respect event ids

logdriver.go

@@ -50,8 +50,10 @@ func (l LogDriver) Tail(filepath string, offset int64) (t *tail.Tail, err error)
 		ReOpen:    true,
 		Logger:    l.Logger,
 	}
-	if offset != 0 {
+	if offset > 0 {
 		config.Location = &tail.SeekInfo{offset, os.SEEK_SET}
+	} else if offset < 0 {
+		config.Location = &tail.SeekInfo{offset, os.SEEK_END}
 	} else {
 		config.Location = &tail.SeekInfo{0, os.SEEK_END}
 	}
@@ -78,9 +80,9 @@ func (l LogDriver) StartServer(address string) {
 func (l LogDriver) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	// get the params from the URL path
 	params := mux.Vars(r)
-	n := r.FormValue("n")
+	n := r.Header.Get("Last-Event-ID")
 	if n == "" {
-		n = r.Header.Get("Last-Event-ID")
+		n = r.FormValue("n")
 		if n == "" {
 			n = "0"
 		}
@@ -130,7 +132,7 @@ func (l LogDriver) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	go func() {
 		for line := range tail.Lines {
 			offset, _ := tail.Tell()
-			fmt.Fprint(w, "event:log\n")
+			fmt.Fprint(w, "event: log\n")
 			fmt.Fprintf(w, "id: %d\n", offset)
 			fmt.Fprintf(w, "data: %s\n", line.Text)
 			fmt.Fprint(w, "retry: 0\n")

logdriver_test.go

@@ -104,7 +104,7 @@ func TestTail(t *testing.T) {
 	filePath := lt.CreateFile("test.txt", "foo\n")
 
 	ld := NewLogDriver("test_tail_file", []string{"*"}, tail.DiscardingLogger)
-	tail, _ := ld.Tail(filePath, 0)
+	tail, _ := ld.Tail(filePath, -12)
 
 	lt.AppendFile("test.txt", "bar\nbaz\n")
 	done := make(chan bool)
@@ -133,16 +133,18 @@ func TestServeHTTP(t *testing.T) {
 
 	ld := NewLogDriver(lt.path, []string{"*"}, tail.DiscardingLogger)
 
-	r, _ := http.NewRequest("GET", "http://localhost:3000/tail/foo.txt", nil)
+	r, _ := http.NewRequest("GET", "http://localhost:3000/tail/foo.txt?n=-12", nil)
 	w := NewClosableRecorder()
-
 	router := ld.NewRouter()
 	go router.ServeHTTP(w, r)
 
 	lt.AppendFile("foo.txt", "bar\nbaz\n")
-	// NOTE: I'm doing something awfully wrong here
 	<-time.After(100 * time.Millisecond)
-	go lt.AssertRecorderOutput(w, []string{"data: foo", "data: bar", "data: baz"}, w.closer)
+	go lt.AssertRecorderOutput(w, []string{
+			"event: log\nid: 4\ndata: foo\nretry: 0",
+			"event: log\nid: 12\ndata: bar\nretry: 0",
+			"event: log\nid: 12\ndata: baz\nretry: 0",
+		}, w.closer)
 
 }