/
readfile.go
318 lines (274 loc) · 6.66 KB
/
readfile.go
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package fs
import (
"bufio"
"compress/gzip"
"github.com/mimecast/dtail/internal/logger"
"errors"
"io"
"os"
"regexp"
"strings"
"sync"
"time"
"github.com/DataDog/zstd"
)
// 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
// Only consider all log lines matching this regular expression.
re *regexp.Regexp
// The glob identifier of the file.
globID string
// Channel to send a server message to the dtail client
serverMessages chan<- string
// Signals to stop tailing the log file.
stop chan struct{}
// 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
// Mutex to control the stopping of the file
mutex *sync.Mutex
limiter chan struct{}
}
// 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
}
// Start tailing a log file.
func (f readFile) Start(lines chan<- LineRead, regex string) error {
defer func() {
select {
case <-f.limiter:
default:
}
}()
select {
case f.limiter <- struct{}{}:
default:
select {
case f.serverMessages <- logger.Warn(f.filePath, f.globID, "Server limit reached. Queuing file..."):
case <-f.stop:
return nil
}
f.limiter <- struct{}{}
}
fd, err := os.Open(f.filePath)
if err != nil {
return err
}
defer fd.Close()
if f.seekEOF {
fd.Seek(0, io.SeekEnd)
}
rawLines := make(chan []byte, 100)
truncate := make(chan struct{})
var wg sync.WaitGroup
wg.Add(1)
go f.periodicTruncateCheck(truncate)
go f.filter(&wg, rawLines, lines, regex)
err = f.read(fd, rawLines, truncate)
close(rawLines)
wg.Wait()
return err
}
func (f readFile) periodicTruncateCheck(truncate chan struct{}) {
for {
select {
case <-time.After(time.Second * 3):
select {
case truncate <- struct{}{}:
case <-f.stop:
}
case <-f.stop:
return
}
}
}
// Stop reading file.
func (f readFile) Stop() {
f.mutex.Lock()
defer f.mutex.Unlock()
select {
case <-f.stop:
return
default:
}
close(f.stop)
}
func (f readFile) makeReader(fd *os.File) (reader *bufio.Reader, err error) {
switch {
case strings.HasSuffix(f.FilePath(), ".gz"):
fallthrough
case strings.HasSuffix(f.FilePath(), ".gzip"):
logger.Info(f.FilePath(), "Detected gzip compression format")
var gzipReader *gzip.Reader
gzipReader, err = gzip.NewReader(fd)
if err != nil {
return
}
reader = bufio.NewReader(gzipReader)
case strings.HasSuffix(f.FilePath(), ".zst"):
logger.Info(f.FilePath(), "Detected zstd compression format")
reader = bufio.NewReader(zstd.NewReader(fd))
default:
reader = bufio.NewReader(fd)
}
return
}
func (f readFile) read(fd *os.File, rawLines chan []byte, truncate <-chan struct{}) error {
reader, err := f.makeReader(fd)
if err != nil {
return err
}
rawLine := make([]byte, 0, 512)
var offset uint64
lineLengthThreshold := 1024 * 1024 // 1mb
longLineWarning := false
for {
select {
case <-truncate:
if isTruncated, err := f.truncated(fd); isTruncated {
return err
}
logger.Info(f.filePath, "Current offset", offset)
case <-f.stop:
return nil
default:
}
// Read some bytes (max 4k at once as of go 1.12). isPrefix will
// be set if line does not fit into 4k buffer.
bytes, isPrefix, err := reader.ReadLine()
if err != nil {
// If EOF, sleep a couple of ms and return with nil error.
// If other error, return with non-nil error.
if err != io.EOF {
return err
}
if !f.seekEOF {
logger.Debug(f.FilePath(), "End of file reached")
return nil
}
time.Sleep(time.Millisecond * 100)
continue
}
rawLine = append(rawLine, bytes...)
offset += uint64(len(bytes))
if !isPrefix {
// last LineRead call returned contend until end of line.
rawLine = append(rawLine, '\n')
select {
case rawLines <- rawLine:
case <-f.stop:
return nil
}
rawLine = make([]byte, 0, 512)
if longLineWarning {
longLineWarning = false
}
continue
}
// Last LineRead call could not read content until end of line, buffer
// was too small. Determine whether we exceed the max line length we
// want dtail to send to the client at once. Possibly split up log line
// into multiple log lines.
if len(rawLine) >= lineLengthThreshold {
if !longLineWarning {
f.serverMessages <- logger.Warn(f.filePath, "Long log line, splitting into multiple lines")
// Only print out one warning per long log line.
longLineWarning = true
}
rawLine = append(rawLine, '\n')
select {
case rawLines <- rawLine:
case <-f.stop:
return nil
}
rawLine = make([]byte, 0, 512)
}
}
}
// Filter log lines matching a given regular expression.
func (f readFile) filter(wg *sync.WaitGroup, rawLines <-chan []byte, lines chan<- LineRead, regex string) {
defer wg.Done()
if regex == "" {
regex = "."
}
re, err := regexp.Compile(regex)
if err != nil {
logger.Error(regex, "Can't compile regex, using '.' instead", err)
re = regexp.MustCompile(".")
}
f.re = re
for {
select {
case line, ok := <-rawLines:
f.updatePosition()
if !ok {
return
}
if filteredLine, ok := f.transmittable(line, len(lines), cap(lines)); ok {
select {
case lines <- filteredLine:
case <-f.stop:
return
}
}
}
}
}
func (f readFile) transmittable(line []byte, length, capacity int) (LineRead, bool) {
var read LineRead
if !f.re.Match(line) {
f.updateLineNotMatched()
f.updateLineNotTransmitted()
return read, false
}
f.updateLineMatched()
// Can we actually send more messages, channel capacity reached?
if f.canSkipLines && length >= capacity {
f.updateLineNotTransmitted()
return read, false
}
f.updateLineTransmitted()
read = LineRead{
Content: line,
GlobID: &f.globID,
Count: f.totalLineCount(),
TransmittedPerc: f.transmittedPerc(),
}
return read, true
}
// Check wether log file is truncated. Returns nil if not.
func (f readFile) truncated(fd *os.File) (bool, error) {
logger.Debug(f.filePath, "File truncation check")
// Can not seek currently open FD.
curPos, err := fd.Seek(0, os.SEEK_CUR)
if err != nil {
return true, err
}
// Can not open file at original path.
pathFd, err := os.Open(f.filePath)
if err != nil {
return true, err
}
defer pathFd.Close()
// Can not seek file at original path.
pathPos, err := pathFd.Seek(0, io.SeekEnd)
if err != nil {
return true, err
}
if curPos > pathPos {
return true, errors.New("File got truncated")
}
return false, nil
}