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OpsWorks Stacks & Layers

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  5. OpsWorks Stacks & Layers
  • It  provides a simple and flexible way to create and manage stacks and applications.
  • Deploy and monitor applications in your stacks.
  • It does not require or create Chef servers;
  • Performs some of the work of a Chef server for you.
  • Monitors instance health, and provisions new instances for you, when necessary, by using Auto Healing and Auto Scaling.

OpsWorks Stacks

  • stack represents set of instances to manage collectively
  • Serves as a container
  • stack have common purpose like serving applications.
  • stack handles tasks applying to group of instances as a whole
  • An example of stack serving web applications has
    • A set of application server instances for incoming traffic
    • A load balancer instance
    • A database instance
  • Best practice to have multiple stacks that represent different environments.
  • Usually a set of stacks includes
    • A development stack to add features and fix bugs for developers
    • A staging stack to verify updates before making it production
    • A production stack

Creating a Stack

To create a new stack

  • Go to the AWS OpsWorks Stacks dashboard
  • click Add stack.

The Add Stack page options

  • Stack name – (Required) identify the stack. Unique not required. stack ID a GUID, identifies the stack and can be used in commands.
  • Region – (Required) region where instances will be launched.
  • VPC – (Optional) The VPC ID, where stack is to be launched. Also supports EC2 Classic, with No VPC. VPC needed if not supporting EC2 Classic.
  • Default Availability Zone/Default subnet – (Optional) It depends, if creating stack in a VPC:
  • If supporting EC2 Classic can set VPC to No VPC.
  • If no EC2 Classic or want a VPC, this field is labeled Default subnet.
  • Default operating system – (Optional) Any one from built-in Linux operating systems, Microsoft Windows Server 2012 R2 or a custom AMI based on one of the supported operating systems.
  • Default SSH key – (Optional) Amazon EC2 key pair from the stack’s region. The default value is none.
  • Chef version – Chef version being selected
  • Use custom Chef cookbooks – Enable installing custom Chef cookbooks on the stack’s instances.
  • For Chef 12, the default setting is Yes. For Chef 11, The default setting is No.
  • Stack color – (Optional) The hue used to represent the stack on the AWS OpsWorks Stacks console.
  • Stack tags – Apply tags at the stack and layer level and all resource within gets tagged.
  • Default root device type – Determines the type of storage to be used for the instance’s root volume.
  • IAM role – (Optional) The stack’s AWS IAM role, to interact with AWS
  • Default IAM instance profile – (Optional) The default IAM role to be associated with the stack’s Amazon EC2 instances.
  • Hostname theme – (Optional) string to generate a default hostname for each instance.
  • Custom JSON – (Optional) One or more custom attributes, formatted as a JSON structure.
  • You cannot modify the region or VPC ID.

Running a stack in a VPC involves following steps

  • Create an appropriately configured VPC, by using the Amazon VPC console or API, or an AWS CloudFormation template.
  • Specify the VPC ID when you create the stack.
  • Launch the stack’s instances in the appropriate subnet.

OpsWorks Layers

  • Every stack contains at least one layers or more
  • Every layer refers to a stack component like load balancer or a set of servers.
  • Every layer should have a minimum of one instance or more.
  • Every instance must be a member of a minimum one layer, except for registered instances.
  • Instances may be a member of multiple layers.
  • With multiple layers in an instance
    • Reduce expenses by hosting the multiple server like database and load balancer, on same instance.
    • For administration, add another admin server instances to that layer.
  • To add the first OpsWorks layer
    • Click Add Layer.
    • On the Add Layer page, select the appropriate layer, showing the layer’s configuration options.
    • Configure the layer and click Add Layer to add it to stack.
  • To edit an OpsWorks layer
    • In navigation pane, click Layers.
    • On the Layers page, select a layer name and open its details page
    • Click Edit and then select the appropriate tab: General Settings, Recipes, Network, EBS Volumes, or Security.
  • OpsWorks Layer’s Configuration Main Settings
    • Auto healing enabled – If auto healing is enabled for the layer’s instances. The default setting is Yes.
    • Custom JSON – Data in JSON format that is passed to your Chef recipes for all instances in this layer. You can use this, for example, to pass data to your own recipes.
  • Instance shutdown timeout – Specifies how long (in seconds) OpsWorks Stacks waits after triggering a Shutdown lifecycle event before stopping or terminating the EC2 instance. The default setting is 120 seconds.

Auto Healing

  • All instances have OpsWorks Stacks agent to communicate regularly with AWS service.
  • Stacks uses the communication for instance health monitoring.
  • If no communication for > 5 minutes, instance is considered as failed.
  • With auto healing Stacks replaces the layer’s failed instances automatically
    • If volume attached to instance and instance failed, the volume and its data are saved and attached to new instance.
    • If volume not attached Stacks creates a new, empty volume with configuration specified by the layer, and attaches that volume to the new instance.
  • By default auto healing is enabled in AWS OpsWorks
  • Auto healing is set at layer level

Elastic Load Balancing Layer

  • Using ELB
    • Use the ELB console or API to create a load balancer
    • then attach it to a presentation layer.
  • ELB function is to
    • Distributing traffic to layer’s instances
    • Detect unhealthy EC2 instances
    • Reroutes traffic to healthy instances
    • Scales request handling capacity as per incoming traffic.
  • Must create separate ELB load balancer for each layer in each stack needing balancing
  • Assign a distinctive name to each ELB load balancer to use

RDS Service Layer

  • It represents an RDS instance.
  • Can represent only existing RDS instances
  • Create RDS instances by RDS console or API.

ECS Cluster Layers

  • ECS manages Docker containers on EC2 instances
  • An ECS Cluster layer provides
    • represents an Amazon ECS cluster
    • Streamlined container instance provisioning and management
    • Container instance operating system and package updates
    • User permissions management
    • Container instance performance monitoring
    • EBS volume management
    • Public and Elastic IP address management
    • Security group management
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