AdGuardHome/coredns_plugin/querylog_file.go

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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
}
}
}