AWS Elastic Beanstalk (Configuration)

Configuration Options

• Allow to customize resources managed by EB
• Specified (precedence)
  • directly applied to the environment (Create/Update) 
  • saved configurations
  • configuration files (.ebextensions)
  • default values

Directly Applied

• applied to the environment during Create and Update API calls
• any client (API, CLI, AWS Console)
• can override "recommended values"
  • may differ from default values
  • allow AWS to apply best practices in backward compatible manner
  • examples
    • aws:elb:loadbalancer - CrossZone
    • aws:elb:policies - ConnectionDrainingEnabled
• Example
  • eb create my-env --instance_type m2.medium

Saved Configuration

• Template that is managed by EB
• Can be created from running environment or JSON file (AWS Console)
  • like creating machine image (snapshot)
• Contains Solution Stack (do not specify again)
• Use API/CLI/Console to manage them
• Can be stored in the Application source bundle
  • .elasticbeanstalk/saved_configs/some_config.cfg.yml
  • S3
• sections
  • metadata
  • solutionstack
  • optionsSettings
  • environmentTier

Configuration files (.ebextension)

• Part of Application source boundle 
  • easy to make changes
• .ebextension folder in the root of the application
• YAML/JSON formatted .config files in the folder
  • e.g. healthcheckurl.config
• sections
  • option_settings
    • modify EB configuration options
      
      • aws:elasticbeanstalk:*
    • set environmental variables
  • resources
    • add additional resources
    • all CloudFormation types are supported
    • Example
      
      • SQS queue with CW Alarm on the queue depth
  • packages
    • Linux: rpm, yum, rubygems, python (pip, easy_install)
    • Windows: msi
  • sources
    • Download file from http location and unpack to target directory
  • files
    • create files
    • content passed inline or downloaded from http location
  • users
    • linux only
  • groups
    • linux only
  • commands
    • execute arbitrary commands
    • run before web server setup
  • container_commands
    • run
      • after web server setup
      • application version extracted
      • before application version has been deployed
      • from staging directory
    • Can be run on "leader_node" only
      • Single instance in the AutoScaling group
  • services
    • control services running on the instance
• use cases
  • customize environment resources
    • add SQS queue and ALARM on queue depth
    • ElastiCache cluster

Environment configuration update

• Rolling update (performed in batches)
• Triggered when serious configuration changes made
• Examples: VPC Settings, Launch Configuration (e.g. Instance Type)

• Type
  • Health
    
    • Basic: healthy as soon as all instances in the batch pass ELB healthcheck
    • Enhanced
      • Web: 12 must pass in 2 minutes
      • Worker: 18 in 3 minutes
    • Timeout 30 minutes (configurable: 15-60)
      • If not reached update is cancelled
  •  Time
    • Pause time between batches
    • Proceed without regard for healthcheck
• Split environment into batches (Maximum batch size)
• Deregister batch from ELB (keep minimum number of instances running)
• Update
• Register with ELB
• Can be triggered by .ebextensions changes

Environment Group

• Collection of environments that work together (e.g. SOA)
• One environment may depend on another (see Environment Links)
• naming "+" allows to create entire groups for different stages
  • specify "group name" 
    • e.g. TEST, PROD

Environment Manifest (env.yml)

• places in the root of application source
• same format as saved configurations
• supports environment groups

Environment Links

• Used when you have multiple components (e.g. web, services, database)
• Each components gets its own environment
• You can specify connections between environments
• Defined in environment manifest (env.yml)