Make Logparser Plugin Check For New Files (influxdata#2141)

* Make Logparser Plugin Check For New Files

Check in the Gather metric to see if any new files matching the glob
have appeared. If so, start tailing them from the beginning.

* changelog update for influxdata#2141

CHANGELOG.md

@@ -1,4 +1,42 @@
 ## v1.2 [unreleased]
+## v1.3 [unreleased]
+
+### Release Notes
+
+- The [Riemann output plugin](./plugins/outputs/riemann) has been rewritten
+and the previous riemann plugin is _incompatible_ with the new one. The reasons
+for this are outlined in issue [#1878](https://github.com/influxdata/telegraf/issues/1878).
+The previous riemann output will still be available using
+`outputs.riemann_legacy` if needed, but that will eventually be deprecated.
+It is highly recommended that all users migrate to the new riemann output plugin.
+
+### Features
+
+- [#2141](https://github.com/influxdata/telegraf/pull/2141): Logparser handles newly-created files.
+- [#2137](https://github.com/influxdata/telegraf/pull/2137): Added userstats to mysql input plugin.
+- [#2179](https://github.com/influxdata/telegraf/pull/2179): Added more InnoDB metric to MySQL plugin.
+- [#2251](https://github.com/influxdata/telegraf/pull/2251): InfluxDB output: use own client for improved through-put and less allocations.
+- [#1900](https://github.com/influxdata/telegraf/pull/1900): Riemann plugin rewrite.
+- [#1453](https://github.com/influxdata/telegraf/pull/1453): diskio: add support for name templates and udev tags.
+- [#2277](https://github.com/influxdata/telegraf/pull/2277): add integer metrics for Consul check health state.
+
+### Bugfixes
+
+- [#2077](https://github.com/influxdata/telegraf/issues/2077): SQL Server Input - Arithmetic overflow error converting numeric to data type int.
+- [#2262](https://github.com/influxdata/telegraf/issues/2262): Flush jitter can inhibit metric collection.
+
+## v1.2.1 [2017-02-01]
+
+### Bugfixes
+
+- [#2317](https://github.com/influxdata/telegraf/issues/2317): Fix segfault on nil metrics with influxdb output.
+- [#2324](https://github.com/influxdata/telegraf/issues/2324): Fix negative number handling.
+
+### Features
+
+- [#2348](https://github.com/influxdata/telegraf/pull/2348): Go version 1.7.4 -> 1.7.5
+
+## v1.2 [2017-01-00]
 
 ### Release Notes
 

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) {