Deploying an Express application with clustering to Elastic Beanstalk - AWS Elastic Beanstalk

Deploying an Express application with clustering to Elastic Beanstalk

This tutorial walks you through deploying a sample application to Elastic Beanstalk using the Elastic Beanstalk Command Line Interface (EB CLI), and then updating the application to use the Express framework, Amazon ElastiCache, and clustering. Clustering enhances your web application's high availability, performance, and security. To learn more about Amazon ElastiCache, go to What Is Amazon ElastiCache for Memcached? in the Amazon ElastiCache for Memcached User Guide.


This example creates AWS resources, which you might be charged for. For more information about AWS pricing, see Some services are part of the AWS Free Usage Tier. If you are a new customer, you can test drive these services for free. See for more information.


This tutorial requires the Node.js language, its package manager called npm, and the Express web application framework. For details on installing these components and setting up your local development environment, see Setting up your Node.js development environment.


For this tutorial, you don't need to install the AWS SDK for Node.js, which is also mentioned in Setting up your Node.js development environment.

The tutorial also requires the Elastic Beanstalk Command Line Interface (EB CLI). For details on installing and configuring the EB CLI, see Install the EB CLI and Configure the EB CLI.

Create an Elastic Beanstalk environment

Configure an EB CLI repository for your application and create an Elastic Beanstalk environment running the Node.js platform.

  1. Create a repository with the eb init command.

    ~/node-express$ eb init --platform node.js --region us-east-2 Application node-express has been created.

    This command creates a configuration file in a folder named .elasticbeanstalk that specifies settings for creating environments for your application, and creates an Elastic Beanstalk application named after the current folder.

  2. Create an environment running a sample application with the eb create command.

    ~/node-express$ eb create --sample node-express-env

    This command creates a load-balanced environment with the default settings for the Node.js platform and the following resources:

    • EC2 instance – An Amazon Elastic Compute Cloud (Amazon EC2) virtual machine configured to run web apps on the platform that you choose.

      Each platform runs a specific set of software, configuration files, and scripts to support a specific language version, framework, web container, or combination of these. Most platforms use either Apache or NGINX as a reverse proxy that sits in front of your web app, forwards requests to it, serves static assets, and generates access and error logs.

    • Instance security group – An Amazon EC2 security group configured to allow inbound traffic on port 80. This resource lets HTTP traffic from the load balancer reach the EC2 instance running your web app. By default, traffic isn't allowed on other ports.

    • Load balancer – An Elastic Load Balancing load balancer configured to distribute requests to the instances running your application. A load balancer also eliminates the need to expose your instances directly to the internet.

    • Load balancer security group – An Amazon EC2 security group configured to allow inbound traffic on port 80. This resource lets HTTP traffic from the internet reach the load balancer. By default, traffic isn't allowed on other ports.

    • Auto Scaling group – An Auto Scaling group configured to replace an instance if it is terminated or becomes unavailable.

    • Amazon S3 bucket – A storage location for your source code, logs, and other artifacts that are created when you use Elastic Beanstalk.

    • Amazon CloudWatch alarms – Two CloudWatch alarms that monitor the load on the instances in your environment and that are triggered if the load is too high or too low. When an alarm is triggered, your Auto Scaling group scales up or down in response.

    • AWS CloudFormation stack – Elastic Beanstalk uses AWS CloudFormation to launch the resources in your environment and propagate configuration changes. The resources are defined in a template that you can view in the AWS CloudFormation console.

    • Domain name – A domain name that routes to your web app in the form

  3. When environment creation completes, use the eb open command to open the environment's URL in the default browser.

    ~/node-express$ eb open

Update the application

Update the sample application in the Elastic Beanstalk environment to use the Express framework.

You can download the final source code from


The prerequisite development environment setup results in an Express project structure in the node-express folder. If you haven't already generated an Express project, run the following command. For more details, see Install Express.

~/node-express$ express && npm install

To update your application to use Express

  1. Rename node-express/app.js to node-express/express-app.js.

    node-express$ mv app.js express-app.js
  2. Update the line var app = express(); in node-express/express-app.js to the following:

    var app = module.exports = express();
  3. On your local computer, create a file named node-express/app.js with the following code.

    var cluster = require('cluster'), app = require('./express-app'); var workers = {}, count = require('os').cpus().length; function spawn(){ var worker = cluster.fork(); workers[] = worker; return worker; } if (cluster.isMaster) { for (var i = 0; i < count; i++) { spawn(); } cluster.on('death', function(worker) { console.log('worker ' + + ' died. spawning a new process...'); delete workers[]; spawn(); }); } else { app.listen(process.env.PORT || 5000); }
  4. Deploy the updated application.

    node-express$ eb deploy
  5. Your environment will be updated after a few minutes. Once the environment is green and ready, refresh the URL to verify it worked. You should see a web page that says "Welcome to Express".

You can access the logs for your EC2 instances running your application. For instructions on accessing your logs, see Viewing logs from Amazon EC2 instances in your Elastic Beanstalk environment.

Next, let's update the Express application to use Amazon ElastiCache.

To update your Express application to use Amazon ElastiCache

  1. On your local computer, create an .ebextensions directory in the top-level directory of your source bundle. In this example, we use node-express/.ebextensions.

  2. Create a configuration file node-express/.ebextensions/elasticache-iam-with-script.config with the following snippet. For more information about the configuration file, see Node.js configuration namespace. This creates an IAM user with the permissions required to discover the elasticache nodes and writes to a file anytime the cache changes. You can also copy the file from For more information on the ElastiCache properties, see Example: ElastiCache.


    YAML relies on consistent indentation. Match the indentation level when replacing content in an example configuration file and ensure that your text editor uses spaces, not tab characters, to indent.

    Resources: MyCacheSecurityGroup: Type: 'AWS::EC2::SecurityGroup' Properties: GroupDescription: "Lock cache down to webserver access only" SecurityGroupIngress: - IpProtocol: tcp FromPort: Fn::GetOptionSetting: OptionName: CachePort DefaultValue: 11211 ToPort: Fn::GetOptionSetting: OptionName: CachePort DefaultValue: 11211 SourceSecurityGroupName: Ref: AWSEBSecurityGroup MyElastiCache: Type: 'AWS::ElastiCache::CacheCluster' Properties: CacheNodeType: Fn::GetOptionSetting: OptionName: CacheNodeType DefaultValue: cache.t2.micro NumCacheNodes: Fn::GetOptionSetting: OptionName: NumCacheNodes DefaultValue: 1 Engine: Fn::GetOptionSetting: OptionName: Engine DefaultValue: redis VpcSecurityGroupIds: - Fn::GetAtt: - MyCacheSecurityGroup - GroupId AWSEBAutoScalingGroup : Metadata : ElastiCacheConfig : CacheName : Ref : MyElastiCache CacheSize : Fn::GetOptionSetting: OptionName : NumCacheNodes DefaultValue: 1 WebServerUser : Type : AWS::IAM::User Properties : Path : "/" Policies: - PolicyName: root PolicyDocument : Statement : - Effect : Allow Action : - cloudformation:DescribeStackResource - cloudformation:ListStackResources - elasticache:DescribeCacheClusters Resource : "*" WebServerKeys : Type : AWS::IAM::AccessKey Properties : UserName : Ref: WebServerUser Outputs: WebsiteURL: Description: sample output only here to show inline string function parsing Value: | http://`{ "Fn::GetAtt" : [ "AWSEBLoadBalancer", "DNSName" ] }` MyElastiCacheName: Description: Name of the elasticache Value: Ref : MyElastiCache NumCacheNodes: Description: Number of cache nodes in MyElastiCache Value: Fn::GetOptionSetting: OptionName : NumCacheNodes DefaultValue: 1 files: "/etc/cfn/cfn-credentials" : content : | AWSAccessKeyId=`{ "Ref" : "WebServerKeys" }` AWSSecretKey=`{ "Fn::GetAtt" : ["WebServerKeys", "SecretAccessKey"] }` mode : "000400" owner : root group : root "/etc/cfn/get-cache-nodes" : content : | # Define environment variables for command line tools export AWS_ELASTICACHE_HOME="/home/ec2-user/elasticache/$(ls /home/ec2-user/elasticache/)" export AWS_CLOUDFORMATION_HOME=/opt/aws/apitools/cfn export PATH=$AWS_CLOUDFORMATION_HOME/bin:$AWS_ELASTICACHE_HOME/bin:$PATH export AWS_CREDENTIAL_FILE=/etc/cfn/cfn-credentials export JAVA_HOME=/usr/lib/jvm/jre # Grab the Cache node names and configure the PHP page aws cloudformation list-stack-resources --stack `{ "Ref" : "AWS::StackName" }` --region `{ "Ref" : "AWS::Region" }` --output text | grep MyElastiCache | awk '{print $4}' | xargs -I {} aws elasticache describe-cache-clusters --cache-cluster-id {} --region `{ "Ref" : "AWS::Region" }` --show-cache-node-info --output text | grep '^ENDPOINT' | awk '{print $2 ":" $3}' > `{ "Fn::GetOptionSetting" : { "OptionName" : "NodeListPath", "DefaultValue" : "/var/www/html/nodelist" } }` mode : "000500" owner : root group : root "/etc/cfn/hooks.d/cfn-cache-change.conf" : "content": | [cfn-cache-size-change] triggers=post.update path=Resources.AWSEBAutoScalingGroup.Metadata.ElastiCacheConfig action=/etc/cfn/get-cache-nodes runas=root sources : "/home/ec2-user/elasticache" : "" commands: make-elasticache-executable: command: chmod -R ugo+x /home/ec2-user/elasticache/*/bin/* packages : "yum" : "aws-apitools-cfn" : [] container_commands: initial_cache_nodes: command: /etc/cfn/get-cache-nodes
  3. On your local computer, create a configuration file node-express/.ebextensions/elasticache_settings.config with the following snippet to configure ElastiCache.

    option_settings: "aws:elasticbeanstalk:customoption": CacheNodeType: cache.t2.micro NumCacheNodes: 1 Engine: memcached NodeListPath: /var/nodelist
  4. On your local computer, replace node-express/express-app.js with the following snippet. This file reads the nodes list from disk (/var/nodelist) and configures express to use memcached as a session store if nodes are present. Your file should look like the following.

    /** * Module dependencies. */ var express = require('express'), session = require('express-session'), bodyParser = require('body-parser'), methodOverride = require('method-override'), cookieParser = require('cookie-parser'), fs = require('fs'), filename = '/var/nodelist', app = module.exports = express(); var MemcachedStore = require('connect-memcached')(session); function setup(cacheNodes) { app.use(bodyParser.raw()); app.use(methodOverride()); if (cacheNodes) { app.use(cookieParser()); console.log('Using memcached store nodes:'); console.log(cacheNodes); app.use(session({ secret: 'your secret here', resave: false, saveUninitialized: false, store: new MemcachedStore({'hosts': cacheNodes}) })); } else { console.log('Not using memcached store.'); app.use(cookieParser('your secret here')); app.use(session()); } app.get('/', function(req, resp){ if (req.session.views) { req.session.views++ resp.setHeader('Content-Type', 'text/html') resp.write('Views: ' + req.session.views) resp.end() } else { req.session.views = 1 resp.end('Refresh the page!') } }); if (!module.parent) { console.log('Running express without cluster.'); app.listen(process.env.PORT || 5000); } } // Load elasticache configuration. fs.readFile(filename, 'UTF8', function(err, data) { if (err) throw err; var cacheNodes = []; if (data) { var lines = data.split('\n'); for (var i = 0 ; i < lines.length ; i++) { if (lines[i].length > 0) { cacheNodes.push(lines[i]); } } } setup(cacheNodes); });
  5. On your local computer, update node-express/package.json to add four dependencies.

    { "name": "node-express", "version": "0.0.0", "private": true, "scripts": { "start": "node ./bin/www" }, "dependencies": { "cookie-parser": "*", "debug": "~2.6.9", "express": "~4.16.0", "http-errors": "~1.6.2", "jade": "~1.11.0", "morgan": "~1.9.0", "connect-memcached": "*", "express-session": "*", "body-parser": "*", "method-override": "*" } }
  6. Deploy the updated application.

    node-express$ eb deploy
  7. Your environment will be updated after a few minutes. After your environment is green and ready, verify that the code worked.

    1. Check the Amazon CloudWatch console to view your ElastiCache metrics. To view your ElastiCache metrics, select Metrics in the left pane, and then search for CurrItems. Select ElastiCache > Cache Node Metrics, and then select your cache node to view the number of items in the cache.


      Make sure you are looking at the same region that you deployed your application to.

      If you copy and paste your application URL into another web browser and refresh the page, you should see your CurrItem count go up after 5 minutes.

    2. Take a snapshot of your logs. For more information about retrieving logs, see Viewing logs from Amazon EC2 instances in your Elastic Beanstalk environment.

    3. Check the file /var/log/nodejs/nodejs.log in the log bundle. You should see something similar to the following:

      Using memcached store nodes: [ '' ]

Clean up

If you no longer want to run your application, you can clean up by terminating your environment and deleting your application.

Use the eb terminate command to terminate your environment and the eb delete command to delete your application.

To terminate your environment

From the directory where you created your local repository, run eb terminate.

$ eb terminate

This process can take a few minutes. Elastic Beanstalk displays a message once the environment is successfully terminated.