aws elastic beanstalk customization

Customization of the Elastic Beanstalk environment is done in a few different ways depending on the Amazon Linux version (1 or 2).

For pre-Amazon Linux 2 environments

• configuration file - define packages to install, create linux users and groups,

run shell commands, enable services, and configure load balancers

• YAML or JSON - these files are written in YAML or JSON format
• Constraints - the file must have a .config extension and be inside a folder

called .ebextensions in the top-level directory of your application source code bundle

Example - myhealthcheckurl.config:

{
    "option_settings": [
        {
            "namespace": "aws:elasticbeanstalk:application",
            "option_name": "My application healthcheck URL",
            "value": "/healthcheck"
        }
    ]
}

The above configures an application health check URL that will be used by a load balancer, which will make an HTTP request to the specified path to check if the instances are healthy.

Amazon Linux 2 environments

Use the Buildfile, Procfile and platform hooks whenever you need to do additional configuration during the application building period.

Buildfile

• Great for commands that run for short periods and then exit upon task completion.
  • Good examples are shell scripts
• Root directory - create your Buildfile in the root directory of your application source
• Format - <process_name>:<command>
  • Example: make: ./build.sh <- reference a script in your source code bundle

Procfile

• Used for long-running processes (like commands to start and run the application)
• Root directory - create a file called Procfile in the root directory of your application source
• Elastic Beanstalk expects processes defined in the Procfile to run continuously
  • Any processes that terminate will be monitored and restarted
• Format - Same as the Buildfile, using key:value pairs
  • <process_name>: <command>

Example:

web: bin/myserver
app: bin/myapp

Platform hooks

• This is for custom scripts or executable files that you would like to be run at

a chosen stage of the EC2 provisioning process.

• Stored in dedicated directories in your application source code
• The build directories are:
  • .platform/hooks/prebuild - files that you want to run before it builds, sets up,
  and configures the application and web server
  • .platform/hooks/predeploy - files that you want to run after it sets up and
  configures the application and web server but before it deploys them to the final runtime location
  • .platform/hooks/postdeploy - files that run after Elastic Beanstalk has deployed
  the application
• Each stage is optional, only include the directories that are required

Exam tips

• Amazon Linux 1 can modify the Elastic Beanstalk environment using the .ebextensions folder
  • Files need a .config extension
• Amazon Linux 2:
  • Buildfile - for scripts that exist upon completion
  • Procfile - used in long running processes (like starting the app)
  • Platform hooks - several stages offering the ability to customize at each stage