ratings服务，是一个node.js写的后端，我知之不多，还好，不用改造，直接使用istion的原生sample代码就ok.

本项目的github地址：

https://github.com/aguncn/bookinfo-ratings

项目总体叙述

https://www.jianshu.com/p/cce33f54ed34

主体代码

var http = require('http')
var dispatcher = require('httpdispatcher')

var port = parseInt(process.argv[2])

var userAddedRatings = [] // used to demonstrate POST functionality

var unavailable = false
var healthy = true

if (process.env.SERVICE_VERSION === 'v-unavailable') {
    // make the service unavailable once in 60 seconds
    setInterval(function () {
        unavailable = !unavailable
    }, 60000);
}

if (process.env.SERVICE_VERSION === 'v-unhealthy') {
    // make the service unavailable once in 15 minutes for 15 minutes.
    // 15 minutes is chosen since the Kubernetes's exponential back-off is reset after 10 minutes
    // of successful execution
    // see https://kubernetes.io/docs/concepts/workloads/pods/pod-lifecycle/#restart-policy
    // Kiali shows the last 10 or 30 minutes, so to show the error rate of 50%,
    // it will be required to run the service for 30 minutes, 15 minutes of each state (healthy/unhealthy)
    setInterval(function () {
        healthy = !healthy
        unavailable = !unavailable
    }, 900000);
}

/**
 * We default to using mongodb, if DB_TYPE is not set to mysql.
 */
if (process.env.SERVICE_VERSION === 'v2') {
  if (process.env.DB_TYPE === 'mysql') {
    var mysql = require('mysql')
    var hostName = process.env.MYSQL_DB_HOST
    var portNumber = process.env.MYSQL_DB_PORT
    var username = process.env.MYSQL_DB_USER
    var password = process.env.MYSQL_DB_PASSWORD
  } else {
    var MongoClient = require('mongodb').MongoClient
    var url = process.env.MONGO_DB_URL
  }
}

dispatcher.onPost(/^\/ratings\/[0-9]*/, function (req, res) {
  var productIdStr = req.url.split('/').pop()
  var productId = parseInt(productIdStr)
  var ratings = {}

  if (Number.isNaN(productId)) {
    res.writeHead(400, {'Content-type': 'application/json'})
    res.end(JSON.stringify({error: 'please provide numeric product ID'}))
    return
  }

  try {
    ratings = JSON.parse(req.body)
  } catch (error) {
    res.writeHead(400, {'Content-type': 'application/json'})
    res.end(JSON.stringify({error: 'please provide valid ratings JSON'}))
    return
  }

  if (process.env.SERVICE_VERSION === 'v2') { // the version that is backed by a database
    res.writeHead(501, {'Content-type': 'application/json'})
    res.end(JSON.stringify({error: 'Post not implemented for database backed ratings'}))
  } else { // the version that holds ratings in-memory
    res.writeHead(200, {'Content-type': 'application/json'})
    res.end(JSON.stringify(putLocalReviews(productId, ratings)))
  }
})

dispatcher.onGet(/^\/ratings\/[0-9]*/, function (req, res) {
  var productIdStr = req.url.split('/').pop()
  var productId = parseInt(productIdStr)

  if (Number.isNaN(productId)) {
    res.writeHead(400, {'Content-type': 'application/json'})
    res.end(JSON.stringify({error: 'please provide numeric product ID'}))
  } else if (process.env.SERVICE_VERSION === 'v2') {
    var firstRating = 0
    var secondRating = 0

    if (process.env.DB_TYPE === 'mysql') {
      var connection = mysql.createConnection({
        host: hostName,
        port: portNumber,
        user: username,
        password: password,
        database: 'test'
      })

      connection.connect(function(err) {
          if (err) {
              res.end(JSON.stringify({error: 'could not connect to ratings database'}))
              console.log(err)
              return
          }
          connection.query('SELECT Rating FROM ratings', function (err, results, fields) {
              if (err) {
                  res.writeHead(500, {'Content-type': 'application/json'})
                  res.end(JSON.stringify({error: 'could not perform select'}))
                  console.log(err)
              } else {
                  if (results[0]) {
                      firstRating = results[0].Rating
                  }
                  if (results[1]) {
                      secondRating = results[1].Rating
                  }
                  var result = {
                      id: productId,
                      ratings: {
                          Reviewer1: firstRating,
                          Reviewer2: secondRating
                      }
                  }
                  res.writeHead(200, {'Content-type': 'application/json'})
                  res.end(JSON.stringify(result))
              }
          })
          // close the connection
          connection.end()
      })
    } else {
      MongoClient.connect(url, function (err, db) {
        if (err) {
          res.writeHead(500, {'Content-type': 'application/json'})
          res.end(JSON.stringify({error: 'could not connect to ratings database'}))
        } else {
          db.collection('ratings').find({}).toArray(function (err, data) {
            if (err) {
              res.writeHead(500, {'Content-type': 'application/json'})
              res.end(JSON.stringify({error: 'could not load ratings from database'}))
            } else {
              firstRating = data[0].rating
              secondRating = data[1].rating
              var result = {
                id: productId,
                ratings: {
                  Reviewer1: firstRating,
                  Reviewer2: secondRating
                }
              }
              res.writeHead(200, {'Content-type': 'application/json'})
              res.end(JSON.stringify(result))
            }
            // close DB once done:
            db.close()
          })
        }
      })
    }
  } else {
      if (process.env.SERVICE_VERSION === 'v-faulty') {
        // in half of the cases return error,
        // in another half proceed as usual
        var random = Math.random(); // returns [0,1]
        if (random <= 0.5) {
          getLocalReviewsServiceUnavailable(res)
        } else {
          getLocalReviewsSuccessful(res, productId)
        }
      }
      else if (process.env.SERVICE_VERSION === 'v-delayed') {
        // in half of the cases delay for 7 seconds,
        // in another half proceed as usual
        var random = Math.random(); // returns [0,1]
        if (random <= 0.5) {
          setTimeout(getLocalReviewsSuccessful, 7000, res, productId)
        } else {
          getLocalReviewsSuccessful(res, productId)
        }
      }
      else if (process.env.SERVICE_VERSION === 'v-unavailable' || process.env.SERVICE_VERSION === 'v-unhealthy') {
          if (unavailable) {
              getLocalReviewsServiceUnavailable(res)
          } else {
              getLocalReviewsSuccessful(res, productId)
          }
      }
      else {
        getLocalReviewsSuccessful(res, productId)
      }
  }
})

dispatcher.onGet('/health', function (req, res) {
    if (healthy) {
        res.writeHead(200, {'Content-type': 'application/json'})
        res.end(JSON.stringify({status: 'Ratings is healthy'}))
    } else {
        res.writeHead(500, {'Content-type': 'application/json'})
        res.end(JSON.stringify({status: 'Ratings is not healthy'}))
    }
})

function putLocalReviews (productId, ratings) {
  userAddedRatings[productId] = {
    id: productId,
    ratings: ratings
  }
  return getLocalReviews(productId)
}

function getLocalReviewsSuccessful(res, productId) {
  res.writeHead(200, {'Content-type': 'application/json'})
  res.end(JSON.stringify(getLocalReviews(productId)))
}

function getLocalReviewsServiceUnavailable(res) {
  res.writeHead(503, {'Content-type': 'application/json'})
  res.end(JSON.stringify({error: 'Service unavailable'}))
}

function getLocalReviews (productId) {
  if (typeof userAddedRatings[productId] !== 'undefined') {
      return userAddedRatings[productId]
  }
  return {
    id: productId,
    ratings: {
      'Reviewer1': 5,
      'Reviewer2': 4
    }
  }
}

function handleRequest (request, response) {
  try {
    console.log(request.method + ' ' + request.url)
    dispatcher.dispatch(request, response)
  } catch (err) {
    console.log(err)
  }
}

var server = http.createServer(handleRequest)

server.listen(port, function () {
  console.log('Server listening on: http://0.0.0.0:%s', port)
})

启动命令

node ratings.js 8004

浏览器效果

可以看到，几个绿色的星星就出来了。
大功告成！
还贴了个图，分别指出每个服务显示的内容。

2021-02-02 21_58_23-悬浮球.png