initial load

.gitignore

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+.*.swp
+.DS_Store
+

cart/Dockerfile

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+FROM node:8
+
+EXPOSE 8080
+
+WORKDIR /opt/server
+
+COPY package.json /opt/server/
+
+RUN npm install
+
+COPY server.js /opt/server/
+
+CMD ["node", "server.js"]
+

cart/package.json

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+{
+  "name": "catalogue",
+  "version": "1.0.0",
+  "description": "product catalogue REST API",
+  "main": "server.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "SteveW",
+  "license": "Apache-2.0",
+  "dependencies": {
+      "body-parser": "^1.18.1",
+      "express": "^4.15.4",
+      "redis": "^2.8.0",
+      "request": "^2.83.0",
+      "instana-nodejs-sensor": "^1.28.0"
+  }
+}

cart/server.js

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+const instana = require('instana-nodejs-sensor');
+const redis = require('redis');
+const request = require('request');
+const bodyParser = require('body-parser');
+const express = require('express');
+
+// init tracing
+instana({
+    tracing: {
+        enabled: true
+    }
+});
+
+var redisConnected = false;
+
+const app = express();
+
+app.use((req, res, next) => {
+    res.set('Timing-Allow-Origin', '*');
+    res.set('Access-Control-Allow-Origin', '*');
+    next();
+});
+
+app.use(bodyParser.urlencoded({ extended: true }));
+app.use(bodyParser.json());
+
+app.get('/health', (req, res) => {
+    var stat = {
+        app: 'OK',
+        redis: redisConnected
+    };
+    res.json(stat);
+});
+
+
+// get cart with id
+app.get('/cart/:id', (req, res) => {
+    redisClient.get(req.params.id, (err, data) => {
+        if(err) {
+            console.log('ERROR', err);
+            res.status(500).send(err);
+        } else {
+            if(data == null) {
+                res.status(404).send('cart not found');
+            } else {
+                res.set('Content-Type', 'application/json');
+                res.send(data);
+            }
+        }
+    });
+});
+
+// update/create cart
+app.get('/add/:id/:sku/:qty', (req, res) => {
+    // check quantity
+    var qty = parseInt(req.params.qty);
+    if(isNaN(qty)) {
+        res.status(400).send('quantity must be a number');
+        return;
+    } else if(qty < 1) {
+        res.status(400).send('negative quantity not allowed');
+        return;
+    }
+
+    // look up product details
+    getProduct(req.params.sku).then((product) => {
+        console.log('got product', product);
+        // is the product in stock?
+        if(product.instock == 0) {
+            res.status(404).send('out of stock');
+            return;
+        }
+        // does the cart already exist?
+        redisClient.get(req.params.id, (err, data) => {
+            if(err) {
+                console.log('ERROR', err);
+                res.status(500).send(err);
+            } else {
+                var cart;
+                if(data == null) {
+                    // create new cart
+                    cart = {
+                        total: 0,
+                        tax: 0,
+                        items: []
+                    };
+                } else {
+                    cart = JSON.parse(data);
+                }
+                console.log('got cart', cart);
+                // add sku to cart
+                var item = {
+                    qty: qty,
+                    sku: req.params.sku,
+                    name: product.name,
+                    price: product.price,
+                    subtotal: qty * product.price
+                };
+                var list = mergeList(cart.items, item, qty);
+                cart.items = list;
+                cart.total = calcTotal(cart.items);
+                // work out tax @ 20%
+                cart.tax = (cart.total - (cart.total / 1.2)).toFixed(2);
+
+                // save the new cart
+                saveCart(req.params.id, cart);
+                res.json(cart);
+            }
+        });
+    }).catch((err) => {
+        res.status(500).send(err);
+    });
+});
+
+// update quantity - remove item when qty == 0
+app.get('/update/:id/:sku/:qty', (req, res) => {
+    // check quantity
+    var qty = parseInt(req.params.qty);
+    if(isNaN(qty)) {
+        res.status(400).send('quantity must be a number');
+        return;
+    }
+
+    // get the cart
+    redisClient.get(req.params.id, (err, data) => {
+        if(err) {
+            console.log('ERROR', err);
+            res.status(500).send(err);
+        } else {
+            if(data == null) {
+                res.status(404).send('cart not found');
+            } else {
+                var cart = JSON.parse(data);
+                var idx;
+                var len = cart.items.length;
+                for(idx = 0; idx < len; idx++) {
+                    if(cart.items[idx].sku == req.params.sku) {
+                        break;
+                    }
+                }
+                if(idx == len) {
+                    // not in list
+                    res.status(404).send('not in cart');
+                } else {
+                    if(qty == 0) {
+                        cart.items.splice(idx, 1);
+                    } else {
+                        cart.items[idx].qty = qty;
+                        cart.items[idx].subtotal = cart.items[idx].price * qty;
+                    }
+                    cart.total = calcTotal(cart.items);
+                    // work out tax @ 20%
+                    cart.tax = (cart.total - (cart.total / 1.2)).toFixed(2);
+                    saveCart(req.params.id, cart);
+                    res.json(cart);
+                }
+            }
+        }
+    });
+});
+
+function mergeList(list, product, qty) {
+    var inlist = false;
+    // loop through looking for sku
+    var idx;
+    var len = list.length;
+    for(idx = 0; idx < len; idx++) {
+        if(list[idx].sku == product.sku) {
+            inlist = true;
+            break;
+        }
+    }
+
+    if(inlist) {
+        list[idx].qty += qty;
+        list[idx].subtotal = list[idx].price * list[idx].qty;
+    } else {
+        list.push(product);
+    }
+
+    return list;
+}
+
+function calcTotal(list) {
+    var total = 0;
+    for(var idx = 0, len = list.length; idx < len; idx++) {
+        total += list[idx].subtotal;
+    }
+
+    return total;
+}
+
+function getProduct(sku) {
+    return new Promise((resolve, reject) => {
+        request('http://catalogue:8080/product/' + sku, (err, res, body) => {
+            if(err) {
+                reject(err);
+            } else if(res.statusCode != 200) {
+                reject(res.statusCode);
+            } else {
+                // return object - body is a string
+                resolve(JSON.parse(body));
+            }
+        });
+    });
+}
+
+function saveCart(id, cart) {
+    console.log('saving cart', cart);
+    redisClient.setex(id, 3600, JSON.stringify(cart), (err, data) => {
+        if(err) {
+            console.log('saveCart ERROR', err);
+        }
+    });
+}
+
+// connect to Redis
+var redisClient = redis.createClient({
+    host: 'redis'
+});
+
+redisClient.on('error', (e) => {
+    console.log('Redis ERROR', e);
+});
+redisClient.on('ready', (r) => {
+    console.log('Redis READY', r);
+    redisConnected = true;
+});
+
+// fire it up!
+const port = process.env.CART_SERVER_PORT || '8080';
+app.listen(port, () => {
+    console.log('Started on port', port);
+});

catalogue/Dockerfile

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+FROM node:8
+
+EXPOSE 8080
+
+WORKDIR /opt/server
+
+COPY package.json /opt/server/
+
+RUN npm install
+
+COPY server.js /opt/server/
+
+CMD ["node", "server.js"]
+

catalogue/package.json

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+{
+  "name": "catalogue",
+  "version": "1.0.0",
+  "description": "product catalogue REST API",
+  "main": "server.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "SteveW",
+  "license": "Apache-2.0",
+  "dependencies": {
+      "body-parser": "^1.18.1",
+      "express": "^4.15.4",
+      "mongodb": "^2.2.33",
+      "instana-nodejs-sensor": "^1.28.0"
+  }
+}