HyperLeger Fabric SDK开发（七）——ledger

HyperLeger Fabric SDK开发（七）--ledger

一、ledger简介

1、ledger简介

ledger包支持在Fabric网络上的指定通道上启用账本查询。如果应用程序需要对多个通道进行账本查询，需要为每个通道的账本客户端创建一个单独实例。账本客户端支持以下查询：QueryInfo，QueryBlock，QueryBlockByHash，QueryBlockByTxID，QueryTransaction和QueryConfig。
官方文档:
https://godoc.org/github.com/hyperledger/fabric-sdk-go/pkg/client/ledger

2、ledger使用流程

ledger使用的基本流程如下：
A、准备通道上下文
B、创建分类帐客户端
C、查询分类帐
使用示例：

ctx := mockChannelProvider("mychannel")c, err := New(ctx)if err != nil {    fmt.Println("failed to create client")}block, err := c.QueryBlock(1)if err != nil {    fmt.Printf("failed to query block: %s\n", err)}if block != nil {    fmt.Println("Retrieved block #1")}// output:// Retrieved block #1      

二、ledger常用接口

1、获取账本客户端实例

type Client struct {   ctx       context.Channel   filter    fab.TargetFilter   ledger    *channel.Ledger   verifier  channel.ResponseVerifier   discovery fab.DiscoveryService}func New(channelProvider context.ChannelProvider, opts ...ClientOption) (*Client, error) 

New返回账本客户端实例。账本客户端实例提供处理程序以查询指定通道上的各种信息。如果应用程序需要对多个通道进行账本查询，需要为每个通道的账本客户端创建一个单独实例。账本客户端仅支持指定查询。
使用示例：

ctx := mockChannelProvider("mychannel")c, err := New(ctx)if err != nil {    fmt.Println(err)}if c != nil {    fmt.Println("ledger client created")}// output:// ledger client created        

2、查询账本

func (c *Client) QueryBlock(blockNumber uint64, options ...RequestOption) (*common.Block, error)
QueryBlock根据区块编号查询区块的账本。
参数:
blockNumber是必需的区块号
options包含可选的请求选项
返回区块信息
使用示例：

c, err := New(mockChannelProvider("mychannel"))if err != nil {    fmt.Println("failed to create client")}block, err := c.QueryBlock(1)if err != nil {    fmt.Printf("failed to query block: %s\n", err)}if block != nil {    fmt.Println("Retrieved block #1")}// output:// Retrieved block #1  

func (c *Client) QueryBlockByHash(blockHash []byte, options ...RequestOption) (*common.Block, error)
QueryBlockByHash根据区块hash查询区块账本。
参数:
blockHash是区块哈希
options包含可选的请求选项
返回区块信息
使用示例：

c, err := New(mockChannelProvider("mychannel"))if err != nil {    fmt.Println("failed to create client")}block, err := c.QueryBlockByHash([]byte("hash"))if err != nil {    fmt.Printf("failed to query block by hash: %s\n", err)}if block != nil {    fmt.Println("Retrieved block by hash")}// output:// Retrieved block by hash   

func (c *Client) QueryBlockByTxID(txID fab.TransactionID, options ...RequestOption) (*common.Block, error)
QueryBlockByTxID查询包含交易的区块
参数:
txID是交易ID
options包含可选的请求选项
返回区块信息
使用示例：

c, err := New(mockChannelProvider("mychannel"))if err != nil {    fmt.Println("failed to create client")}block, err := c.QueryBlockByTxID("123")if err != nil {    fmt.Printf("failed to query block by transaction ID: %s\n", err)}if block != nil {    fmt.Println("Retrieved block by transaction ID")}// output:// Retrieved block by transaction ID   

3、查询通道配置

func (c *Client) QueryConfig(options ...RequestOption) (fab.ChannelCfg, error)
QueryConfig查询通道配置。
参数:
options包含可选的请求选项
返回通道配置信息
使用示例：

c, err := New(mockChannelProvider("mychannel"))if err != nil {    fmt.Println("failed to create client")}cfg, err := c.QueryConfig(WithTargets(mockPeerWithConfigBlock()))if err != nil {    fmt.Printf("failed to query config: %s\n", err)}if cfg != nil {    fmt.Println("Retrieved channel configuration")}// output:// Retrieved channel configuration   

4、查询通道信息

func (c *Client) QueryInfo(options ...RequestOption) (*fab.BlockchainInfoResponse, error)
QueryInfo查询此通道上的各种区块链信息，例如区块高度和当前区块哈希。
参数:
options是可选的请求选项
返回区块链信息
使用示例：

c, err := New(mockChannelProvider("mychannel"))if err != nil {    fmt.Println("failed to create client")}bci, err := c.QueryInfo()if err != nil {    fmt.Printf("failed to query for blockchain info: %s\n", err)}if bci != nil {    fmt.Println("Retrieved ledger info")}// output:// Retrieved ledger info  

5、查询交易信息

func (c *Client) QueryTransaction(transactionID fab.TransactionID, options ...RequestOption) (*pb.ProcessedTransaction, error)
QueryTransaction通过交易ID查询账本上的已处理交易。
参数:
txID是必需的交易ID
options包含可选的请求选项
返回已经处理交易的信息
使用示例：

c, err := New(mockChannelProvider("mychannel"))if err != nil {    fmt.Println("failed to create client")}t, err := c.QueryTransaction("123")if err != nil {    fmt.Printf("failed to query transaction: %s\n", err)}if t != nil {    fmt.Println("Retrieved transaction")}// output:// Retrieved transaction  

6、为客户端设置过滤器

type ClientOption func(*Client) error// WithDefaultTargetFilter option to configure newfunc WithDefaultTargetFilter(filter fab.TargetFilter) ClientOption 使用示例:ctx := mockChannelProvider("mychannel")c, err := New(ctx, WithDefaultTargetFilter(&urlTargetFilter{url: "example.com"}))if err != nil {    fmt.Println(err)}if c != nil {    fmt.Println("ledger client created with url target filter")}// output:// ledger client created with url target filter   

7、RequestOption参数构建

type RequestOption func(ctx context.Client, opts *requestOptions) error//requestOptions contains options for operations performed by LedgerClienttype requestOptions struct {   Targets       []fab.Peer                        // target peers   TargetFilter  fab.TargetFilter                  // target filter   MaxTargets    int                               // maximum number of targets to select   MinTargets    int                               // min number of targets that have to respond with no error (or agree on result)   Timeouts      map[fab.TimeoutType]time.Duration //timeout options for ledger query operations   ParentContext reqContext.Context                //parent grpc context for ledger operations}func WithMaxTargets(maxTargets int) RequestOption

WithMaxTargets指定每个请求选择的最大目标数。最大目标数的默认值为1.
func WithMinTargets(minTargets int) RequestOption
WithMinTargets指定必须响应且没有错误（或同意结果）的最小目标数。 最小目标数的默认值为1。
func WithParentContext(parentContext reqContext.Context) RequestOption
WithParentContext封装了grpc父上下文
使用示例：

c, err := New(mockChannelProvider("mychannel"))if err != nil {    fmt.Println(err)}channelContext, err := mockChannelProvider("mychannel")()if err != nil {    fmt.Println("failed to return channel context")    return}// get parent context and cancelparentContext, cancel := sdkCtx.NewRequest(channelContext, sdkCtx.WithTimeout(20*time.Second))defer cancel()bci, err := c.QueryInfo(WithParentContext(parentContext))if err != nil {    fmt.Printf("failed to query for blockchain info: %s\n", err)}if bci != nil {    fmt.Println("Retrieved blockchain info")}// output:// Retrieved blockchain info      

func WithTargetEndpoints(keys ...string) RequestOption
withTargetEndpoints允许每个请求覆盖目标Peer节点。目标由名称或URL指定，SDK将创建底层Peer节点对象。
func WithTargetFilter(targetFilter fab.TargetFilter) RequestOption
WithTargetFilter指定每个请求的目标Peer节点过滤器。
使用示例：

c, err := New(mockChannelProvider("mychannel"))if err != nil {    fmt.Println(err)}block, err := c.QueryBlock(1, WithTargetFilter(&urlTargetFilter{url: "example.com"}))if err != nil {    fmt.Printf("failed to query block: %s\n", err)}if block != nil {    fmt.Println("Retrieved block #1 from example.com")}// output:// Retrieved block #1 from example.com

func WithTargets(targets ...fab.Peer) RequestOption
WithTargets允许每个请求覆盖目标Peer节点。
使用示例：

c, err := New(mockChannelProvider("mychannel"))if err != nil {    fmt.Println("failed to create client")}cfg, err := c.QueryConfig(WithTargets(mockPeerWithConfigBlock()))if err != nil {    fmt.Printf("failed to query config with target peer: %s\n", err)}if cfg != nil {    fmt.Println("Retrieved config from target peer")}// output:// Retrieved config from target peer 

func WithTimeout(timeoutType fab.TimeoutType, timeout time.Duration) RequestOption
WithTimeout封装了超时类型、超时时间的键值对到Options选项，次选项用于QueryInfo，QueryBlock，QueryBlockByHash，QueryBlockByTxID，QueryTransaction，QueryConfig等函数。

三、ledger示例

var (   sdk           *fabsdk.FabricSDK   channelName   = "assetchannel"   org           = "org1"   user          = "Admin")// 账本查询func queryBlockchain() {   ctx := sdk.ChannelContext(channelName, fabsdk.WithOrg(org), fabsdk.WithUser(user))   cli, err := ledger.New(ctx)   if err != nil {      panic(err)   }   resp, err := cli.QueryInfo(ledger.WithTargetEndpoints("peer0.org1.example.com"))   if err != nil {      panic(err)   }   fmt.Println(resp)   // 1   cli.QueryBlockByHash(resp.BCI.CurrentBlockHash)   // 2   for i := uint64(0); i <= resp.BCI.Height; i++ {      cli.QueryBlock(i)   }}