HyperLeger Fabric SDK開發（七）——ledger
HyperLeger Fabric SDK開發（七）——ledger
一、ledger簡介
1、ledger簡介
ledger包支援在Fabric網路上的指定通道上啟用賬本查詢。如果應用程式需要對多個通道進行賬本查詢，需要為每個通道的賬本客戶端建立一個單獨例項。賬本客戶端支援以下查詢：QueryInfo，QueryBlock，QueryBlockByHash，QueryBlockByTxID，QueryTransaction和QueryConfig。
官方文件:
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、準備通道上下文
B、建立分類帳客戶端
C、查詢分類帳
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常用介面
1、獲取賬本客戶端例項
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返回賬本客戶端例項。賬本客戶端例項提供處理程式以查詢指定通道上的各種資訊。如果應用程式需要對多個通道進行賬本查詢，需要為每個通道的賬本客戶端建立一個單獨例項。賬本客戶端僅支援指定查詢。
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、查詢賬本
func (c *Client) QueryBlock(blockNumber uint64, options ...RequestOption) (*common.Block, error)
QueryBlock根據區塊編號查詢區塊的賬本。
引數:
blockNumber是必需的區塊號
options包含可選的請求選項
返回區塊資訊
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根據區塊hash查詢區塊賬本。
引數:
blockHash是區塊雜湊
options包含可選的請求選項
返回區塊資訊
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查詢包含交易的區塊
引數:
txID是交易ID
options包含可選的請求選項
返回區塊資訊
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、查詢通道配置
func (c *Client) QueryConfig(options ...RequestOption) (fab.ChannelCfg, error)
QueryConfig查詢通道配置。
引數:
options包含可選的請求選項
返回通道配置資訊
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、查詢通道資訊
func (c *Client) QueryInfo(options ...RequestOption) (*fab.BlockchainInfoResponse, error)
QueryInfo查詢此通道上的各種區塊鏈資訊，例如區塊高度和當前區塊雜湊。
引數:
options是可選的請求選項
返回區塊鏈資訊
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、查詢交易資訊
func (c *Client) QueryTransaction(transactionID fab.TransactionID, options ...RequestOption) (*pb.ProcessedTransaction, error)
QueryTransaction通過交易ID查詢賬本上的已處理交易。
引數:
txID是必需的交易ID
options包含可選的請求選項
返回已經處理交易的資訊
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、為客戶端設定過濾器
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引數構建
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指定每個請求選擇的最大目標數。最大目標數的預設值為1.func WithMinTargets(minTargets int) RequestOption
WithMinTargets指定必須響應且沒有錯誤（或同意結果）的最小目標數。 最小目標數的預設值為1。func WithParentContext(parentContext reqContext.Context) RequestOption
WithParentContext封裝了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允許每個請求覆蓋目標Peer節點。目標由名稱或URL指定，SDK將建立底層Peer節點物件。func WithTargetFilter(targetFilter fab.TargetFilter) RequestOption
WithTargetFilter指定每個請求的目標Peer節點過濾器。
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允許每個請求覆蓋目標Peer節點。
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封裝了超時型別、超時時間的鍵值對到Options選項，次選項用於QueryInfo，QueryBlock，QueryBlockByHash，QueryBlockByTxID，QueryTransaction，QueryConfig等函式。
三、ledger示例
var (
sdk *fabsdk.FabricSDK
channelName = "assetchannel"
org = "org1"
user = "Admin"
)
// 賬本查詢
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)
}
}