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rotator.go
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rotator.go
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package logging
import (
"bufio"
"bytes"
"fmt"
"io/ioutil"
"os"
"path/filepath"
"sort"
"strconv"
"strings"
"sync"
"time"
hclog "github.com/hashicorp/go-hclog"
)
const (
// logBufferSize is the size of the buffer.
logBufferSize = 64 * 1024
// bufferFlushDuration is the duration at which we flush the buffer.
bufferFlushDuration = 100 * time.Millisecond
// lineScanLimit is the number of bytes we will attempt to scan for new
// lines when approaching the end of the file to avoid a log line being
// split between two files. Any single line that is greater than this limit
// may be split.
lineScanLimit = 32 * 1024
// newLineDelimiter is the delimiter used for new lines.
newLineDelimiter = '\n'
)
// FileRotator writes bytes to a rotated set of files
type FileRotator struct {
MaxFiles int // MaxFiles is the maximum number of rotated files allowed in a path
FileSize int64 // FileSize is the size a rotated file is allowed to grow
path string // path is the path on the file system where the rotated set of files are opened
baseFileName string // baseFileName is the base file name of the rotated files
logFileIdx int // logFileIdx is the current index of the rotated files
oldestLogFileIdx int // oldestLogFileIdx is the index of the oldest log file in a path
closed bool
fileLock sync.Mutex
currentFile *os.File // currentFile is the file that is currently getting written
currentWr int64 // currentWr is the number of bytes written to the current file
bufw *bufio.Writer
bufLock sync.Mutex
flushTicker *time.Ticker
logger hclog.Logger
purgeCh chan struct{}
doneCh chan struct{}
}
// NewFileRotator returns a new file rotator
func NewFileRotator(path string, baseFile string, maxFiles int,
fileSize int64, logger hclog.Logger) (*FileRotator, error) {
logger = logger.Named("rotator")
rotator := &FileRotator{
MaxFiles: maxFiles,
FileSize: fileSize,
path: path,
baseFileName: baseFile,
flushTicker: time.NewTicker(bufferFlushDuration),
logger: logger,
purgeCh: make(chan struct{}, 1),
doneCh: make(chan struct{}),
}
if err := rotator.lastFile(); err != nil {
return nil, err
}
go rotator.purgeOldFiles()
go rotator.flushPeriodically()
return rotator, nil
}
// Write writes a byte array to a file and rotates the file if it's size becomes
// equal to the maximum size the user has defined.
func (f *FileRotator) Write(p []byte) (n int, err error) {
n = 0
var forceRotate bool
for n < len(p) {
// Check if we still have space in the current file, otherwise close and
// open the next file
if forceRotate || f.currentWr >= f.FileSize {
forceRotate = false
f.flushBuffer()
f.currentFile.Close()
if err := f.nextFile(); err != nil {
f.logger.Error("error creating next file", "error", err)
return 0, err
}
}
// Calculate the remaining size on this file and how much we have left
// to write
remainingSpace := f.FileSize - f.currentWr
remainingToWrite := int64(len(p[n:]))
// Check if we are near the end of the file. If we are we attempt to
// avoid a log line being split between two files.
var nw int
if (remainingSpace - lineScanLimit) < remainingToWrite {
// Scan for new line and if the data up to new line fits in current
// file, write to buffer
idx := bytes.IndexByte(p[n:], newLineDelimiter)
if idx >= 0 && (remainingSpace-int64(idx)-1) >= 0 {
// We have space so write it to buffer
nw, err = f.writeToBuffer(p[n : n+idx+1])
} else if idx >= 0 {
// We found a new line but don't have space so just force rotate
forceRotate = true
} else if remainingToWrite > f.FileSize || f.FileSize-lineScanLimit < 0 {
// There is no new line remaining but there is no point in
// rotating since the remaining data will not even fit in the
// next file either so just fill this one up.
li := int64(n) + remainingSpace
if remainingSpace > remainingToWrite {
li = int64(n) + remainingToWrite
}
nw, err = f.writeToBuffer(p[n:li])
} else {
// There is no new line in the data remaining for us to write
// and it will fit in the next file so rotate.
forceRotate = true
}
} else {
// Write all the bytes in the current file
nw, err = f.writeToBuffer(p[n:])
}
// Increment the number of bytes written so far in this method
// invocation
n += nw
// Increment the total number of bytes in the file
f.currentWr += int64(n)
if err != nil {
f.logger.Error("error writing to file", "error", err)
// As bufio writer does not automatically recover in case of any
// io error, we need to recover from it manually resetting the
// writter.
f.createOrResetBuffer()
return
}
}
return
}
// nextFile opens the next file and purges older files if the number of rotated
// files is larger than the maximum files configured by the user
func (f *FileRotator) nextFile() error {
nextFileIdx := f.logFileIdx
for {
nextFileIdx += 1
logFileName := filepath.Join(f.path, fmt.Sprintf("%s.%d", f.baseFileName, nextFileIdx))
if fi, err := os.Stat(logFileName); err == nil {
if fi.IsDir() || fi.Size() >= f.FileSize {
continue
}
}
f.logFileIdx = nextFileIdx
if err := f.createFile(); err != nil {
return err
}
break
}
// Purge old files if we have more files than MaxFiles
f.fileLock.Lock()
defer f.fileLock.Unlock()
if f.logFileIdx-f.oldestLogFileIdx >= f.MaxFiles && !f.closed {
select {
case f.purgeCh <- struct{}{}:
default:
}
}
return nil
}
// lastFile finds out the rotated file with the largest index in a path.
func (f *FileRotator) lastFile() error {
finfos, err := ioutil.ReadDir(f.path)
if err != nil {
return err
}
prefix := fmt.Sprintf("%s.", f.baseFileName)
for _, fi := range finfos {
if fi.IsDir() {
continue
}
if strings.HasPrefix(fi.Name(), prefix) {
fileIdx := strings.TrimPrefix(fi.Name(), prefix)
n, err := strconv.Atoi(fileIdx)
if err != nil {
continue
}
if n > f.logFileIdx {
f.logFileIdx = n
}
}
}
if err := f.createFile(); err != nil {
return err
}
return nil
}
// createFile opens a new or existing file for writing
func (f *FileRotator) createFile() error {
logFileName := filepath.Join(f.path, fmt.Sprintf("%s.%d", f.baseFileName, f.logFileIdx))
cFile, err := os.OpenFile(logFileName, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0644)
if err != nil {
return err
}
f.currentFile = cFile
fi, err := f.currentFile.Stat()
if err != nil {
return err
}
f.currentWr = fi.Size()
f.createOrResetBuffer()
return nil
}
// flushPeriodically flushes the buffered writer every 100ms to the underlying
// file
func (f *FileRotator) flushPeriodically() {
for {
select {
case <-f.flushTicker.C:
f.flushBuffer()
case <-f.doneCh:
return
}
}
}
// Close flushes and closes the rotator. It never returns an error.
func (f *FileRotator) Close() error {
f.fileLock.Lock()
defer f.fileLock.Unlock()
// Stop the ticker and flush for one last time
f.flushTicker.Stop()
f.flushBuffer()
// Stop the go routines
if !f.closed {
close(f.doneCh)
close(f.purgeCh)
f.closed = true
f.currentFile.Close()
}
return nil
}
// purgeOldFiles removes older files and keeps only the last N files rotated for
// a file
func (f *FileRotator) purgeOldFiles() {
for {
select {
case <-f.purgeCh:
var fIndexes []int
files, err := ioutil.ReadDir(f.path)
if err != nil {
f.logger.Error("error getting directory listing", "error", err)
return
}
// Inserting all the rotated files in a slice
for _, fi := range files {
if strings.HasPrefix(fi.Name(), f.baseFileName) {
fileIdx := strings.TrimPrefix(fi.Name(), fmt.Sprintf("%s.", f.baseFileName))
n, err := strconv.Atoi(fileIdx)
if err != nil {
f.logger.Error("error extracting file index", "error", err)
continue
}
fIndexes = append(fIndexes, n)
}
}
// Not continuing to delete files if the number of files is not more
// than MaxFiles
if len(fIndexes) <= f.MaxFiles {
continue
}
// Sorting the file indexes so that we can purge the older files and keep
// only the number of files as configured by the user
sort.Ints(fIndexes)
toDelete := fIndexes[0 : len(fIndexes)-f.MaxFiles]
for _, fIndex := range toDelete {
fname := filepath.Join(f.path, fmt.Sprintf("%s.%d", f.baseFileName, fIndex))
err := os.RemoveAll(fname)
if err != nil {
f.logger.Error("error removing file", "filename", fname, "error", err)
}
}
f.fileLock.Lock()
f.oldestLogFileIdx = fIndexes[0]
f.fileLock.Unlock()
case <-f.doneCh:
return
}
}
}
// flushBuffer flushes the buffer
func (f *FileRotator) flushBuffer() error {
f.bufLock.Lock()
defer f.bufLock.Unlock()
if f.bufw != nil {
return f.bufw.Flush()
}
return nil
}
// writeToBuffer writes the byte array to buffer
func (f *FileRotator) writeToBuffer(p []byte) (int, error) {
f.bufLock.Lock()
defer f.bufLock.Unlock()
return f.bufw.Write(p)
}
// createOrResetBuffer creates a new buffer if we don't have one otherwise
// resets the buffer
func (f *FileRotator) createOrResetBuffer() {
f.bufLock.Lock()
defer f.bufLock.Unlock()
if f.bufw == nil {
f.bufw = bufio.NewWriterSize(f.currentFile, logBufferSize)
} else {
f.bufw.Reset(f.currentFile)
}
}