The Wayback Machine - https://web.archive.org/web/20230605060719/https://anton.belodedenko.me/cheaper-aws-beanstalk/

home

Motorhome

Netflix

FortiGate

Home Improvement

Belodedexit

12 November 2019
/ belodetek Ltd.

on reducing AWS Elastic Beanstalk costs... 💰

There appears to be plenty of documentation and examples on how to deploy web applications using AWS Elastic Beanstalk (EBS). There is also significant body of work on how to reduce AWS costs using EC2 Spot instances, RIs, etc. However there doesn't appear to be much in a way of combining the two.

This post makes a number of assumptions - the most important one is that the reader is familiar with the specific technology and the terminology. The other one is that everything we do is performed through the DevOps "infrastrucutre-as-code" tenet. In this case, this essentially means we will be using AWS CloudFormation (CFN). So let's dive right in...

Deploying EBS through CFN produces an environment running an application with an auto-scaling policy in a form of an EC2 Auto Scaling Group (ASG).

In CFN templates, an EBS environment is usually provisioned with the following resource definition:

Environment:
Type: 'AWS::ElasticBeanstalk::Environment'
Properties:
ApplicationName: !Sub '${Application}'
Description: !Sub '${NameTag} environment'
TemplateName: !Sub '${ConfigurationTemplate}'
VersionLabel: !Sub '${ApplicationVersion}'
Tags:
- Key: NameTag
Value: !Sub '${NameTag}'

This effectively kicks off deployment of a nested CFN stack (e.g. awseb-e-tonvh4892d-stack), which is maintained by AWS/EBS and we have no visibility into it. This stack produces no outputs/exports we can leverage, aside from AWSEBLoadBalancerURL output. This nested stack deploys all of the resources, including ASG, auto-scaling policy, etc.

To provision cheaper Spot instances in our EBS environment, we just need to specify the EC2_SPOT_PRICE environment variable in our configuration template definition:

ConfigurationTemplate:
Type: 'AWS::ElasticBeanstalk::ConfigurationTemplate'
Properties:
ApplicationName: !Ref 'Application'
Description: !Sub '${NameTag} spot configuration template'
OptionSettings:
- Namespace: 'aws:elasticbeanstalk:application:environment'
OptionName: EC2_SPOT_PRICE
Value: !If [ HasSpot, !Ref 'MaxSpotPrice', !Ref 'AWS::NoValue' ]
...

This is covered in the following post. However, this provisions 100% Spot capacity with no On-Demand instances. This is not ideal for mission critical applications, unless additional logic is wired in to listen for termination events and provision replacement capacity automatically.

Ideally, we would want to provision something like 50% Spot and 50% On-Demand capacity within our EBS environment. This can be achieved with MixedInstancesPolicy, set on the ASG, but requires the ASG to be configured to launch instances using a Launch Template (LT), rather than the default Launch Configuration (LC), which is configured by EBS. It is posible to copy LC to LT using AWS Console, but since we need to be able to do it programatically inside our CFN template, we would need to legerage some custom resources.

First, we need to obtain the ASG name first via a call to our custom resource provider Lambda function:

AutoScalingGroupName:
Type: 'Custom::AutoScalingGroupName'
DependsOn: Environment
Properties:
ServiceToken: !Sub 'arn:${AWS::Partition}:lambda:${AWS::Region}:${AWS::AccountId}:function:generic-custom-resource-provider'
AgentService: autoscaling
AgentType: client
AgentCreateMethod: describe_auto_scaling_groups
AgentWaitQueryExpr: !Sub '$.AutoScalingGroups[*].Tags[?(@.Key=="elasticbeanstalk:environment-name" && @.Value=="${Environment}")].ResourceId'

Once we have the ASG name, we can get the name of the LC:

AutoScalingLaunchConfigurationName:
Type: 'Custom::AutoScalingLaunchConfigurationName'
DependsOn: AutoScalingGroupName
Properties:
ServiceToken: !Sub 'arn:${AWS::Partition}:lambda:${AWS::Region}:${AWS::AccountId}:function:generic-custom-resource-provider'
AgentService: autoscaling
AgentType: client
AgentWaitQueryExpr: !Sub '$.AutoScalingGroups[?(@.AutoScalingGroupName=="${AutoScalingGroupName}")].LaunchConfigurationName'

After obtaining both, we can copy the LC to LT:

CreateLaunchTemplateFromConfiguration:
Type: 'Custom::CreateLaunchTemplateFromConfiguration'
DependsOn: AutoScalingLaunchConfigurationName
Version: 1.0
Properties:
ServiceToken: !Sub 'arn:${AWS::Partition}:lambda:${AWS::Region}:${AWS::AccountId}:function:generic-custom-resource-provider'
Version: 1.0
# custom module: autoscaling.py
AgentService: autoscaling
AgentType: custom
AgentResponseNode: LaunchTemplate
AgentCreateMethod: create_launch_template_from_configuration
AgentDeleteMethod: delete_launch_template
AgentCreateArgs:
LaunchConfigurationName: !Sub '${AutoScalingLaunchConfigurationName}'
LaunchTemplateName: !Sub '${NameTag}-launch-template'
Description: !Sub 'Created from ${AutoScalingLaunchConfigurationName}.'
TagSpecifications:
- ResourceType: 'launch-template'
Tags:
- Key: 'Name'
Value: !Sub '${NameTag}'
AgentDeleteArgs:
LaunchTemplateName: !Sub '${NameTag}-launch-template'

We can now reference ${CreateLaunchTemplateFromConfiguration.LaunchTemplateId} in our further CFN resources and configure our ASG to use the new LT with the MixedInstancesPolicy defined:

MixedInstancesPolicy:
Type: 'Custom::MixedInstancesPolicy'
DependsOn: CreateLaunchTemplateFromConfiguration
Version: 1.0
Properties:
ServiceToken: !Sub 'arn:${AWS::Partition}:lambda:${AWS::Region}:${AWS::AccountId}:function:generic-custom-resource-provider'
Version: 1.0
# custom module: autoscaling.py
AgentService: autoscaling
AgentType: custom
AgentResponseNode: ResponseMetadata
AgentCreateMethod: update_auto_scaling_group
AgentUpdateMethod: update_auto_scaling_group
AgentCreateArgs: !Sub |
{
"AutoScalingGroupName": "${AutoScalingGroupName}",
"MixedInstancesPolicy": {
"LaunchTemplate": {
"LaunchTemplateSpecification": {
"LaunchTemplateId": "${CreateLaunchTemplateFromConfiguration.LaunchTemplateId}",
"Version": "1",
},
"Overrides": [
{
"InstanceType": "${InstanceSize}"
}
]
},
"InstancesDistribution": {
"OnDemandBaseCapacity": ${OnDemandBaseCapacity},
"OnDemandPercentageAboveBaseCapacity": ${OnDemandPercentageAboveBaseCapacity}
}
}
}
AgentUpdateArgs: !Sub |
...

These resources effectively convert our EBS environments ASG to use a LT instead of LC and set a policy to deploy a % of Spot instances vs. On-Demand, thus significantly lowering running costs. This approach survives EBS re(deployments) using CFN and maintains our "infrastructure-as-code".

Hope this helps... 👀

--belodetek 😬

Anton Belodedenko

I am a jack of all trades, master of none (DevOps). My wife and I ski, snowboard and rock climb. Oh, and I like Futurama, duh!

Read More

— on many things randomly and in no particular order —

belodetek Ltd.

A real hand job...🕹

Deploy private CAs with CloudFormation

G Suite authentication at the load-balancer

See all 6 posts →

brew

Got Apples? Make (hard) Cider. 🍺

Hard cider on a budget using mostly recycled/up-cycled kit, a few bits from Home Depot and minimal specialist hardware from a brew supplier.

Anton Belodedenko

belodetek Ltd.

Deploy private CAs with CloudFormation

Create private CA programmatically in AWS using CloudFormation without manual intervention 🤓

Anton Belodedenko

on many things randomly and in no particular order

—

on reducing AWS Elastic Beanstalk costs... 💰

Share this

All content copyright Anton and Anna Belodedenko © 2023

Latest Posts

Ghost