Make Logparser Plugin Check For New Files

plugins/inputs/logparser/logparser.go

@@ -26,7 +26,7 @@ type LogParserPlugin struct {
 	Files         []string
 	FromBeginning bool
 
-	tailers []*tail.Tail
+	tailers map[string]*tail.Tail
 	lines   chan string
 	done    chan struct{}
 	wg      sync.WaitGroup
@@ -46,7 +46,9 @@ const sampleConfig = `
   ##   /var/log/*/*.log    -> find all .log files with a parent dir in /var/log
   ##   /var/log/apache.log -> only tail the apache log file
   files = ["/var/log/apache/access.log"]
-  ## Read file from beginning.
+  ## Read files that currently exist from the beginning. Files that are created
+  ## while telegraf is running (and that match the "files" globs) will always
+  ## be read from the beginning.
   from_beginning = false
 
   ## Parse logstash-style "grok" patterns:
@@ -77,7 +79,11 @@ func (l *LogParserPlugin) Description() string {
 }
 
 func (l *LogParserPlugin) Gather(acc telegraf.Accumulator) error {
-	return nil
+	l.Lock()
+	defer l.Unlock()
+
+	// always start from the beginning of files that appear while we're running
+	return l.tailNewfiles(true)
 }
 
 func (l *LogParserPlugin) Start(acc telegraf.Accumulator) error {
@@ -87,6 +93,7 @@ func (l *LogParserPlugin) Start(acc telegraf.Accumulator) error {
 	l.acc = acc
 	l.lines = make(chan string, 1000)
 	l.done = make(chan struct{})
+	l.tailers = make(map[string]*tail.Tail)
 
 	// Looks for fields which implement LogParser interface
 	l.parsers = []LogParser{}
@@ -121,14 +128,22 @@ func (l *LogParserPlugin) Start(acc telegraf.Accumulator) error {
 		return err
 	}
 
+	l.wg.Add(1)
+	go l.parser()
+
+	return l.tailNewfiles(l.FromBeginning)
+}
+
+// check the globs against files on disk, and start tailing any new files.
+// Assumes l's lock is held!
+func (l *LogParserPlugin) tailNewfiles(fromBeginning bool) error {
 	var seek tail.SeekInfo
-	if !l.FromBeginning {
+	if !fromBeginning {
 		seek.Whence = 2
 		seek.Offset = 0
 	}
 
-	l.wg.Add(1)
-	go l.parser()
+	errChan := errchan.New(len(l.Files))
 
 	// Create a "tailer" for each file
 	for _, filepath := range l.Files {
@@ -139,7 +154,13 @@ func (l *LogParserPlugin) Start(acc telegraf.Accumulator) error {
 		}
 		files := g.Match()
 		errChan = errchan.New(len(files))
+
 		for file, _ := range files {
+			if _, ok := l.tailers[file]; ok {
+				// we're already tailing this file
+				continue
+			}
+
 			tailer, err := tail.TailFile(file,
 				tail.Config{
 					ReOpen:    true,
@@ -152,7 +173,7 @@ func (l *LogParserPlugin) Start(acc telegraf.Accumulator) error {
 			// create a goroutine for each "tailer"
 			l.wg.Add(1)
 			go l.receiver(tailer)
-			l.tailers = append(l.tailers, tailer)
+			l.tailers[file] = tailer
 		}
 	}
 
@@ -166,6 +187,7 @@ func (l *LogParserPlugin) receiver(tailer *tail.Tail) {
 
 	var line *tail.Line
 	for line = range tailer.Lines {
+
 		if line.Err != nil {
 			log.Printf("E! Error tailing file %s, Error: %s\n",
 				tailer.Filename, line.Err)

plugins/inputs/logparser/logparser_test.go

@@ -1,6 +1,8 @@
 package logparser
 
 import (
+	"io/ioutil"
+	"os"
 	"runtime"
 	"strings"
 	"testing"
@@ -80,6 +82,47 @@ func TestGrokParseLogFiles(t *testing.T) {
 		map[string]string{})
 }
 
+func TestGrokParseLogFilesAppearLater(t *testing.T) {
+	emptydir, err := ioutil.TempDir("", "TestGrokParseLogFilesAppearLater")
+	defer os.RemoveAll(emptydir)
+	assert.NoError(t, err)
+
+	thisdir := getCurrentDir()
+	p := &grok.Parser{
+		Patterns:           []string{"%{TEST_LOG_A}", "%{TEST_LOG_B}"},
+		CustomPatternFiles: []string{thisdir + "grok/testdata/test-patterns"},
+	}
+
+	logparser := &LogParserPlugin{
+		FromBeginning: true,
+		Files:         []string{emptydir + "/*.log"},
+		GrokParser:    p,
+	}
+
+	acc := testutil.Accumulator{}
+	assert.NoError(t, logparser.Start(&acc))
+
+	time.Sleep(time.Millisecond * 500)
+	assert.Equal(t, acc.NFields(), 0)
+
+	os.Symlink(
+		thisdir+"grok/testdata/test_a.log",
+		emptydir+"/test_a.log")
+	assert.NoError(t, logparser.Gather(&acc))
+	time.Sleep(time.Millisecond * 500)
+
+	logparser.Stop()
+
+	acc.AssertContainsTaggedFields(t, "logparser_grok",
+		map[string]interface{}{
+			"clientip":      "192.168.1.1",
+			"myfloat":       float64(1.25),
+			"response_time": int64(5432),
+			"myint":         int64(101),
+		},
+		map[string]string{"response_code": "200"})
+}
+
 // Test that test_a.log line gets parsed even though we don't have the correct
 // pattern available for test_b.log
 func TestGrokParseLogFilesOneBad(t *testing.T) {