基于Vue、web3的以太坊项目开发及交易内幕初探

本文通过宏观和微观两个层面窥探以太坊底层执行逻辑。
宏观层面描述创建并运行一个小型带钱包的发币APP的过程,微观层面是顺藤摸瓜从http api深入go-ethereum源码执行过程。

分析思路:自上而下,从APP深入EVM。

从应用入手,如果一头扎进ethereum,收获的可能是纯理论的东西,要想有所理解还得结合以后的实践才能恍然大悟。所以我始终坚持从应用入手、自上而下是一种正确、事半功倍的方法论。

我在讲解以太坊基础概念的那篇专题文章里,用的是从整体到局部的方法论,因为研究目标就是一个抽象的理论的东西,我对一个全然未知的东西的了解总是坚持从整体到局部的思路。

项目创建、部署合约到私链
之前用truffle框架做项目开发,这个框架封装了合约的创建、编译、部署过程,为了研究清楚自上至下的架构,这里就不用truffle构建项目了。

项目前端基于vue,后端是geth节点,通过web3 http api通信。

开发vue、solidity等前端IDE还是webstorm好,Atom和goland就免了不太好用!
1、全局安装vue-cli

npm i -g vue-cli
2、初始化一个基于webpack的vue项目

vue init webpack XXXProject
3、项目里安装web3依赖

web3.js是ethereum的javascript api库,通过rpc方式与以太坊节点交互。

npm install --save web3@1.0.0-beta.34
尽量用npm安装,不要用cnpm,有时候是个坑玩意,会生成“_”开头的很多垃圾还要求各种install。也可以写好了package.json,删除node_modules文件夹,再执行npm i。
web3版本用1.0以上,和1.0以下语法有很大不同。

4、项目里创建全局web3对象

用vuex有点啰嗦,这里就写个vue插件,提供全局的web3对象。

import Web3 from "web3"

export default {
install: function (Vue, options) {
var web3 = window.web3
if (typeof web3 !== 'undefined') {
web3 = new Web3(web3.currentProvider)
} else {
web3 = new Web3(new Web3.providers.HttpProvider('http://localhost:8545'))
}
Vue.prototype.$web3 = web3
}
}
在main.js里启用该插件,以后就可以这样使用this.$web3这个全局对象了。

Vue.use(插件名)
5、写一个ERC20合约

代码省略
项目全部代码地址:
https://github.com/m3shine/To...

6、编译&部署合约

有必要说明一下编译和部署方式的选择,它严重关系到你实际项目的开发:

1)使用Remix,把自己写好的合约拷贝到Remix里进行编译和部署。这种方式最方便。
2)使用truffle这类的框架,这种方式是需要项目基于框架开发了,编译和部署也是在truffle控制台进行。
3)基于web3和solc依赖,写编译(solc)和部署(web3)程序,这些代码就独立(vue是前端,nodejs是后端,运行环境不同)于项目了,用node单独运行。
4)本地安装solidity进行编译,部署的话也需要自己想办法完成。
5)使用geth钱包、mist等编译部署。
……

从geth1.6.0开始,剥离了solidity编译函数,所以web3也不能调用编译方法了。可以本地安装solidity带编译器,也可以在项目里依赖solc进行编译。
编译部署的方式眼花缭乱,这里选择方式3。

编译部署参考代码(web3的1.0及以上版本):token_deploy.js

const Web3 = require('web3')
const fs = require('fs')
const solc = require('solc')

const web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));
const input = fs.readFileSync('../contracts/Token.sol');
const output = solc.compile(input.toString(), 1);
fs.writeFile('../abi/Token.abi', output.contracts[':Token'].interface, err => {
if (err) {
console.log(err)
}
})
const bytecode = output.contracts[':Token'].bytecode;
const abi = JSON.parse(output.contracts[':Token'].interface);
const tokenContract = new web3.eth.Contract(abi);

let log = {
time: new Date(Date.now()),
transactionHash: '',
contractAddress: ''
}

// 部署合约
tokenContract.deploy({
data: '0x' + bytecode,
arguments: ['200000000', '魔法币', 'MFC'] // Token.sol构造参数
})
.send({
from: '0x2d2afb7d0ef71f85dfbdc89d288cb3ce8e049e10', //写你自己的矿工(发币)地址
gas: 5000000, // 这个值很微妙
}, (err, transactionHash) => {
if (err) {
console.log(err);
return;
}
log.transactionHash = transactionHash
})
.on('error', error => {
console.log(error);
})
// 不是总能成功获取newContractInstance, 包括监听receipt也可能发生异常,原因是receipt获取时机可能发生在交易未完成前。
.then(function (newContractInstance) {
if(newContractInstance){
log.contractAddress = newContractInstance.options.address
}
fs.appendFile('Token_deploy.log',JSON.stringify(log) + '\r\n', err => {
if (err) {
console.log(err)
}
})
});
;
7、在执行部署脚本前,需要有一个账户并解锁,在geth控制台执行以下命令:

personal.newAccount('密码')

personal.unlockAccount(eth.coinbase,'密码','20000')
8、发布合约是需要eth币的,所以先挖矿弄点以太币:

miner.start()
9、现在可以执行编译部署脚本了:

node token_deploy.js
如果前面miner.stop()过,那么在执行部署的时候,要确保miner.start(),有矿工打包才能出块。
这里还要知道,因为就是本矿工账户创建合约,所以交易费又回到了本账户,因此余额看起来总是没有减少。
至此,我们已经在私链上部署了一个合约,产生了一笔交易(即创建合约本身这个交易)、一个矿工账户、一个合约账户。

常见错误
Error: insufficient funds for gas * price + value
意思是账户里没有足够的eth币,给创建合约的账户里弄些比特币。

Error: intrinsic gas too low
调高以下发布合约时的gas值。

Error: Invalid number of parameters for "undefined". Got 0 expected 3! (类似这样的)
没有传入合约构造函数参数

调用链上合约
合约部署成功,就有了合约地址,根据合约地址构建合约实例。

let tokenContract = new this.$web3.eth.Contract(JSON.parse(abi),'合约地址')
tokenContract.methods.myMethod.

call()调用的都是abi里的constant方法,即合约里定义的状态属性,EVM里不会发送交易,不会改变合约状态。

send()调用的是合约里定义的函数,是要发送交易到合约并执行合约方法的,会改变合约状态。

以上就简单说一下,不写太多了。看官可以自行下载本项目源码(上面第5步有github链接),自己运行起来看看界面和发币/转账操作。

源码交易过程分析
当我们在项目中创建一个合约的时候,发生了什么?
geth节点默认开放了8545 RPC端口,web3通过连接这个rpc端口,以http的方式调用geth开放的rpc方法。从这一web3与以太坊节点交互基本原理入手,先分析web3源码是怎样调用rpc接口,对应的geth接口是否同名,再看geth源码该接口又是怎么执行的。

new web3.eth.Contract(jsonInterface[, address][, options])
这个函数,jsonInterface就是abi,不管传不传options,options.data属性总是abi的编码。
这个web3接口源码中调用eth.sendTransaction,options.data编码前面加了签名,options.to赋值一个地址,最后返回这笔交易的hash。

再返回上面第6步看一下部署脚本,代码截止到deploy都是在构造web3里的对象,首次与本地geth节点通信的方法是send,它是web3的一个接口方法。

deploy返回的是个web3定义的泛型TransactionObject
Contract对send接口方法的实现如下:

var sendTransaction = (new Method({
name: 'sendTransaction',
call: 'eth_sendTransaction',
params: 1,
inputFormatter: [formatters.inputTransactionFormatter],
requestManager: _this._parent._requestManager,
accounts: Contract._ethAccounts, // is eth.accounts (necessary for wallet signing)
defaultAccount: _this._parent.defaultAccount,
defaultBlock: _this._parent.defaultBlock,
extraFormatters: extraFormatters
})).createFunction();

return sendTransaction(args.options, args.callback);
这个send最终由XMLHttpRequest2的request.send(JSON.stringify(payload))与节点通信。

var sendSignedTx = function(sign){

payload.method = 'eth_sendRawTransaction';
payload.params = [sign.rawTransaction];

method.requestManager.send(payload, sendTxCallback);
};

所以send方法对应的节点api是eth_sendRawTransaction。

go-ethereum/ethclient/ethclient.go

func (ec *Client) SendTransaction(ctx context.Context, tx *types.Transaction) error {
data, err := rlp.EncodeToBytes(tx)
if err != nil {
return err
}
return ec.c.CallContext(ctx, nil, "eth_sendRawTransaction", common.ToHex(data))
}
找到该api执行入口
go-ethereum/internal/ethapi.SendTransaction

func (s *PublicTransactionPoolAPI) SendTransaction(ctx context.Context, args SendTxArgs) (common.Hash, error) {

// Look up the wallet containing the requested signer
account := accounts.Account{Address: args.From}

wallet, err := s.b.AccountManager().Find(account)
if err != nil {
    return common.Hash{}, err
}
……
return submitTransaction(ctx, s.b, signed)

}
我们在这个函数处打一个断点!然后执行部署脚本(可以多次执行),运行到断点处:

要调试geth需要对其重新编译,去掉它原来编译的优化,参见下面“调试源码”一节。
(dlv) p args
github.com/ethereum/go-ethereum/internal/ethapi.SendTxArgs {
From: github.com/ethereum/go-ethereum/common.Address [45,42,251,125,14,247,31,133,223,189,200,157,40,140,179,206,142,4,158,16],
To: *github.com/ethereum/go-ethereum/common.Address nil,
Gas: *5000000,
GasPrice: *github.com/ethereum/go-ethereum/common/hexutil.Big {
neg: false,
abs: math/big.nat len: 1, cap: 1, [18000000000],},
Value: *github.com/ethereum/go-ethereum/common/hexutil.Big nil,
Nonce: *github.com/ethereum/go-ethereum/common/hexutil.Uint64 nil,
Data: *github.com/ethereum/go-ethereum/common/hexutil.Bytes len: 2397, cap: 2397, [96,96,96,64,82,96,2,128,84,96,255,25,22,96,18,23,144,85,52,21,97,0,28,87,96,0,128,253,91,96,64,81,97,8,125,56,3,128,97,8,125,131,57,129,1,96,64,82,128,128,81,145,144,96,32,1,128,81,130,1,145,144,96,32,...+2333 more],
Input: github.com/ethereum/go-ethereum/common/hexutil.Bytes nil,}
(dlv) p wallet
github.com/ethereum/go-ethereum/accounts.Wallet(
github.com/ethereum/go-ethereum/accounts/keystore.keystoreWallet) {
account: github.com/ethereum/go-ethereum/accounts.Account {
Address: github.com/ethereum/go-ethereum/common.Address [45,42,251,125,14,247,31,133,223,189,200,157,40,140,179,206,142,4,158,16],
URL: (
github.com/ethereum/go-ethereum/accounts.URL)(0xc4200d9f18),},
keystore: github.com/ethereum/go-ethereum/accounts/keystore.KeyStore {
storage: github.com/ethereum/go-ethereum/accounts/keystore.keyStore(
github.com/ethereum/go-ethereum/accounts/keystore.keyStorePassphrase) ...,
cache: (github.com/ethereum/go-ethereum/accounts/keystore.accountCache)(0xc4202fe360),
changes: chan struct {} {
qcount: 0,
dataqsiz: 1,
buf: [1]struct struct {} [
{},
],
elemsize: 0,
closed: 0,
elemtype: runtime._type {
size: 0,
ptrdata: 0,
hash: 670477339,
tflag: 2,
align: 1,
fieldalign: 1,
kind: 153,
alg: (runtime.typeAlg)(0x59e69d0),
gcdata: 1,
str: 67481,
ptrToThis: 601472,},
sendx: 0,
recvx: 0,
recvq: waitq<struct {}> {
first: (sudog<struct {}>)(0xc42006ed20),
last: (sudog<struct {}>)(0xc42006ed20),},
sendq: waitq<struct {}> {
first: sudog<struct {}> nil,
last: sudog<struct {}> nil,},
lock: runtime.mutex {key: 0},},
unlocked: map[github.com/ethereum/go-ethereum/common.Address]
github.com/ethereum/go-ethereum/accounts/keystore.unlocked [...],
wallets: []github.com/ethereum/go-ethereum/accounts.Wallet len: 2, cap: 2, [
...,
...,
],
updateFeed: (
github.com/ethereum/go-ethereum/event.Feed)(0xc4202c4040),
updateScope: (
github.com/ethereum/go-ethereum/event.SubscriptionScope)(0xc4202c40b0),
updating: true,
mu: (
sync.RWMutex)(0xc4202c40cc),},}
(dlv) p s.b
github.com/ethereum/go-ethereum/internal/ethapi.Backend(
github.com/ethereum/go-ethereum/eth.EthApiBackend) *{
eth: *github.com/ethereum/go-ethereum/eth.Ethereum {
config: (github.com/ethereum/go-ethereum/eth.Config)(0xc420153000),
chainConfig: (github.com/ethereum/go-ethereum/params.ChainConfig)(0xc4201da540),
shutdownChan: chan bool {
qcount: 0,
dataqsiz: 0,
buf: *[0]bool [],
elemsize: 1,
closed: 0,
elemtype: *runtime._type {
size: 1,
ptrdata: 0,
hash: 335480517,
tflag: 7,
align: 1,
fieldalign: 1,
kind: 129,
alg: (runtime.typeAlg)(0x59e69e0),
gcdata: *1,
str: 21072,
ptrToThis: 452544,},
sendx: 0,
recvx: 0,
recvq: waitq {
first: (sudog)(0xc420230ba0),
last: (sudog)(0xc420231440),},
sendq: waitq {
first: sudog nil,
last: sudog nil,},
lock: runtime.mutex {key: 0},},
stopDbUpgrade: nil,
txPool: (github.com/ethereum/go-ethereum/core.TxPool)(0xc420012380),
blockchain: (github.com/ethereum/go-ethereum/core.BlockChain)(0xc42029c000),
protocolManager: (github.com/ethereum/go-ethereum/eth.ProtocolManager)(0xc420320270),
lesServer: github.com/ethereum/go-ethereum/eth.LesServer nil,
chainDb: github.com/ethereum/go-ethereum/ethdb.Database(
github.com/ethereum/go-ethereum/ethdb.LDBDatabase) ...,
eventMux: (github.com/ethereum/go-ethereum/event.TypeMux)(0xc4201986c0),
engine: github.com/ethereum/go-ethereum/consensus.Engine(
github.com/ethereum/go-ethereum/consensus/ethash.Ethash) ...,
accountManager: (github.com/ethereum/go-ethereum/accounts.Manager)(0xc420089860),
bloomRequests: chan chan *github.com/ethereum/go-ethereum/core/bloombits.Retrieval {
qcount: 0,
dataqsiz: 0,
buf: *[0]chan *github.com/ethereum/go-ethereum/core/bloombits.Retrieval [],
elemsize: 8,
closed: 0,
elemtype: *runtime._type {
size: 8,
ptrdata: 8,
hash: 991379238,
tflag: 2,
align: 8,
fieldalign: 8,
kind: 50,
alg: (runtime.typeAlg)(0x59e6a10),
gcdata: *1,
str: 283111,
ptrToThis: 0,},
sendx: 0,
recvx: 0,
recvq: waitq<chan *github.com/ethereum/go-ethereum/core/bloombits.Retrieval> {
first: (sudog<chan *github.com/ethereum/go-ethereum/core/bloombits.Retrieval>)(0xc420230c00),
last: (sudog<chan *github.com/ethereum/go-ethereum/core/bloombits.Retrieval>)(0xc4202314a0),},
sendq: waitq<chan *github.com/ethereum/go-ethereum/core/bloombits.Retrieval> {
first: *sudog<chan github.com/ethereum/go-ethereum/core/bloombits.Retrieval> nil,
last: sudog<chan github.com/ethereum/go-ethereum/core/bloombits.Retrieval> nil,},
lock: runtime.mutex {key: 0},},
bloomIndexer: unsafe.Pointer(0xc4201b23c0),
ApiBackend: (github.com/ethereum/go-ethereum/eth.EthApiBackend)(0xc4202b8910),
miner: (github.com/ethereum/go-ethereum/miner.Miner)(0xc420379540),
gasPrice: (math/big.Int)(0xc420233c40),
etherbase: github.com/ethereum/go-ethereum/common.Address [45,42,251,125,14,247,31,133,223,189,200,157,40,140,179,206,142,4,158,16],
networkId: 13,
netRPCService: (github.com/ethereum/go-ethereum/internal/ethapi.PublicNetAPI)(0xc42007feb0),
lock: (
sync.RWMutex)(0xc4202ea528),},
gpo: github.com/ethereum/go-ethereum/eth/gasprice.Oracle {
backend: github.com/ethereum/go-ethereum/internal/ethapi.Backend(
github.com/ethereum/go-ethereum/eth.EthApiBackend) ...,
lastHead: github.com/ethereum/go-ethereum/common.Hash [139,147,220,247,224,227,136,250,220,62,217,102,160,96,23,182,90,90,108,254,82,158,234,95,150,120,163,5,61,248,168,168],
lastPrice: (math/big.Int)(0xc420233c40),
cacheLock: (
sync.RWMutex)(0xc420010938),
fetchLock: (
sync.Mutex)(0xc420010950),
checkBlocks: 20,
maxEmpty: 10,
maxBlocks: 100,
percentile: 60,},}
// submitTransaction is a helper function that submits tx to txPool and logs a message.
func submitTransaction(ctx context.Context, b Backend, tx *types.Transaction) (common.Hash, error) {
if err := b.SendTx(ctx, tx); err != nil {
return common.Hash{}, err
}
if tx.To() == nil {
signer := types.MakeSigner(b.ChainConfig(), b.CurrentBlock().Number())
from, err := types.Sender(signer, tx)
if err != nil {
return common.Hash{}, err
}
addr := crypto.CreateAddress(from, tx.Nonce())
log.Info("Submitted contract creation", "fullhash", tx.Hash().Hex(), "contract", addr.Hex())
} else {
log.Info("Submitted transaction", "fullhash", tx.Hash().Hex(), "recipient", tx.To())
}
return tx.Hash(), nil
}
(dlv) p tx
*github.com/ethereum/go-ethereum/core/types.Transaction {
data: github.com/ethereum/go-ethereum/core/types.txdata {
AccountNonce: 27,
Price: (math/big.Int)(0xc4217f5640),
GasLimit: 5000000,
Recipient: *github.com/ethereum/go-ethereum/common.Address nil,
Amount: (math/big.Int)(0xc4217f5620),
Payload: []uint8 len: 2397, cap: 2397, [96,96,96,64,82,96,2,128,84,96,255,25,22,96,18,23,144,85,52,21,97,0,28,87,96,0,128,253,91,96,64,81,97,8,125,56,3,128,97,8,125,131,57,129,1,96,64,82,128,128,81,145,144,96,32,1,128,81,130,1,145,144,96,32,...+2333 more],
V: (math/big.Int)(0xc4217e0a20),
R: (math/big.Int)(0xc4217e09c0),
S: (math/big.Int)(0xc4217e09e0),
Hash: github.com/ethereum/go-ethereum/common.Hash nil,},
hash: sync/atomic.Value {
noCopy: sync/atomic.noCopy {},
v: interface {} nil,},
size: sync/atomic.Value {
noCopy: sync/atomic.noCopy {},
v: interface {} nil,},
from: sync/atomic.Value {
noCopy: sync/atomic.noCopy {},
v: interface {} nil,},}
(dlv) bt
0 0x00000000048d9248 in github.com/ethereum/go-ethereum/internal/ethapi.submitTransaction
at ./go/src/github.com/ethereum/go-ethereum/internal/ethapi/api.go:1130
1 0x00000000048d9bd1 in github.com/ethereum/go-ethereum/internal/ethapi.(
PublicTransactionPoolAPI).SendTransaction
at ./go/src/github.com/ethereum/go-ethereum/internal/ethapi/api.go:1176
(dlv) frame 0 l

github.com/ethereum/go-ethereum/internal/ethapi.submitTransaction() ./go/src/github.com/ethereum/go-ethereum/internal/ethapi/api.go:1130 (PC: 0x48d9248)
Warning: debugging optimized function
1125: if err := b.SendTx(ctx, tx); err != nil {
1126: return common.Hash{}, err
1127: }
1128: if tx.To() == nil {
1129: signer := types.MakeSigner(b.ChainConfig(), b.CurrentBlock().Number())
=>1130: from, err := types.Sender(signer, tx)
1131: if err != nil {
1132: return common.Hash{}, err
1133: }
1134: addr := crypto.CreateAddress(from, tx.Nonce())
1135: log.Info("Submitted contract creation", "fullhash", tx.Hash().Hex(), "contract", addr.Hex())
(dlv) frame 1 l
Goroutine 3593 frame 1 at /Users/jiang/go/src/github.com/ethereum/go-ethereum/internal/ethapi/api.go:1176 (PC: 0x48d9bd1)
1171: }
1172: signed, err := wallet.SignTx(account, tx, chainID)
1173: if err != nil {
1174: return common.Hash{}, err
1175: }
=>1176: return submitTransaction(ctx, s.b, signed)
1177: }
1178:
1179: // SendRawTransaction will add the signed transaction to the transaction pool.
1180: // The sender is responsible for signing the transaction and using the correct nonce.
1181: func (s *PublicTransactionPoolAPI) SendRawTransaction(ctx context.Context, encodedTx hexutil.Bytes) (common.Hash, error) {
先把调试结果展示出来,通过对一个交易的内部分析,可以了解EVM执行的大部分细节,此处需要另开篇幅详述。请关注后续专题。

源码调试
1、重新强制编译geth,去掉编译内联优化,方便跟踪调试。

cd path/go-ethereum
sudo go install -a -gcflags '-N -l' -v ./cmd/geth
编译后的geth执行文件就在$gopath/bin下。

2、在datadir下启动这个重新编译后的geth

geth --datadir "./" --rpc --rpccorsdomain="*" --networkid 13 console 2>>00.glog
3、调试这个进程

dlv attach
4、给交易api入口函数设置断点

b ethapi.(*PublicTransactionPoolAPI).SendTransaction
下面是一个区块链小程序,供大家参考。
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