isabella232 / jenkins-infrastructure

Cloudformation to create and update an ECS cluster that runs jenkins

Amazon ECS, AWS CloudFormation, and an Application Load Balancer for Jenkins

This reference architecture provides a set of YAML templates for deploying microservices to Amazon EC2 Container Service (Amazon ECS) with AWS CloudFormation.

You can launch this CloudFormation stack in your account:

AWS Region	Short name
US East (N. Virginia)	us-east-1

Overview

The repository consists of a set of nested templates that deploy the following:

• A tiered VPC with public and private subnets, spanning an AWS region.
• A highly available ECS cluster deployed across two Availability Zones in an Auto Scaling group and that are AWS SSM enabled.
• A pair of NAT gateways (one in each zone) to handle outbound traffic.
• An Application Load Balancer (ALB) to the public subnets to handle inbound traffic.
• Centralized container logging with Amazon CloudWatch Logs.

Intelligent updating & rollback

CloudFormation not only handles the initial deployment of your infrastructure and environments, but it can also manage the whole lifecycle, including future updates. During updates, you have fine-grained control and visibility over how changes are applied, using functionality such as change sets, rolling update policies and stack policies.

Template details

The templates below are included in this repository and reference architecture:

Template	Description
master.yaml	This is the master template - deploy it to CloudFormation and it includes all of the others automatically.
infrastructure/vpc.yaml	This template deploys a VPC with a pair of public and private subnets spread across two Availability Zones. It deploys an Internet gateway, with a default route on the public subnets. It deploys a pair of NAT gateways (one in each zone), and default routes for them in the private subnets.
infrastructure/security-groups.yaml	This template contains the security groups required by the entire stack. They are created in a separate nested template, so that they can be referenced by all of the other nested templates.
infrastructure/load-balancers.yaml	This template deploys an ALB to the public subnets, which exposes the various ECS services. It is created in in a separate nested template, so that it can be referenced by all of the other nested templates and so that the various ECS services can register with it.
infrastructure/ecs-cluster.yaml	This template deploys an ECS cluster to the private subnets using an Auto Scaling group and installs the AWS SSM agent with related policy requirements.
infrastructure/lifecyclehook.yaml	This template deploys a Lambda Function and Auto Scaling Lifecycle Hook to drain Tasks from your Container Instances when an Instance is selected for Termination in your Auto Scaling Group.

Create a new ECS service

1. Push your container to a registry somewhere (e.g., Amazon ECR).
2. Copy one of the existing service templates in services/*.
3. Update the ContainerName and Image parameters to point to your container image instead of the example container.
4. Increment the ListenerRule priority number (no two services can have the same priority number - this is used to order the ALB path based routing rules).
5. Copy one of the existing service definitions in master.yaml and point it at your new service template. Specify the HTTP Path at which you want the service exposed.
6. Deploy the templates as a new stack, or as an update to an existing stack.

Setup centralized container logging

By default, the containers in your ECS tasks/services are already configured to send log information to CloudWatch Logs and retain them for 365 days. Within each service's template (in services/*), a LogGroup is created that is named after the CloudFormation stack. All container logs are sent to that CloudWatch Logs log group.

You can view the logs by looking in your CloudWatch Logs console (make sure you are in the correct AWS region).

ECS also supports other logging drivers, including syslog, journald, splunk, gelf, json-file, and fluentd. To configure those instead, adjust the service template to use the alternative LogDriver. You can also adjust the log retention period from the default 365 days by tweaking the RetentionInDays parameter.

For more information, see the LogConfiguration API operation.

Change the ECS host instance type

This is specified in the master.yaml template.

By default, t2.large instances are used, but you can change this by modifying the following section:

ECS:
  Type: AWS::CloudFormation::Stack
    Properties:
      TemplateURL: ...
      Parameters:
        ... 
        InstanceType: t2.large
        InstanceCount: 4
        ... 

Adjust the Auto Scaling parameters for ECS hosts and services

The Auto Scaling group scaling policy provided by default launches and maintains a cluster of 4 ECS hosts distributed across two Availability Zones (min: 4, max: 4, desired: 4).

It is not set up to scale automatically based on any policies (CPU, network, time of day, etc.).

If you would like to configure policy or time-based automatic scaling, you can add the ScalingPolicy property to the AutoScalingGroup deployed in infrastructure/ecs-cluster.yaml.

As well as configuring Auto Scaling for the ECS hosts (your pool of compute), you can also configure scaling each individual ECS service. This can be useful if you want to run more instances of each container/task depending on the load or time of day (or a custom CloudWatch metric). To do this, you need to create AWS::ApplicationAutoScaling::ScalingPolicy within your service template.

Deploy multiple environments (e.g., dev, test, pre-production)

Deploy another CloudFormation stack from the same set of templates to create a new environment. The stack name provided when deploying the stack is prefixed to all taggable resources (e.g., EC2 instances, VPCs, etc.) so you can distinguish the different environment resources in the AWS Management Console.

Change the VPC or subnet IP ranges

This set of templates deploys the following network design:

Item	CIDR Range	Usable IPs	Description
VPC	10.180.0.0/16	65,536	The whole range used for the VPC and all subnets
Public Subnet	10.180.8.0/21	2,041	The public subnet in the first Availability Zone
Public Subnet	10.180.16.0/21	2,041	The public subnet in the second Availability Zone
Private Subnet	10.180.24.0/21	2,041	The private subnet in the first Availability Zone
Private Subnet	10.180.32.0/21	2,041	The private subnet in the second Availability Zone

You can adjust the CIDR ranges used in this section of the master.yaml template:

VPC:
  Type: AWS::CloudFormation::Stack
    Properties:
      TemplateURL: !Sub ${TemplateLocation}/infrastructure/vpc.yaml
      Parameters:
        EnvironmentName:    !Ref AWS::StackName
        VpcCIDR:            10.180.0.0/16
        PublicSubnet1CIDR:  10.180.8.0/21
        PublicSubnet2CIDR:  10.180.16.0/21
        PrivateSubnet1CIDR: 10.180.24.0/21
        PrivateSubnet2CIDR: 10.180.32.0/21

Update an ECS service to a new Docker image version

ECS has the ability to perform rolling upgrades to your ECS services to minimize downtime during deployments. For more information, see Updating a Service.

To update one of your services to a new version, adjust the Image parameter in the service template (in services/* to point to the new version of your container image. For example, if 1.0.0 was currently deployed and you wanted to update to 1.1.0, you could update it as follows:

TaskDefinition:
  Type: AWS::ECS::TaskDefinition
  Properties:
    ContainerDefinitions:
      - Name: your-container
        Image: registry.example.com/your-container:1.1.0

After you've updated the template, update the deployed CloudFormation stack; CloudFormation and ECS handle the rest.

To adjust the rollout parameters (min/max number of tasks/containers to keep in service at any time), you need to configure DeploymentConfiguration for the ECS service.

For example:

Service: 
  Type: AWS::ECS::Service
    Properties: 
      ...
      DesiredCount: 4
      DeploymentConfiguration: 
        MaximumPercent: 200
        MinimumHealthyPercent: 50

Use the SSM Run Command function to see details in the ECS instances

The AWS SSM Run Command function, in the EC2 console, can be used to execute commands at the shell on the ECS instances. These can be helpful for examining the installed configuration of the instances without requiring direct access to them.

Spot Instances and the Hibernate Agent.

In order to use Spot with this template, you will need to enable SpotPrice under the AWS::AutoScaling::LaunchConfiguration or add in AWS::EC2::SpotFleet support. To fully use Hibernation with Spot instances, please review Spot Instance Interruptions.