Fleet vs Cluster

Question

I really confused and didn't know what is the difference between "fleet" and "cluster" in aws. For me, they are all "a bunch of something", and can't distinguish them.

I found that nobody would ask this question since they are on a different level and it's a definition problem that I misunderstand the critical part of them.

We call it an EC2 fleet. We call it an ECS cluster. We call it an EKS cluster.

Answer 1

The term ECS cluster is used for "a logical grouping of tasks or services" or in case of using the EC2 launch-type a "grouping of container instances". [1]
The term EKS cluster defines "the Amazon EKS control plane and Amazon EKS worker nodes that are registered with the control plane". [2]
The term EC2 fleet is used for "configuration information to launch a fleet—or group—of instances". [3]

These terms are usually used to refer to a grouping of resources. The type of resources differs from service to service:

• In EC2, fleets are useful to launch multiple instances at once which are configured with different types (e.g. 1 x t2 and 2 x m5) or purchasing options (e.g. 1 x on-demand and remaining 4 x spot).
• In ECS (with EC2 launch type), we need a way to define which EC2 instances should be used by a particular ECS service (i.e. on which underlying instances the docker containers should run). That group of instances is called a cluster. For the Fargate launch-type, a cluster is provided by AWS automatically, since the underlying infrastructure is launched and managed on-demand.
• In EKS, the term is apparently used to tell apart different EKS environments. It should be consistent with the definition by the official Kubernetes glossary. [4]

References

[1] https://docs.aws.amazon.com/AmazonECS/latest/developerguide/ECS_clusters.html
[2] https://docs.aws.amazon.com/eks/latest/userguide/clusters.html
[3] https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-fleet.html
[4] https://kubernetes.io/docs/reference/glossary/?all=true#term-cluster