A module for deploying Jenkins in a highly available and highly scalable manner.
Related blog post can be found on the Neiman Marcus Medium page.
- Highly available architecture with agents and master in an autoscaling group
- EFS volume used for master node persistence
- Jenkins versions incremented through variable
- Complete Infrastructure as code deployment, no plugin configuration required
- Spot instance pricing for agents
- Custom user data available
To be used with a local map of tags.
module "jenkins_ha_agents" {
source = "neiman-marcus/jenkins-ha-agents/aws"
admin_password = "foo"
bastion_sg_name = "bastion-sg"
domain_name = "foo.io."
private_subnet_name_az1 = "private-subnet-a"
private_subnet_name_az2 = "private-subnet-b"
public_subnet_name_az1 = "public-subnet-a"
public_subnet_name_az2 = "public-subnet-b"
r53_record = "jenkins.foo.io"
ssl_certificate = "*.foo.io"
ssm_parameter = "/jenkins/foo"
tags = "${local.tags}"
vpc_name = "prod-vpc"
}Note: It is better to use a template file, but the template data sources below illistrate the point.
module "jenkins_ha_agents" {
source = "neiman-marcus/jenkins-ha-agents/aws"
admin_password = "foo"
agent_max = 6
agent_min = 2
ami_name = "amzn2-ami-hvm-2.0.*-x86_64-gp2"
ami_owner = "amazon"
api_ssm_parameter = "/api_key"
application = "jenkins"
bastion_sg_name = "bastion-sg"
domain_name = "foo.io."
extra_agent_userdata = "${data.template_file.extra_agent_userdata.rendered}"
extra_agent_userdata_merge = "list(append)+dict(recurse_array)+str()"
extra_master_userdata = "${data.template_file.extra_master_userdata.rendered}"
extra_master_userdata_merge = "list(append)+dict(recurse_array)+str()"
executors = "4"
instance_type = "t2.large"
jenkins_version = "2.164.3"
password_ssm_parameter = "/admin_password"
private_cidr_ingress = ["10.0.0.0/8"]
private_subnet_name_az1 = "private-subnet-a"
private_subnet_name_az2 = "private-subnet-b"
public_cidr_ingress = ["0.0.0.0/0"]
public_subnet_name_az1 = "public-subnet-a"
public_subnet_name_az2 = "public-subnet-b"
r53_record = "jenkins.foo.io"
spot_price = "0.0928"
ssl_certificate = "*.foo.io"
ssm_parameter = "/jenkins/foo"
swarm_version = "3.15"
tags = "${local.tags}"
vpc_name = "prod-vpc"
}
data "template_file" "extra_agent_userdata" {
vars {
foo = "bar"
}
template = <<EOF
---
runcmd:
- echo 'foo = ${foo}'
EOF
}
data "template_file" "extra_master_userdata" {
vars {
foo = "bar"
}
template = <<EOF
---
runcmd:
- echo 'foo = ${foo}'
EOF
}| Name | Description | Type | Default | Required |
|---|---|---|---|---|
| admin_password | The master admin password. Used to bootstrap and login to the master. Also pushed to ssm parameter store for posterity. | string | N/A |
yes |
| agent_max | The maximum number of agents to run in the agent ASG. | int | 6 |
no |
| agent_min | The minimum number of agents to run in the agent ASG. | int | 2 |
no |
| ami_name | The name of the amzn2 ami. Used for searching for AMI id. | string | amzn2-ami-hvm-2.0.*-x86_64-gp2 |
no |
| ami_owner | The owner of the amzn2 ami. | string | amazon |
no |
| api_ssm_parameter | The path value of the API key, stored in ssm parameter store. | string | /api_key |
no |
| application | The application name, to be interpolated into many resources and tags. Unique to this project. | string | jenkins |
no |
| bastion_sg_name | The bastion security group name to allow to ssh to the master/agents. | string | N/A |
yes |
| domain_name | The root domain name used to lookup the route53 zone information. | string | N/A |
yes |
| executors | The number of executors to assign to each agent. Must be an even number, divisible by two. | int | 4 |
no |
| extra_agent_userdata | Extra agent user-data to add to the default built-in. | string | empty |
no |
| extra_agent_userdata_merge | Control how cloud-init merges custom agent user-data sections. | string | list(append)+dict(recurse_array)+str() |
no |
| extra_master_userdata | Extra master user-data to add to the default built-in. | string | empty |
no |
| extra_master_userdata_merge | Control how cloud-init merges custom master user-data sections. | string | list(append)+dict(recurse_array)+str() |
no |
| instance_type | The type of instance to use for both ASG's. | string | t2.large |
no |
| jenkins_version | The version number of Jenkins to use on the master. Change this value when a new version comes out, and it will update the launch configuration and the autoscaling group. | string | 2.164.3 |
no |
| password_ssm_parameter | The path value of the master admin passowrd, stored in ssm parameter store. | string | /admin_password |
no |
| private_cidr_ingress | Private IP address cidr ranges allowed access to the instances. | string | ["10.0.0.0/8"] |
no |
| private_subnet_name_az1 | The name prefix of the private subnet in the first AZ to pull in as a data source. | string | N/A |
yes |
| private_subnet_name_az2 | The name prefix of the private subnet in the second AZ to pull in as a data source. | string | N/A |
yes |
| public_cidr_ingress | Public IP address cidr ranges allowed access to the instances. | string | ["0.0.0.0/0"] |
no |
| public_subnet_name_az1 | The name prefix of the public subnet in the first AZ to pull in as a data source. | string | N/A |
yes |
| public_subnet_name_az2 | The name prefix of the public subnet in the second AZ to pull in as a data source. | string | N/A |
yes |
| r53_record | The FQDN for the route 53 record. | string | N/A |
yes |
| region | The AWS region to deploy the infrastructure too. | string | N/A |
yes |
| spot_price | The spot price map for each instance type. | map | t2.micro=0.0116, t2.large=0.0928, t2.xlarge=0.1856 |
no |
| ssl_certificate | The name of the SSL certificate to use on the load balancer. | string | N/A |
yes |
| ssm_parameter | The full ssm parameter path that will house the api key and master admin password. Also used to grant IAM access to this resource. | string | N/A |
yes |
| swarm_version | The version of swarm plugin to install on the agents. Update by updating this value. | int | 3.15 |
no |
| tags | tags to define locally, and interpolate into the tags in this module. | string | N/A |
yes |
| vpc_name | The name of the VPC the infrastructure will be deployed to. | string | N/A |
yes |
| Name | Description |
|---|---|
| lb_arn_suffix | The ARN suffix of the load balancer. |
| lb_dns_name | The DNS name of the load balancer. |
| lb_id | The ID/ARN of the load balancer. |
| lb_zone_id | The canonical hosted zone ID of the load balancer. |
| r53_record_name | The name of the route 53 record. |
| r53_record_fqdn | The fqdn of the route 53 record. |
N/A
The architecture, on the surface, is simple, but has a lot of things going on under the hood. Similar to a basic web-application architecture, a load balancer sits in front of the master auto scaling group, which connects directly to the agent autoscaling group.
The Master node sits in an autoscaling group, using the Amazon Linux 2 AMI. The autoscaling group is set to a minimum and maximum of one instance. The autoscaling group does not scale out or in. It can be in one of two availability zones. It is fronted by an ELB which can control the autoscaling group based on a health check. If port 8080 is not functioning properly, the ELB will terminate the instance.
The name of the master autoscaling group is identical to the master launch configuration. This is intentional. If the launch configuration is updated, the master autoscaling group will be recreated with the new launch configuration.
Data are persisted through an EFS volume, with a mount target in each availability zone.
During initial launch, the master will generate an API key and publish it to SSM Parameter store.
Agent nodes are also set in an autoscaling group, using the Amazon Linux 2 AMI, set in the same availability zones.
Agents connect to the master node through the Jenkins SWARM plugin. The agents are smart enough to get the master's IP address using the AWS CLI and API key from the parameter store. Agents launch, configure themselves, and connect to the master. If agents cannot connect or get disconnected, the agent will self-terminate, causing the autoscaling group to create a new instance. This helps in the case that the agents launch, and the master has not yet published the API key to the parameter store. After it is published, the agents and master will sync up. If the master is terminated, the agents will automatically terminate.
Agents are spot instances, keeping cost down.
Agents scale based on CPU, and on the Jenkins build queue. The master node will poll itself to see how many executors are busy and send a CloudWatch metric alarm. If the number of executors available is less than half, then the autoscaling group will scale up. If executors are idle, then the agents will scale down. This is configured in the cloud-init user data.
To update Jenkins or the SWARM plugin, update the variable in the terraform.tfvars files and redeploy the stack. The master will rebuild with the new version of Jenkins, maintaining configuration on the EFS volume. The agents will redeploy with the new version of SWARM.
ECS still requires managing instances with an autoscaling group, in addition to the ECS containers and configuration. Just using autoscaling groups is less management overhead.
Fargate cannot be used with the master node as it cannot currently mount EFS volumes. It is also more costly than spot pricing for the agents.
The goal is to completely define the deployment with code. If a plugin is used and configured for agent deployment, defining the solution as code would be more challenging. With the SWARM plugin, and the current configuration, the infrastructure deploys instances, and the instance user data connects. The master is only used for scaling in and out based on executor load.
- Clay Danford - Project creation and development.
- Refer to our contribution guidelines to contribute to this project. See CONTRIBUTING.md.
- All contributions must follow our code of conduct. See CONDUCT.md.
- This project is licensed under the Apache 2.0 license. See LICENSE.
- Cloudonaut.io Template - Original cloudformation template, this project is based on.