lz4: start read from offset

Author: DmitryRomanov

plugin/input/file/provider.go

@@ -60,13 +60,15 @@ type jobProvider struct {
 }
 
 type Job struct {
-	file      *os.File
-	inode     inodeID
-	sourceID  pipeline.SourceID // some value to distinguish jobs with same inode
-	filename  string
-	symlink   string
-	curOffset int64  // offset to not call Seek() everytime
-	tail      []byte // some data of a new line read by worker, to not seek backwards to read from line start
+	file         *os.File
+	mimeType     string
+	isCompressed bool
+	inode        inodeID
+	sourceID     pipeline.SourceID // some value to distinguish jobs with same inode
+	filename     string
+	symlink      string
+	curOffset    int64  // offset to not call Seek() everytime
+	tail         []byte // some data of a new line read by worker, to not seek backwards to read from line start
 
 	ignoreEventsLE uint64 // events with seq id less or equal than this should be ignored in terms offset commitment
 	lastEventSeq   uint64
@@ -83,10 +85,15 @@ type Job struct {
 	mu *sync.Mutex
 }
 
-func (j *Job) seek(offset int64, whence int, hint string) int64 {
-	n, err := j.file.Seek(offset, whence)
-	if err != nil {
-		logger.Infof("file seek error hint=%s, name=%s, err=%s", hint, j.filename, err.Error())
+func (j *Job) seek(offset int64, whence int, hint string) (n int64) {
+	var err error
+	if !j.isCompressed {
+		n, err = j.file.Seek(offset, whence)
+		if err != nil {
+			logger.Infof("file seek error hint=%s, name=%s, err=%s", hint, j.filename, err.Error())
+		}
+	} else {
+		n = 0
 	}
 	j.curOffset = n
 
@@ -354,6 +361,10 @@ func (jp *jobProvider) checkFileWasTruncated(job *Job, size int64) {
 	}
 }
 
+func isCompressed(mimeType string) bool {
+	return mimeType == "application/x-lz4"
+}
+
 func (jp *jobProvider) addJob(file *os.File, stat os.FileInfo, filename string, symlink string) {
 	sourceID := sourceIDByStat(stat, symlink)
 
@@ -370,12 +381,16 @@ func (jp *jobProvider) addJob(file *os.File, stat os.FileInfo, filename string,
 	}
 
 	inode := getInode(stat)
+	mimeType := getMimeType(filename)
+
 	job := &Job{
-		file:     file,
-		inode:    inode,
-		filename: filename,
-		symlink:  symlink,
-		sourceID: sourceID,
+		file:         file,
+		isCompressed: isCompressed(mimeType),
+		mimeType:     mimeType,
+		inode:        inode,
+		filename:     filename,
+		symlink:      symlink,
+		sourceID:     sourceID,
 
 		isVirgin:   true,
 		isDone:     true,

plugin/input/file/worker.go

@@ -5,6 +5,7 @@ import (
 	"io"
 	"mime"
 	"os"
+	"os/exec"
 	"path/filepath"
 	"strings"
 
@@ -89,11 +90,24 @@ func (w *worker) work(controller inputer, jobProvider *jobProvider, readBufferSi
 			}
 		}
 
-		mimeType := getMimeType(file.Name())
 		var reader io.Reader
-
-		if mimeType == "application/x-lz4" {
+		if job.mimeType == "application/x-lz4" {
+			if isNotFileBeingWritten(file.Name()) {
+				logger.Error("cannot lock file", zap.String("filename", file.Name()))
+				break
+			}
 			lz4Reader := lz4.NewReader(file)
+			if len(offsets) > 0 {
+				for lastOffset+int64(readBufferSize) < offsets[0].Offset {
+					n, err := lz4Reader.Read(readBuf)
+					if err != nil {
+						if err == io.EOF {
+							break // End of file reached
+						}
+					}
+					lastOffset += int64(n)
+				}
+			}
 			reader = lz4Reader
 		} else {
 			reader = file
@@ -196,17 +210,39 @@ func getMimeType(filename string) string {
 	return mimeType
 }
 
+func isNotFileBeingWritten(filePath string) bool {
+	// Run the lsof command to check open file descriptors
+	cmd := exec.Command("lsof", filePath)
+	output, err := cmd.Output()
+	if err != nil {
+		return false // Error running lsof
+	}
+
+	// Check the output for write access
+	lines := strings.Split(string(output), "\n")
+	for _, line := range lines {
+		// Check if the line contains 'w' indicating write access
+		if strings.Contains(line, "w") {
+			return true // File is being written to
+		}
+	}
+
+	return false // File is not being written to
+}
+
 func (w *worker) processEOF(file *os.File, job *Job, jobProvider *jobProvider, totalOffset int64) error {
 	stat, err := file.Stat()
 	if err != nil {
 		return err
 	}
 
-	// files truncated from time to time, after logs from file was processed.
-	// Position > stat.Size() means that data was truncated and
-	// caret pointer must be moved to start of file.
-	if totalOffset > stat.Size() {
-		jobProvider.truncateJob(job)
+	if !job.isCompressed {
+		// files truncated from time to time, after logs from file was processed.
+		// Position > stat.Size() means that data was truncated and
+		// caret pointer must be moved to start of file.
+		if totalOffset > stat.Size() {
+			jobProvider.truncateJob(job)
+		}
 	}
 
 	// Mark job as done till new lines has appeared.