AWS Elastic Beanstalk
Elastic Beanstalk is a service for deploying and scaling web applications. You simply upload your code and Elastic Beanstalk automatically handles the deployment, from capacity provisioning, load balancing, auto-scaling to application health monitoring. You still retain full control of the underlying AWS resources.
There is not additional charge for Elastic Beanstalk, you pay only for the AWS resources needed to store and run your applications.
Deployment Policies
Elastic Beanstalk supports several options for processing deployment.
All at Once
Deploys the new version to all instances simultaneously. All of your instances are out of service while the deployment takes place. You will experience an outage while the deployment is taking place.
Rolling
Deploys the new version in batches. Each batch of instances is taken out of service while the deployment takes place. Your environment capacity will be reduced by the number of instances in a batch while the deployment takes place. This isn't ideal for performance sensitive systems.
Rolling with Additional Batch
Launches an additional batch of instances and deploys the new version in batches. The deployment method maintains full capacity during the deployment process.
Immutable
Deploys the new version to a fresh group of instances in their own new auto scaling group. When the new instances pass their health checks, they are moved to your existing auto scaling group; and finally the old instances are terminated. This maintains full capacity during the deployment process. This is the preferred option for mission critical production systems.
Configuration
You can customize your Elastic Beanstalk environment using configuration
files. You can define requirements, create Linux users and groups, run shell
commands, specify services to enable, etc. These files are written in YAML or
JSON. They have a filename of your choice but must have a .config extension
and be saved inside a folder called .ebextensions. This folder must be
located in the top level directory of your application source code bundle.
RDS and Elastic Beanstalk
You may launch an RDS instance from within Elastic Beanstalk. This can be done through the console. This will place the instance within your Elastic Beanstalk environment, coupling the RDS instance with your EC2 instances.
You can also launch an RDS instance outside of Elastic Beanstalk. For production environments, this is preferred. In this case you'd launch the RDS instance from the RDS section of the console then specify the database in your Elastic Beanstalk configuration file. This option gives you a lot more flexibility, allows you to connect multiple environments to the same database, provides a wider choice of database types, and allows you to tear down your application environment without affecting your database instance.