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do not truncate log files on each LogWriter calls #626

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Merged
merged 2 commits into from
Jun 15, 2025
Merged

do not truncate log files on each LogWriter calls #626

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67aace0
do not truncate log files on each LogWriter calls
tucksaun Jun 12, 2025
606fd41
use sync.Once to make `PidFile.LogWriter` calls safe
tucksaun Jun 14, 2025
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34 changes: 28 additions & 6 deletions local/pid/pidfile.go
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@ import (
"os"
"path/filepath"
"strings"
"sync"
"syscall"
"time"

Expand All @@ -49,6 +50,9 @@ type PidFile struct {
CustomName string `json:"name"`

path string

lwInit sync.Once // used to ensure that the log writer is only created once
lw io.WriteCloser // log writer, used to write logs to the log file
}

func New(dir string, args []string) *PidFile {
Expand Down Expand Up @@ -257,16 +261,34 @@ func (p *PidFile) LogReader() (io.ReadCloser, error) {
return r, nil
}

// LogWriter returns a writer to write logs to the log file. It creates the log
// file if it does not exist, and truncates it if it does. It is safe to call
// this method multiple times, it will only create the log file once per process
// lifetime: it is useful to have a single truncation (and thus a clean log
// file) at the beginning of the process management but not to truncate the log
// file when the process is restarted.
// Please note this method might not return a writer even if the error is nil
// (the error is returned only for the first call).
func (p *PidFile) LogWriter() (io.WriteCloser, error) {
logFile := p.LogFile()
if err := os.MkdirAll(filepath.Dir(logFile), 0755); err != nil {
return nil, err
}
w, err := os.OpenFile(logFile, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
var err error

p.lwInit.Do(func() {
logFile := p.LogFile()
if err = errors.WithStack(os.MkdirAll(filepath.Dir(logFile), 0755)); err != nil {
return
}
p.lw, err = os.OpenFile(logFile, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
if err != nil {
err = errors.WithStack(err)
return
}
})

if err != nil {
return nil, err
}
return w, nil

return p.lw, err
}

func (p *PidFile) Binary() string {
Expand Down