Limit the number of bytes read by LineReader in Filebeat (elastic#19552)

(cherry picked from commit 0e049f0)

CHANGELOG.next.asciidoc

@@ -39,6 +39,7 @@ https://github.com/elastic/beats/compare/v6.8.0...6.8.1[Check the HEAD diff]
 
 *Filebeat*
 
+- Fix Filebeat OOMs on very long lines {issue}19500[19500], {pull}19552[19552]
 
 *Heartbeat*
 

filebeat/input/log/harvester.go

@@ -557,6 +557,8 @@ func (h *Harvester) newLogFileReader() (reader.Reader, error) {
 	var r reader.Reader
 	var err error
 
+	logp.Debug("harvester", "newLogFileReader with config.MaxBytes: %d", h.config.MaxBytes)
+
 	// TODO: NewLineReader uses additional buffering to deal with encoding and testing
 	//       for new lines in input stream. Simple 8-bit based encodings, or plain
 	//       don't require 'complicated' logic.
@@ -570,7 +572,13 @@ func (h *Harvester) newLogFileReader() (reader.Reader, error) {
 		return nil, err
 	}
 
-	r, err = readfile.NewEncodeReader(reader, h.encoding, h.config.BufferSize)
+	// Configure MaxBytes limit for EncodeReader as multiplied by 4
+	// for the worst case scenario where incoming UTF32 charchers are decoded to the single byte UTF-8 characters.
+	// This limit serves primarily to avoid memory bload or potential OOM with expectedly long lines in the file.
+	// The further size limiting is performed by LimitReader at the end of the readers pipeline as needed.
+	encReaderMaxBytes := h.config.MaxBytes * 4
+
+	r, err = readfile.NewEncodeReader(reader, h.encoding, h.config.BufferSize, encReaderMaxBytes)
 	if err != nil {
 		return nil, err
 	}

filebeat/reader/multiline/multiline_test.go

@@ -277,7 +277,7 @@ func createMultilineTestReader(t *testing.T, in *bytes.Buffer, cfg Config) reade
 	}
 
 	var r reader.Reader
-	r, err = readfile.NewEncodeReader(in, enc, 4096)
+	r, err = readfile.NewEncodeReader(in, enc, 4096, 4096)
 	if err != nil {
 		t.Fatalf("Failed to initialize line reader: %v", err)
 	}

filebeat/reader/readfile/encode.go

@@ -36,9 +36,9 @@ type EncoderReader struct {
 func NewEncodeReader(
 	r io.Reader,
 	codec encoding.Encoding,
-	bufferSize int,
+	bufferSize, maxBytes int,
 ) (EncoderReader, error) {
-	eReader, err := NewLineReader(r, codec, bufferSize)
+	eReader, err := NewLineReader(r, codec, bufferSize, maxBytes)
 	return EncoderReader{eReader}, err
 }
 

filebeat/reader/readfile/line.go

@@ -18,6 +18,7 @@
 package readfile
 
 import (
+	"bytes"
 	"io"
 
 	"golang.org/x/text/encoding"
@@ -34,6 +35,7 @@ type LineReader struct {
 	reader     io.Reader
 	codec      encoding.Encoding
 	bufferSize int
+	maxBytes   int
 	nl         []byte
 	inBuffer   *streambuf.Buffer
 	outBuffer  *streambuf.Buffer
@@ -43,7 +45,7 @@ type LineReader struct {
 }
 
 // New creates a new reader object
-func NewLineReader(input io.Reader, codec encoding.Encoding, bufferSize int) (*LineReader, error) {
+func NewLineReader(input io.Reader, codec encoding.Encoding, bufferSize, maxBytes int) (*LineReader, error) {
 	encoder := codec.NewEncoder()
 
 	// Create newline char based on encoding
@@ -56,6 +58,7 @@ func NewLineReader(input io.Reader, codec encoding.Encoding, bufferSize int) (*L
 		reader:     input,
 		codec:      codec,
 		bufferSize: bufferSize,
+		maxBytes:   maxBytes,
 		nl:         nl,
 		decoder:    codec.NewDecoder(),
 		inBuffer:   streambuf.New(nil),
@@ -138,6 +141,29 @@ func (r *LineReader) advance() error {
 
 		// Check if buffer has newLine character
 		idx = r.inBuffer.IndexFrom(r.inOffset, r.nl)
+
+		// If max bytes limit per line is set, then drop the lines that are longer
+		if r.maxBytes != 0 {
+			// If newLine is found, drop the lines longer than maxBytes
+			for idx != -1 && idx > r.maxBytes {
+				logp.Warn("Exceeded %d max bytes in line limit, skipped %d bytes line", r.maxBytes, idx)
+				err = r.inBuffer.Advance(idx + len(r.nl))
+				r.inBuffer.Reset()
+				r.inOffset = 0
+				idx = r.inBuffer.IndexFrom(r.inOffset, r.nl)
+			}
+
+			// If newLine is not found and the incoming data buffer exceeded max bytes limit, then skip until the next newLine
+			if idx == -1 && r.inBuffer.Len() > r.maxBytes {
+				skipped, err := r.skipUntilNewLine(buf)
+				if err != nil {
+					logp.Err("Error skipping until new line, err: %s", err)
+					return err
+				}
+				logp.Warn("Exceeded %d max bytes in line limit, skipped %d bytes line", r.maxBytes, skipped)
+				idx = r.inBuffer.IndexFrom(r.inOffset, r.nl)
+			}
+		}
 	}
 
 	// found encoded byte sequence for '\n' in buffer
@@ -163,6 +189,49 @@ func (r *LineReader) advance() error {
 	return err
 }
 
+func (r *LineReader) skipUntilNewLine(buf []byte) (int, error) {
+	// The length of the line skipped
+	skipped := r.inBuffer.Len()
+
+	// Clean up the buffer
+	err := r.inBuffer.Advance(skipped)
+	r.inBuffer.Reset()
+
+	// Reset inOffset
+	r.inOffset = 0
+
+	if err != nil {
+		return 0, err
+	}
+
+	// Read until the new line is found
+	for idx := -1; idx == -1; {
+		n, err := r.reader.Read(buf)
+
+		// Check bytes read for newLine
+		if n > 0 {
+			idx = bytes.Index(buf[:n], r.nl)
+
+			if idx != -1 {
+				r.inBuffer.Append(buf[idx+len(r.nl) : n])
+				skipped += idx
+			} else {
+				skipped += n
+			}
+		}
+
+		if err != nil {
+			return skipped, err
+		}
+
+		if n == 0 {
+			return skipped, streambuf.ErrNoMoreBytes
+		}
+	}
+
+	return skipped, nil
+}
+
 func (r *LineReader) decode(end int) (int, error) {
 	var err error
 	buffer := make([]byte, 1024)

filebeat/reader/readfile/line_test.go

@@ -21,8 +21,12 @@ package readfile
 
 import (
 	"bytes"
+	"encoding/hex"
+	"io"
 	"math/rand"
+	"strings"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/assert"
 	"golang.org/x/text/transform"
@@ -68,7 +72,7 @@ func TestReaderEncodings(t *testing.T) {
 		}
 
 		// create line reader
-		reader, err := NewLineReader(buffer, codec, 1024)
+		reader, err := NewLineReader(buffer, codec, 1024, 1024)
 		if err != nil {
 			t.Errorf("failed to initialize reader: %v", err)
 			continue
@@ -159,7 +163,8 @@ func testReadLines(t *testing.T, inputLines [][]byte) {
 	// initialize reader
 	buffer := bytes.NewBuffer(inputStream)
 	codec, _ := encoding.Plain(buffer)
-	reader, err := NewLineReader(buffer, codec, buffer.Len())
+	bufLen := buffer.Len()
+	reader, err := NewLineReader(buffer, codec, bufLen, bufLen)
 	if err != nil {
 		t.Fatalf("Error initializing reader: %v", err)
 	}
@@ -185,3 +190,137 @@ func testReadLines(t *testing.T, inputLines [][]byte) {
 func testReadLine(t *testing.T, line []byte) {
 	testReadLines(t, [][]byte{line})
 }
+
+func randomInt(r *rand.Rand, min, max int) int {
+	return r.Intn(max+1-min) + min
+}
+
+func randomBool(r *rand.Rand) bool {
+	n := randomInt(r, 0, 1)
+	return n != 0
+}
+
+func randomBytes(r *rand.Rand, sz int) ([]byte, error) {
+	bytes := make([]byte, sz)
+	if _, err := rand.Read(bytes); err != nil {
+		return nil, err
+	}
+	return bytes, nil
+}
+
+func randomString(r *rand.Rand, sz int) (string, error) {
+	if sz == 0 {
+		return "", nil
+	}
+
+	var bytes []byte
+	var err error
+	if bytes, err = randomBytes(r, sz/2+sz%2); err != nil {
+		return "", err
+	}
+	s := hex.EncodeToString(bytes)
+	return s[:sz], nil
+}
+
+func setupTestMaxBytesLimit(lineMaxLimit, lineLen int, nl []byte) (lines []string, data string, err error) {
+	rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
+
+	lineCount := randomInt(rnd, 11, 142)
+	lines = make([]string, lineCount)
+
+	var b strings.Builder
+
+	for i := 0; i < lineCount; i++ {
+		var sz int
+		// Non-empty line
+		if randomBool(rnd) {
+			// Boundary to the lineMaxLimit
+			if randomBool(rnd) {
+				sz = randomInt(rnd, lineMaxLimit-1, lineMaxLimit+1)
+			} else {
+				sz = randomInt(rnd, 0, lineLen)
+			}
+		} else {
+			// Randomly empty or one characters lines(another possibly boundary conditions)
+			sz = randomInt(rnd, 0, 1)
+		}
+
+		s, err := randomString(rnd, sz)
+		if err != nil {
+			return nil, "", err
+		}
+
+		lines[i] = s
+		if len(s) > 0 {
+			b.WriteString(s)
+		}
+		b.Write(nl)
+	}
+	return lines, b.String(), nil
+}
+
+func TestMaxBytesLimit(t *testing.T) {
+	const (
+		enc           = "plain"
+		numberOfLines = 102
+		bufferSize    = 1024
+		lineMaxLimit  = 3012
+		lineLen       = 5720 // exceeds lineMaxLimit
+	)
+
+	codecFactory, ok := encoding.FindEncoding(enc)
+	if !ok {
+		t.Fatalf("can not find encoding '%v'", enc)
+	}
+
+	buffer := bytes.NewBuffer(nil)
+	codec, _ := codecFactory(buffer)
+
+	// Generate random lines lengths including empty lines
+	nl := []byte("\n")
+	lines, input, err := setupTestMaxBytesLimit(lineMaxLimit, lineLen, nl)
+	if err != nil {
+		t.Fatal("failed to generate random input:", err)
+	}
+
+	// Create line reader
+	reader, err := NewLineReader(strings.NewReader(input), codec, bufferSize, lineMaxLimit)
+	if err != nil {
+		t.Fatal("failed to initialize reader:", err)
+	}
+
+	// Read decodec lines and test
+	var idx int
+	for i := 0; ; i++ {
+		b, n, err := reader.Next()
+		if err != nil {
+			if err == io.EOF {
+				break
+			} else {
+				t.Fatal("unexpected error:", err)
+			}
+		}
+
+		// Find the next expected line from the original test array
+		var line string
+		for ; idx < len(lines); idx++ {
+			// Expected to be dropped
+			if len(lines[idx]) > lineMaxLimit {
+				continue
+			}
+			line = lines[idx]
+			idx++
+			break
+		}
+
+		gotLen := n - len(nl)
+		s := string(b[:len(b)-len(nl)])
+		if len(line) != gotLen {
+			t.Fatalf("invalid line length, expected: %d got: %d", len(line), gotLen)
+		}
+
+		if line != s {
+			t.Fatalf("lines do not match, expected: %s got: %s", line, s)
+		}
+	}
+}

filebeat/scripts/tester/main.go

@@ -133,7 +133,7 @@ func getLogsFromFile(logfile string, conf *logReaderConfig) ([]string, error) {
 	}
 
 	var r reader.Reader
-	r, err = readfile.NewEncodeReader(f, enc, 4096)
+	r, err = readfile.NewEncodeReader(f, enc, 4096, 4096)
 	if err != nil {
 		return nil, err
 	}