Question

在Corda中的哪里设置共识算法？答案期待技术角度来看，如果我们正在使用多重共识算法，那么我们在哪里切换这些算法？

Answer 1

从Corda 3开始，实现自定义公证服务仍是一项实验功能。用于实现自定义公证服务的API将来可能会更改。此外，尚不完全支持自定义Raft或BFT公证人。如果要编写自己的Raft公证人，则必须实现自定义数据库连接器（或为公证人使用单独的数据库），并使用自定义配置文件。

实现自定义公证人的第一步是在CorDapp中创建一个公证人服务类（即一个用@CordaService注释的公证服务类）。 Corda节点扫描这些服务类，并在启动时将其初始化。定制公证服务类应提供采用AppServiceHub和PublicKey的构造函数：

@CordaService
class MyCustomValidatingNotaryService(override val services: AppServiceHub, override val notaryIdentityKey: PublicKey) : TrustedAuthorityNotaryService() {
    override val uniquenessProvider = PersistentUniquenessProvider()

    override fun createServiceFlow(otherPartySession: FlowSession): FlowLogic<Void?> = MyValidatingNotaryFlow(otherPartySession, this)

    override fun start() {}
    override fun stop() {}
}

下一步是编写公证服务流程。您可以自由地复制和修改现有的内置流程，例如ValidatingNotaryFlow，NonValidatingNotaryFlow，也可以从头开始实现自己的流程（遵循NotaryFlow.Service模板）。以下是验证公证服务的自定义流程示例：

class MyValidatingNotaryFlow(otherSide: FlowSession, service: MyCustomValidatingNotaryService) : NotaryFlow.Service(otherSide, service) {
    /**
     * The received transaction is checked for contract-validity, for which the caller also has to to reveal the whole
     * transaction dependency chain.
     */
    @Suspendable
    override fun receiveAndVerifyTx(): TransactionParts {
        try {
            val stx = receiveTransaction()
            val notary = stx.notary
            checkNotary(notary)
            verifySignatures(stx)
            resolveAndContractVerify(stx)
            val timeWindow: TimeWindow? = if (stx.coreTransaction is WireTransaction) stx.tx.timeWindow else null
            return TransactionParts(stx.id, stx.inputs, timeWindow, notary!!)
        } catch (e: Exception) {
            throw when (e) {
                is TransactionVerificationException,
                is SignatureException -> NotaryInternalException(NotaryError.TransactionInvalid(e))
                else -> e
            }
        }
    }

    @Suspendable
    private fun receiveTransaction(): SignedTransaction {
        return otherSideSession.receive<NotarisationPayload>().unwrap {
            val stx = it.signedTransaction
            validateRequest(NotarisationRequest(stx.inputs, stx.id), it.requestSignature)
            stx
        }
    }

    @Suspendable
    private fun resolveAndContractVerify(stx: SignedTransaction) {
        subFlow(ResolveTransactionsFlow(stx, otherSideSession))
        stx.verify(serviceHub, false)
        customVerify(stx)
    }

    private fun verifySignatures(stx: SignedTransaction) {
        val transactionWithSignatures = stx.resolveTransactionWithSignatures(serviceHub)
        checkSignatures(transactionWithSignatures)
    }

    private fun checkSignatures(tx: TransactionWithSignatures) {
        try {
            tx.verifySignaturesExcept(service.notaryIdentityKey)
        } catch (e: SignatureException) {
            throw NotaryInternalException(NotaryError.TransactionInvalid(e))
        }
    }

    private fun customVerify(stx: SignedTransaction) {
        // Add custom verification logic
    }
}

要启用该服务，请将以下内容添加到节点的配置中：

notary : {
    validating : true # Set to false if your service is non-validating
    custom : true
}

在Corda中的哪里设置共识算法？

1 个答案: