Tandem
/
certspotter
mirror of https://github.com/SSLMate/certspotter.git
2
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

monitor: fsync state files before renaming them 

Without fsync, there's a risk of zero-length files being persisted if
there's a power failure.

Don't bother fsyncing the parent directory because it's OK if the data rolls
back to the previous version; we only need to avoid data corruption.

Closes: #101
This commit is contained in:
Andrew Ayer 2025-05-04 20:44:36 -04:00
parent b856d7f163
commit c967253f80
1 changed files with 16 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
monitor/fileutils.go
View File

@ -25,9 +25,24 @@ func randomFileSuffix() string {
return hex.EncodeToString(randomBytes[:])
}
func writeSyncFile(filename string, data []byte, perm os.FileMode) error {
f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
if err != nil {
return err
}
_, err = f.Write(data)
if err2 := f.Sync(); err2 != nil && err == nil {
err = err2
}
if err2 := f.Close(); err2 != nil && err == nil {
err = err2
}
return err
}
func writeFile(filename string, data []byte, perm os.FileMode) error {
tempname := filename + ".tmp." + randomFileSuffix()
if err := os.WriteFile(tempname, data, perm); err != nil {
if err := writeSyncFile(tempname, data, perm); err != nil {
return fmt.Errorf("error writing %s: %w", filename, err)
}
if err := os.Rename(tempname, filename); err != nil {