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 new
func 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 LedgerClient
type 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) RequestOptionWithMaxTargets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 cancel
parentContext, 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.comfunc 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)
}
}