AWS OpsWorks Stacks (Layer)

Layer

• Group of instances within a stack
• Recipes are added to its lifecycle events
• Contains 1+ instance
  • Add new or existing instance
  • Online instance (member of layer already) cannot be added to another layer
    
    • Must be added prior to starting the instance

Layer Configuration

• Custom Recipes
  • Configure, Deploy, Setup, Shutdown, Undeploy
• Networking
  • ELB
  • Public IP assignment
  • EIPs
• Load based scaling
• EBS
  • Mount Point
  • Number of volumes
  • RAID Type
    • None
    • 0
    • 1
    • 10
  • Watch out for conflict with ephemeral disks (autofs)
• Security Groups
• Instance Profile

Security Groups

• OpsWorks creates built-in Security Group for a layer
• Use OpsWorks security groups
  • YES
    
    • Custom SG can be added but cannot restrict access this way (UNION)
  • NO
    • Associate custom SG with a layer

Auto Healing

• Automatic replacement of failed instance
  • Compare ASG: instance replacement
• If no communication with OpsWorks Agent for ~5 minutes instance consider failed
• Configured on the Layer level (each instance in the layer inherits it)
  
  • If instance belongs to many layers the flag is AND'ed 
• Enabled by default 
• Behavior
  • Instance Store 
    • Terminate EC2 instance and verify it has shut down
    • Delete data on root volume
    • Launch instance with the same hostname, configuration, layer membership
    • Assign new public and private IP
    • Associate existing EIP (if applicatble)
  • EBS-backed
    • Stop the instance 
    • Start the instance
  • When online trigger "Configure" event on all instances

Elastic Load Balancing  Layer Type

• Elastic Load Balancing is part of OpsWorks Layer
  • Attach to existing layer
    • OpsWorks deregisters existing instances in ELB
    • Registers layer instances
  • Connection Draining
    • OpsWorks delays Shutdown event

RDS Layer Type

• Represents existing RDS instance
• Can register existing RDS instance
• OW adds RDS configuration to [:opsworks][:stack] attribute

ECS Layer Type

• Linux only
• Represents single ECS Cluster
  • 1-1 relationship with stack
• ECS cluster is registered with a stack and then a layer is created
• Settings
  
  • ELB attachment
  • EIP/Public IP management

Custom Layer Type

• Minimal set of recipes