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0868329936
My favorite part of generics. Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
225 lines
5.4 KiB
Go
225 lines
5.4 KiB
Go
// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package filelogger provides localdisk log writing & rotation, primarily for Windows
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// clients. (We get this for free on other platforms.)
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package filelogger
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import (
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"bytes"
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"fmt"
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"io/ioutil"
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"log"
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"os"
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"path/filepath"
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"runtime"
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"strings"
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"sync"
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"time"
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"tailscale.com/types/logger"
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)
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const (
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maxSize = 100 << 20
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maxFiles = 50
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)
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// New returns a logf wrapper that appends to local disk log
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// files on Windows, rotating old log files as needed to stay under
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// file count & byte limits.
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func New(fileBasePrefix, logID string, logf logger.Logf) logger.Logf {
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if runtime.GOOS != "windows" {
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panic("not yet supported on any platform except Windows")
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}
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if logf == nil {
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panic("nil logf")
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}
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dir := filepath.Join(os.Getenv("ProgramData"), "Tailscale", "Logs")
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if err := os.MkdirAll(dir, 0700); err != nil {
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log.Printf("failed to create local log directory; not writing logs to disk: %v", err)
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return logf
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}
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logf("local disk logdir: %v", dir)
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lfw := &logFileWriter{
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fileBasePrefix: fileBasePrefix,
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logID: logID,
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dir: dir,
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wrappedLogf: logf,
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}
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return lfw.Logf
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}
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// logFileWriter is the state for the log writer & rotator.
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type logFileWriter struct {
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dir string // e.g. `C:\Users\FooBarUser\AppData\Local\Tailscale\Logs`
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logID string // hex logID
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fileBasePrefix string // e.g. "tailscale-service" or "tailscale-gui"
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wrappedLogf logger.Logf // underlying logger to send to
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mu sync.Mutex // guards following
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buf bytes.Buffer // scratch buffer to avoid allocs
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fday civilDay // day that f was opened; zero means no file yet open
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f *os.File // file currently opened for append
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}
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// civilDay is a year, month, and day in the local timezone.
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// It's a comparable value type.
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type civilDay struct {
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year int
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month time.Month
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day int
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}
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func dayOf(t time.Time) civilDay {
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return civilDay{t.Year(), t.Month(), t.Day()}
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}
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func (w *logFileWriter) Logf(format string, a ...any) {
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w.mu.Lock()
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defer w.mu.Unlock()
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w.buf.Reset()
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fmt.Fprintf(&w.buf, format, a...)
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if w.buf.Len() == 0 {
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return
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}
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out := w.buf.Bytes()
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w.wrappedLogf("%s", out)
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// Make sure there's a final newline before we write to the log file.
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if out[len(out)-1] != '\n' {
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w.buf.WriteByte('\n')
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out = w.buf.Bytes()
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}
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w.appendToFileLocked(out)
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}
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// out should end in a newline.
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// w.mu must be held.
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func (w *logFileWriter) appendToFileLocked(out []byte) {
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now := time.Now()
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day := dayOf(now)
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if w.fday != day {
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w.startNewFileLocked()
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}
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out = removeDatePrefix(out)
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if w.f != nil {
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// RFC3339Nano but with a fixed number (3) of nanosecond digits:
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const formatPre = "2006-01-02T15:04:05"
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const formatPost = "Z07:00"
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fmt.Fprintf(w.f, "%s.%03d%s: %s",
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now.Format(formatPre),
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now.Nanosecond()/int(time.Millisecond/time.Nanosecond),
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now.Format(formatPost),
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out)
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}
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}
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func isNum(b byte) bool { return '0' <= b && b <= '9' }
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// removeDatePrefix returns a subslice of v with the log package's
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// standard datetime prefix format removed, if present.
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func removeDatePrefix(v []byte) []byte {
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const format = "2009/01/23 01:23:23 "
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if len(v) < len(format) {
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return v
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}
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for i, b := range v[:len(format)] {
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fb := format[i]
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if isNum(fb) {
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if !isNum(b) {
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return v
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}
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continue
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}
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if b != fb {
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return v
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}
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}
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return v[len(format):]
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}
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// startNewFileLocked opens a new log file for writing
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// and also cleans up any old files.
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//
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// w.mu must be held.
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func (w *logFileWriter) startNewFileLocked() {
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var oldName string
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if w.f != nil {
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oldName = filepath.Base(w.f.Name())
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w.f.Close()
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w.f = nil
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w.fday = civilDay{}
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}
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w.cleanLocked()
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now := time.Now()
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day := dayOf(now)
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name := filepath.Join(w.dir, fmt.Sprintf("%s-%04d%02d%02dT%02d%02d%02d-%d.txt",
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w.fileBasePrefix,
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day.year,
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day.month,
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day.day,
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now.Hour(),
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now.Minute(),
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now.Second(),
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now.Unix()))
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var err error
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w.f, err = os.Create(name)
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if err != nil {
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w.wrappedLogf("failed to create log file: %v", err)
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return
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}
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if oldName != "" {
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fmt.Fprintf(w.f, "(logID %q; continued from log file %s)\n", w.logID, oldName)
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} else {
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fmt.Fprintf(w.f, "(logID %q)\n", w.logID)
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}
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w.fday = day
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}
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// cleanLocked cleans up old log files.
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//
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// w.mu must be held.
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func (w *logFileWriter) cleanLocked() {
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fis, _ := ioutil.ReadDir(w.dir)
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prefix := w.fileBasePrefix + "-"
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fileSize := map[string]int64{}
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var files []string
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var sumSize int64
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for _, fi := range fis {
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baseName := filepath.Base(fi.Name())
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if !strings.HasPrefix(baseName, prefix) {
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continue
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}
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size := fi.Size()
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fileSize[baseName] = size
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sumSize += size
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files = append(files, baseName)
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}
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if sumSize > maxSize {
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w.wrappedLogf("cleaning log files; sum byte count %d > %d", sumSize, maxSize)
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}
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if len(files) > maxFiles {
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w.wrappedLogf("cleaning log files; number of files %d > %d", len(files), maxFiles)
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}
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for (sumSize > maxSize || len(files) > maxFiles) && len(files) > 0 {
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target := files[0]
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files = files[1:]
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targetSize := fileSize[target]
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targetFull := filepath.Join(w.dir, target)
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err := os.Remove(targetFull)
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if err != nil {
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w.wrappedLogf("error cleaning log file: %v", err)
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} else {
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sumSize -= targetSize
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w.wrappedLogf("cleaned log file %s (size %d); new bytes=%v, files=%v", targetFull, targetSize, sumSize, len(files))
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}
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}
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}
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