Node.js 当mongoose模型被实例化时，应用程序速度会减慢

作为学习的一部分，我正在开发购物车。我面临的问题是，无论何时将项目添加到购物车，装载时间都会显著增加（下面的基准测试），当购物车为空时，装载时间会恢复正常

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基准
当购物车为空时：装载时间小于1s

GET / 304 154.242 ms - -
GET /stylesheets/bootstrap.css 304 81.079 ms - -
GET /stylesheets/style.css 304 79.363 ms - -
GET /fonts/font-awesome/css/font-awesome.min.css 304 84.550 ms - -
GET /product/58c179fb2148643f5865d4ca/image 304 86.347 ms - -
GET /product/58c151f95b18373990f1c714/image 304 113.943 ms - -
GET /product/58c17c9e32f18e2eb86fbd44/image 304 120.220 ms - -
GET /product/58c17ced9697ec3e44bba381/image 304 82.483 ms - -
GET /product/58c210c5e5ca5b2298724b77/image 304 83.583 ms - -
GET /fonts/font-awesome/fonts/fontawesome-webfont.woff2?v=4.7.0 304 15.826 ms - -

当物品在购物车中时：装载时间平均为10秒

GET / 304 3441.581 ms - -
GET /stylesheets/bootstrap.css 304 17074.679 ms - -
GET /stylesheets/style.css 304 18020.767 ms - -
GET /fonts/font-awesome/css/font-awesome.min.css 304 19067.181 ms - -
GET /product/58c17c9e32f18e2eb86fbd44/image 304 13065.619 ms - -
GET /product/58c151f95b18373990f1c714/image 304 15917.767 ms - -
GET /product/58c179fb2148643f5865d4ca/image 304 22550.998 ms - -
GET /product/58c17ced9697ec3e44bba381/image 304 23376.352 ms - -
GET /product/58c210c5e5ca5b2298724b77/image 304 20143.963 ms - -
GET /fonts/font-awesome/fonts/fontawesome-webfont.woff2?v=4.7.0 304 4767.430 ms - -

---

下面的代码是最低限度的实现：

models/product.js

var schema = new Schema({
  image: {data: Buffer, contentType: String},
  title: {type: String, required: true},
  description: {type: String, required: true},
  price: {type: Number, required: true}
});
module.exports = mongoose.model('Product', schema);

module.exports = function Cart(oldCart) {
// associative array
  this.items = oldCart.items || {};

  this.add = function(product) {
// if item is not in cart => assign argument to product properties
    if(!this.items[product._id])
      this.items[product._id] = {product: product, qty: 0, price: 0};
// if item is already in cart => just increase the qty and price
    this.items[product._id].qty++;
    this.items[product._id].price += product.price;
  }


  this.removeItems = function (productId) {
    delete this.items[productId];
  }
}

router.get('/add-to-cart/:id', function (req, res, next) {
  var productId = req.params.id;
// req.session from: express-session module
  var cart = new Cart(req.session.cart);

  Product.findById(productId, function (err, product) {

    cart.add(product);

    req.session.cart = cart;
    res.redirect('/');
  });
});


router.get('/remove/:id', function (req, res, next) {
  var productId = req.params.id;
  var cart = new Cart(req.session.cart);

  cart.removeItems(productId);

  req.session.cart = cart;
  res.redirect('/cart');
});

模型/cart.js

var schema = new Schema({
  image: {data: Buffer, contentType: String},
  title: {type: String, required: true},
  description: {type: String, required: true},
  price: {type: Number, required: true}
});
module.exports = mongoose.model('Product', schema);

module.exports = function Cart(oldCart) {
// associative array
  this.items = oldCart.items || {};

  this.add = function(product) {
// if item is not in cart => assign argument to product properties
    if(!this.items[product._id])
      this.items[product._id] = {product: product, qty: 0, price: 0};
// if item is already in cart => just increase the qty and price
    this.items[product._id].qty++;
    this.items[product._id].price += product.price;
  }


  this.removeItems = function (productId) {
    delete this.items[productId];
  }
}

router.get('/add-to-cart/:id', function (req, res, next) {
  var productId = req.params.id;
// req.session from: express-session module
  var cart = new Cart(req.session.cart);

  Product.findById(productId, function (err, product) {

    cart.add(product);

    req.session.cart = cart;
    res.redirect('/');
  });
});


router.get('/remove/:id', function (req, res, next) {
  var productId = req.params.id;
  var cart = new Cart(req.session.cart);

  cart.removeItems(productId);

  req.session.cart = cart;
  res.redirect('/cart');
});

路线/cart.js

var schema = new Schema({
  image: {data: Buffer, contentType: String},
  title: {type: String, required: true},
  description: {type: String, required: true},
  price: {type: Number, required: true}
});
module.exports = mongoose.model('Product', schema);

module.exports = function Cart(oldCart) {
// associative array
  this.items = oldCart.items || {};

  this.add = function(product) {
// if item is not in cart => assign argument to product properties
    if(!this.items[product._id])
      this.items[product._id] = {product: product, qty: 0, price: 0};
// if item is already in cart => just increase the qty and price
    this.items[product._id].qty++;
    this.items[product._id].price += product.price;
  }


  this.removeItems = function (productId) {
    delete this.items[productId];
  }
}

router.get('/add-to-cart/:id', function (req, res, next) {
  var productId = req.params.id;
// req.session from: express-session module
  var cart = new Cart(req.session.cart);

  Product.findById(productId, function (err, product) {

    cart.add(product);

    req.session.cart = cart;
    res.redirect('/');
  });
});


router.get('/remove/:id', function (req, res, next) {
  var productId = req.params.id;
  var cart = new Cart(req.session.cart);

  cart.removeItems(productId);

  req.session.cart = cart;
  res.redirect('/cart');
});

---

尝试：
我曾试图将不需要的对象设置为

null

，我猜想内存可能会泄漏到某个地方。问题仍然存在

---

---

产品图像不超过16MB，所以我将它们作为二进制数据存储在mongo中。我真的不知道加载时间是如何增加的。感谢您的每一个建议。我愿意编辑这篇文章以提供更多信息。

您的问题可能是由于您在按id查找产品时加载了图像缓冲区造成的

...
image: {data: Buffer, contentType: String},
...

由于添加到购物车时不需要这些信息，请在find by id上告诉mongo不要返回该字段

Product.findById(productId).select('-image').exec(function(){})

然后，当有人看到他们的购物车时，可能会再次调用检索图像

编辑：

确保在检索图像时也在缓存图像。这将确保您的服务器能够快速提供图像

你看，它应该能满足你的需要

在客户端，您可能需要确保您的图像也被缓存在那里（这可能已经自动发生）

编辑2: 我相信像这样的东西应该对你的心尖痛有效。你可能需要稍微调整一下

var apicache = require('apicache');
let cache = apicache.middleware;

...

app.get('/image/:productId', cache('1 hour'), function(req, response) {
  var buffer = ""; //get the image buffer from mongo

  //return to client
  response.writeHead(200, {
    'Content-Type': 'image/jpeg' //Or whatever filetype its supposed to be... png, gif etc
  });
  response.write(buffer);
  response.end();
});

...

---

我尝试了你的建议，它解决了我的问题。我的另一个疑问是，如果是因为加载了缓冲区，那么只有涉及购物车的请求/代码（即添加到卡和视图购物车）才会减慢速度。然而，问题是，每当购物车中有物品时，整个应用程序的加载时间就会增加，包括主页、登录、注册等。@NERDYLIZARD我认为整个应用程序的速度很慢，因为您将图像缓冲区存储在会话变量中，每次应用程序重新加载时，都必须再次加载整个图像缓冲区。只是一个想法。可能是错的。也许在确认你没有在那里存储数据后，可以尝试清除你的会话。@NERDYLIZARD哇哇。我现在明白你的意思了。也许可以看看是否有办法为客户端缓存该图像信息，这样他们只需要加载一次图像。你的服务器端抓取图像的路线，可以做缓存，我看了一下文档。我应该把缓存放在哪里？@NERDYLIZARD如果你把这个答案标记为解决方案，会非常感激的如果你需要其他帮助。让我知道！