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Yu is a highly customizable blockchain framework.

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Overall Structure

Usage

type Example struct {
    *tripod.Tripod
}

// Here is a custom development of an Writing
func (e *Example) Write(ctx *context.WriteContext) error {
    caller := ctx.GetCaller()
    // set this Writing lei cost
    ctx.SetLei(100)
    // Store data in on-chain state.
    e.Set([]byte("1"), []byte("yu"))
    // Emit an event.
    ctx.EmitStringEvent(fmt.Printf("execute success, caller: %s", caller.String()))
    return nil
}

// Here is a custom development of a Reading
func (e *Example) Read(ctx *context.ReadContext) {
    key := ctx.GetString("key")
    value, err := e.Get(key.Bytes())
    if err != nil {
        ctx.JsonOk(err)
        return
    }
    ctx.String(string(value))
    return nil
}

Then, register your Writing and Reading and start with main.

func NewExample() *Example {
    tri := tripod.NewTripod()
    e := &Example{tri}

    e.SetWritings(e.Write)
    e.SetReadings(e.Read)

    return e
}

func main() {
	poaConf := poa.DefaultCfg(0)
	startup.InitDefaultKernelConfig()
	startup.DefaultStartup(poa.NewPoa(poaConf), NewExample())
}

Build and Run

go build -o yu-example

./yu-example 
 

Introduction

By using Yu, you can customize three levels to develop your own blockchain. The Tripod is for developers to customize their own business.
First level is define Writing and Reading on chain.
Second level is define blockchain lifecycle. ( including customizable Consensus Algorithm )
Third level is define basic components, such as block data structures, blockchain, txdb, txpool.

• Define your Writing and Reading on chain.
  Writing is State-Transition, like Transaction in Ethereum but not only for transfer of Token, it changes the state on the chain and must be consensus on all nodes.
  Reading is like query in Ethereum, it doesn't change state, just query some data from the chain.
  P2pHandler is a p2p server handler. You can define the services in P2P server. Just like TCP handler.

type (
    Writing func(ctx *context.WriteContext) error
	
    Reading func(ctx *context.ReadContext)

    P2pHandler func([]byte) ([]byte, error)
)

• Define Your blockchain lifecycle, this function is in Tripod interface.
  CheckTxn defines the rules for checking transactions(Writings) before inserting txpool.
  VerifyBlock defines the rules for verifying blocks.
  InitChain defines business when the blockchain starts up. You should use it to define Genesis Block.
  StartBlock defines business when a new block starts. In this func, you can set some attributes (including pack txns from txpool, mining) in the block.
  EndBlock defines business when all nodes accept the new block, usually we execute the txns of new block and append block into the chain.
  FinalizeBlock defines business when the block is finalized in the chain by all nodes.

type Tripod interface {

    ......
    
    CheckTxn(*txn.SignedTxn) error   

    VerifyBlock(block *types.Block) bool

    InitChain(genesisBlock *types.Block) 

    StartBlock(block *types.Block) 

    EndBlock(block *types.Block) 

    FinalizeBlock(block *types.Block) 
}

Examples

Asset Tripod
Asset Tripod imitates an Asset function, it has transfer accounts, create accounts.
QueryBalance queries someone's account balance. It implements type func Reading.

func (a *Asset) QueryBalance(ctx *context.ReadContext) error {
    account := ctx.GetAddress("account")
    if !a.existAccount(account) {
        return nil, AccountNotFound(account)
    }
    amount := a.getBalance(account)
    return ctx.Json(context.H{"amount": amount})
}

CreateAccount creates an account. It implements type func Writing.
EmitStringEvent will emit a string event out of the chain.
The error returned will emit out of the chain.

func (a *Asset) CreateAccount(ctx *context.WriteContext) error {
    ctx.SetLei(100)
    addr := ctx.Caller
    amount := big.NewInt(int64(ctx.GetUint64("amount")))

    if a.existAccount(addr) {
        ctx.EmitStringEvent("Account Exists!")
        return nil
    }

    a.setBalance(addr, amount)
    ctx.EmitStringEvent("Account Created Success!")
    return nil
}

We need use SetExec and SetQueries to set Writing and Reading into Asset Tripod.
When we set a Writing, we need declare how much Lei(耜) it consumes. (Lei is the same as gas in ethereum )

func NewAsset(tokenName string) *Asset {
    df := NewDefaultTripod("asset")

    a := &Asset{df, tokenName}
    a.SetWritings(a.Transfer, a.CreateAccount)
    a.SetReadings(a.QueryBalance)

    return a
}

Finally set Asset Tripod into land in main func.

func main() {
    startup.DefaultStartup(asset.NewAsset("YuCoin"))
}

Poa Tripod
Poa Tripod imitates a Consensus algorithm for proof of authority. It customizes the lower-level code.

• Start a new block
  If there are no verified blocks from P2P network, we pack some txns, mine a new block and broadcast it to P2P network.

func (h *Poa) StartBlock(block *Block) {
    ......
	
    // Get a leader who produce the block of this round. 
    miner := h.CompeteLeader(block.Height)
    logrus.Debugf("compete a leader(%s) in round(%d)", miner.String(), block.Height)
	
    // If it is not local node for this round, use other node's block and skip follows.
    if miner != h.LocalAddress() {
        if h.useP2pOrSkip(block) {
            logrus.Infof("--------USE P2P Height(%d) block(%s) miner(%s)",
            block.Height, block.Hash.String(), ToHex(block.MinerPubkey))
            return
        }
    }
	
    // Pack transactions(Writings) from Txpool. 
    txns, err := h.env.Pool.Pack(3000)
    if err != nil {
		logrus.Error(err)
        return 
    }
    // Make blockHash from trasactions. 
    hashes := FromArray(txns...).Hashes()
    block.TxnsHashes = hashes
    txnRoot, err := MakeTxnRoot(txns)
    if err != nil {
        logrus.Error(err)
        return 
    }
    block.TxnRoot = txnRoot
	
    ......

    // signs block
    block.MinerSignature, err = h.myPrivKey.SignData(block.Hash.Bytes())
    if err != nil {
        logrus.Error(err)
        return 
    }
    block.MinerPubkey = h.myPubkey.BytesWithType()
	
    // Reset Txpool for the next block.
    err = h.env.Pool.Reset(block)
    if err != nil {
        logrus.Error(err)
        return
    }
    
    ......
	
    // Publish the block to P2P so that other nodes get it.
    return h.env.P2pNetwork.PubP2P(StartBlockTopic, rawBlockByt)
}

• End the block
  We execute the txns of the block and append the block into the chain.

func (h *Poa) EndBlock(block *Block) {
    ......
    // Execute all transactions(Writings) of this block.
    err := h.env.Execute(block)
    if err != nil {
        logrus.Error(err)
        return 
    }

    // Append the block into the chain.
    err = chain.AppendBlock(block)
    if err != nil {
        logrus.Error(err)
        return 
    }  
    ......
}

• Finalize the block

func (h *Poa) FinalizeBlock(block *Block) {
    h.env.Chain.Finalize(block.Hash)
}

Same as Asset Tripod , finally set Poa Tripod into land in main function.

func main() {
    startup.InitConfigFromPath("yu_conf/kernel.toml")
    startup.DefaultStartup(
        poa.NewPoa(poaConf),
        asset.NewAsset("YuCoin"),
    )
}