fabric gossip 源碼解析 DeliverService

接口描述

fabric/core/deliverservice/deliveryclient.go
        

// DeliverService used to communicate with orderers to obtain
// new block and send the to the committer service
type DeliverService interface {
    // StartDeliverForChannel dynamically starts delivery of new blocks from ordering service
    // to channel peers.
    StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo) error

    // StopDeliverForChannel dynamically stops delivery of new blocks from ordering service
    // to channel peers.
    StopDeliverForChannel(chainID string) error
    // Stop terminates delivery service and closes the connection
    Stop()
}

根據(jù)描述可以很明顯的看出來是與order服務(wù)進行收發(fā)block的接口，接下來閱讀以下主要代碼，三個函數(shù)只有 StartDeliverForChannel是重點，其余兩個都不是重點，所以我們主要就搞懂這個就可以了，既然是收發(fā)代碼，就是找到收發(fā)邏輯就可以了。

接口實現(xiàn)

// StartDeliverForChannel starts blocks delivery for channel
// initializes the grpc stream for given chainID, creates blocks provider instance
// that spawns in go routine to read new blocks starting from the position provided by ledger
// info instance.
func (d *deliverServiceImpl) StartDeliverForChannel(chainID string, ledgerInfo blocksprovider.LedgerInfo) error {
    d.lock.Lock()
    defer d.lock.Unlock()
    if d.stopping {
        errMsg := fmt.Sprintf("Delivery service is stopping cannot join a new channel %s", chainID)
        logger.Errorf(errMsg)
        return errors.New(errMsg)
    }
    if _, exist := d.clients[chainID]; exist {
        errMsg := fmt.Sprintf("Delivery service - block provider already exists for %s found, can't start delivery", chainID)
        logger.Errorf(errMsg)
        return errors.New(errMsg)
    } else {
        abc, err := d.clientsFactory.Create()
        if err != nil {
            logger.Errorf("Unable to initialize atomic broadcast, due to %s", err)
            return err
        }
        logger.Debug("This peer will pass blocks from orderer service to other peers")
        d.clients[chainID] = blocksprovider.NewBlocksProvider(chainID, abc, d.gossip)

        if err := d.clients[chainID].RequestBlocks(ledgerInfo); err == nil {
            // Start reading blocks from ordering service in case this peer is a leader for specified chain
            go d.clients[chainID].DeliverBlocks()
        }
    }
    return nil
}

通過代碼可以看出來 blocksprovider.NewBlocksProvider 產(chǎn)生了真正的連接，在這個連接上會先 RequestBlocks，然后 DeliverBlocks ，我們只要搞清楚 與 誰建立的連接，RequestBlocks，DeliverBlocks 的邏輯后就弄清楚了 這個service的主要功能了

  • 連接的建立
func NewDeliverService(gossip blocksprovider.GossipServiceAdapter, endpoints []string) (DeliverService, error) {
    indices := rand.Perm(len(endpoints))
    for _, idx := range indices {
        logger.Infof("Creating delivery service to get blocks from the ordering service, %s", endpoints[idx])

        dialOpts := []grpc.DialOption{grpc.WithInsecure(), grpc.WithTimeout(3 * time.Second), grpc.WithBlock()}

        if comm.TLSEnabled() {
            dialOpts = append(dialOpts, grpc.WithTransportCredentials(comm.InitTLSForPeer()))
        } else {
            dialOpts = append(dialOpts, grpc.WithInsecure())
        }

        conn, err := grpc.Dial(endpoints[idx], dialOpts...)
        if err != nil {
            logger.Errorf("Cannot dial to %s, because of %s", endpoints[idx], err)
            continue
        }
        return NewFactoryDeliverService(gossip, &blocksDelivererFactoryImpl{conn}, conn), nil
    }
    return nil, fmt.Errorf("Wasn't able to connect to any of ordering service endpoints %s", endpoints)
}

可以看到連接是建立到了，endpoints，通過追蹤代碼可以發(fā)現(xiàn)就是 order 節(jié)點的地址，這里需要注意一點， 傳過來的 endpoints 是一個數(shù)組，但是只隨機的與某一個節(jié)點建立連接。
現(xiàn)在我們知道了是與order通信，由于fabric是基于grpc的，所以我們還要找出來與order的哪個服務(wù)進行通信，blocksDelivererFactoryImpl 這個struct定義了與哪個服務(wù)通信，我們一起看下

fabric/core/deliverservice/deliveryclient.go

type blocksDelivererFactoryImpl struct {
    conn *grpc.ClientConn
}

// Create a factory method which is capable to instantiate new BlocksDeliverer
func (factory *blocksDelivererFactoryImpl) Create() (blocksprovider.BlocksDeliverer, error) {
    var abc orderer.AtomicBroadcast_DeliverClient
    var err error
    abc, err = orderer.NewAtomicBroadcastClient(factory.conn).Deliver(context.TODO())
    if err != nil {
        return nil, err
    }

    return abc, nil
}

明顯是AtomicBroadcast 服務(wù)的 Deliver 接口通信

  • RequestBlocks
fabric/core/deliverservice/blocksprovider/blocksprovider.go

func (b *blocksProviderImpl) RequestBlocks(ledgerInfoProvider LedgerInfo) error {
    height, err := ledgerInfoProvider.LedgerHeight()
    if err != nil {
        logger.Errorf("Can't get legder height from committer [%s]", err)
        return err
    }

    if height > 0 {
        logger.Debugf("Starting deliver with block [%d]", height)
        if err := b.seekLatestFromCommitter(height); err != nil {
            return err
        }
    } else {
        logger.Debug("Starting deliver with olders block")
        if err := b.seekOldest(); err != nil {
            return err
        }
    }

    return nil
}

func (b *blocksProviderImpl) seekLatestFromCommitter(height uint64) error {
    seekInfo := &orderer.SeekInfo{
        Start:    &orderer.SeekPosition{Type: &orderer.SeekPosition_Specified{Specified: &orderer.SeekSpecified{Number: height}}},
        Stop:     &orderer.SeekPosition{Type: &orderer.SeekPosition_Specified{Specified: &orderer.SeekSpecified{Number: math.MaxUint64}}},
        Behavior: orderer.SeekInfo_BLOCK_UNTIL_READY,
    }

    //TODO- epoch and msgVersion may need to be obtained for nowfollowing usage in orderer/configupdate/configupdate.go
    msgVersion := int32(0)
    epoch := uint64(0)
    env, err := utils.CreateSignedEnvelope(common.HeaderType_CONFIG_UPDATE, b.chainID, localmsp.NewSigner(), seekInfo, msgVersion, epoch)
    if err != nil {
        return err
    }
    return b.client.Send(env)
}

明顯 可以看出來只是在請求 start - stop 之間的block

  • DeliverBlocks
func (b *blocksProviderImpl) DeliverBlocks() {
    for !b.isDone() {
        msg, err := b.client.Recv()   // 接收Request請求的代碼
        if err != nil {
            logger.Warningf("Receive error: %s", err.Error())
            return
        }
        switch t := msg.Type.(type) {
        case *orderer.DeliverResponse_Status:
            if t.Status == common.Status_SUCCESS {
                logger.Warning("ERROR! Received success for a seek that should never complete")
                return
            }
            logger.Warning("Got error ", t)
        case *orderer.DeliverResponse_Block:
            seqNum := t.Block.Header.Number

            numberOfPeers := len(b.gossip.PeersOfChannel(gossipcommon.ChainID(b.chainID)))
            // Create payload with a block received
            payload := createPayload(seqNum, t.Block)
            // Use payload to create gossip message
            gossipMsg := createGossipMsg(b.chainID, payload)

            logger.Debugf("Adding payload locally, buffer seqNum = [%d], peers number [%d]", seqNum, numberOfPeers)
            // Add payload to local state payloads buffer
            b.gossip.AddPayload(b.chainID, payload)

            // Gossip messages with other nodes
            logger.Debugf("Gossiping block [%d], peers number [%d]", seqNum, numberOfPeers)
            b.gossip.Gossip(gossipMsg)  // gossip 發(fā)送
        default:
            logger.Warning("Received unknown: ", t)
            return
        }
    }
}

可以看出來，request 來的 block，在這邊都通過 gossip 廣播出去了

總結(jié)

這個這個代碼很清晰了，DeliverService 就是從 order 請求 block，然后廣播出去。 當(dāng)然在整個fabric中的業(yè)務(wù)作用目前看不出來，還需要深入分析

最后編輯于 ：
?著作權(quán)歸作者所有,轉(zhuǎn)載或內(nèi)容合作請聯(lián)系作者
平臺聲明：文章內(nèi)容（如有圖片或視頻亦包括在內(nèi)）由作者上傳并發(fā)布，文章內(nèi)容僅代表作者本人觀點，簡書系信息發(fā)布平臺，僅提供信息存儲服務(wù)。

推薦閱讀更多精彩內(nèi)容

  • Spring Cloud為開發(fā)人員提供了快速構(gòu)建分布式系統(tǒng)中一些常見模式的工具（例如配置管理，服務(wù)發(fā)現(xiàn)，斷路器，智...
    卡卡羅2017閱讀 134,923評論 18贊 139
  • 國家電網(wǎng)公司企業(yè)標(biāo)準(zhǔn)（Q/GDW）- 面向?qū)ο蟮挠秒娦畔?shù)據(jù)交換協(xié)議 - 報批稿：20170802 前言： 排版 ...
    庭說閱讀 11,145評論 6贊 13
  • Android 自定義View的各種姿勢1 Activity的顯示之ViewRootImpl詳解 Activity...
    passiontim閱讀 173,269評論 25贊 708
  • 發(fā)現(xiàn) 關(guān)注 消息 iOS 第三方庫、插件、知名博客總結(jié) 作者大灰狼的小綿羊哥哥關(guān)注 2017.06.26 09:4...
    肇東周閱讀 12,229評論 4贊 61
  • 【第278期】世界第一的企業(yè)是怎樣煉成的？車間堪比實驗室 2016-01-07 對于企業(yè)來說，創(chuàng)新是生存與發(fā)展的根...
    大富大貴閱讀 364評論 0贊 0