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本文次要钻研一下klog的Flush
Flush
k8s.io/klog/v2@v2.4.0/klog.go
// Flush flushes all pending log I/O.func Flush() { logging.lockAndFlushAll()}Flush办法执行的是logging.lockAndFlushAll()
init
k8s.io/klog/v2@v2.4.0/klog.go
// init sets up the defaults and runs flushDaemon.func init() { logging.stderrThreshold = errorLog // Default stderrThreshold is ERROR. logging.setVState(0, nil, false) logging.logDir = "" logging.logFile = "" logging.logFileMaxSizeMB = 1800 logging.toStderr = true logging.alsoToStderr = false logging.skipHeaders = false logging.addDirHeader = false logging.skipLogHeaders = false logging.oneOutput = false go logging.flushDaemon()}klog的init办法异步协程执行logging.flushDaemon()
logging.flushDaemon()
k8s.io/klog/v2@v2.4.0/klog.go
// flushDaemon periodically flushes the log file buffers.func (l *loggingT) flushDaemon() { for range time.NewTicker(flushInterval).C { l.lockAndFlushAll() }}flushDaemon办法range新建ticker的channel，而后执行l.lockAndFlushAll()
lockAndFlushAll
k8s.io/klog/v2@v2.4.0/klog.go
// lockAndFlushAll is like flushAll but locks l.mu first.func (l *loggingT) lockAndFlushAll() { l.mu.Lock() l.flushAll() l.mu.Unlock()}lockAndFlushAll应用lock执行flushAll
flushAll
k8s.io/klog/v2@v2.4.0/klog.go
const ( infoLog severity = iota warningLog errorLog fatalLog numSeverity = 4)// flushAll flushes all the logs and attempts to "sync" their data to disk.// l.mu is held.func (l *loggingT) flushAll() { // Flush from fatal down, in case there's trouble flushing. for s := fatalLog; s >= infoLog; s-- { file := l.file[s] if file != nil { file.Flush() // ignore error file.Sync() // ignore error } }}flushAll办法从fatalLog开始递加到infoLog级别挨个执行l.file[s]的Flush及Sync办法
flushSyncWriter
k8s.io/klog/v2@v2.4.0/klog.go
// flushSyncWriter is the interface satisfied by logging destinations.type flushSyncWriter interface { Flush() error Sync() error io.Writer}type Writer interface { Write(p []byte) (n int, err error)}flushSyncWriter接口定义了Flush、Sync办法，内嵌了io.Writer接口
redirectBuffer
k8s.io/klog/v2@v2.4.0/klog.go
// redirectBuffer is used to set an alternate destination for the logstype redirectBuffer struct { w io.Writer}func (rb *redirectBuffer) Sync() error { return nil}func (rb *redirectBuffer) Flush() error { return nil}func (rb *redirectBuffer) Write(bytes []byte) (n int, err error) { return rb.w.Write(bytes)}redirectBuffer内嵌了io.Writer，其Write办法通过io.Writer来写；其Sync及Flush办法都为空操作
syncBuffer
k8s.io/klog/v2@v2.4.0/klog.go
// syncBuffer joins a bufio.Writer to its underlying file, providing access to the// file's Sync method and providing a wrapper for the Write method that provides log// file rotation. There are conflicting methods, so the file cannot be embedded.// l.mu is held for all its methods.type syncBuffer struct { logger *loggingT *bufio.Writer file *os.File sev severity nbytes uint64 // The number of bytes written to this file maxbytes uint64 // The max number of bytes this syncBuffer.file can hold before cleaning up.}func (sb *syncBuffer) Sync() error { return sb.file.Sync()}func (sb *syncBuffer) Write(p []byte) (n int, err error) { if sb.nbytes+uint64(len(p)) >= sb.maxbytes { if err := sb.rotateFile(time.Now(), false); err != nil { sb.logger.exit(err) } } n, err = sb.Writer.Write(p) sb.nbytes += uint64(n) if err != nil { sb.logger.exit(err) } return}syncBuffer定义了logger、file、sev、nbytes、maxbytes属性，内嵌了*bufio.Writer；其Sync办法执行的是*os.File.Sync；其Flush办法执行的是*bufio.Writer.Flush
Flush
/usr/local/go/src/bufio/bufio.go
type Writer struct { err error buf []byte n int wr io.Writer}// Flush writes any buffered data to the underlying io.Writer.func (b *Writer) Flush() error { if b.err != nil { return b.err } if b.n == 0 { return nil } n, err := b.wr.Write(b.buf[0:b.n]) if n < b.n && err == nil { err = io.ErrShortWrite } if err != nil { if n > 0 && n < b.n { copy(b.buf[0:b.n-n], b.buf[n:b.n]) } b.n -= n b.err = err return err } b.n = 0 return nil}*bufio.Writer.Flush办法执行的是底层io.Writer的Write办法syncBuffer.rotateFile
// rotateFile closes the syncBuffer's file and starts a new one.// The startup argument indicates whether this is the initial startup of klog.// If startup is true, existing files are opened for appending instead of truncated.func (sb *syncBuffer) rotateFile(now time.Time, startup bool) error { if sb.file != nil { sb.Flush() sb.file.Close() } var err error sb.file, _, err = create(severityName[sb.sev], now, startup) if err != nil { return err } if startup { fileInfo, err := sb.file.Stat() if err != nil { return fmt.Errorf("file stat could not get fileinfo: %v", err) } // init file size sb.nbytes = uint64(fileInfo.Size()) } else { sb.nbytes = 0 } sb.Writer = bufio.NewWriterSize(sb.file, bufferSize) if sb.logger.skipLogHeaders { return nil } // Write header. var buf bytes.Buffer fmt.Fprintf(&buf, "Log file created at: %s\n", now.Format("2006/01/02 15:04:05")) fmt.Fprintf(&buf, "Running on machine: %s\n", host) fmt.Fprintf(&buf, "Binary: Built with %s %s for %s/%s\n", runtime.Compiler, runtime.Version(), runtime.GOOS, runtime.GOARCH) fmt.Fprintf(&buf, "Log line format: [IWEF]mmdd hh:mm:ss.uuuuuu threadid file:line] msg\n") n, err := sb.file.Write(buf.Bytes()) sb.nbytes += uint64(n) return err}syncBuffer.rotateFile办法会设置其Writer为bufio.NewWriterSize(sb.file, bufferSize)，底层writer为syncBuffer的file
小结
klog的init办法异步协程执行logging.flushDaemon()，它外部执行的是l.lockAndFlushAll()；Flush办法是执行l.lockAndFlushAll()；l.lockAndFlushAll()办法应用lock执行flushAll；flushAll办法从fatalLog开始递加到infoLog级别挨个执行l.file[s]的Flush及Sync办法；对于redirectBuffer，其Flush及Sync办法为空操作；对于syncBuffer，其Sync办法执行的是*os.File.Sync；其Flush办法执行的是*bufio.Writer.Flush，*bufio.Writer.Flush办法执行的是底层io.Writer的Write办法，即syncBuffer的file的Write办法。
doc
- klog