Tail unit tests and README tweaks

plugins/inputs/tail/README.md

@@ -5,14 +5,14 @@ The tail plugin "tails" a logfile and parses each log message.
 By default, the tail plugin acts like the following unix tail command:
 
 ```
-tail --follow=name --lines=0 --retry myfile.log
+tail -F --lines=0 myfile.log
 ```
 
-- `--follow=name` means that it will follow the _name_ of the given file, so
-that it will be compatible with log-rotated files.
+- `-F` means that it will follow the _name_ of the given file, so
+that it will be compatible with log-rotated files, and that it will retry on
+inaccessible files.
 - `--lines=0` means that it will start at the end of the file (unless
 the `from_beginning` option is set).
-- `--retry` means it will retry on inaccessible files.
 
 see http://man7.org/linux/man-pages/man1/tail.1.html for more details.
 
@@ -24,6 +24,23 @@ The plugin expects messages in one of the
 ```toml
 # Stream a log file, like the tail -f command
 [[inputs.tail]]
-  # SampleConfig
+  ## files to tail.
+  ## These accept standard unix glob matching rules, but with the addition of
+  ## ** as a "super asterisk". ie:
+  ##   "/var/log/**.log"  -> recursively find all .log files in /var/log
+  ##   "/var/log/*/*.log" -> find all .log files with a parent dir in /var/log
+  ##   "/var/log/apache.log" -> just tail the apache log file
+  ##
+  ## See https://github.com/gobwas/glob for more examples
+  ##
+  files = ["/var/mymetrics.out"]
+  ## Read file from beginning.
+  from_beginning = false
+
+  ## Data format to consume.
+  ## Each data format has it's own unique set of configuration options, read
+  ## more about them here:
+  ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
+  data_format = "influx"
 ```
 

plugins/inputs/tail/tail.go

@@ -25,6 +25,12 @@ type Tail struct {
 	sync.Mutex
 }
 
+func NewTail() *Tail {
+	return &Tail{
+		FromBeginning: false,
+	}
+}
+
 const sampleConfig = `
   ## files to tail.
   ## These accept standard unix glob matching rules, but with the addition of
@@ -145,8 +151,6 @@ func (t *Tail) SetParser(parser parsers.Parser) {
 
 func init() {
 	inputs.Add("tail", func() telegraf.Input {
-		return &Tail{
-			FromBeginning: false,
-		}
+		return NewTail()
 	})
 }

plugins/inputs/tail/tail_test.go

@@ -1 +1,101 @@
 package tail
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/influxdata/telegraf/plugins/parsers"
+	"github.com/influxdata/telegraf/testutil"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestTailFromBeginning(t *testing.T) {
+	tmpfile, err := ioutil.TempFile("", "")
+	require.NoError(t, err)
+	defer os.Remove(tmpfile.Name())
+
+	tt := NewTail()
+	tt.FromBeginning = true
+	tt.Files = []string{tmpfile.Name()}
+	p, _ := parsers.NewInfluxParser()
+	tt.SetParser(p)
+	defer tt.Stop()
+	defer tmpfile.Close()
+
+	acc := testutil.Accumulator{}
+	require.NoError(t, tt.Start(&acc))
+
+	_, err = tmpfile.WriteString("cpu,mytag=foo usage_idle=100\n")
+	require.NoError(t, err)
+	require.NoError(t, tt.Gather(&acc))
+	time.Sleep(time.Millisecond * 50)
+
+	acc.AssertContainsTaggedFields(t, "cpu",
+		map[string]interface{}{
+			"usage_idle": float64(100),
+		},
+		map[string]string{
+			"mytag": "foo",
+		})
+}
+
+func TestTailFromEnd(t *testing.T) {
+	tmpfile, err := ioutil.TempFile("", "")
+	require.NoError(t, err)
+	defer os.Remove(tmpfile.Name())
+	_, err = tmpfile.WriteString("cpu,mytag=foo usage_idle=100\n")
+	require.NoError(t, err)
+
+	tt := NewTail()
+	tt.Files = []string{tmpfile.Name()}
+	p, _ := parsers.NewInfluxParser()
+	tt.SetParser(p)
+	defer tt.Stop()
+	defer tmpfile.Close()
+
+	acc := testutil.Accumulator{}
+	require.NoError(t, tt.Start(&acc))
+	time.Sleep(time.Millisecond * 100)
+
+	_, err = tmpfile.WriteString("cpu,othertag=foo usage_idle=100\n")
+	require.NoError(t, err)
+	require.NoError(t, tt.Gather(&acc))
+	time.Sleep(time.Millisecond * 50)
+
+	acc.AssertContainsTaggedFields(t, "cpu",
+		map[string]interface{}{
+			"usage_idle": float64(100),
+		},
+		map[string]string{
+			"othertag": "foo",
+		})
+	assert.Len(t, acc.Metrics, 1)
+}
+
+func TestTailBadLine(t *testing.T) {
+	tmpfile, err := ioutil.TempFile("", "")
+	require.NoError(t, err)
+	defer os.Remove(tmpfile.Name())
+
+	tt := NewTail()
+	tt.FromBeginning = true
+	tt.Files = []string{tmpfile.Name()}
+	p, _ := parsers.NewInfluxParser()
+	tt.SetParser(p)
+	defer tt.Stop()
+	defer tmpfile.Close()
+
+	acc := testutil.Accumulator{}
+	require.NoError(t, tt.Start(&acc))
+
+	_, err = tmpfile.WriteString("cpu mytag= foo usage_idle= 100\n")
+	require.NoError(t, err)
+	require.NoError(t, tt.Gather(&acc))
+	time.Sleep(time.Millisecond * 50)
+
+	assert.Len(t, acc.Metrics, 0)
+}