使用Fabric Node SDK进行Invoke和Query

前面的文章都是在讲解Fabric网络的搭建和ChainCode的开发，那么在ChainCode开发完毕后，我们就需要使用Fabric SDK做应用程序的开发了。官方虽然提供了Node.JS，Java，Go，Python等多种语言的SDK，但是由于整个Fabric太新了，很多SDK还不成熟和完善，所以我采用Node JS的SDK，毕竟这个是功能毕竟齐全，而且也是官方示例的时候使用的SDK。由于我从来没有接触过Node.JS的开发，对这个语言理解不深，所以讲的比较肤浅，希望大家见谅。

1.环境准备

Node.js是一个跨平台的语言，可以在Linux，Window和Mac上安装，我们在开发的时候可以在Windows下开发，最后生产环境一般都是Linux，所以我们这里就以Ubuntu为例。Fabric Node SDK支持的Node版本是v6，不支持最新的v8版本。NodeJS官方给我们提供了很方便的安装方法，具体文档在：https://nodejs.org/en/download/package-manager/#debian-and-ubuntu-based-linux-distributions

我们只需要执行以下命令即可安装NodeJS的最新v6版本：

curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -
sudo apt-get install -y nodejs

安装完成后我们可以使用以下两个命令来查看安装的Node版本和npm版本。

node –v
npm -v

关于NPM，这个是一个包管理器，我觉得很像VS里面的NuGet，关于NPM的基础知识，我们可以参考这篇博客：http://www.ruanyifeng.com/blog/2016/01/npm-install.html

只要安装好node和npm，接下来我们就可以进行Fabric Node SDK Application的开发了。

由于我们想基于官方Example的e2e_cli里面的Fabric网络来写程序，关于Fabric网络的搭建我就不多说，大家可以参考我之前的博客。总之结果就是我们现在已经成功运行了e2e_cli这个网络，也就是说Example02这个ChainCode已经安装部署，并且测试通过了，我们接下来只是换用Node SDK的方式进行查询和调用。

2.编写package.json并下载依赖模块

我们首先在当前用户的根目录建立一个nodeTest的文件夹，用于存放我们关于node的相关项目文件，然后在其中新建一个包配置文件，package.json

mkdir ~/nodeTest
cd ~/nodeTest
vi package.json

在这个文件中，我们可以定义很多项目相关的属性，这篇博客详细的介绍了每个属性有什么用，大家可以参考：http://www.cnblogs.com/tzyy/p/5193811.html

总之，最后我们在package.json中放入了以下内容：

{ 
     "name": "nodeTest", 
     "version": "1.0.0", 
     "description": "Hyperledger Fabric Node SDK Test Application", 
     "scripts": { 
         "test": "echo "Error: no test specified" && exit 1" 
     }, 
     "dependencies": { 
         "fabric-ca-client": "^1.0.0", 
         "fabric-client": "^1.0.0" 
     }, 
     "author": "Devin Zeng", 
     "license": "Apache-2.0", 
     "keywords": [ 
         "Hyperledger", 
         "Fabric", 
         "Test", 
         "Application" 
     ] 
}

最主要的就是dependencies，这里我们放了Fabric CA Client和Fabric Node SDK的Client，虽然本示例中没用到CA Client，但是以后会用到，所以先放在这里了。

编辑保存好该文件后，我们就可以运行npm install命令来下载所有相关的依赖模块，但是由于npm服务器在国外，所以下载可能会很慢，感谢淘宝为我们提供了国内的npm镜像，使得安装npm模块快很多。运行的命令是：

npm install --registry=https://registry.npm.taobao.org

运行完毕后我们查看一下nodeTest目录，可以看到多了一个node_modules文件夹。这里就是使用刚才的命令下载下来的所有依赖包。

2.编写对Fabric的Query方法

下面我们新建一个query.js文件，开始我们的Fabric Node SDK编码工作。由于代码比较长，所以我就不分步讲了，直接在代码中增加注释，将完整代码贴出来：

'use strict';

var hfc = require('fabric-client'); 
var path = require('path'); 
var sdkUtils = require('fabric-client/lib/utils') 
var fs = require('fs'); 
var options = { 
    user_id: 'Admin@org1.example.com', 
    msp_id:'Org1MSP', 
    channel_id: 'mychannel', 
    chaincode_id: 'mycc', 
    network_url: 'grpcs://localhost:7051',//因为启用了TLS，所以是grpcs,如果没有启用TLS，那么就是grpc 
    privateKeyFolder:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/users/Admin@org1.example.com/msp/keystore', 
    signedCert:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/users/Admin@org1.example.com/msp/signcerts/Admin@org1.example.com-cert.pem', 
    tls_cacerts:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/peers/peer0.org1.example.com/tls/ca.crt', 
    server_hostname: "peer0.org1.example.com" 
};

var channel = {}; 
var client = null; 
const getKeyFilesInDir = (dir) => { 
//该函数用于找到keystore目录下的私钥文件的路径 
    var files = fs.readdirSync(dir) 
    var keyFiles = [] 
    files.forEach((file_name) => { 
        let filePath = path.join(dir, file_name) 
        if (file_name.endsWith('_sk')) { 
            keyFiles.push(filePath) 
        } 
    }) 
    return keyFiles 
} 
Promise.resolve().then(() => { 
    console.log("Load privateKey and signedCert"); 
    client = new hfc(); 
    var    createUserOpt = { 
                username: options.user_id, 
                 mspid: options.msp_id, 
                cryptoContent: { privateKey: getKeyFilesInDir(options.privateKeyFolder)[0], 
  signedCert: options.signedCert } 
        } 
//以上代码指定了当前用户的私钥，证书等基本信息 
return sdkUtils.newKeyValueStore({ 
                        path: "/tmp/fabric-client-stateStore/" 
                }).then((store) => { 
                        client.setStateStore(store) 
                         return client.createUser(createUserOpt) 
                 }) 
}).then((user) => { 
    channel = client.newChannel(options.channel_id); 
    
    let data = fs.readFileSync(options.tls_cacerts); 
    let peer = client.newPeer(options.network_url, 
         { 
            pem: Buffer.from(data).toString(), 
             'ssl-target-name-override': options.server_hostname 
        } 
    ); 
    peer.setName("peer0"); 
    //因为启用了TLS，所以上面的代码就是指定TLS的CA证书 
    channel.addPeer(peer); 
    return; 
}).then(() => { 
    console.log("Make query"); 
    var transaction_id = client.newTransactionID(); 
    console.log("Assigning transaction_id: ", transaction_id._transaction_id); 
//构造查询request参数 
    const request = { 
        chaincodeId: options.chaincode_id, 
        txId: transaction_id, 
        fcn: 'query', 
        args: ['a'] 
    }; 
     return channel.queryByChaincode(request); 
}).then((query_responses) => { 
    console.log("returned from query"); 
    if (!query_responses.length) { 
        console.log("No payloads were returned from query"); 
    } else { 
        console.log("Query result count = ", query_responses.length) 
    } 
    if (query_responses[0] instanceof Error) { 
        console.error("error from query = ", query_responses[0]); 
    } 
    console.log("Response is ", query_responses[0].toString());//打印返回的结果 
}).catch((err) => { 
    console.error("Caught Error", err); 
});

编写完代码，我们想要测试一下我们的代码是否靠谱，直接运行

node query.js

即可，我们可以看到，a账户的余额是90元。

studyzy@ubuntu1:~/nodeTest$ node query.js 
Load privateKey and signedCert 
Make query 
Assigning transaction_id:  ee3ac35d40d8510813546a2216ad9c0d91213b8e1bba9b7fe19cfeff3014e38a 
returned from query 
Query result count =  1 
Response is  90

为什么a账户是90？因为我们跑e2e_cli的Fabric网络时，系统会自动安装Example02的ChainCode，然后自动跑查询，转账等操作。

3.编写对Fabric的Invoke方法

相比较于Query方法，Invoke方法要复杂的多，主要是因为Invoke需要和Orderer通信，而且发起了Transaction之后，还要设置EventHub来接收消息。下面贴出invoke.js的全部内容，对于比较重要的部分我进行了注释:

'use strict';

var hfc = require('fabric-client'); 
var path = require('path'); 
var util = require('util'); 
var sdkUtils = require('fabric-client/lib/utils') 
const fs = require('fs'); 
var options = { 
    user_id: 'Admin@org1.example.com', 
     msp_id:'Org1MSP', 
    channel_id: 'mychannel', 
    chaincode_id: 'mycc', 
    peer_url: 'grpcs://localhost:7051',//因为启用了TLS，所以是grpcs,如果没有启用TLS，那么就是grpc 
    event_url: 'grpcs://localhost:7053',//因为启用了TLS，所以是grpcs,如果没有启用TLS，那么就是grpc 
    orderer_url: 'grpcs://localhost:7050',//因为启用了TLS，所以是grpcs,如果没有启用TLS，那么就是grpc 
    privateKeyFolder:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/users/Admin@org1.example.com/msp/keystore', 
    signedCert:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/users/Admin@org1.example.com/msp/signcerts/Admin@org1.example.com-cert.pem', 
    peer_tls_cacerts:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/peerOrganizations/org1.example.com/peers/peer0.org1.example.com/tls/ca.crt', 
    orderer_tls_cacerts:'/home/studyzy/go/src/github.com/hyperledger/fabric/examples/e2e_cli/crypto-config/ordererOrganizations/example.com/orderers/orderer.example.com/tls/ca.crt', 
    server_hostname: "peer0.org1.example.com" 
};

var channel = {}; 
var client = null; 
var targets = []; 
var tx_id = null; 
const getKeyFilesInDir = (dir) => { 
//该函数用于找到keystore目录下的私钥文件的路径 
        const files = fs.readdirSync(dir) 
        const keyFiles = [] 
        files.forEach((file_name) => { 
                let filePath = path.join(dir, file_name) 
                if (file_name.endsWith('_sk')) { 
                        keyFiles.push(filePath) 
                } 
        }) 
        return keyFiles 
} 
Promise.resolve().then(() => { 
    console.log("Load privateKey and signedCert"); 
    client = new hfc(); 
    var    createUserOpt = { 
                username: options.user_id, 
                mspid: options.msp_id, 
                cryptoContent: { privateKey: getKeyFilesInDir(options.privateKeyFolder)[0], 
  signedCert: options.signedCert } 
         } 
//以上代码指定了当前用户的私钥，证书等基本信息 
return sdkUtils.newKeyValueStore({ 
                        path: "/tmp/fabric-client-stateStore/" 
                }).then((store) => { 
                        client.setStateStore(store) 
                        return client.createUser(createUserOpt) 
                }) 
}).then((user) => { 
    channel = client.newChannel(options.channel_id); 
    let data = fs.readFileSync(options.peer_tls_cacerts); 
    let peer = client.newPeer(options.peer_url, 
        { 
            pem: Buffer.from(data).toString(), 
            'ssl-target-name-override': options.server_hostname 
        } 
    ); 
    //因为启用了TLS，所以上面的代码就是指定Peer的TLS的CA证书 
    channel.addPeer(peer); 
    //接下来连接Orderer的时候也启用了TLS，也是同样的处理方法 
    let odata = fs.readFileSync(options.orderer_tls_cacerts); 
    let caroots = Buffer.from(odata).toString(); 
    var orderer = client.newOrderer(options.orderer_url, { 
        'pem': caroots, 
        'ssl-target-name-override': "orderer.example.com" 
    }); 
    
    channel.addOrderer(orderer); 
    targets.push(peer); 
    return; 
}).then(() => { 
    tx_id = client.newTransactionID(); 
    console.log("Assigning transaction_id: ", tx_id._transaction_id); 
//发起转账行为，将a->b 10元 
    var request = { 
        targets: targets, 
        chaincodeId: options.chaincode_id, 
        fcn: 'invoke', 
        args: ['a', 'b', '10'], 
        chainId: options.channel_id, 
        txId: tx_id 
    }; 
    return channel.sendTransactionProposal(request); 
}).then((results) => { 
    var proposalResponses = results[0]; 
    var proposal = results[1]; 
    var header = results[2]; 
    let isProposalGood = false; 
    if (proposalResponses && proposalResponses[0].response && 
        proposalResponses[0].response.status === 200) { 
        isProposalGood = true; 
        console.log('transaction proposal was good'); 
    } else { 
        console.error('transaction proposal was bad'); 
    } 
    if (isProposalGood) { 
        console.log(util.format( 
            'Successfully sent Proposal and received ProposalResponse: Status - %s, message - "%s", metadata - "%s", endorsement signature: %s', 
            proposalResponses[0].response.status, proposalResponses[0].response.message, 
            proposalResponses[0].response.payload, proposalResponses[0].endorsement.signature)); 
        var request = { 
            proposalResponses: proposalResponses, 
             proposal: proposal, 
            header: header 
        }; 
         // set the transaction listener and set a timeout of 30sec 
        // if the transaction did not get committed within the timeout period, 
        // fail the test 
        var transactionID = tx_id.getTransactionID(); 
        var eventPromises = []; 
        let eh = client.newEventHub(); 
        //接下来设置EventHub，用于监听Transaction是否成功写入，这里也是启用了TLS 
        let data = fs.readFileSync(options.peer_tls_cacerts); 
        let grpcOpts = { 
             pem: Buffer.from(data).toString(), 
            'ssl-target-name-override': options.server_hostname 
        } 
        eh.setPeerAddr(options.event_url,grpcOpts); 
        eh.connect();

        let txPromise = new Promise((resolve, reject) => { 
            let handle = setTimeout(() => { 
                eh.disconnect(); 
                reject(); 
            }, 30000); 
//向EventHub注册事件的处理办法 
            eh.registerTxEvent(transactionID, (tx, code) => { 
                clearTimeout(handle); 
                eh.unregisterTxEvent(transactionID); 
                eh.disconnect();

                if (code !== 'VALID') { 
                    console.error( 
                        'The transaction was invalid, code = ' + code); 
                    reject(); 
                 } else { 
                    console.log( 
                         'The transaction has been committed on peer ' + 
                         eh._ep._endpoint.addr); 
                    resolve(); 
                } 
            }); 
        }); 
        eventPromises.push(txPromise); 
        var sendPromise = channel.sendTransaction(request); 
        return Promise.all([sendPromise].concat(eventPromises)).then((results) => { 
            console.log(' event promise all complete and testing complete'); 
             return results[0]; // the first returned value is from the 'sendPromise' which is from the 'sendTransaction()' call 
        }).catch((err) => { 
            console.error( 
                'Failed to send transaction and get notifications within the timeout period.' 
            ); 
            return 'Failed to send transaction and get notifications within the timeout period.'; 
         }); 
    } else { 
        console.error( 
            'Failed to send Proposal or receive valid response. Response null or status is not 200. exiting...' 
        ); 
        return 'Failed to send Proposal or receive valid response. Response null or status is not 200. exiting...'; 
    } 
}, (err) => { 
    console.error('Failed to send proposal due to error: ' + err.stack ? err.stack : 
        err); 
    return 'Failed to send proposal due to error: ' + err.stack ? err.stack : 
        err; 
}).then((response) => { 
    if (response.status === 'SUCCESS') { 
        console.log('Successfully sent transaction to the orderer.'); 
        return tx_id.getTransactionID(); 
    } else { 
        console.error('Failed to order the transaction. Error code: ' + response.status); 
        return 'Failed to order the transaction. Error code: ' + response.status; 
    } 
}, (err) => { 
    console.error('Failed to send transaction due to error: ' + err.stack ? err 
         .stack : err); 
    return 'Failed to send transaction due to error: ' + err.stack ? err.stack : 
        err; 
});

保存文件并退出，接下来测试一下我们的代码，运行：

node invoke.js

我们可以看到系统返回如下结果：

Load privateKey and signedCert 
Assigning transaction_id:  1adbf20ace0d1601b00cc2b9dfdd4a431cfff9a13f6a6f5e5e4a80c897e0f7a8 
transaction proposal was good 
Successfully sent Proposal and received ProposalResponse: Status - 200, message - "OK", metadata - "", endorsement signature: 0D x��N��n�#���/�G���QD�w�����As� ]��FfWҡ�+������=m9I���� 6�i 
info: [EventHub.js]: _connect - options {"grpc.ssl_target_name_override":"peer0.org1.example.com","grpc.default_authority":"peer0.org1.example.com"} 
The transaction has been committed on peer localhost:7053 
  event promise all complete and testing complete 
Successfully sent transaction to the orderer.

从打印出的结果看，我们的转账已经成功了，我们可以重新调用之前写的query.js重新查询，可以看到a账户的余额已经变少了10元。

4.总结

我们以上的query和Invoke都是参照了官方的fabcar示例，该示例在https://github.com/hyperledger/fabric-samples/tree/release/fabcar

这只是简单的测试Node SDK是否可用，如果我们要做项目，那么就会复杂很多，可以参考官方的两个项目：

https://github.com/hyperledger/fabric-samples/tree/release/balance-transfer

https://github.com/IBM-Blockchain/marbles

我之前一直卡在怎么基于某个用户的私钥和证书来设置当前的Context，后来感谢neswater的帮助，终于才解决了这个问题。还有就是TLS的问题，官方给出的fabcar是没有TLS的，我搞了半天才搞定，原来除了制定TLS证书之外，我们访问Peer的URL也是不一样的。

最后，大家如果想进一步探讨Fabric或者使用中遇到什么问题可以加入QQ群【494085548】大家一起讨论。