[libbeat] Fix encoding and file offset issues in the disk queue

CHANGELOG.next.asciidoc

@@ -236,6 +236,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Fix ILM alias creation when write alias exists and initial index does not exist {pull}26143[26143]
 - Omit full index template from errors that occur while loading the template. {pull}25743[25743]
 - In the script processor, the `decode_xml` and `decode_xml_wineventlog` processors are now available as `DecodeXML` and `DecodeXMLWineventlog` respectively.
+- Fix encoding errors when using the disk queue on nested data with multi-byte characters {pull}26484[26484]
 
 *Auditbeat*
 

libbeat/publisher/queue/diskqueue/core_loop_test.go

@@ -235,7 +235,7 @@ func TestHandleWriterLoopResponse(t *testing.T) {
 
 	// Write to one segment (no segments should be moved to reading list)
 	dq.handleWriterLoopResponse(writerLoopResponse{
-		segments: []writerLoopResponseSegment{
+		segments: []writerLoopSegmentResponse{
 			{bytesWritten: 100},
 		},
 	})
@@ -250,7 +250,7 @@ func TestHandleWriterLoopResponse(t *testing.T) {
 
 	// Write to two segments (the first one should be moved to reading list)
 	dq.handleWriterLoopResponse(writerLoopResponse{
-		segments: []writerLoopResponseSegment{
+		segments: []writerLoopSegmentResponse{
 			{bytesWritten: 100},
 			{bytesWritten: 100},
 		},
@@ -270,7 +270,7 @@ func TestHandleWriterLoopResponse(t *testing.T) {
 
 	// Write to three segments (the first two should be moved to reading list)
 	dq.handleWriterLoopResponse(writerLoopResponse{
-		segments: []writerLoopResponseSegment{
+		segments: []writerLoopSegmentResponse{
 			{bytesWritten: 100},
 			{bytesWritten: 100},
 			{bytesWritten: 500},

libbeat/publisher/queue/diskqueue/reader_loop.go

@@ -20,6 +20,7 @@ package diskqueue
 import (
 	"encoding/binary"
 	"fmt"
+	"io"
 	"os"
 )
 
@@ -100,13 +101,12 @@ func (rl *readerLoop) processRequest(request readerLoopRequest) readerLoopRespon
 
 	// Open the file and seek to the starting position.
 	handle, err := request.segment.getReader(rl.settings)
+	rl.decoder.useJSON = request.segment.shouldUseJSON()
 	if err != nil {
 		return readerLoopResponse{err: err}
 	}
 	defer handle.Close()
-	// getReader positions us at the start of the data region, so we use
-	// a relative seek to advance to the request position.
-	_, err = handle.Seek(int64(request.startPosition), os.SEEK_CUR)
+	_, err = handle.Seek(int64(request.startPosition), io.SeekStart)
 	if err != nil {
 		return readerLoopResponse{err: err}
 	}
@@ -179,58 +179,58 @@ func (rl *readerLoop) nextFrame(
 	// Ensure we are allowed to read the frame header.
 	if maxLength < frameHeaderSize {
 		return nil, fmt.Errorf(
-			"Can't read next frame: remaining length %d is too low", maxLength)
+			"can't read next frame: remaining length %d is too low", maxLength)
 	}
 	// Wrap the handle to retry non-fatal errors and always return the full
 	// requested data length if possible.
 	reader := autoRetryReader{handle}
 	var frameLength uint32
 	err := binary.Read(reader, binary.LittleEndian, &frameLength)
 	if err != nil {
-		return nil, fmt.Errorf("Couldn't read data frame header: %w", err)
+		return nil, fmt.Errorf("couldn't read data frame header: %w", err)
 	}
 
 	// If the frame extends past the area we were told to read, return an error.
 	// This should never happen unless the segment file is corrupted.
 	if maxLength < uint64(frameLength) {
 		return nil, fmt.Errorf(
-			"Can't read next frame: frame size is %d but remaining data is only %d",
+			"can't read next frame: frame size is %d but remaining data is only %d",
 			frameLength, maxLength)
 	}
 	if frameLength <= frameMetadataSize {
 		// Valid enqueued data must have positive length
 		return nil, fmt.Errorf(
-			"Data frame with no data (length %d)", frameLength)
+			"data frame with no data (length %d)", frameLength)
 	}
 
 	// Read the actual frame data
 	dataLength := frameLength - frameMetadataSize
 	bytes := rl.decoder.Buffer(int(dataLength))
 	_, err = reader.Read(bytes)
 	if err != nil {
-		return nil, fmt.Errorf("Couldn't read data frame content: %w", err)
+		return nil, fmt.Errorf("couldn't read data frame content: %w", err)
 	}
 
 	// Read the footer (checksum + duplicate length)
 	var checksum uint32
 	err = binary.Read(reader, binary.LittleEndian, &checksum)
 	if err != nil {
-		return nil, fmt.Errorf("Couldn't read data frame checksum: %w", err)
+		return nil, fmt.Errorf("couldn't read data frame checksum: %w", err)
 	}
 	expected := computeChecksum(bytes)
 	if checksum != expected {
 		return nil, fmt.Errorf(
-			"Data frame checksum mismatch (%x != %x)", checksum, expected)
+			"data frame checksum mismatch (%x != %x)", checksum, expected)
 	}
 
 	var duplicateLength uint32
 	err = binary.Read(reader, binary.LittleEndian, &duplicateLength)
 	if err != nil {
-		return nil, fmt.Errorf("Couldn't read data frame footer: %w", err)
+		return nil, fmt.Errorf("couldn't read data frame footer: %w", err)
 	}
 	if duplicateLength != frameLength {
 		return nil, fmt.Errorf(
-			"Inconsistent data frame length (%d vs %d)",
+			"inconsistent data frame length (%d vs %d)",
 			frameLength, duplicateLength)
 	}
 
@@ -242,7 +242,7 @@ func (rl *readerLoop) nextFrame(
 		// TODO: Rather than pass this error back to the read request, which
 		// discards the rest of the segment, we should just log the error and
 		// advance to the next frame, which is likely still valid.
-		return nil, fmt.Errorf("Couldn't decode data frame: %w", err)
+		return nil, fmt.Errorf("couldn't decode data frame: %w", err)
 	}
 
 	frame := &readFrame{

libbeat/publisher/queue/diskqueue/segments.go

@@ -91,7 +91,10 @@ type queueSegment struct {
 	// If this segment was loaded from a previous session, schemaVersion
 	// points to the file schema version that was read from its header.
 	// This is only used by queueSegment.headerSize(), which is used in
-	// maybeReadPending to calculate the position of the first data frame.
+	// maybeReadPending to calculate the position of the first data frame,
+	// and by queueSegment.shouldUseJSON(), which is used in the reader
+	// loop to detect old segments that used JSON encoding instead of
+	// the current CBOR.
 	schemaVersion *uint32
 
 	// The number of bytes occupied by this segment on-disk, as of the most
@@ -198,6 +201,14 @@ func (segment *queueSegment) headerSize() uint64 {
 	return segmentHeaderSize
 }
 
+// The initial release of the disk queue used JSON to encode events
+// on disk. Since then, we have switched to CBOR to address issues
+// with encoding multi-byte characters, and for lower encoding
+// overhead.
+func (segment *queueSegment) shouldUseJSON() bool {
+	return segment.schemaVersion != nil && *segment.schemaVersion == 0
+}
+
 // Should only be called from the reader loop. If successful, returns an open
 // file handle positioned at the beginning of the segment's data region.
 func (segment *queueSegment) getReader(
@@ -207,14 +218,14 @@ func (segment *queueSegment) getReader(
 	file, err := os.Open(path)
 	if err != nil {
 		return nil, fmt.Errorf(
-			"Couldn't open segment %d: %w", segment.id, err)
+			"couldn't open segment %d: %w", segment.id, err)
 	}
 	// We don't need the header contents here, we just want to advance past the
 	// header region, so discard the return value.
 	_, err = readSegmentHeader(file)
 	if err != nil {
 		file.Close()
-		return nil, fmt.Errorf("Couldn't read segment header: %w", err)
+		return nil, fmt.Errorf("couldn't read segment header: %w", err)
 	}
 
 	return file, nil
@@ -231,7 +242,7 @@ func (segment *queueSegment) getWriter(
 	}
 	err = writeSegmentHeader(file, 0)
 	if err != nil {
-		return nil, fmt.Errorf("Couldn't write segment header: %w", err)
+		return nil, fmt.Errorf("couldn't write segment header: %w", err)
 	}
 
 	return file, nil
@@ -306,7 +317,7 @@ func readSegmentHeaderWithFrameCount(path string) (*segmentHeader, error) {
 		// the current frame to make sure the trailing length matches before
 		// advancing to the next frame (otherwise we might accept an impossible
 		// length).
-		_, err = file.Seek(int64(frameLength-8), os.SEEK_CUR)
+		_, err = file.Seek(int64(frameLength-8), io.SeekCurrent)
 		if err != nil {
 			break
 		}
@@ -341,7 +352,7 @@ func readSegmentHeader(in io.Reader) (*segmentHeader, error) {
 		return nil, err
 	}
 	if header.version > currentSegmentVersion {
-		return nil, fmt.Errorf("Unrecognized schema version %d", header.version)
+		return nil, fmt.Errorf("unrecognized schema version %d", header.version)
 	}
 	if header.version >= 1 {
 		err = binary.Read(in, binary.LittleEndian, &header.frameCount)

libbeat/publisher/queue/diskqueue/serialize.go

@@ -28,6 +28,7 @@ import (
 	"github.com/elastic/beats/v7/libbeat/common"
 	"github.com/elastic/beats/v7/libbeat/outputs/codec"
 	"github.com/elastic/beats/v7/libbeat/publisher"
+	"github.com/elastic/go-structform/cborl"
 	"github.com/elastic/go-structform/gotype"
 	"github.com/elastic/go-structform/json"
 )
@@ -40,7 +41,13 @@ type eventEncoder struct {
 type eventDecoder struct {
 	buf []byte
 
-	parser   *json.Parser
+	jsonParser  *json.Parser
+	cborlParser *cborl.Parser
+
+	// Current serialization all uses CBOR. Set this flag when decoding
+	// from old (schema 0) segment files generated by the disk queue beta.
+	useJSON bool
+
 	unfolder *gotype.Unfolder
 }
 
@@ -60,7 +67,7 @@ func newEventEncoder() *eventEncoder {
 func (e *eventEncoder) reset() {
 	e.folder = nil
 
-	visitor := json.NewVisitor(&e.buf)
+	visitor := cborl.NewVisitor(&e.buf)
 	// This can't return an error: NewIterator is deterministic based on its
 	// input, and doesn't return an error when called with valid options. In
 	// this case the options are hard-coded to fixed values, so they are
@@ -109,7 +116,8 @@ func (d *eventDecoder) reset() {
 	unfolder, _ := gotype.NewUnfolder(nil)
 
 	d.unfolder = unfolder
-	d.parser = json.NewParser(unfolder)
+	d.jsonParser = json.NewParser(unfolder)
+	d.cborlParser = cborl.NewParser(unfolder)
 }
 
 // Buffer prepares the read buffer to hold the next event of n bytes.
@@ -131,7 +139,11 @@ func (d *eventDecoder) Decode() (publisher.Event, error) {
 	d.unfolder.SetTarget(&to)
 	defer d.unfolder.Reset()
 
-	err = d.parser.Parse(d.buf)
+	if d.useJSON {
+		err = d.jsonParser.Parse(d.buf)
+	} else {
+		err = d.cborlParser.Parse(d.buf)
+	}
 
 	if err != nil {
 		d.reset() // reset parser just in case

libbeat/publisher/queue/diskqueue/serialize_test.go

@@ -0,0 +1,62 @@
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you under
+// the Apache License, Version 2.0 (the "License"); you may
+// not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package diskqueue
+
+import (
+	"testing"
+
+	"github.com/elastic/beats/v7/libbeat/beat"
+	"github.com/elastic/beats/v7/libbeat/common"
+	"github.com/elastic/beats/v7/libbeat/publisher"
+	"github.com/stretchr/testify/assert"
+)
+
+// A test to make sure serialization works correctly on multi-byte characters.
+func TestSerializeMultiByte(t *testing.T) {
+	asciiOnly := "{\"name\": \"Momotaro\"}"
+	multiBytes := "{\"name\": \"桃太郎\"}"
+
+	encoder := newEventEncoder()
+	event := publisher.Event{
+		Content: beat.Event{
+			Fields: common.MapStr{
+				"ascii_only":  asciiOnly,
+				"multi_bytes": multiBytes,
+			},
+		},
+	}
+	serialized, err := encoder.encode(&event)
+	if err != nil {
+		t.Fatalf("Couldn't encode event: %v", err)
+	}
+
+	// Use decoder to decode the serialized bytes.
+	decoder := newEventDecoder()
+	buf := decoder.Buffer(len(serialized))
+	copy(buf, serialized)
+	decoded, err := decoder.Decode()
+	if err != nil {
+		t.Fatalf("Couldn't decode serialized data: %v", err)
+	}
+
+	decodedAsciiOnly, _ := decoded.Content.Fields.GetValue("ascii_only")
+	assert.Equal(t, asciiOnly, decodedAsciiOnly)
+
+	decodedMultiBytes, _ := decoded.Content.Fields.GetValue("multi_bytes")
+	assert.Equal(t, multiBytes, decodedMultiBytes)
+}