聊聊kingbus的commandgo

序

本文主要研究一下 kingbus 的 command.go

Close

kingbus/mysql/command.go

//Close the Conn
func (c *Conn) Close() {if c.closed.Load() == true {return}
    c.closed.Store(true)
    c.Conn.Close()
    c.cancel()
    c.Conn = nil
}

• Close 方法执行 c.closed.Store(true)、c.Conn.Close()、c.cancel()

handleQuery

kingbus/mysql/command.go

func (c *Conn) handleQuery(sql string) (err error) {defer func() {if e := recover(); e != nil {if myerr, ok := e.(error); ok {
                const size = 4096
                buf := make([]byte, size)
                buf = buf[:runtime.Stack(buf, false)]
                log.Log.Errorf("Conn handleQuery error,err:%s,sql:%s,stack:%s", myerr, sql, string(buf))
                err = myerr
            }
            return
        }
    }()

    log.Log.Infof("handleQuery sql:%s", sql)
    sqlParser := parser.New()
    stmt, err := sqlParser.ParseOneStmt(sql, "","")
    if err != nil {return err}
    switch v := stmt.(type) {
    case *ast.ShowStmt:
        return c.handleShow(v)
    case *ast.SelectStmt:
        return c.handleSelect(v)
    case *ast.SetStmt:
        return c.handleSet(v)
    case *ast.KillStmt:
        return c.handleKill(v)
    //todo get metrics of slave
    default:
        return ErrSQLNotSupport
    }
    return
}

• handleQuery 方法通过 sqlParser 来解析 stmt，然后根据 stmt 的 type 来执行不同的方法；对于 ShowStmt 执行 c.handleShow(v)，对于 SelectStmt 执行 c.handleSelect(v)，对于 SetStmt 执行 c.handleSet(v)，对于 KillStmt 执行 c.handleKill(v)

writeOK

kingbus/mysql/resp.go

func (c *Conn) writeOK(r *gomysql.Result) error {
    if r == nil {r = &gomysql.Result{}
    }

    r.Status |= c.status

    data := make([]byte, 4, 32)

    data = append(data, gomysql.OK_HEADER)

    data = append(data, gomysql.PutLengthEncodedInt(r.AffectedRows)...)
    data = append(data, gomysql.PutLengthEncodedInt(r.InsertId)...)

    if c.capability&gomysql.CLIENT_PROTOCOL_41 > 0 {data = append(data, byte(r.Status), byte(r.Status>>8))
        data = append(data, 0, 0)
    }

    return c.WritePacket(data)
}

• writeOK 方法用于响应 ping 命令

handleBinlogDumpGtid

kingbus/mysql/command.go

//todo kill the slave with same uuid
func (c *Conn) handleBinlogDumpGtid(ctx context.Context, data []byte) error {
    var (
        err             error
        heartbeatPeriod time.Duration
    )

    slaveGtidExecuted, slaveServerID, err := c.parseMysqlGtidDumpPacket(data)
    if err != nil {return err}

    //UnregisterSlave
    slaveUUID := c.userVariables[SlaveUUID].(string)
    defer c.binlogServer.UnregisterSlave(slaveUUID)

    err = c.binlogServer.CheckGtidSet(gomysql.MySQLFlavor, slaveGtidExecuted)
    if err != nil {log.Log.Errorf("CheckGtidSet error,err:%s,slaveGtids:%v", err, slaveGtidExecuted)
        return err
    }

    //get the previousGtidEvent raft index
    preGtidEventIndex, err := c.binlogServer.GetMySQLDumpAt(slaveGtidExecuted)
    if err != nil {log.Log.Errorf("GetMySQLDumpAt error,err:%s,slaveGtids:%v", err, slaveGtidExecuted)
        return err
    }

    fde, err := c.binlogServer.GetFde(preGtidEventIndex)
    if err != nil {
        log.Log.Errorf("handleBinlogDumpGtid:GetFde error,err:%s, gtidSet: %s,flavor:%s",
            err, slaveGtidExecuted.String(), gomysql.MySQLFlavor)
        return err
    }

    //1.send fake rotate event
    masterServerID := binary.LittleEndian.Uint32(fde[5:])
    fileName, err := c.binlogServer.GetNextBinlogFile(preGtidEventIndex)
    if err != nil {
        log.Log.Errorf("handleBinlogDumpGtid:GetNextBinlogFile error,err:%s, gtidSet: %s,flavor:%s",
            err, slaveGtidExecuted.String(), gomysql.MySQLFlavor)
        return err
    }
    err = c.sendFakeRotateEvent(masterServerID, fileName)
    if err != nil {
        log.Log.Errorf("handleBinlogDumpGtid:sendFakeRotateEvent error,err:%s, serverId: %d,fileName:%s",
            err, masterServerID, fileName)
        return err
    }

    //2.send fde
    err = c.sendFormatDescriptionEvent(fde)
    if err != nil {
        log.Log.Errorf("handleBinlogDumpGtid:sendFormatDescriptionEvent error,err:%s, fde:%v",
            err, fde)
        return err
    }

    //3.send event
    eventC := make(chan *storagepb.BinlogEvent, 2000)
    errorC := make(chan error, 1)
    err = c.binlogServer.DumpBinlogAt(ctx, preGtidEventIndex, slaveGtidExecuted, eventC, errorC)
    if err != nil {
        log.Log.Errorf("DumpBinlogAt error,err:%s,preGtidEventIndex:%d,slaveGtidExecuted:%v",
            err, preGtidEventIndex, slaveGtidExecuted)
        return err
    }

    //4.new metrics
    slaveEps := metrics.NewMeter()
    slaveThroughput := metrics.NewMeter()
    metrics.Register(fmt.Sprintf("slave_eps_%d", slaveServerID), slaveEps)
    metrics.Register(fmt.Sprintf("slave_thoughput_%d", slaveServerID), slaveThroughput)

    if period, ok := c.userVariables[MasterHeartbeatPeriod]; ok {heartbeatPeriod = time.Duration(period.(int64))
    } else {heartbeatPeriod = MaxHeartbeatPeriod}
    timer := time.NewTimer(heartbeatPeriod)
    for {
        select {
        case event := <-eventC:
            //event is not divided or the first divided event
            //WriteEvent need write a ok_header(one byte),after the header size
            if event.DividedCount == 0 || (0 < event.DividedCount && event.DividedSeqNum == 0) {err = c.WriteEvent(event.Data, true)
                if err != nil {log.Log.Errorf("WriteEvent error,err:%s,event:%v", err, *event)
                    return err
                }
            } else {err = c.WriteEvent(event.Data, false)
                if err != nil {log.Log.Errorf("WriteEvent error,err:%s,event:%v", err, *event)
                    return err
                }
                //event is divided,and the last packet size is MaxPayloadLen
                //need send a empty packet
                //https://dev.mysql.com/doc/internals/en/sending-more-than-16mbyte.html
                if event.DividedSeqNum == event.DividedCount-1 && len(event.Data) == MaxPayloadLen {err = c.WriteEvent(nil, false)
                    if err != nil {log.Log.Errorf("WriteEvent error,err:%s,event:%v", err, *event)
                        return err
                    }
                }
            }
            slaveEps.Mark(1)
            slaveThroughput.Mark(int64(len(event.Data)))
            //reset heartbeat period
            resetTime(timer, heartbeatPeriod)
        case err = <-errorC:
            log.Log.Errorf("binlog server DumpBinlogAt error,err:%s", err)
            return err
        case <-ctx.Done():
            log.Log.Errorf("handleBinlogDumpGtid:ctx done,quit")
            return ctx.Err()
        case <-timer.C:
            //kingbus send the heartbeat log event which received by syncer to slave
            log.Log.Debugf("send a heartbeat log event to slave")
            err = c.sendHeartbeatEvent(masterServerID)
            if err != nil {return err}
            //reset heartbeat period
            resetTime(timer, heartbeatPeriod)
        }
    }
    return nil
}

• handleBinlogDumpGtid 方法先执行 c.sendFakeRotateEvent，再执行 c.sendFormatDescriptionEvent，接着执行 c.binlogServer.DumpBinlogAt，然后通过 select 来响应相应事件

handleRegisterSlave

kingbus/mysql/command.go

func (c *Conn) handleRegisterSlave(data []byte) error {
    var s Slave
    pos := 0

    s.ServerID = int32(binary.LittleEndian.Uint32(data[pos:]))
    pos += 4

    hostNameLen := int(data[pos])
    pos++

    s.HostName = string(data[pos : pos+hostNameLen])
    pos += hostNameLen

    userLen := int(data[pos])
    pos++

    s.User = string(data[pos : pos+userLen])
    pos += userLen

    passwordLen := int(data[pos])
    pos++

    s.Password = string(data[pos : pos+passwordLen])
    pos += passwordLen

    s.Port = int16(binary.LittleEndian.Uint16(data[pos:]))
    pos += 2

    s.Rank = binary.LittleEndian.Uint32(data[pos:])
    pos += 4

    s.MasterID = binary.LittleEndian.Uint32(data[pos:])
    s.State = REGISTERED

    //kill the zombie dump thread with same uuid
    c.killZombieDumpThreads()

    if uuid, ok := c.userVariables[SlaveUUID]; ok {s.UUID = uuid.(string)
    } else {s.UUID = ""}
    s.ConnectTime = time.Now()
    s.Conn = c
    err := c.binlogServer.RegisterSlave(&s)
    if err != nil {return err}
    log.Log.Infof("handleRegisterSlave:slave info:%v", s)
    return c.writeOK(nil)
}

• handleRegisterSlave 方法用于处理 COM_REGISTER_SLAVE 命令，这里先执行 c.killZombieDumpThreads()，然后执行 c.binlogServer.RegisterSlave(&s)

小结

kingbus 的 command.go 提供了 Close、handleQuery、writeOK、handleBinlogDumpGtid、handleRegisterSlave 等方法

doc

• command