AWS Elastic Beanstalk

Overview

• PAAS offering for application management of simple 3-tiered applications.
• "overlay" on many other services (e.g. EC2, S3 ELB, RDS, Route53)
• Less complex than OpsWorks
• Use cases
  • Simplified deployment as EB takes care of all the resource provisioning
    • Implements many best practices
    • Good for simple tiered applications
    • Optimized for many common Web and Web Services patterns

Model

• Application
  • logical collection of:
    • application versions
    • environments
    • environment configurations
• Application Version
  • iteration of deployable code (~CodeDeploy: revision)
  • Points to S3

• Environment - application version deployed onto specific AWS resources
  • Runs single application version at a time
  • Can be grouped together
  • ~CloudFormation: Stack
• Environment Tier - see below
• Environment Configuration - configuration of resources.
  • Defines how environment and its resources should behave
  • It can be updated and EB will automatically apply changes (see Deployments below)
• Platform - see below

Platform

• Machine setup that allows to run user application 
  • Supports specific lanuage/framework (e.g. IIS, Apache, Ruby, Docker) 
  • Versioned
    • Underlying platform may be updated automatically (weekly maintenance window)
• Predefined: Ruby, Java, PHP,  Node.js, .NET, Go, Python
  • Docker
    • Single-container, Multi-container, Pre-configured
• Custom
  • Based on custom AMI (Ubuntu, RHEL, or A-Linux)
  • Uses Packer
    • Open-source tool for creating machine images

Environment Tier

• Web: processes HTTP requests
  • Route53 entry created
  • Environment Type
    • single instance
    • ELB + auto-scaling
  • environment URL
    • e.g. testapplication-env.eu-central-1.elasticbeanstalk.com
• Worker: instance reading off SQS queue
  
  • auto-scaling     

Host Manager (agent)

• EB agent running on EC2 instance
• Responsibilities
  • Deploy application version
  • Aggregate events and metrics
  • Generate instance-level events
  • Monitor application logs for critical errors
  • Monitor the application server
  • Patch instance components
  • Rotate application logs and publish them to S3

Healthcheck

• Basic
  • ELB environments -> uses ELB healtcheck
  • Single instance environment -> EC2 healtchecks
  • Colors
    • Grey - environment is being updated
    • Green - passed most recent checks, at least 1 instance is availale
    • Yellow - failed 1 or more checks
    • Red - requests are constantly failing
  • Additional checks
    • ASG available and has at least 1 instance
    • SG has port 80 open
    • CNAME exists and points to ELB
    • SQS polled at least 1 per 3 minutes (worker environment)
• Enhanced
  • Higher bar 
  • Uses Host Manager (agent)
    • monitors web server logs and system metrics
    • reports directly to EB service (every 10 seconds)
    • can publish "EnvironmentHealth" CloudWatch metric
  • Displays "cause" next to the color status
  • Not supported on Windows
  • Contains all basic healthchecks plus:
    • HTTP requests status (number, result, latency)
    • OS metrics

Application Version deployment

• Rolling
  • Similar to Rolling Configuration Update
  • Healthcheck can be ignored
  • DeploymentPolicy
    • Rolling - Rolling Deployment
    • AllAtOnce - No rolling
    • RollingWithAdditionalBatch - maintain constant number of servers in-service (n+m = more expensive)
• Blue/Green
  • DNS based - swap Environment Url (CNAME)
  • All or Nothing

Instance Log Management

• On demand
  • Tail logs
    • 100 last lines of most commonly used logs
    • Web server, EB operatational etc.
    • When requested agent on instance concatenates and uploads to S3
  • Bundle logs (Full Logs)
    • wide range of log files (including cron, yum, CF, etc.)
    • When requested zip archive created an uploaded 
  • Stored 15 minutes in S3
• Published (log rotation)
  
  • Enable in Environment Configuration settings
• Extending
  • Non-standard location
    
    • Use .ebextensions to specify
  • Add .config entries for custom log files
• EB uses logrotate on instances

Permissions

• Instance profile - for launched EC2 instances
• Service role - allows AWS EB service  to monitor environment resources

Limitations

• Environment cannot be stopped (it is terminated)
• No static IP references
• EBS disk persistence requires additional setup
• Database must be managed separately 
• Inflexible for complex setups
  • Consider OpsWorks or CloudFormation