feat: enable retry for addItem and add more debug info

Signed-off-by: Raymond Feng <[email protected]>

package.json

@@ -60,6 +60,7 @@
     "@loopback/repository": "^0.16.5",
     "@loopback/rest": "^0.22.2",
     "bcryptjs": "^2.4.3",
+    "debug": "^4.0.1",
     "isemail": "^3.1.3",
     "loopback-connector-kv-redis": "^3.0.0",
     "loopback-connector-mongodb": "^3.7.1"
@@ -71,6 +72,7 @@
     "@loopback/build": "^0.7.3",
     "@loopback/testlab": "^0.12.2",
     "@types/bcryptjs": "^2.4.1",
+    "@types/debug": "0.0.30",
     "@types/mocha": "^5.0.0",
     "@types/node": "^10.9.4",
     "commitizen": "^2.10.1",

src/controllers/shopping-cart.controller.ts

@@ -15,6 +15,9 @@ import {
 import {repository} from '@loopback/repository';
 import {ShoppingCartRepository} from '../repositories';
 import {ShoppingCart, ShoppingCartItem} from '../models';
+import * as debugFactory from 'debug';
+const debug = debugFactory('loopback:example:shopping');
+import {retry} from '../utils/retry';
 
 /**
  * Controller for shopping cart
@@ -35,6 +38,7 @@ export class ShoppingCartController {
     @param.path.string('userId') userId: string,
     @requestBody({description: 'shopping cart'}) cart: ShoppingCart,
   ) {
+    debug('Create shopping cart %s: %j', userId, cart);
     if (userId !== cart.userId) {
       throw new HttpErrors.BadRequest(
         `User id does not match: ${userId} !== ${cart.userId}`,
@@ -49,7 +53,9 @@ export class ShoppingCartController {
    */
   @get('/shoppingCarts/{userId}')
   async get(@param.path.string('userId') userId: string) {
+    debug('Get shopping cart %s', userId);
     const cart = await this.shoppingCartRepository.get(userId);
+    debug('Shopping cart %s: %j', userId, cart);
     if (cart == null) {
       throw new HttpErrors.NotFound(
         `Shopping cart not found for user: ${userId}`,
@@ -65,6 +71,7 @@ export class ShoppingCartController {
    */
   @del('/shoppingCarts/{userId}')
   async remove(@param.path.string('userId') userId: string) {
+    debug('Remove shopping cart %s', userId);
     await this.shoppingCartRepository.delete(userId);
   }
 
@@ -78,6 +85,14 @@ export class ShoppingCartController {
     @param.path.string('userId') userId: string,
     @requestBody({description: 'shopping cart item'}) item: ShoppingCartItem,
   ) {
-    await this.shoppingCartRepository.addItem(userId, item);
+    debug('Add item %j to shopping cart %s', item, userId);
+    return retry<ShoppingCart>(
+      {
+        run: () => this.shoppingCartRepository.addItem(userId, item),
+        description: `update the shopping cart for '${userId}'`,
+      },
+      10,
+      100,
+    );
   }
 }

src/repositories/shopping-cart.repository.ts

@@ -42,6 +42,9 @@ export class ShoppingCartRepository extends DefaultKeyValueRepository<
    * @param userId User id
    * @param check A function that checks the current value and produces a new
    * value. It returns `null` to abort.
+   *
+   * @returns A promise of the updated ShoppingCart instance or `null` if the
+   * transaction fails. See https://github.com/NodeRedis/node_redis#optimistic-locks
    */
   async checkAndSet(
     userId: string,
@@ -66,7 +69,7 @@ export class ShoppingCartRepository extends DefaultKeyValueRepository<
     if (!cart) return null;
     await execute('MULTI', []);
     await this.set(userId, cart);
-    await execute('EXEC', []);
-    return cart;
+    const result = await execute('EXEC', []);
+    return result == null ? null : cart;
   }
 }