Pull request: * all: move internal Go packages to internal/

Merge in DNS/adguard-home from 2234-move-to-internal to master

Squashed commit of the following:

commit d26a288cabeac86f9483fab307677b1027c78524
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Fri Oct 30 12:44:18 2020 +0300

    * all: move internal Go packages to internal/

    Closes #2234.

internal/querylog/querylog_file.go

@@ -0,0 +1,139 @@
+package querylog
+
+import (
+	"bytes"
+	"encoding/json"
+	"os"
+	"time"
+
+	"github.com/AdguardTeam/golibs/log"
+)
+
+// flushLogBuffer flushes the current buffer to file and resets the current buffer
+func (l *queryLog) flushLogBuffer(fullFlush bool) error {
+	if !l.conf.FileEnabled {
+		return nil
+	}
+
+	l.fileFlushLock.Lock()
+	defer l.fileFlushLock.Unlock()
+
+	// flush remainder to file
+	l.bufferLock.Lock()
+	needFlush := len(l.buffer) >= int(l.conf.MemSize)
+	if !needFlush && !fullFlush {
+		l.bufferLock.Unlock()
+		return nil
+	}
+	flushBuffer := l.buffer
+	l.buffer = nil
+	l.flushPending = false
+	l.bufferLock.Unlock()
+	err := l.flushToFile(flushBuffer)
+	if err != nil {
+		log.Error("Saving querylog to file failed: %s", err)
+		return err
+	}
+	return nil
+}
+
+// flushToFile saves the specified log entries to the query log file
+func (l *queryLog) flushToFile(buffer []*logEntry) error {
+	if len(buffer) == 0 {
+		log.Debug("querylog: there's nothing to write to a file")
+		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.Error("Failed to marshal entry: %s", err)
+			return err
+		}
+	}
+
+	elapsed := time.Since(start)
+	log.Debug("%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)))
+
+	var err error
+	var zb bytes.Buffer
+	filename := l.logFile
+	zb = b
+
+	l.fileWriteLock.Lock()
+	defer l.fileWriteLock.Unlock()
+	f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644)
+	if err != nil {
+		log.Error("failed to create file \"%s\": %s", filename, err)
+		return err
+	}
+	defer f.Close()
+
+	n, err := f.Write(zb.Bytes())
+	if err != nil {
+		log.Error("Couldn't write to file: %s", err)
+		return err
+	}
+
+	log.Debug("querylog: ok \"%s\": %v bytes written", filename, n)
+
+	return nil
+}
+
+func (l *queryLog) rotate() error {
+	from := l.logFile
+	to := l.logFile + ".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.Error("querylog: failed to rename file: %s", err)
+		return err
+	}
+
+	log.Debug("querylog: renamed %s -> %s", from, to)
+	return nil
+}
+
+func (l *queryLog) readFileFirstTimeValue() int64 {
+	f, err := os.Open(l.logFile)
+	if err != nil {
+		return -1
+	}
+	defer f.Close()
+
+	buf := make([]byte, 500)
+	r, err := f.Read(buf)
+	if err != nil {
+		return -1
+	}
+	buf = buf[:r]
+
+	val := readJSONValue(string(buf), "T")
+	t, err := time.Parse(time.RFC3339Nano, val)
+	if err != nil {
+		return -1
+	}
+
+	log.Debug("querylog: the oldest log entry: %s", val)
+	return t.Unix()
+}
+
+func (l *queryLog) periodicRotate() {
+	intervalSeconds := uint64(l.conf.Interval) * 24 * 60 * 60
+	for {
+		oldest := l.readFileFirstTimeValue()
+		if uint64(oldest)+intervalSeconds <= uint64(time.Now().Unix()) {
+			_ = l.rotate()
+		}
+
+		time.Sleep(24 * time.Hour)
+	}
+}