Adding an extra learning challenge

README.md

@@ -454,7 +454,25 @@ And you can get logs for the service using `copilot svc logs`
 
 Bonus Points: Try deploying another copy of the load test job, but this time make the load test target the AWS App Runner deployment.
 
-## Step Eight: Tear everything down
+## Extra Learning
+
+If you are down for an extra challenge, then try deploying the application in the `hit-counter` folder.
+This containerized application implements a simple hit counter that counts the number of requests the
+application receives. It stores its state inside of a DynamoDB table.
+
+Hint: You can use the `copilot storage init` command to automatically create a DynamoDB table for the application
+prior to deploying it using AWS Copilot. The application is expecting:
+
+```
+  Table Name: hits
+  Table primary key: counter
+  Table primary key type: string
+```
+
+Copilot will automatically take care of creating the permissions between the application and the table. See if you
+can deploy this more complicated application!
+
+## Final Step: Tear everything down
 
 If you want to clean everything up you can go back to Cloud9 and run:
 

hit-counter/.dockerignore

@@ -0,0 +1 @@
+node_modules

hit-counter/Dockerfile

@@ -0,0 +1,10 @@
+FROM public.ecr.aws/docker/library/node:18 AS build
+WORKDIR /srv
+ADD package.json .
+RUN npm install
+
+FROM public.ecr.aws/docker/library/node:18-slim
+COPY --from=build /srv .
+ADD . .
+EXPOSE 80
+CMD ["node", "index.js"]

hit-counter/index.js

@@ -0,0 +1,49 @@
+var aws = require('aws-sdk');
+const express = require('express');
+const app = express();
+const table = process.env.HITS_NAME;
+const PORT = 80; // The port to listen on
+
+const dynamodb = new aws.DynamoDB.DocumentClient();
+
+if (!table) {
+  console.error('Warning: The HITS_NAME environment variable needs to be set with the name of a DynamoDB table');
+}
+
+const os = require('os');
+const hostname = os.hostname();
+
+app.get('*', function (req, res) {
+  if (!table) {
+    console.error('Error: The HITS_NAME environment variable needs to be set with the name of a DynamoDB table');
+    return res.send('Error: The HITS_NAME environment variable needs to be set with the name of a DynamoDB table');
+  }
+
+  dynamodb.update({
+    TableName: table,
+    Key: {
+      counter: 'global',
+    },
+    UpdateExpression: 'SET hitCount = if_not_exists(hitCount, :zero) + :value',
+    ExpressionAttributeValues: {
+      ':zero': 0,
+      ':value': 1,
+    },
+    ReturnValues: 'ALL_NEW'
+  }, function (err, results) {
+    if (err) {
+      return res.send(err);
+    } else {
+      var hitCount = results.Attributes.hitCount;
+      res.send(`There have been ${hitCount} hits. (${hostname})`);
+    }
+  });
+});
+
+app.listen(PORT, () => console.log(`Listening on port ${PORT}!`));
+
+// This causes the process to respond to "docker stop" faster
+process.on('SIGTERM', function () {
+  console.log('Received SIGTERM, shutting down');
+  app.close();
+});