Microservices - Service Discovery

Step-1: What are we going to learn?

• We are going to enable the service discovery for Notificaiton Microservice.
• User Management Microservice will call Notification Service using AWS Cloud Map Namespace.
• In that way calls from User Management Microservice to Notificaiton Microservice will be internal to VPC.
• For introduction slides refer the presentation slides.

Step-2: AWS CloudMap - Create Namespace

• Introduction to AWS CloudMap
• Create a namespace in AWS Cloud Map to just go through the console and delete it.
• For introduction slides refer the presentation slides.

Step-3: Notification Microservice - Create Service with Service Discovery enabled

• Configure Service
  • Launch Type: Fargate
  • Task Definition:
    • Family: notification-microservice-td
    • Version: 1(latest)
  • Service Name: svc-notification-microservice-Service-Discovery
  • Number of Tasks: 1
• Configure Network
  • VPC: ecs-vpc
  • Subnets: us-east-1a, us-east-1b
  • Security Groups: ecs-notificaiton-microservice-ServiceDiscovery-Inbound
    • Allow traffic from UserManagement Service security (ecs-microservice-inboud) group or anywhere
    • Inbound Port 8096 (for both notification service)
    • Notification Service uses Port 8096
  • AutoAssign Public IP: Enabled
  • Load Balancing
    • Load Balancer Type: None
    • Important Note: As we are using Service Discovery DNS name for Notification Service, this service doesnt need load balancing via ALB.
  • Service Discovery
    • Enable service discovery integration: Checked
    • Namespace: create new private name space
    • Namespace Name: microservices.local
    • Configure service discovery service: Create new service discovery service
    • Service discovery name: notification-service
    • Enable ECS task health propagation: checked
    • Rest all defaults
• Verify in AWS Cloud Map about the newly created Namespace, Service and registered Service Instance for Notification Microservice.

Step-4: User Management Microservice - Update Task Definition

• Update User Management Microservice Task definition, respective container definition environment variables of Notificaiton service host and port.
• Configure Container Definition
  • Environment Variables
    • NOTIFICATION_SERVICE_HOST=notification-service.microservices.local
    • NOTIFICATION_SERVICE_PORT=8096

Step-5: User Management Microservice - Update Service

• Update the User Management Microservice ECS Service svc-usermgmt-microservice with new updated version of task defintion.

Step-6: Test User Management Microservices using Postman

User Management Service

• Create User
  • Verify the email id to confirm account creation email received.
• List User
  • Verify if newly created user got listed.

Step-7: Increase Number of Tasks to 4 in Notification Microservice ECS Service.

• Increase Number of Tasks to 4 in Notification Microservice ECS Service.
  • ECS Service Name: svc-notification-microservice-Service-Discovery
• Verify in AWS Cloud Map about the newly registered Service Instances for Notification Microservice.

Step-8: Additional Observations

• Now the request from User Management Microservice to Notification Microservice is local to VPC and not via internet or using any private internal load balancer.
• In this approach we really dont see Elastic load balancing.
• One service will call other service with service name and those service names are DNS registered in private DNS hosted zone with record set.
• Example: If we have 3 notification service containers
  • 3 private IP addresses we will have for those 3 containers
  • 3 recordsets (A Records) will be created in Route53 with name "notification.microservices.local"
• This is achieved using Route53 Multivalue Routing Policy.
• Conclusion:
  • In short, Service load balancing happens using Route53 multivalue routing policy.
  • Its not a substitute for Elastic Load balancing but it will do the job for RESTful API's which are stateless.
  • In addition, with Service Discovery there is no special proxy like load balancer in between two microservices, so no additional network hop which means very good performance improvement using Service Discovery.
• For additional reference about Route53 Multivalue Routing Policy refer below link.
• Documentation Reference: https://aws.amazon.com/premiumsupport/knowledge-center/multivalue-versus-simple-policies/

Step-9: Clean Up Resources

• Update the following ECS services Number Of Tasks to 0
  • svc-usermgmt-microservice
  • svc-notification-microservice
  • svc-notification-microservice-Service-Discovery