Fix bug that state was not persisted for rotated files.

Closes #1010

.gitignore

@@ -7,6 +7,7 @@
 .DS_Store
 /glide.lock
 /beats.iml
+*.dev.yml
 
 # Editor swap files
 *.swp

CHANGELOG.asciidoc

@@ -48,6 +48,7 @@ https://github.com/elastic/beats/compare/v1.1.0...master[Check the HEAD diff]
 - Stop filebeat if filebeat is started without any prospectors defined or empty prospectors {pull}644[644] {pull}647[647]
 - Improve shutdown of crawler and prospector to wait for clean completion {pull}720[720]
 - Omit `fields` from Filebeat events when null {issue}899[899]
+- - Fix registrar bug for rotated files {pull}1010[1010]
 
 *Winlogbeat*
 

filebeat/crawler/prospector_log.go

@@ -149,11 +149,12 @@ func (p ProspectorLog) checkNewFile(h *harvester.Harvester) {
 
 	logp.Debug("prospector", "Start harvesting unknown file: %s", h.Path)
 
+	// Call crawler if there if there exists a state for the given file
+	offset, resuming := p.Prospector.registrar.fetchState(h.Path, h.Stat.Fileinfo)
+
 	if p.checkOldFile(h) {
 
 		logp.Debug("prospector", "Fetching old state of file to resume: %s", h.Path)
-		// Call crawler if there if there exists a state for the given file
-		offset, resuming := p.Prospector.registrar.fetchState(h.Path, h.Stat.Fileinfo)
 
 		// Are we resuming a dead file? We have to resume even if dead so we catch any old updates to the file
 		// This is safe as the harvester, once it hits the EOF and a timeout, will stop harvesting
@@ -172,8 +173,6 @@ func (p ProspectorLog) checkNewFile(h *harvester.Harvester) {
 	} else if previousFile, err := p.getPreviousFile(h.Path, h.Stat.Fileinfo); err == nil {
 		p.continueExistingFile(h, previousFile)
 	} else {
-		// Call crawler if there if there exists a state for the given file
-		offset, _ := p.Prospector.registrar.fetchState(h.Path, h.Stat.Fileinfo)
 		p.resumeHarvesting(h, offset)
 	}
 }

filebeat/tests/system/test_registrar.py

@@ -153,3 +153,47 @@ def test_custom_registry_file_location(self):
         filebeat.check_kill_and_wait()
 
         assert os.path.isfile(os.path.join(self.working_dir, "a/b/c/registry"))
+
+    def test_rotating_file(self):
+        """
+        Checks that the registry is properly updated after a file is rotated
+        """
+        self.render_config_template(
+                path=os.path.abspath(self.working_dir) + "/log/*"
+        )
+
+        os.mkdir(self.working_dir + "/log/")
+        testfile = self.working_dir + "/log/test.log"
+
+        filebeat = self.start_beat()
+
+        with open(testfile, 'w') as f:
+            f.write("offset 9\n")
+
+        self.wait_until(
+                lambda: self.output_has(lines=1),
+                max_timeout=10)
+
+
+        testfilerenamed = self.working_dir + "/log/test.1.log"
+        os.rename(testfile, testfilerenamed)
+
+        with open(testfile, 'w') as f:
+            f.write("offset 10\n")
+
+
+        self.wait_until(
+                lambda: self.output_has(lines=2),
+                max_timeout=10)
+
+        filebeat.check_kill_and_wait()
+
+        # Check that file exist
+        data = self.get_dot_filebeat()
+
+        # Make sure the offsets are correctly set
+        data[os.path.abspath(testfile)]["offset"] = 10
+        data[os.path.abspath(testfilerenamed)]["offset"] = 9
+
+        # Check that 2 files are port of the registrar file
+        assert len(data) == 2