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Elastic Beanstalk - EB

  • It is a platform as a service (PaaS) product in AWS, meaning the vendors handles all the infrastructure, we provide the code only
  • EB is a developer focused product, providing managed application environments
  • At a high level, developers provide code and EB handles infrastructure
  • EB is fully customizable - uses AWS products under the covers provisioned with CloudFormation
  • Using EB requires application support, there are things to do as a developer. This does not come for free, and it not something a non-technical end-user could do

Platforms

  • EB is capable of accepting code in many languages known as platforms
  • EB has support for built-in languages, Docker and custom platforms
  • Built-in supported languages: Go, Java SE, Java Tomcat, .NET Core (Linux) and .NET (Windows), Node.JS, PHP, Python, Ruby
  • Docker options: single container docker and multi container docker (ECS)
  • Pre-configured Docker: way to provide runtimes which are not yet natively supported, example Java with Glassfish
  • We can create our own custom platform using packer which can be used with Beanstalk

EB Terminology

  • Elastic Beanstalk Application: is a collection of things relating to an application - a container/folder
  • Application Version: specific labeled version of deployable code for an application. The source bundle is stored in S3
  • Environments: are containers of infrastructure and configuration for a specific version
  • Each environment is either a web server tier or a worker tier. The web server tier is designed to communicate with the end-users. The worker tier is designed to process work from the web tiers. Web server tier and worker tier communicate using SQS queues
  • Each environment is running a specific version at any given time
  • Each environment has its own CNAME, a CNAME SWAP can be done to exchange to environment DNS

Deployment Policies

  • All at once:
    • Deploy to all instances at once
    • It is quick and simple, but it will cause a brief outage
    • Recommended for testing and development environments
  • Rolling:
    • Application code is deployed in rolling batches
    • It is safer, since the deployment will continue only if the previous batch is healthy
    • The application will encounter loss in capacity
  • Rolling with additional batch:
    • Same as rolling deployment, with the addition of having a new batch in order to maintain capacity during the deployment process
    • Recommended for production environment with real load
  • Immutable:
    • New temporary ASG is created with the newer version of the application
    • Once the validation is complete, the older stack is removed
    • It is easier to roll back
  • Traffic Splitting:
    • Fresh instances are created in a similar way as in case of immutable deployment
    • Traffic will be split between the older and the newer version
    • Allows to perform A/B testing on the application
    • It does not have capacity drops, but it will come with an additional cost
  • Blue/Green:
    • Not automatically supported by EB
    • Requires manual CNAME swap between 2 environments
    • Provides full control in terms of when we would want to switch to the new environment

EB and RDS

  • In order to access an RDS instance from EB we can create an RDS instance within an EB environment
  • If we do this, the RDS is linked to the environment
  • If we delete the environment, the database will also be deleted
  • If we link a database to an environment, we get access to the following environment properties:
    • RDS_HOSTNAME
    • RDS_PORT
    • RDS_DB_NAME
    • RDS_USERNAME
    • RDS_PASSWORD
  • Other alternative is to create the RDS instance outside of the EB
  • The environment properties above are not automatically provided in this case, we can create them manually
  • With this method the RDS lifecycle is not tied to the EB environment
  • Decoupling an existing RDS from an EB environment:
    1. Create a Snapshot
    2. Enable Delete Protection
    3. Create a new EB environment with the same app version
    4. Ensure new environment can connect to the DB
    5. Swap environment (CNAME or DNS)
    6. Terminate the old environment - this will try to terminate the RDS instance
    7. Locate the DELETE_FAILED stack in CloudFormation console, manually delete the stack and pick to retain stuck resources

Customizing via .ebextensions

  • We can include directive to customize EB environments using .ebextensions folder
  • Anything added in this folder as YAML or JSON and it ends in .config is regarded to be an EB extension configuration file. These configurations files are CloudFormation definitions, and they are used to influence the EB environment itself to change its configuration or provision new resources
  • EB will use CFN to create additional resources within the environment specified in the .config files
  • These files can have the following sections:
    • option_settings: allows us to set options of resources (example: use NLB instead of ALB for the EB environment)
    • Resources: allows us to create new resources using CFN (example: configure OpenSearch cluster for our environment)
    • Additional sections: packages, sources, files, users, groups, commands, container_commands and services

EB with HTTPS

  • To use HTTPS with EB we need to apply an SSL certificate to the load balancer
  • We can do this using the EB console or we can use the .ebextensions/securelistener-[alb|nlb].config feature
  • We can configure the security group as well to allow SSL connections

Environment Cloning

  • Cloning allows to create new EB environment by cloning existing environments
  • By cloning an environment we don't have to manually configure options, environment variables, resources and other settings
  • A clone does copy any RDS instance defined, but the data is not copied by default
  • EB cloning does not include any un-managed changes to resources from the environment. Changes to AWS resources we make using tools other than the EB console/CLI/API are considered un-managed changes
  • To clone an environment from the eb command line we can use eb clone <ENV> command

EB and Docker

Single Container Mode

  • We can only run one container in one Docker host
  • This mode uses EC2 with Docker, not ECS
  • In order to use this mode we have to provide a few configurations:
    • Dockerfile: used to create a new container image from this file
    • Dockerrun.aws.json (version 1): to use an existing docker image. We can configure ports, volumes and other Docker attributes
    • Docker-compose.yml: if we want to use Docker compose

Multi-Container Mode

  • Elastic Beanstalk uses ECS to create a cluster
  • ECS uses EC2 instances provisioned in the cluster and an ELB for HA
  • EB takes care of ECS tasks, cluster creation, task definition and task execution
  • We need to provide an Dockerrun.aws.json (version 2 version 3) file in the application source bundle (root level)
  • Any images need to be stored in a container registry such as ECR