Hyperledger Fabric 2.0 gRPC接口

本文基於 Fabric v2.0.1 ，與 v1.x 版不同，v2 版將 protos 定義放到一個獨立倉庫 fabric-protos 進行管理，並且使用 protoc 工具生成的具體語言代碼也使用獨立的倉庫存放，如 golang 版 fabric-protos-go。

一、 Orderer

1. AtomicBroadcast

服務定義於 orderer/ab.proto

service AtomicBroadcast {
    // broadcast receives a reply of Acknowledgement for each common.Envelope in order, indicating success or type of failure
    rpc Broadcast(stream common.Envelope) returns (stream BroadcastResponse);

    // deliver first requires an Envelope of type DELIVER_SEEK_INFO with Payload data as a mashaled SeekInfo message, then a stream of block replies is received.
    rpc Deliver(stream common.Envelope) returns (stream DeliverResponse);
}

1.1 Broadcast

Broadcast 接口用於接收待排序的消息，包括普通事務 tx 消息和 channel 配置消息。
客戶端將事務消息提交到 endorsing peers 預執行 chaincode 並背書讀寫集結果，由客戶端將返回結果提交到 Orderer 進行排序。

1.2 Deliver

Deliver 接口用於向 peers 分發已經過排序 block 數據，peer 節點通過 join channel 從 Orderer 獲取已排序的 block 。

2. Cluster

服務定義於 orderer/cluster.proto

// Cluster defines communication between cluster members.
service Cluster {
    // Step passes an implementation-specific message to another cluster member.
    rpc Step(stream StepRequest) returns (stream StepResponse);
}

Fabric v1.1 之後支持 EtcdRaft 共識算法，與使用 Kafka 共識算法各orderer獨立連接中心化的 kafka 集羣不同，使用 EtcdRaft 共識算法各 orderer 組成一個集羣， Step 用於集羣節點間消息交換。

二、Peer

1. Endorser

服務定義於 peer/peer.proto

service Endorser {
    rpc ProcessProposal(SignedProposal) returns (ProposalResponse);
}

ProcessProposal 接口用於客戶端將已簽名的事務消息提交到 endorsing peers 進行預執行並背書讀寫集。所謂預執行是指使用當前本地賬本狀態執行 chaincode 生成讀寫集，但執行結果不寫入賬本。

2. Deliver

服務定義於 peer/events.proto

service Deliver {
    // Deliver first requires an Envelope of type ab.DELIVER_SEEK_INFO with
    // Payload data as a marshaled orderer.SeekInfo message,
    // then a stream of block replies is received
    rpc Deliver (stream common.Envelope) returns (stream DeliverResponse) {
    }
    // DeliverFiltered first requires an Envelope of type ab.DELIVER_SEEK_INFO with
    // Payload data as a marshaled orderer.SeekInfo message,
    // then a stream of **filtered** block replies is received
    rpc DeliverFiltered (stream common.Envelope) returns (stream DeliverResponse) {
    }
    // DeliverWithPrivateData first requires an Envelope of type ab.DELIVER_SEEK_INFO with
    // Payload data as a marshaled orderer.SeekInfo message,
    // then a stream of block and private data replies is received
    rpc DeliverWithPrivateData (stream common.Envelope) returns (stream DeliverResponse) {
    }
}

2.1 Deliver & DeliverFiltered

Deliver 接口用於向客戶端分發已寫入本地賬本的 block 數據。客戶端將 endorsing peers 返回的結果提交給 orderer 後，等待 peer 通知事務處理完畢。

2.2 DeliverWithPrivateData

DeliverWithPrivateData v2.0 版本新增，分發帶私密數據的 block 數據

三、Chaincode

1. ChaincodeSupport

服務定義於 peer/chaincode_shim.proto

// Interface that provides support to chaincode execution. ChaincodeContext
// provides the context necessary for the server to respond appropriately.
service ChaincodeSupport {
    rpc Register(stream ChaincodeMessage) returns (stream ChaincodeMessage);
}

Register 用於 Chaincode 啓動時向 peer 註冊當前 Chaincode

2. Chaincode

服務定義於 peer/chaincode_shim.proto

// Chaincode as a server - peer establishes a connection to the chaincode as a client
// Currently only supports a stream connection.
service Chaincode {
    rpc Connect(stream ChaincodeMessage) returns (stream ChaincodeMessage);
}

v2 新增服務，Chaincode 啓動並作爲服務端，由 peer 通過 Connect 接口連接 Chaincode

四、Gossip

服務定義於 gossip/message.proto

// Gossip
service Gossip {

    // GossipStream is the gRPC stream used for sending and receiving messages
    rpc GossipStream (stream Envelope) returns (stream Envelope);

    // Ping is used to probe a remote peer's aliveness
    rpc Ping (Empty) returns (Empty);
}

爲減輕 Orderer 壓力，組織內只有少量 peer 連接 orderer 獲取最新 block，組織內各 peer 通過 Gossip 互聯，通過 Gossip 交換 block 數據及私密數據。

五、Discovery

服務定義於 discovery/protocol.proto

// Discovery defines a service that serves information about the fabric network
// like which peers, orderers, chaincodes, etc.
service Discovery {
    // Discover receives a signed request, and returns a response.
    rpc Discover (SignedRequest) returns (Response);
}

Discovery 服務用於方便客戶端獲取整個 Fabric 網絡的情況，只需要知道一個初始節點便可查詢到 channel 內的 peers、config、membership、chaincode 等。

參考：

• fabric應用grpc解讀