Detailed analysis of the process of creating a channel (Channel) and adding a node to the channel in the blance transfer example.
Create Channel
1. First look at the routing function of app.js
var createChannel = require('./app/create-channel.js');
app.post('/channels', async function(req, res) {
// 接收参数channel名称和配置文件的路径
// 通道配置交易路径： ./artifacts/channel/mychannel.tx
var channelName = req.body.channelName;
var channelConfigPath = req.body.channelConfigPath;
if (!channelName) {
res.json(getErrorMessage('\'channelName\''));
return;
}
if (!channelConfigPath) {
res.json(getErrorMessage('\'channelConfigPath\''));
return;
}
// 创建通道(username和orgname参数从token中获取)
let message = await createChannel.createChannel(channelName, channelConfichannelNamegPath, req.username, req.orgname);
res.send(message);
});2. create-channel.jsLook at the createChannel()method in
// 通过发送交易的方法向orderer节点发送创建channel的请求
var createChannel = async function(channelName, channelConfigPath, username, orgName) {
try {
// 生成组织的客户端实例
var client = await helper.getClientForOrg(orgName);
// 从channel配置交易（mychannel.tx）读取源字节
var envelope = fs.readFileSync(path.join(__dirname, channelConfigPath));
// 提取channel配置信息
var channelConfig = client.extractChannelConfig(envelope);
// 客户端使用 组织管理员 的私钥 签名，作为背书（endorsement）
// "../artifacts/channel/crypto-config/peerOrganizations/org1.example.com/users/[email protected]/msp/signcerts"
// 在内部通过_getSigningIdentity(true)获取org admin的私钥 进行签名
let signature = client.signChannelConfig(channelConfig);
// 请求结构：
let request = {
config: channelConfig,
signatures: [signature],
name: channelName,
txId: client.newTransactionID(true)
};
// 发送给orderer节点
var response = await client.createChannel(request)
if (response && response.status === 'SUCCESS') {
logger.debug('Successfully created the channel.');
let response = {
success: true,
message: 'Channel \'' + channelName + '\' created Successfully'
};
return response;
} else {
throw new Error('Failed to create the channel \'' + channelName + '\'');
}
} catch (err) {
logger.error('Failed to initialize the channel: ' + err.stack ? err.stack : err);
throw new Error('Failed to initialize the channel: ' + err.toString());
}
};Add node to Channel
1. First look at the routing function in app.js
// 首先看app.js中的路由函数
app.post('/channels/:channelName/peers', async function(req, res) {
// 接收参数 channel名称（URL中）和peers（body中）
var channelName = req.params.channelName;
var peers = req.body.peers;
if (!channelName) {
res.json(getErrorMessage('\'channelName\''));
return;
}
if (!peers || peers.length == 0) {
res.json(getErrorMessage('\'peers\''));
return;
}
// 将peers加入channel
let message = await join.joinChannel(channelName, peers, req.username, req.orgname);
res.send(message);
});2. Then look at the joinChannel() function in join-channel.js
// 然后看join-channel.js中的joinChannel()函数
var joinChannel = async function(channel_name, peers, username, org_name) {
var error_message = null;
var all_eventhubs = [];
try {
// 首先创建client对象
var client = await helper.getClientForOrg(org_name, username);
// 生成channel对象
var channel = client.getChannel(channel_name);
if(!channel) {
let message = util.format('Channel %s was not defined in the connection profile', channel_name);
logger.error(message);
throw new Error(message);
}
// 生成基于组织管理员的 TransactionID 对象
// 该对象包含一个随机数（nonce）以及t(nonce + signingIdentity)的hash值
let request = {
txId : client.newTransactionID(true)
};
// 从orderer节点获取创世区块（genesis block）
let genesis_block = await channel.getGenesisBlock(request);
// 告诉节点加入channel，等待每个节点的event hub通知我们节点加入channel成功
var promises = [];
var block_registration_numbers = [];
// 给组织中的每个节点分配一个EventHub对象
let event_hubs = client.getEventHubsForOrg(org_name);
#event_hubs.forEach((eh) => {
#let configBlockPromise = new Promise((resolve, reject) => {
// 设置超时时间
#let event_timeout = setTimeout(() => {
let message = 'REQUEST_TIMEOUT:' + eh._ep._endpoint.addr;
logger.error(message);
eh.disconnect();
reject(new Error(message));
}, 60000);
// 注册区块监听
#let block_registration_number = eh.registerBlockEvent((block) => {
clearTimeout(event_timeout);
// 配置区块中只能有一个交易
if (block.data.data.length === 1) {
// 一个节点可能属于多个channel
// 所以需要检验该区块是否来自目标channel
var channel_header = block.data.data[0].payload.header.channel_header;
if (channel_header.channel_id === channel_name) {
let message = util.format('EventHub %s has reported a block update for channel %s',eh._ep._endpoint.addr,channel_name);
logger.info(message)
resolve(message);
} else {
let message = util.format('Unknown channel block event received from %s',eh._ep._endpoint.addr);
logger.error(message);
reject(new Error(message));
}
}
}, (err) => {
clearTimeout(event_timeout);
let message = 'Problem setting up the event hub :'+ err.toString();
logger.error(message);
reject(new Error(message));
});
// 每一个client实例对应一个注册number，后面将作为参数对监听进行注销
block_registration_numbers.push(block_registration_number);
// 保存EventHub对象，方便后面对事件流断开连接
all_eventhubs.push(eh);
});
promises.push(configBlockPromise);
// 开启事件流
eh.connect();
});
// 封装加入channel的请求
let join_request = {
targets: peers, // 要加入channel的节点
txId: client.newTransactionID(true), // 基于组织管理员的TransactionID
block: genesis_block // 创世区块
};
// 调用SDK中的joinChannel()方法，主要是通过sendPeersProposal()将
// 加入channel的交易提案发送给背书节点进行背书
let join_promise = channel.joinChannel(join_request);
// 保存返回结果：提案响应（ProposalResponse）的Promise
promises.push(join_promise);
let results = await Promise.all(promises);
logger.debug(util.format('Join Channel RESPONSE : %j', results));
// 检查所有Promise返回（包括监听事件和发送join请求）
// 只要有一个结果异常则宣布join channel失败
let peers_results = results.pop();
for(let i in peers_results) {
let peer_result = peers_results[i];
if(peer_result.response && peer_result.response.status == 200) {
logger.info('Successfully joined peer to the channel %s',channel_name);
} else {
let message = util.format('Failed to joined peer to the channel %s',channel_name);
error_message = message;
logger.error(message);
}
}
// 查看事件中心的消息报告
for(let i in results) {
let event_hub_result = results[i];
let event_hub = event_hubs[i];
let block_registration_number = block_registration_numbers[i];
logger.debug('Event results for event hub :%s',event_hub._ep._endpoint.addr);
if(typeof event_hub_result === 'string') {
logger.debug(event_hub_result);
} else {
if(!error_message) error_message = event_hub_result.toString();
logger.debug(event_hub_result.toString());
}
// 注销事件监听
event_hub.unregisterBlockEvent(block_registration_number);
}
} catch(error) {
logger.error('Failed to join channel due to error: ' + error.stack ? error.stack : error);
error_message = error.toString();
}
// 断开所有event hub事件流
all_eventhubs.forEach((eh) => {
eh.disconnect();
});
};test
create channel
curl -s -X POST \ http://localhost:4000/channels \ -H "authorization: Bearer $ORG1_TOKEN" \ -H "content-type: application/json" \ -d '{ "channelName":"mychannel", "channelConfigPath":"../artifacts/channel/mychannel.tx" }'return result
{"success":true,"message":"Channel 'mychannel' created Successfully"}Add two peers in Org1 to the channel
curl -s -X POST \ http://localhost:4000/channels/mychannel/peers \ -H "authorization: Bearer $ORG1_TOKEN" \ -H "content-type: application/json" \ -d '{ "peers": ["peer0.org1.example.com","peer1.org1.example.com"] }'return result
{"success":true,"message":"Successfully joined peers in organization Org1 to the channel:mychannel"}
Summarize
Create a channel:
- Generate object to extract configuration information
clientfrom channel configuration transactionmychannel.tx - Using the organization
admin's private key to sign, this process is equivalent to an endorsement - Encapsulate the request structure (including channel configuration information, signature for configuration information, channelName, txId based on admin), and call
clinet.createChannel()to send the request to the orderer node - In fact, it is called internally
orderer.sendBroadcast()toorder servicebroadcast the transaction, andordererthe configuration transaction is packaged into a block and broadcast to each accounting node, which is recorded in the ledger. (This configuration block is the creation block of the chain corresponding to the created channel)
Join the channel:
- generate
clientobject, generatechannelobject - Get from
orderernodegenesis block(callorderer.sendDeliver()interface ) channelSet event block monitoring for each peer to be added , and judge whether thejoin channelprocess is successful according to whether the specified channel generates a new configuration block- Encapsulate the request structure (including target peers, txId based on the organization admin, genesis block), call the
channel.joinChannel()method, internallypeer.sendProposal()send the transaction proposal to the endorsement node for endorsement, return the endorsement responsePromise
The client sends the endorsed transaction to the orderer service, After sorting, broadcast it to the accounting node, record the configuration block in the ledger, andEventHublisten to the event at this time. - After joining the channel successfully, cancel the block event listener and disconnect all
event hubevent streams.