*(dnsforward): qlogreader implementation

querylog/qlog_file.go

@@ -11,10 +11,18 @@ import (
 	"github.com/pkg/errors"
 )
 
+// ErrSeekNotFound is returned from the Seek method
+// if we failed to find the desired record
 var ErrSeekNotFound = errors.New("Seek not found the record")
 
 const bufferSize = 256 * 1024 // 256 KB is the buffer size
 
+// QLogFile represents a single query log file
+// It allows reading from the file in the reverse order
+//
+// Please note that this is a stateful object.
+// Internally, it contains a pointer to a specific position in the file,
+// and it reads lines in reverse order starting from that position.
 type QLogFile struct {
 	file     *os.File // the query log file
 	position int64    // current position in the file
@@ -40,7 +48,8 @@ func NewQLogFile(path string) (*QLogFile, error) {
 }
 
 // Seek performs binary search in the query log file looking for a record
-// with the specified timestamp.
+// with the specified timestamp. Once the record is found, it sets
+// "position" so that the next ReadNext call returned that record.
 //
 // The algorithm is rather simple:
 // 1. It starts with the position in the middle of a file
@@ -86,7 +95,7 @@ func (q *QLogFile) Seek(timestamp uint64) (int64, error) {
 		}
 
 		// Get the timestamp from the query log record
-		ts := q.readTimestamp(line)
+		ts := readQLogTimestamp(line)
 
 		if ts == 0 {
 			return 0, ErrSeekNotFound
@@ -130,6 +139,9 @@ func (q *QLogFile) Seek(timestamp uint64) (int64, error) {
 // SeekStart changes the current position to the end of the file
 // Please note that we're reading query log in the reverse order
 // and that's why log start is actually the end of file
+//
+// Returns nil if we were able to change the current position.
+// Returns error in any other case.
 func (q *QLogFile) SeekStart() (int64, error) {
 	q.lock.Lock()
 	defer q.lock.Unlock()
@@ -292,20 +304,20 @@ func (q *QLogFile) readProbeLine(position int64) (string, int64, error) {
 	return string(buffer[startLine:endLine]), lineIdx, nil
 }
 
-// readTimestamp reads the timestamp field from the query log line
-func (q *QLogFile) readTimestamp(str string) uint64 {
+// readQLogTimestamp reads the timestamp field from the query log line
+func readQLogTimestamp(str string) uint64 {
 	val := readJSONValue(str, "T")
 	if len(val) == 0 {
 		val = readJSONValue(str, "Time")
 	}
 
 	if len(val) == 0 {
-		log.Error("Couldn't find timestamp in %s: %s", q.file.Name(), str)
+		log.Error("Couldn't find timestamp: %s", str)
 		return 0
 	}
-	tm, err := time.Parse(time.RFC3339, val)
+	tm, err := time.Parse(time.RFC3339Nano, val)
 	if err != nil {
-		log.Error("Couldn't parse timestamp in %s: %s", q.file.Name(), val)
+		log.Error("Couldn't parse timestamp: %s", val)
 		return 0
 	}
 	return uint64(tm.UnixNano())

querylog/qlog_file_test.go

@@ -22,6 +22,7 @@ func TestQLogFileEmpty(t *testing.T) {
 	q, err := NewQLogFile(testFile)
 	assert.Nil(t, err)
 	assert.NotNil(t, q)
+	defer q.Close()
 
 	// seek to the start
 	pos, err := q.SeekStart()
@@ -46,6 +47,7 @@ func TestQLogFileLarge(t *testing.T) {
 	q, err := NewQLogFile(testFile)
 	assert.Nil(t, err)
 	assert.NotNil(t, q)
+	defer q.Close()
 
 	// seek to the start
 	pos, err := q.SeekStart()
@@ -78,18 +80,19 @@ func TestQLogFileSeekLargeFile(t *testing.T) {
 	q, err := NewQLogFile(testFile)
 	assert.Nil(t, err)
 	assert.NotNil(t, q)
+	defer q.Close()
 
 	// CASE 1: NOT TOO OLD LINE
-	testSeekLine(t, q, 300)
+	testSeekLineQLogFile(t, q, 300)
 
 	// CASE 2: OLD LINE
-	testSeekLine(t, q, count-300)
+	testSeekLineQLogFile(t, q, count-300)
 
 	// CASE 3: FIRST LINE
-	testSeekLine(t, q, 0)
+	testSeekLineQLogFile(t, q, 0)
 
 	// CASE 4: LAST LINE
-	testSeekLine(t, q, count)
+	testSeekLineQLogFile(t, q, count)
 
 	// CASE 5: Seek non-existent (too low)
 	_, err = q.Seek(123)
@@ -113,18 +116,19 @@ func TestQLogFileSeekSmallFile(t *testing.T) {
 	q, err := NewQLogFile(testFile)
 	assert.Nil(t, err)
 	assert.NotNil(t, q)
+	defer q.Close()
 
 	// CASE 1: NOT TOO OLD LINE
-	testSeekLine(t, q, 2)
+	testSeekLineQLogFile(t, q, 2)
 
 	// CASE 2: OLD LINE
-	testSeekLine(t, q, count-2)
+	testSeekLineQLogFile(t, q, count-2)
 
 	// CASE 3: FIRST LINE
-	testSeekLine(t, q, 0)
+	testSeekLineQLogFile(t, q, 0)
 
 	// CASE 4: LAST LINE
-	testSeekLine(t, q, count)
+	testSeekLineQLogFile(t, q, count)
 
 	// CASE 5: Seek non-existent (too low)
 	_, err = q.Seek(123)
@@ -136,10 +140,10 @@ func TestQLogFileSeekSmallFile(t *testing.T) {
 	assert.NotNil(t, err)
 }
 
-func testSeekLine(t *testing.T, q *QLogFile, lineNumber int) {
-	line, err := getQLogLine(q, lineNumber)
+func testSeekLineQLogFile(t *testing.T, q *QLogFile, lineNumber int) {
+	line, err := getQLogFileLine(q, lineNumber)
 	assert.Nil(t, err)
-	ts := q.readTimestamp(line)
+	ts := readQLogTimestamp(line)
 	assert.NotEqual(t, uint64(0), ts)
 
 	// try seeking to that line now
@@ -152,7 +156,7 @@ func testSeekLine(t *testing.T, q *QLogFile, lineNumber int) {
 	assert.Equal(t, line, testLine)
 }
 
-func getQLogLine(q *QLogFile, lineNumber int) (string, error) {
+func getQLogFileLine(q *QLogFile, lineNumber int) (string, error) {
 	_, err := q.SeekStart()
 	if err != nil {
 		return "", err
@@ -177,6 +181,7 @@ func TestQLogFile(t *testing.T) {
 	q, err := NewQLogFile(testFile)
 	assert.Nil(t, err)
 	assert.NotNil(t, q)
+	defer q.Close()
 
 	// seek to the start
 	pos, err := q.SeekStart()
@@ -206,27 +211,37 @@ func TestQLogFile(t *testing.T) {
 
 // prepareTestFile - prepares a test query log file with the specified number of lines
 func prepareTestFile(dir string, linesCount int) string {
+	return prepareTestFiles(dir, 1, linesCount)[0]
+}
+
+// prepareTestFiles - prepares several test query log files
+// each of them -- with the specified linesCount
+func prepareTestFiles(dir string, filesCount, linesCount int) []string {
 	format := `{"IP":"${IP}","T":"${TIMESTAMP}","QH":"example.org","QT":"A","QC":"IN","Answer":"AAAAAAABAAEAAAAAB2V4YW1wbGUDb3JnAAABAAEHZXhhbXBsZQNvcmcAAAEAAQAAAAAABAECAwQ=","Result":{},"Elapsed":0,"Upstream":"upstream"}`
 
 	lineTime, _ := time.Parse(time.RFC3339Nano, "2020-02-18T22:36:35.920973+03:00")
 	lineIP := uint32(0)
 
-	f, _ := ioutil.TempFile(dir, "*.txt")
+	files := make([]string, 0)
+	for j := 0; j < filesCount; j++ {
+		f, _ := ioutil.TempFile(dir, "*.txt")
+		files = append(files, f.Name())
 
-	for i := 0; i < linesCount; i++ {
-		lineIP += 1
-		lineTime = lineTime.Add(time.Second)
+		for i := 0; i < linesCount; i++ {
+			lineIP += 1
+			lineTime = lineTime.Add(time.Second)
 
-		ip := make(net.IP, 4)
-		binary.BigEndian.PutUint32(ip, lineIP)
+			ip := make(net.IP, 4)
+			binary.BigEndian.PutUint32(ip, lineIP)
 
-		line := format
-		line = strings.ReplaceAll(line, "${IP}", ip.String())
-		line = strings.ReplaceAll(line, "${TIMESTAMP}", lineTime.Format(time.RFC3339Nano))
+			line := format
+			line = strings.ReplaceAll(line, "${IP}", ip.String())
+			line = strings.ReplaceAll(line, "${TIMESTAMP}", lineTime.Format(time.RFC3339Nano))
 
-		_, _ = f.WriteString(line)
-		_, _ = f.WriteString("\n")
+			_, _ = f.WriteString(line)
+			_, _ = f.WriteString("\n")
+		}
 	}
 
-	return f.Name()
+	return files
 }

querylog/qlog_reader.go

@@ -0,0 +1,139 @@
+package querylog
+
+import (
+	"io"
+
+	"github.com/joomcode/errorx"
+)
+
+// QLogReader allows reading from multiple query log files in the reverse order.
+//
+// Please note that this is a stateful object.
+// Internally, it contains a pointer to a particular query log file, and
+// to a specific position in this file, and it reads lines in reverse order
+// starting from that position.
+type QLogReader struct {
+	// qFiles - array with the query log files
+	// The order is - from oldest to newest
+	qFiles []*QLogFile
+
+	currentFile int // Index of the current file
+}
+
+// NewQLogReader initializes a QLogReader instance
+// with the specified files
+func NewQLogReader(files []string) (*QLogReader, error) {
+	qFiles := make([]*QLogFile, 0)
+
+	for _, f := range files {
+		q, err := NewQLogFile(f)
+		if err != nil {
+			// Close what we've already opened
+			_ = closeQFiles(qFiles)
+			return nil, err
+		}
+
+		qFiles = append(qFiles, q)
+	}
+
+	return &QLogReader{
+		qFiles:      qFiles,
+		currentFile: (len(qFiles) - 1),
+	}, nil
+}
+
+// Seek performs binary search of a query log record with the specified timestamp.
+// If the record is found, it sets QLogReader's position to point to that line,
+// so that the next ReadNext call returned this line.
+//
+// Returns nil if the record is successfully found.
+// Returns an error if for some reason we could not find a record with the specified timestamp.
+func (r *QLogReader) Seek(timestamp uint64) error {
+	for i := len(r.qFiles) - 1; i >= 0; i-- {
+		q := r.qFiles[i]
+		_, err := q.Seek(timestamp)
+		if err == nil {
+			// Our search is finished, we found the element we were looking for
+			// Update currentFile only, position is already set properly in the QLogFile
+			r.currentFile = i
+			return nil
+		}
+	}
+
+	return ErrSeekNotFound
+}
+
+// SeekStart changes the current position to the end of the newest file
+// Please note that we're reading query log in the reverse order
+// and that's why log start is actually the end of file
+//
+// Returns nil if we were able to change the current position.
+// Returns error in any other case.
+func (r *QLogReader) SeekStart() error {
+	if len(r.qFiles) == 0 {
+		return nil
+	}
+
+	r.currentFile = len(r.qFiles) - 1
+	_, err := r.qFiles[r.currentFile].SeekStart()
+	return err
+}
+
+// ReadNext reads the next line (in the reverse order) from the query log files.
+// and shifts the current position left to the next (actually prev) line (or the next file).
+// returns io.EOF if there's nothing to read more.
+func (r *QLogReader) ReadNext() (string, error) {
+	if len(r.qFiles) == 0 {
+		return "", io.EOF
+	}
+
+	for r.currentFile >= 0 {
+		q := r.qFiles[r.currentFile]
+		line, err := q.ReadNext()
+		if err != nil {
+			// Shift to the older file
+			r.currentFile--
+			if r.currentFile < 0 {
+				break
+			}
+
+			q = r.qFiles[r.currentFile]
+
+			// Set it's position to the start right away
+			_, err = q.SeekStart()
+
+			// This is unexpected, return an error right away
+			if err != nil {
+				return "", err
+			}
+		} else {
+			return line, nil
+		}
+	}
+
+	// Nothing to read anymore
+	return "", io.EOF
+}
+
+// Close closes the QLogReader
+func (r *QLogReader) Close() error {
+	return closeQFiles(r.qFiles)
+}
+
+// closeQFiles - helper method to close multiple QLogFile instances
+func closeQFiles(qFiles []*QLogFile) error {
+	var errs []error
+
+	for _, q := range qFiles {
+		err := q.Close()
+		if err != nil {
+			errs = append(errs, err)
+		}
+	}
+
+	if len(errs) > 0 {
+		return errorx.DecorateMany("Error while closing QLogReader", errs...)
+	}
+
+	return nil
+}

querylog/qlog_reader_test.go

@@ -0,0 +1,157 @@
+package querylog
+
+import (
+	"io"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestQLogReaderEmpty(t *testing.T) {
+	r, err := NewQLogReader([]string{})
+	assert.Nil(t, err)
+	assert.NotNil(t, r)
+	defer r.Close()
+
+	// seek to the start
+	err = r.SeekStart()
+	assert.Nil(t, err)
+
+	line, err := r.ReadNext()
+	assert.Equal(t, "", line)
+	assert.Equal(t, io.EOF, err)
+}
+
+func TestQLogReaderOneFile(t *testing.T) {
+	// let's do one small file
+	count := 10
+	filesCount := 1
+
+	testDir := prepareTestDir()
+	defer func() { _ = os.RemoveAll(testDir) }()
+	testFiles := prepareTestFiles(testDir, filesCount, count)
+
+	r, err := NewQLogReader(testFiles)
+	assert.Nil(t, err)
+	assert.NotNil(t, r)
+	defer r.Close()
+
+	// seek to the start
+	err = r.SeekStart()
+	assert.Nil(t, err)
+
+	// read everything
+	read := 0
+	var line string
+	for err == nil {
+		line, err = r.ReadNext()
+		if err == nil {
+			assert.True(t, len(line) > 0)
+			read += 1
+		}
+	}
+
+	assert.Equal(t, count*filesCount, read)
+	assert.Equal(t, io.EOF, err)
+}
+
+func TestQLogReaderMultipleFiles(t *testing.T) {
+	// should be large enough
+	count := 10000
+	filesCount := 5
+
+	testDir := prepareTestDir()
+	defer func() { _ = os.RemoveAll(testDir) }()
+	testFiles := prepareTestFiles(testDir, filesCount, count)
+
+	r, err := NewQLogReader(testFiles)
+	assert.Nil(t, err)
+	assert.NotNil(t, r)
+	defer r.Close()
+
+	// seek to the start
+	err = r.SeekStart()
+	assert.Nil(t, err)
+
+	// read everything
+	read := 0
+	var line string
+	for err == nil {
+		line, err = r.ReadNext()
+		if err == nil {
+			assert.True(t, len(line) > 0)
+			read += 1
+		}
+	}
+
+	assert.Equal(t, count*filesCount, read)
+	assert.Equal(t, io.EOF, err)
+}
+
+func TestQLogReaderSeek(t *testing.T) {
+	// more or less big file
+	count := 10000
+	filesCount := 2
+
+	testDir := prepareTestDir()
+	defer func() { _ = os.RemoveAll(testDir) }()
+	testFiles := prepareTestFiles(testDir, filesCount, count)
+
+	r, err := NewQLogReader(testFiles)
+	assert.Nil(t, err)
+	assert.NotNil(t, r)
+	defer r.Close()
+
+	// CASE 1: NOT TOO OLD LINE
+	testSeekLineQLogReader(t, r, 300)
+
+	// CASE 2: OLD LINE
+	testSeekLineQLogReader(t, r, count-300)
+
+	// CASE 3: FIRST LINE
+	testSeekLineQLogReader(t, r, 0)
+
+	// CASE 4: LAST LINE
+	testSeekLineQLogReader(t, r, count)
+
+	// CASE 5: Seek non-existent (too low)
+	err = r.Seek(123)
+	assert.NotNil(t, err)
+
+	// CASE 6: Seek non-existent (too high)
+	ts, _ := time.Parse(time.RFC3339, "2100-01-02T15:04:05Z07:00")
+	err = r.Seek(uint64(ts.UnixNano()))
+	assert.NotNil(t, err)
+}
+
+func testSeekLineQLogReader(t *testing.T, r *QLogReader, lineNumber int) {
+	line, err := getQLogReaderLine(r, lineNumber)
+	assert.Nil(t, err)
+	ts := readQLogTimestamp(line)
+	assert.NotEqual(t, uint64(0), ts)
+
+	// try seeking to that line now
+	err = r.Seek(ts)
+	assert.Nil(t, err)
+
+	testLine, err := r.ReadNext()
+	assert.Nil(t, err)
+	assert.Equal(t, line, testLine)
+}
+
+func getQLogReaderLine(r *QLogReader, lineNumber int) (string, error) {
+	err := r.SeekStart()
+	if err != nil {
+		return "", err
+	}
+
+	for i := 1; i < lineNumber; i++ {
+		_, err := r.ReadNext()
+		if err != nil {
+			return "", err
+		}
+	}
+	return r.ReadNext()
+}

querylog/querylog_file.go

@@ -3,7 +3,6 @@ package querylog
 import (
 	"bufio"
 	"bytes"
-	"compress/gzip"
 	"encoding/base64"
 	"encoding/json"
 	"io"
@@ -17,8 +16,6 @@ import (
 	"github.com/miekg/dns"
 )
 
-const enableGzip = false
-
 // TODO: Check this when we append a new line -- we don't want to have a line longer than this
 const maxEntrySize = 1000
 
@@ -70,29 +67,7 @@ func (l *queryLog) flushToFile(buffer []*logEntry) error {
 	var err error
 	var zb bytes.Buffer
 	filename := l.logFile
-
-	// gzip enabled?
-	if enableGzip {
-		filename += ".gz"
-
-		zw := gzip.NewWriter(&zb)
-		zw.Name = l.logFile
-		zw.ModTime = time.Now()
-
-		_, err = zw.Write(b.Bytes())
-		if err != nil {
-			log.Error("Couldn't compress to gzip: %s", err)
-			zw.Close()
-			return err
-		}
-
-		if err = zw.Close(); err != nil {
-			log.Error("Couldn't close gzip writer: %s", err)
-			return err
-		}
-	} else {
-		zb = b
-	}
+	zb = b
 
 	l.fileWriteLock.Lock()
 	defer l.fileWriteLock.Unlock()
@@ -118,11 +93,6 @@ func (l *queryLog) rotate() error {
 	from := l.logFile
 	to := l.logFile + ".1"
 
-	if enableGzip {
-		from = l.logFile + ".gz"
-		to = l.logFile + ".gz.1"
-	}
-
 	if _, err := os.Stat(from); os.IsNotExist(err) {
 		// do nothing, file doesn't exist
 		return nil
@@ -135,7 +105,6 @@ func (l *queryLog) rotate() error {
 	}
 
 	log.Debug("Rotated from %s to %s successfully", from, to)
-
 	return nil
 }