package dnsfilter import ( "bytes" "compress/gzip" "encoding/json" "fmt" "log" "os" "sync" "time" "github.com/go-test/deep" ) const ( queryLogRotationPeriod = time.Hour * 24 // rotate the log every 24 hours queryLogFileName = "querylog.json" // .gz added during compression ) var ( fileWriteLock sync.Mutex ) func flushToFile(buffer []logEntry) error { if len(buffer) == 0 { return nil } start := time.Now() var b bytes.Buffer e := json.NewEncoder(&b) for _, entry := range buffer { err := e.Encode(entry) if err != nil { log.Printf("Failed to marshal entry: %s", err) return err } } elapsed := time.Since(start) log.Printf("%d elements serialized via json in %v: %d kB, %v/entry, %v/entry", len(buffer), elapsed, b.Len()/1024, float64(b.Len())/float64(len(buffer)), elapsed/time.Duration(len(buffer))) err := checkBuffer(buffer, b) if err != nil { log.Printf("failed to check buffer: %s", err) return err } filenamegz := queryLogFileName + ".gz" var zb bytes.Buffer zw := gzip.NewWriter(&zb) zw.Name = queryLogFileName zw.ModTime = time.Now() _, err = zw.Write(b.Bytes()) if err != nil { log.Printf("Couldn't compress to gzip: %s", err) zw.Close() return err } if err = zw.Close(); err != nil { log.Printf("Couldn't close gzip writer: %s", err) return err } fileWriteLock.Lock() defer fileWriteLock.Unlock() f, err := os.OpenFile(filenamegz, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644) if err != nil { log.Printf("failed to create file \"%s\": %s", filenamegz, err) return err } defer f.Close() n, err := f.Write(zb.Bytes()) if err != nil { log.Printf("Couldn't write to file: %s", err) return err } log.Printf("ok \"%s\": %v bytes written", filenamegz, n) return nil } func checkBuffer(buffer []logEntry, b bytes.Buffer) error { l := len(buffer) d := json.NewDecoder(&b) i := 0 for d.More() { var entry logEntry err := d.Decode(&entry) if err != nil { log.Printf("Failed to decode: %s", err) return err } if diff := deep.Equal(entry, buffer[i]); diff != nil { log.Printf("decoded buffer differs: %s", diff) return fmt.Errorf("decoded buffer differs: %s", diff) } i++ } if i != l { err := fmt.Errorf("check fail: %d vs %d entries", l, i) log.Print(err) return err } log.Printf("check ok: %d entries", i) return nil } func rotateQueryLog() error { from := queryLogFileName + ".gz" to := queryLogFileName + ".gz.1" if _, err := os.Stat(from); os.IsNotExist(err) { // do nothing, file doesn't exist return nil } err := os.Rename(from, to) if err != nil { log.Printf("Failed to rename querylog: %s", err) return err } log.Printf("Rotated from %s to %s successfully", from, to) return nil } func periodicQueryLogRotate(t time.Duration) { for range time.Tick(t) { err := rotateQueryLog() if err != nil { log.Printf("Failed to rotate querylog: %s", err) // do nothing, continue rotating } } }