Elastic Beanstalk
Elastic Beanstalk (Platform as a Service)
Application
At the Base level is Application. Container of environments, versions, environment configs.
Environment
An environment of a given tier(web server / worker batch jobs).
Application Version
Distinct Version of application, eg: ApplicationName-V1.jar).
- In the background it uses CloudFormation.
- Supports Blue-Green Deployments natively.
- Recommended to deploy databases outside of Beanstalk as the data can be deleted when the environment is removed.
- eb-extensions folder inside Application Versions to allow config info to connect to SQS or other etc.
AWS Elastic Beanstalk provides several options for how deployments are processed, including deployment
policies (All at once, Rolling, Rolling with additional batch, and Immutable) and options that let you
configure batch size and health check behavior during deployments.
By default, your environment uses :
- Rolling deployments if you created it with the console or EB CLI, or
- All-at-once deployments if you created it with a different client (API, SDK, or AWS CLI).
Beanstalk takes care :
- Provisioning
- Capacity Provisioning
- Autoscaling
- Load-balancing
- Application Health Monitoring.
To alter application settings and software configurations that run on the EC2 instances created by Elastic Beanstalk, configuration files can be added to a specifically named folder in the application code versions, which are applied during the deployment process.
To use configuration files, a folder named .ebextensions is created at the top level of the project's source code. Then files with the extension .config are added to specify options.
Configuration Presets:
- Low cost,
- HA,
- Custom configuration
Elastic Beanstalk Creation of RDS DB Instances
Elastic Beanstalk takes care of creating the RDS databased instances automatically,
but since the database hostname is not known until this environment is created, this
may leave you asking, "How will the application know "what to use to connect to the database?"
Elastic Beanstalk takes care of this by providing access to such information through
environment properties. For RDS, it exposes all of the necessary connection parameter
information to the application as environment properties. These properties are passed
in the application when the Elastic Beanstalk creates the environment.
So, the database hostname, DB name, the port, the username, and password can all be
accessed through environment variables.
Rolling Deployments
With rolling deployments, Elastic Beanstalk splits the environment's EC2 instances into batches and deploys the new version of the application to one batch at a time, leaving the rest of the instances in the environment running the old version of the application. During a rolling deployment, some instances serve requests with the old version of the application, while instances in completed batches serve other requests with the new version.