3.2. greeting-service 示例

greeting-service 导入断路器附加组件。greeting -service 通过将这些调用嵌套在断路器对象中来保护对远程名称服务 的调用。

greeting-service 会公开以下端点：

/api/greeting 端点从请求问候的 Web 客户端接收调用。作为处理客户端请求的一部分，/api/greeting 端点会向远程 name-service 中的 /api/name 端点发送调用。对 /api/name 端点的调用被嵌套在断路器对象中。如果远程 name-service 当前可用，/api/greeting 端点会向客户端发送问候端点。但是，如果远程 name-service 当前不可用，/api/greeting 端点会向客户端发送错误响应。
/api/cb-state 端点返回断路器的当前状态。如果设置为 open，则断路器目前阻止请求到达失败的服务。如果此值设为 closed，则断路器目前允许请求访问服务。

以下代码示例演示了如何开发 greeting-service ：

'use strict';
const path = require('path');
const http = require('http');
const express = require('express');
const bodyParser = require('body-parser');

// Import the circuit breaker add-on
const Opossum = require('@redhat/opossum');

const probe = require('kube-probe');
const nameService = require('./lib/name-service-client');

const app = express();
const server = http.createServer(app);

// Add basic health check endpoints
probe(app);

const nameServiceHost = process.env.NAME_SERVICE_HOST || 'http://nodejs-circuit-breaker-redhat-name:8080';

// Set some circuit breaker options
const circuitOptions = {
  timeout: 3000, // If name service takes longer than 0.3 seconds,
                 // trigger a failure
  errorThresholdPercentage: 50, // When 50% of requests fail,
                                // trip the circuit
  resetTimeout: 10000 // After 10 seconds, try again.
};

// Create a new circuit breaker instance and pass the remote nameService
// as its first parameter
const circuit = new Opossum(nameService, circuitOptions);

// Create the app with an initial websocket endpoint
require('./lib/web-socket')(server, circuit);

// Serve index.html from the file system
app.use(express.static(path.join(__dirname, 'public')));
// Expose the license.html at http[s]://[host]:[port]/licences/licenses.html
app.use('/licenses', express.static(path.join(__dirname, 'licenses')));

// Send and receive json
app.use(bodyParser.json());

// Greeting API
app.get('/api/greeting', (request, response) => {
  // Use the circuit breaker’s fire method to execute the call
  // to the name service
  circuit.fire(`${nameServiceHost}/api/name`).then(name => {
    response.send({ content: `Hello, ${name}`, time: new Date() });
  }).catch(console.error);
});

// Circuit breaker state API
app.get('/api/cb-state', (request, response) => {
  response.send({ state: circuit.opened ? 'open' : 'closed' });
});

app.get('/api/name-service-host', (request, response) => {
  response.send({ host: nameServiceHost });
});

module.exports = server;

'use strict';
const path = require('path');
const http = require('http');
const express = require('express');
const bodyParser = require('body-parser');

// Import the circuit breaker add-on
const Opossum = require('@redhat/opossum');

const probe = require('kube-probe');
const nameService = require('./lib/name-service-client');

const app = express();
const server = http.createServer(app);

// Add basic health check endpoints
probe(app);

const nameServiceHost = process.env.NAME_SERVICE_HOST || 'http://nodejs-circuit-breaker-redhat-name:8080';

// Set some circuit breaker options
const circuitOptions = {
  timeout: 3000, // If name service takes longer than 0.3 seconds,
                 // trigger a failure
  errorThresholdPercentage: 50, // When 50% of requests fail,
                                // trip the circuit
  resetTimeout: 10000 // After 10 seconds, try again.
};

// Create a new circuit breaker instance and pass the remote nameService
// as its first parameter
const circuit = new Opossum(nameService, circuitOptions);

// Create the app with an initial websocket endpoint
require('./lib/web-socket')(server, circuit);

// Serve index.html from the file system
app.use(express.static(path.join(__dirname, 'public')));
// Expose the license.html at http[s]://[host]:[port]/licences/licenses.html
app.use('/licenses', express.static(path.join(__dirname, 'licenses')));

// Send and receive json
app.use(bodyParser.json());

// Greeting API
app.get('/api/greeting', (request, response) => {
  // Use the circuit breaker’s fire method to execute the call
  // to the name service
  circuit.fire(`${nameServiceHost}/api/name`).then(name => {
    response.send({ content: `Hello, ${name}`, time: new Date() });
  }).catch(console.error);
});

// Circuit breaker state API
app.get('/api/cb-state', (request, response) => {
  response.send({ state: circuit.opened ? 'open' : 'closed' });
});

app.get('/api/name-service-host', (request, response) => {
  response.send({ host: nameServiceHost });
});

module.exports = server;

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3.2. greeting-service 示例

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