# 如何实现一个监听txpool功能的以太坊客户端

By [shily.eth](https://paragraph.com/@shily) · 2022-09-14

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官方的 go-ethereum 库使用 SubscribePendingTransactions 监听最新的交易，只能得到对应的 hash 值，为了实现监听 txpool 的功能，需要以下改动

参考下面这个 go-ethereum 的 pr

[https://github.com/ethereum/go-ethereum/pull/25186](https://github.com/ethereum/go-ethereum/pull/25186)

合并该 pr 的代码后，自己 build 出 docker 镜像

然后编写 docker-compose 文件

    version: "3"
    
    services:
      geth:
        image: go-ethereum
        pull_policy: always
        container_name: gethnode
        restart: unless-stopped
        ports:
          - "30303:30303"
          - "30303:30303/udp"
          - "38545:8545"
          - "38546:8546"
        volumes:
          - ./data:/root/.ethereum
        stop_signal: SIGINT
        stop_grace_period: 2m
        command:
          - --http
          - --http.api
          - "eth,net,web3,txpool,personal"
          - --http.addr=0.0.0.0
          - --http.vhosts=*
          - --http.corsdomain=*
          - --ws
          - --ws.api
          - --ws.origins=*
          - --ws.addr=0.0.0.0
          - --ws.api
          - "eth,net,web3,txpool,personal"
          - --graphql
          - --graphql.corsdomain=*
          - --graphql.vhosts=*
          # Minimum number of executable transaction slots guaranteed per account (default: 16)
          # - --txpool.accountslots=16
          # Maximum number of non-executable transaction slots for all accounts (default: 1024)
          # --txpool.globalqueue=1024
          # Maximum number of executable transaction slots for all accounts (default: 4096)
          # - --txpool.globalslots=10000
          # Maximum amount of time non-executable transaction are queued (default: 3h0m0s)
          # - --txpool.lifetime=3h0m0s
          # Megabytes of memory allocated to internal caching (default: 1024)
          # - --cache=4096
          # Maximum number of network peers (network disabled if set to 0) (default: 25)
          # - --maxpeers=100
          # Blockchain sync mode ("fast", "full", or "light")
          # - --syncmode=fast
          # Blockchain garbage collection mode ("full", "archive") (default: "full")
          # - --gcmode=full
        logging:
          driver: "json-file"
          options:
            max-size: "20m"
            max-file: "10"
    

go-ethereum的客户端依赖也要改为对应合并 pr 后的

然后使用节点 [ws:// ip:38546](https://etherscan.io/address/38.242.158.30:38546) 连接 eth 客户端，即可使用 SubscribePendingTransactions 方法监听到完整的 tx 信息

    func TestTxPool(t *testing.T) {
        ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
        defer cancel()
    
        rpcClient, err := rpc.Dial("ws://xxx:38546")
        if err != nil {
            t.Fatal(err)
        }
    
        ec := gethclient.New(rpcClient)
    
        ch := make(chan *types.Transaction)
        sub, err := ec.SubscribePendingTransactions(ctx, ch)
        if err != nil {
            t.Fatal(err)
        }
    
        for {
            select {
            case err = <-sub.Err():
                t.Fatal(err)
            case tx := <-ch:
                if tx.To() == nil {
                    continue
                }
                if strings.ToLower(tx.To().String()) == strings.ToLower("0x68b3465833fb72A70ecDF485E0e4C7bD8665Fc45") {
                    t.Logf("gas:%d hash: %s", tx.GasPrice(), tx.Hash())
                }
            }
        }
    }

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*Originally published on [shily.eth](https://paragraph.com/@shily/txpool)*