tests: to be implemented
+# * Check if registrar file can be configured, set config param
+# * Check "updating" of registrar file
+# * Check what happens when registrar file is deleted
+
+
+class Test(BaseTest):
+
+    def test_registrar_file_content(self):
+        """
+        Check if registrar file is created correctly and content is as expected
+        """
+
+        self.render_config_template(
+            path=os.path.abspath(self.working_dir) + "/log/*",
+            publish_async=True
+        )
+        os.mkdir(self.working_dir + "/log/")
+
+        filebeat = self.start_beat()
+
+        testfile = self.working_dir + "/log/test.log"
+        file = open(testfile, 'w')
+
+        iterations = 5
+        for n in range(0, iterations):
+            file.write("line " + str(n+1))
+            file.write("\n")
+
+        file.close()
+
+        # Let it read the file
+        self.wait_until(
+            lambda: self.output_has(lines=iterations), max_timeout=10)
+
+        self.wait_until(
+            lambda: self.output_has(lines=iterations), max_timeout=10)
+
+        # Wait until registry file is written
+        self.wait_until(
+            lambda: self.log_contains(
+                "Registry file updated."),
+            max_timeout=15)
+
+        filebeat.check_kill_and_wait()
+
+        data = self.get_registry()
+        assert len(data) == 1
+        assert self.output_has(lines=iterations)
+