This document explains the requirements and recommendations for creating an Amazon Elastic Kubernetes Service (EKS) cluster for ScalarDL Ledger deployment. For details on how to deploy ScalarDL Ledger on an EKS cluster, see Deploy ScalarDL Ledger on Amazon EKS.

Before you begin

You must create an EKS cluster based on the following requirements, recommendations, and your project’s requirements. For specific details about how to create an EKS cluster, see the official Amazon documentation at Creating an Amazon EKS cluster.

Requirements

When deploying ScalarDL Ledger, you must:

  • Create the EKS cluster by using Kubernetes version 1.21 or higher.
  • Configure the EKS cluster based on the version of Kubernetes and your project’s requirements.

Note

For Byzantine fault detection in ScalarDL to work properly, do not deploy your application pods on the same EKS cluster as the ScalarDL Ledger deployment.

Recommendations (optional)

The following are some recommendations for deploying ScalarDL Ledger. These recommendations are not required, so you can choose whether or not to apply these recommendations based on your needs.

Use 4vCPU / 8GB memory nodes for the worker node in the ScalarDL Ledger node group

From the perspective of commercial licenses, resources for one pod running ScalarDL Ledger are limited to 2vCPU / 4GB memory. In addition, we recommend deploying one ScalarDL Ledger pod and one Envoy pod on one worker node.

In other words, the following components run on one worker node:

  • ScalarDL Ledger pod (2vCPU / 4GB)
  • Envoy proxy (0.2–0.3 vCPU / 256–328 MB)
  • Kubernetes components

With this in mind, you should use a worker node that has 4vCPU / 8GB memory resources. We recommend running only the above components on the worker node for ScalarDL Ledger. And remember, for Byzantine fault detection to work properly, you cannot deploy your application pods on the same EKS cluster as the ScalarDL Ledger deployment.

Note that you should configure resource limits based on your system’s workload if the Envoy pod exceeds the above resource usage. In addition, you should consider scaling out the worker node and the ScalarDL Ledger pod if the ScalarDL Ledger pod exceeds the above resource usage and if latency is high (throughput is low) in your system.

Create a node group for monitoring components (kube-prometheus-stack and loki-stack)

We recommend running only pods related to ScalarDL Ledger on the worker node for ScalarDL Ledger. If you want to run monitoring pods (e.g., Prometheus, Grafana, Loki, etc.) by using kube-prometheus-stack and loki-stack on the same EKS cluster, you should create other node groups for monitoring pods.

Configure Cluster Autoscaler in EKS

If you want to scale ScalarDL Ledger pods automatically by using Horizontal Pod Autoscaler, you should configure Cluster Autoscaler in EKS too. For details, see the official Amazon documentation at Autoscaling.

In addition, if you configure Cluster Autoscaler, you should create a subnet in an Amazon Virtual Private Cloud (VPC) for EKS with the prefix (e.g., /24) to ensure a sufficient number of IPs exist so that EKS can work without network issues after scaling.

Create the EKS cluster on a private network

You should create the EKS cluster on a private network (private subnet in a VPC) since ScalarDL Ledger does not provide any services to users directly via internet access. We recommend accessing ScalarDL Ledger via a private network from your applications.

Use three availability zones

To ensure that the EKS cluster has high availability, you should use several resources in three availability zones as follows:

  • Create three subnets in different availability zones in the VPC.
  • Create at least three worker nodes.

Restrict connections by using some security features based on your requirements

You should restrict unused connections in ScalarDL Ledger. To restrict unused connections, you can use some security features in AWS, like security groups and network access control lists.

The connections (ports) that ScalarDL Ledger uses by default are as follows. Note that, if you change the default listening port for ScalarDL Ledger in the configuration file (ledger.properties), you must allow connections by using the port that you configured.

  • ScalarDL Ledger
    • 50051/TCP (Accept the requests from a client)
    • 50052/TCP (accepts privileged requests from a client)
    • 50053/TCP (accepts pause and unpause requests from a scalar-admin client tool)
    • 8080/TCP (accepts monitoring requests)
  • Scalar Envoy (used with ScalarDL Ledger)
    • 50051/TCP (load balancing for ScalarDL Ledger)
    • 50052/TCP (load balancing for ScalarDL Ledger)
    • 9001/TCP (accepts monitoring requests for Scalar Envoy itself)

Note that you also must allow the connections that EKS uses itself. For more details about Amazon EKS security group requirements, refer to Amazon EKS security group requirements and considerations.

Add a label to the worker node that is used for nodeAffinity

You can make a specific worker node dedicated to ScalarDL Ledger by using nodeAffinity and taint/toleration, which are Kubernetes features. In other words, you can avoid deploying non-ScalarDL Ledger pods (e.g., application pods) on the worker node for ScalarDL Ledger. To add a label to the worker node, you can use the kubectl command as follows.

  • ScalarDL Ledger example 
    kubectl label node <WORKER_NODE_NAME> scalar-labs.com/dedicated-node=scalardl-ledger

In addition, if you use managed node groups in EKS, you can set this label when you create a managed node group. If you add this label to make specific worker nodes dedicated to ScalarDL Ledger, you must configure nodeAffinity in your custom values file as follows.

  • ScalarDL Ledger example 
    envoy:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
          - matchExpressions:
              - key: scalar-labs.com/dedicated-node
                operator: In
                values:
                  - scalardl-ledger

ledger:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
          - matchExpressions:
              - key: scalar-labs.com/dedicated-node
                operator: In
                values:
                  - scalardl-ledger

Add taint to the worker node that is used for toleration

You can make a specific worker node dedicated to ScalarDL Ledger by using nodeAffinity and taint/toleration, which are Kubernetes features. In other words, you can avoid deploying non-ScalarDL Ledger pods (e.g., application pods) on the worker node for ScalarDL Ledger. To add taint to the worker node, you can use the kubectl command as follows.

  • ScalarDL Ledger example 
    kubectl taint node <WORKER_NODE_NAME> scalar-labs.com/dedicated-node=scalardl-ledger:NoSchedule

In addition, if you use managed node groups in EKS, you can set this taint when you create a managed node group. For details on how to configure Kubernetes taints through managed node groups, refer to Node taints on managed node groups.

If you add this taint to make specific worker nodes dedicated to ScalarDL Ledger, you must configure tolerations in your custom values file as follows.

  • ScalarDL Ledger example 
    envoy:
  tolerations:
    - effect: NoSchedule
      key: scalar-labs.com/dedicated-node
      operator: Equal
      value: scalardl-ledger

ledger:
  tolerations:
    - effect: NoSchedule
      key: scalar-labs.com/dedicated-node
      operator: Equal
      value: scalardl-ledger