I am a little hazy about the need for both. I am using both in ECS CloudFormation. It appears that AWS::AutoScaling::AutoScalingGroup is for scaling EC2 instances whereas AWS::ApplicationAutoScaling::ScalableTarget is for scaling containers/tasks. Is my understanding correct?
That is pretty much correct.
AWS::AutoScaling::AutoScalingGroup is used for creating an Auto Scaling group of EC2 instances
AWS::ApplicationAutoScaling::ScalableTarget is used to specify an application resource that can scale - that is any of a range of resources including ECS service, EMR cluster or DynamoDB. A list of all the resources that can be scaled can be found in the ResourceId parameter description for RegisterScalableTarget.
Related
I created a cluster in ECS with basic settings, nothing specific about the configuration except that I am using 1 On Demand t2.micro EC2 instance for the cluster.
I wanted to see what exactly was created and took a look at the CloudFormation template the cluster created.
I noticed in the template it has a configuration for EcsSpotFleet
EcsSpotFleet:
Condition: CreateWithSpot
Type: AWS::EC2::SpotFleet
Properties:
SpotFleetRequestConfigData:
AllocationStrategy: !Ref SpotAllocationStrategy
IamFleetRole: !Ref IamSpotFleetRoleArn
TargetCapacity: !Ref AsgMaxSize
SpotPrice: !If [ CreateWithSpotPrice, !Ref SpotPrice, !Ref 'AWS::NoValue' ]
TerminateInstancesWithExpiration: true
LaunchSpecifications:
....
I am wondering why is this created? Because I know the Cluster instances are created with ASG + LC. My only explanation is this fleet is used for running the CloudFormation stack. I cannot find an explanation to this in the documentation, not even sure if instances are needed for CloudFormation stack run.
p.s. I am very new to AWS, also have very little knowledge on CloudFormation.
Not all code in CloudFormation will be executed. It still depends on the "Condition" flag.
AWS usually create a template that covers most of the user cases and enables/disable parts of the template using the "Condition"
You can read more about Condition in AWS documentation here: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/conditions-section-structure.html
How can I make user defined instances from AWS CloudFormation?
Example:
Question: How many instances do you want?
Answer: 4
AWS CloudFormation should install 4 same instances.
You don't really need custom-resource for that. You can just create your instances as part of AWS::AutoScaling::AutoScalingGroup. ASG will create required number of instances once you set DesiredCapacity and MaxSize. So if you want 4 instances, you set these values to 4.
You have two options
Autoscaling Group - DesiredCapacity and MaxSize - AWS::AutoScaling::AutoScalingGroup
Spot fleet ( cost savings by 90%) - TargetCapacity - AWS::EC2::SpotFleet
In my CloudFormation file, I created an instance, a Launch Configuration and an Auto Scaling Group.
LogstashInstance:
Type: AWS::EC2::Instance
Properties:
IamInstanceProfile:
Ref: LogstashInstanceProfile
InstanceType: t2.micro
KeyName: chuongtest
ImageId: ami-0cd31be676780afa7
UserData:
SecurityGroupIds:
- Ref: LogstashSecurityGroup
SubnetId: subnet-0e5691582096fe1e6
Tags:
- Key: Name
Value: Logstash Instance
LogstashLaunchConfiguration:
Type: AWS::AutoScaling::LaunchConfiguration
Properties:
EbsOptimized: false
IamInstanceProfile:
Ref: LogstashInstanceProfile
ImageId: ami-0cd31be676780afa7
InstanceMonitoring: true
InstanceType: t2.micro
KeyName: chuongtest
LaunchConfigurationName: LogstashLaunchConfiguration
SecurityGroups:
- Ref: LogstashSecurityGroup
UserData:
LogstashAutoScalingGroup:
Type: AWS::AutoScaling::AutoScalingGroup
Properties:
AutoScalingGroupName: LogstashAutoScalingGroup
AvailabilityZones:
- ap-southeast-1b
DesiredCapacity: 1
LaunchConfigurationName:
Ref: LogstashLaunchConfiguration
MaxSize: 1
MinSize: 1
Tags:
- Key: Name
PropagateAtLaunch: "false"
Value: Logstash ASG
- Key: Instances
PropagateAtLaunch: "true"
Value: Logstash
My idea is to create an instance, attach it to the ASG and use the ASG to keep the work continue.
But this code will launch 2 instances.
The first instances has userdata different from the later instances so I can not delete the instance.
I have looked in the documentation but I can not find anything make sense. Is there a way to configure in the template, or the only way is scripting?
I have looked in the documentation but I can not find anything make sense. Is there a way to configure in the template, or the only way is scripting?
It does not make sense, because its not practical. ASG will be launching instances only from the associated AWS::AutoScaling::LaunchConfiguration. Thus, there is not much sense on "manually" attaching instances in your cause the the ASG. ASG will not re-launch it when it fails.
If the "manually" attached instances gets terminated for some reason, e.g. hardware failure, ASG will launch a replacement based on the launch configuration.
userdata different from the later instances
In this case the best would be to provide some condition in your UserData which would determine which version of your UserData to run.
Alternatively, just have two ASGs. One for the first instance, while the other group for the remaining instances.
Edit
Having discussed via the comments I would highly recommend the approach of using EFS as it is designed for the workload design you're doing.
In addition it is multi AZ vs the approach of rotating a single EBS volume as instances fail in an autoscaling group which would not persist should the AZ fail and potentially lead to loss of data.
Original
If that first instance is different from the rest you should be careful about adding it to the autoscaling group (as you want it to persist), especially in how it handles the replacement of instances.
Autoscaling groups are designed to scale similar instances that are generally immutable, so by having your host in this autoscaling group it will be treated as if it is one of the other hosts.
An Auto Scaling group contains a collection of Amazon EC2 instances that are treated as a logical grouping for the purposes of automatic scaling and management.
If you must add it to the autoscaling group here is the general approach:
Create a Custom Resource which involves a Lambda attaching the EC2 to the ASG using attach_instances
Add set_instance_protection to your instance to prevent it being replaced during a scale in event (or the instance failing)
Also ensure you set both the MinSize and DesiredCapacity to 0 to remove any extra instance that gets launched.
As I stated earlier you should not add this instance to the ASG if it can be avoided, tt will probably lead to confusion.
I would like to perform the following operations in order with CloudFormation.
Start up an EC2 instance.
Give it privileges to access the full internet using security group A.
Download particular versions of Java and Python
Remove its internet privileges by removing security group A and adding a security group B.
I observe that there is a DependsOn attribute for specifying the order in which to create resources, but I was unable to find a feature that would allow me to update the security groups on the same EC2 instance twice over the course of creating a stack.
Is this possible with CloudFormation?
Not in CloudFormation natively, but you could launch the EC2 instance with a configured userdata script that itself downloads Java/Python and the awscli, as necessary, and then uses the awscli to switch security groups for the current EC2 instance.
However, if all you need is Java and Python pre-loaded then why not simply create an AMI with them already installed and launch from that AMI?
The best way out is to utilise a Cloudformation custom resource here. You can create a lambda function that does exactly what you need. This lambda function can then be called as a custom resource function in the cloud formation template.
You can pass your new security group ID and instance ID to the lambda function and code the lambda function to use AWS SDK and do the modifications that you need.
I have leveraged it to post an update to my web server about the progress of the cloud formation template. Below is the sample code of the template.
EC2InstanceProfile:
Type: AWS::IAM::InstanceProfile
Properties:
Path: /
Roles: [!Ref 'EC2Role']
MarkInstanceProfileComplete:
Type: 'Custom::EC2InstanceProfileDone'
Version: '1.0'
DependsOn: EC2InstanceProfile
Properties:
ServiceToken: !Ref CustomResourceArn
HostURL: !Ref Host
LoginType: !Ref LoginType
SecretId: !Ref SecretId
WorkspaceId: !Ref WorkspaceId
Event: 2
Total: 3
Here the resource MarkInstanceProfileComplete is a custom resource that calls a Lambda function. It takes the event count and total count as input and processes them to calculate percentage progress. Based on that it sends out a request to my web server. For all we care, this Lambda function can do potentially anything you want it to do.
By default, AWS ElasticBeanstalk scales on NetworkOut
However, I am wanting to scale on two scenarios, network out and CPU utilization.
Is there a way to do this so that if either of these exceeds their limit, it will scale?
In ElasticBeanstalk console Configuration > Scaling > Scaling Trigger you can only set one Trigger Measurement like CPUUtilization or NetworkIn or NetworkOut or other options present.
If you need multiple scaling policies, you can add them manually or through ebextensions config file to ElasticBeanstalk's Auto Scaling group like described here. Add a Simple Scaling policy or Target Tracking Scaling policy.
Add below to ebextension config file to create a Target tracking scaling policy:
Resources:
POL:
Type: 'AWS::AutoScaling::ScalingPolicy'
Properties:
AutoScalingGroupName: !Ref AWSEBAutoScalingGroup
PolicyType: TargetTrackingScaling
TargetTrackingConfiguration:
PredefinedMetricSpecification:
PredefinedMetricType: ASGAverageCPUUtilization
TargetValue: 80
To create a Simple scaling policy, you should create a scaling policy and CloudWatch resource like here