mdb/kvstore/sync-send.go

package kvstore

import (
	"encoding/binary"
	"log"
	"net"
	"time"
)

func (kv *KV) SyncSend(conn net.Conn) {
	defer conn.Close()

	var (
		seqNumBuf = make([]byte, 8)
		headerBuf = make([]byte, recHeaderSize)
		empty     = make([]byte, recHeaderSize)
		err       error
	)

	// Read afterSeqNum from the conn.
	conn.SetReadDeadline(time.Now().Add(connTimeout))
	if _, err := conn.Read(seqNumBuf[:8]); err != nil {
		log.Printf("SyncSend failed to read afterSeqNum: %v", err)
		return
	}

	afterSeqNum := binary.LittleEndian.Uint64(seqNumBuf[:8])

POLL:

	for i := 0; i < 4; i++ {
		if kv.MaxSeqNum() > afterSeqNum {
			goto REPLAY
		}
		time.Sleep(pollInterval)
	}

	goto HEARTBEAT

HEARTBEAT:

	conn.SetWriteDeadline(time.Now().Add(connTimeout))
	if _, err := conn.Write(empty); err != nil {
		log.Printf("SendWAL failed to send heartbeat: %v", err)
		return
	}

	goto POLL

REPLAY:

	err = kv.replay(afterSeqNum, func(rec record) error {
		conn.SetWriteDeadline(time.Now().Add(connTimeout))

		afterSeqNum = rec.SeqNum
		encodeRecordHeader(rec, headerBuf)
		if _, err := conn.Write(headerBuf); err != nil {
			log.Printf("SendWAL failed to send header %v", err)
			return err
		}

		if _, err := conn.Write([]byte(rec.Collection)); err != nil {
			log.Printf("SendWAL failed to send collection name %v", err)
			return err
		}

		if !rec.Store {
			return nil
		}

		if _, err := conn.Write(rec.Data); err != nil {
			log.Printf("SendWAL failed to send data %v", err)
			return err
		}

		return nil
	})

	if err != nil {
		return
	}

	goto POLL
}

func (kv *KV) replay(afterSeqNum uint64, each func(rec record) error) error {
	rec := record{}
	rows, err := kv.logIterateStmt.Query(afterSeqNum)
	must(err)
	defer rows.Close()

	rec.Data = GetDataBuf(0)
	defer RecycleDataBuf(rec.Data)

	for rows.Next() {
		must(rows.Scan(
			&rec.SeqNum,
			&rec.Collection,
			&rec.ID,
			&rec.Store,
			&rec.Data))

		if err = each(rec); err != nil {
			return err
		}
	}
	return nil
}