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package fs
import (
"bufio"
"compress/gzip"
"context"
"errors"
"fmt"
"io"
"os"
"strings"
"time"
"github.com/mimecast/dtail/internal/io/dlog"
)
type readStatus int
const (
nothing readStatus = iota
abortReading readStatus = iota
continueReading readStatus = iota
defaultMaxLineLength = 1024 * 1024
)
// Used to tail and filter a local log file.
type readFile struct {
// Various statistics (e.g. regex hit percentage, transfer percentage).
stats
// Path of log file to tail.
filePath string
// Rooted target used for validated server-side re-opens.
validatedTarget *ValidatedReadTarget
// The glob identifier of the file.
globID string
// Channel to send a server message to the dtail client
serverMessages chan<- string
// Periodically retry reading file.
retry bool
// Can I skip messages when there are too many?
canSkipLines bool
// Seek to the EOF before processing file?
seekEOF bool
// Warned already about a long line.
warnedAboutLongLine bool
// Maximum line length before a line is split.
maxLineLength int
}
// String returns the string representation of the readFile
func (f readFile) String() string {
return fmt.Sprintf(
"readFile(filePath:%s,globID:%s,retry:%v,canSkipLines:%v,seekEOF:%v)",
f.filePath,
f.globID,
f.retry,
f.canSkipLines,
f.seekEOF)
}
// FilePath returns the full file path.
func (f readFile) FilePath() string {
return f.filePath
}
// Retry reading the file on error?
func (f readFile) Retry() bool {
return f.retry
}
func (f *readFile) lineLimit() int {
if f.maxLineLength <= 0 {
return defaultMaxLineLength
}
return f.maxLineLength
}
func (f *readFile) warnAboutLongLine(ctx context.Context) bool {
if f.warnedAboutLongLine {
return true
}
if f.serverMessages == nil {
f.warnedAboutLongLine = true
return true
}
select {
case f.serverMessages <- dlog.Common.Warn(f.filePath,
"Long log line, splitting into multiple lines") + "\n":
f.warnedAboutLongLine = true
return true
case <-ctx.Done():
return false
}
}
func (f *readFile) makeReader() (*bufio.Reader, *os.File, io.Closer, error) {
if f.filePath == "" && f.globID == "-" {
return f.makePipeReader()
}
return f.makeFileReader()
}
func (f *readFile) makeFileReader() (reader *bufio.Reader, fd *os.File, decompressor io.Closer, err error) {
if fd, err = f.openFile(); err != nil {
return
}
if f.seekEOF {
if _, err = fd.Seek(0, io.SeekEnd); err != nil {
return
}
}
reader, decompressor, err = f.makeCompressedFileReader(fd)
return
}
func (f *readFile) openFile() (*os.File, error) {
if f.validatedTarget != nil {
return f.validatedTarget.Open()
}
return os.Open(f.filePath)
}
func (f *readFile) makePipeReader() (*bufio.Reader, *os.File, io.Closer, error) {
return bufio.NewReader(os.Stdin), nil, nil, nil
}
func (f *readFile) periodicTruncateCheck(ctx context.Context, truncate chan<- struct{}) {
ticker := time.NewTicker(time.Second * 3)
defer ticker.Stop()
for {
select {
case <-ticker.C:
select {
case truncate <- struct{}{}:
case <-ctx.Done():
return
}
case <-ctx.Done():
return
}
}
}
func (f *readFile) makeCompressedFileReader(fd *os.File) (reader *bufio.Reader, decompressor io.Closer, err error) {
switch {
case strings.HasSuffix(f.FilePath(), ".gz"):
fallthrough
case strings.HasSuffix(f.FilePath(), ".gzip"):
dlog.Common.Info(f.FilePath(), "Detected gzip compression format")
var gzipReader *gzip.Reader
gzipReader, err = gzip.NewReader(fd)
if err != nil {
return
}
decompressor = gzipReader
reader = bufio.NewReader(gzipReader)
case strings.HasSuffix(f.FilePath(), ".zst"):
return f.makeZstdReader(fd)
default:
reader = bufio.NewReader(fd)
}
return
}
// Check wether log file is truncated. Returns nil if not.
func (f *readFile) truncated(fd *os.File) (bool, error) {
if fd == nil {
return false, nil
}
dlog.Common.Debug(f.filePath, "File truncation check")
// Can not seek currently open FD.
currentPosition, err := fd.Seek(0, io.SeekCurrent)
if err != nil {
return true, err
}
// Can not open file at original path.
pathFd, err := f.openFile()
if err != nil {
return true, err
}
defer pathFd.Close()
// Can not seek file at original path.
pathPosition, err := pathFd.Seek(0, io.SeekEnd)
if err != nil {
return true, err
}
if currentPosition > pathPosition {
return true, errors.New("File got truncated")
}
return false, nil
}
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