cloudflared-mirror/sshlog/logger.go

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package sshlog
import (
"bufio"
"errors"
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"fmt"
"os"
"path/filepath"
"sync"
"time"
"github.com/sirupsen/logrus"
)
const (
logTimeFormat = "2006-01-02T15-04-05.000"
megabyte = 1024 * 1024
defaultFileSizeLimit = 100 * megabyte
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)
// Logger will buffer and write events to disk
type Logger struct {
sync.Mutex
filename string
file *os.File
writeBuffer *bufio.Writer
logger *logrus.Logger
flushInterval time.Duration
maxFileSize int64
done chan struct{}
once sync.Once
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}
// NewLogger creates a Logger instance. A buffer is created that needs to be
// drained and closed when the caller is finished, so instances should call
// Close when finished with this Logger instance. Writes will be flushed to disk
// every second (fsync). filename is the name of the logfile to be created. The
// logger variable is a logrus that will log all i/o, filesystem error etc, that
// that shouldn't end execution of the logger, but are useful to report to the
// caller.
func NewLogger(filename string, logger *logrus.Logger, flushInterval time.Duration, maxFileSize int64) (*Logger, error) {
if logger == nil {
return nil, errors.New("logger can't be nil")
}
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f, err := os.OpenFile(filename, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, os.FileMode(0600))
if err != nil {
return nil, err
}
l := &Logger{filename: filename,
file: f,
writeBuffer: bufio.NewWriter(f),
logger: logger,
flushInterval: flushInterval,
maxFileSize: maxFileSize,
done: make(chan struct{}),
}
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go l.writer()
return l, nil
}
// Writes to a log buffer. Implements the io.Writer interface.
func (l *Logger) Write(p []byte) (n int, err error) {
l.Lock()
defer l.Unlock()
return l.writeBuffer.Write(p)
}
// Close drains anything left in the buffer and cleans up any resources still
// in use.
func (l *Logger) Close() error {
l.once.Do(func() {
close(l.done)
})
if err := l.write(); err != nil {
return err
}
return l.file.Close()
}
// writer is the run loop that handles draining the write buffer and syncing
// data to disk.
func (l *Logger) writer() {
ticker := time.NewTicker(l.flushInterval)
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defer ticker.Stop()
for {
select {
case <-ticker.C:
if err := l.write(); err != nil {
l.logger.Errorln(err)
}
case <-l.done:
return
}
}
}
// write does the actual system write calls to disk and does a rotation if the
// file size limit has been reached. Since the rotation happens at the end,
// the rotation is a soft limit (aka the file can be bigger than the max limit
// because of the final buffer flush)
func (l *Logger) write() error {
l.Lock()
defer l.Unlock()
if l.writeBuffer.Buffered() <= 0 {
return nil
}
if err := l.writeBuffer.Flush(); err != nil {
return err
}
if err := l.file.Sync(); err != nil {
return err
}
if l.shouldRotate() {
return l.rotate()
}
return nil
}
// shouldRotate checks to see if the current file should be rotated to a new
// logfile.
func (l *Logger) shouldRotate() bool {
info, err := l.file.Stat()
if err != nil {
return false
}
return info.Size() >= l.maxFileSize
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}
// rotate creates a new logfile with the existing filename and renames the
// existing file with a current timestamp.
func (l *Logger) rotate() error {
if err := l.file.Close(); err != nil {
return err
}
// move the existing file
newname := rotationName(l.filename)
if err := os.Rename(l.filename, newname); err != nil {
return fmt.Errorf("can't rename log file: %s", err)
}
f, err := os.OpenFile(l.filename, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, os.FileMode(0600))
if err != nil {
return fmt.Errorf("failed to open new logfile %s", err)
}
l.file = f
l.writeBuffer = bufio.NewWriter(f)
return nil
}
// rotationName creates a new filename from the given name, inserting a timestamp
// between the filename and the extension.
func rotationName(name string) string {
dir := filepath.Dir(name)
filename := filepath.Base(name)
ext := filepath.Ext(filename)
prefix := filename[:len(filename)-len(ext)]
t := time.Now()
timestamp := t.Format(logTimeFormat)
return filepath.Join(dir, fmt.Sprintf("%s-%s%s", prefix, timestamp, ext))
}