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Yu is a highly customizable blockchain framework.
Overall Structure
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 Execution
and Query
on chain.
Second level is define blockchain lifecycle
. ( including customizable Consensus Algorithm )
Third level is define basic components
, such as block data structures
, blockchain
, yudb
, txpool
.
- Define your
Execution
andQuery
on chain.
Execution
is likeTransaction
in Ethereum but not only for transfer of Token, it changes the state on the chain and must be consensus on all nodes.
Query
is likequery
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 (
Execution func(ctx *context.Context, currentBlock *types.Block) error
Query func(ctx *context.Context, blockHash Hash) (respObj interface{}, err error)
P2pHandler func([]byte) ([]byte, error)
)
- Define Your
blockchain lifecycle
, this function is inTripod
interface.
CheckTxn
defines the rules for checking transactions(Executions) before inserting txpool.
VerifyBlock
defines the rules for verifying blocks.
InitChain
defines business when the blockchain starts up. You should use it to defineGenesis 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, then you should tell the framework whether broadcast the block to other nodes or not.
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)
VerifyBlock(block *types.Block) bool
InitChain()
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 Query
.
func (a *Asset) QueryBalance(ctx *context.Context, _ Hash) (interface{}, error) {
account := ctx.GetAddress("account")
if !a.existAccount(account) {
return nil, AccountNotFound(account)
}
amount := a.getBalance(account)
return amount, nil
}
CreateAccount
creates an account. It implements type func Execution
.
EmitEvent
will emit an event out of the chain.
The error returned will emit out of the chain.
func (a *Asset) CreateAccount(ctx *context.Context, _ *Block) error {
addr := ctx.Caller
amount := big.NewInt(int64(ctx.GetUint64("amount")))
if a.existAccount(addr) {
_ = ctx.EmitEvent("Account Exists!")
return nil
}
a.setBalance(addr, amount)
_ = ctx.EmitEvent("Account Created Success!")
return nil
}
We need use SetExec
and SetQueries
to set Execution
and Query
into Asset Tripod
.
When we set a Execution
, 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.SetExec(a.Transfer, 100).SetExec(a.CreateAccount, 10)
a.SetQueries(a.QueryBalance)
return a
}
Finally set Asset Tripod
into land
in main func
.
func main() {
startup.StartUp(pow.NewPow(1024), asset.NewAsset("YuCoin"))
}
Poa Tripod
Pow 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) error {
......
// 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 nil
}
}
// Pack transactions(Executions) from Txpool.
txns, err := h.env.Pool.Pack(3000)
if err != nil {
return err
}
// Make blockHash from trasactions.
hashes := FromArray(txns...).Hashes()
block.TxnsHashes = hashes
txnRoot, err := MakeTxnRoot(txns)
if err != nil {
return err
}
block.TxnRoot = txnRoot
......
// signs block
block.MinerSignature, err = h.myPrivKey.SignData(block.Hash.Bytes())
if err != nil {
return err
}
block.MinerPubkey = h.myPubkey.BytesWithType()
// Reset Txpool for the next block.
err = h.env.Pool.Reset(block)
if err != nil {
return err
}
......
// 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 *Pow) EndBlock(block *Block) error {
......
// Execute all transactions(executions) of this block.
err := h.env.Execute(block)
if err != nil {
return err
}
// Append the block into the chain.
err = chain.AppendBlock(block)
if err != nil {
return err
}
......
}
- Finalize the block
func (h *Poa) FinalizeBlock(block *Block) error {
return h.env.Chain.Finalize(block.Hash)
}
Same as Asset Tripod
, finally set Pow Tripod
into land
in main function
.
func main() {
startup.StartUp(poa.NewPoa(myPubkey, myPrivkey, validatorsAddrs), asset.NewAsset("YuCoin"))
}