If specified the MaxLineSize, then set to the bufio.reader MaxLineSize.

tail.go

@@ -171,7 +171,7 @@ func (tail *Tail) reopen() error {
 
 func (tail *Tail) readLine() ([]byte, error) {
 	line, isPrefix, err := tail.reader.ReadLine()
-	if !isPrefix {
+	if !isPrefix || tail.MaxLineSize > 0 {
 		return line, err
 	}
 
@@ -208,7 +208,7 @@ func (tail *Tail) tailFileSync() {
 		}
 	}
 
-	tail.reader = bufio.NewReader(tail.file)
+	tail.reader = tail.newReader()
 
 	// Read line by line.
 	for {
@@ -289,7 +289,7 @@ func (tail *Tail) waitForChanges() error {
 				return err
 			}
 			tail.Logger.Printf("Successfully reopened %s", tail.Filename)
-			tail.reader = bufio.NewReader(tail.file)
+			tail.reader = tail.newReader()
 			return nil
 		} else {
 			tail.Logger.Printf("Stopping tail as file no longer exists: %s", tail.Filename)
@@ -302,7 +302,7 @@ func (tail *Tail) waitForChanges() error {
 			return err
 		}
 		tail.Logger.Printf("Successfully reopened truncated %s", tail.Filename)
-		tail.reader = bufio.NewReader(tail.file)
+		tail.reader = tail.newReader()
 		return nil
 	case <-tail.Dying():
 		return ErrStop
@@ -310,6 +310,14 @@ func (tail *Tail) waitForChanges() error {
 	panic("unreachable")
 }
 
+func (tail *Tail) newReader() *bufio.Reader {
+	if tail.MaxLineSize > 0 {
+		return bufio.NewReaderSize(tail.file, tail.MaxLineSize+2)
+	} else {
+		return bufio.NewReader(tail.file)
+	}
+}
+
 // sendLine sends the line(s) to Lines channel, splitting longer lines
 // if necessary. Return false if rate limit is reached.
 func (tail *Tail) sendLine(line []byte) bool {

tail_test.go

@@ -10,6 +10,7 @@ import (
 	_ "fmt"
 	"io/ioutil"
 	"os"
+	"strings"
 	"testing"
 	"time"
 )
@@ -66,6 +67,35 @@ func TestMaxLineSize(_t *testing.T) {
 	Cleanup()
 }
 
+func TestOver4096ByteLine(_t *testing.T) {
+	t := NewTailTest("Over4096ByteLine", _t)
+	testString := strings.Repeat("a", 4097)
+	t.CreateFile("test.txt", "test\n"+testString+"\nhello\nworld\n")
+	tail := t.StartTail("test.txt", Config{Follow: true, Location: nil})
+	go t.VerifyTailOutput(tail, []string{"test", testString, "hello", "world"})
+
+	// Delete after a reasonable delay, to give tail sufficient time
+	// to read all lines.
+	<-time.After(100 * time.Millisecond)
+	t.RemoveFile("test.txt")
+	tail.Stop()
+	Cleanup()
+}
+func TestOver4096ByteLineWithSetMaxLineSize(_t *testing.T) {
+	t := NewTailTest("Over4096ByteLineMaxLineSize", _t)
+	testString := strings.Repeat("a", 4097)
+	t.CreateFile("test.txt", "test\r\n"+testString+"\r\nhello\r\nworld\r\n")
+	tail := t.StartTail("test.txt", Config{Follow: true, Location: nil, MaxLineSize: 4097})
+	go t.VerifyTailOutput(tail, []string{"test", testString, "hello", "world"})
+
+	// Delete after a reasonable delay, to give tail sufficient time
+	// to read all lines.
+	<-time.After(100 * time.Millisecond)
+	t.RemoveFile("test.txt")
+	tail.Stop()
+	Cleanup()
+}
+
 func TestLocationFull(_t *testing.T) {
 	t := NewTailTest("location-full", _t)
 	t.CreateFile("test.txt", "hello\nworld\n")