Laboratory work nr. 1 and 2 on Distributed Systems Programming

Setup

• Install Docker
• Make sure kubernetes is turned on in docker (Settings -> Kubernetes -> Enable -> Apply)
• Install Linkerd (for load balancing)

Run the commands

make init

Start the app

make run

Enjoy.

Stop the app

make stop

Run unit tests

make tests

Veterinary clinics services and pet data management

Distributed app for veterinary clinics and pet data management. Includes pet registration, appointments, notifications/emails about pet vaccination, pet records update after each consultation.

Endpoints

Postman collection

Status endpoint

Health check endpoint for all services

Endpoint: /status
Method: GET
Response: 200 OK
Body: {
    "status": "ok"
}

API Gateway

Owner service endpoints from gateway

Endpoint: /api/owner/register
Method: POST
Payload: {
    "email": "email@asd.com"
}
Response: 201 Created
Body: {
    "message": "Register successful",
    "ownerId": "0b2f4780-46f0-4d0f-806a-2b3033f9b285"
}

Endpoint: /api/owner/register-pet
Method: POST
Payload: {
    "email": "{{email}}",
    "type": "Dog",
    "race": "Chihuaua",
    "name": "Devil incarnate"
}
Response: 201 Created
Body: {
    "message": "Pet Register successful"
}

Endpoint: /api/owner/{{email}}/pets
Method: GET
Response: 200 OK
Body: {
    "message": "ok",
    "pets": [
        {
            "Type": "Dog",
            "Race": "Chihuaua",
            "Name": "Devil incarnate"
        }
    ]
}

Endpoint: /api/owner/remove-data/{{email}}
Method: DELETE
Response: 200 OK
Body: {
    "message": "Owner deleted successfully"
}

Veterinary service endpoints from gateway

Endpoint: /api/veterinary/make-appointment
Method: POST
Payload: {
    "petId": "1",
    "dateTime": "2023-09-09T13:00:00.000Z"
}
Response: 201 Created
Body: {
    "message": "Appointment made"
}

Endpoint: /end-appointment
Method: POST
Payload: {
    "appointmentId": "73346b7d-288e-4ec3-a801-042576603372",
    "details": "dog is evil"
}
Response: 200 OK
Body: {
    "message": "Appointment ended"
}

Test endpoints

Endpoint: /api/test/timeout
Method: GET
Response: 408 Request Timeout
Body: {
    "error": "Request timed out"
}

Spam this until you get 429

Endpoint: /api/test/rate-limit
Method: GET
Response: 429 Too Many Requests
Body: {
    "error": "You're being rate limited"
}

Endpoint: /api/test/circuit-breaker
Method: GET
Response: 500 Internal Server Error
Body: {
    "error": "Exception thrown on purpose"
}

Application Suitability

Microservice architecture is suitable for veterinary clinic services and pet data management. These are the main pros for a microservice architecture:

• Microservices allow for individual components to scale independently. If the veterinary clinic's services and pet data management require scalability due to varying loads, microservices can be beneficial.

• Microservices offer flexibility in technology choices for each service. This can be helpful if different aspects of the application require different technologies or updates.

• Isolating different functions or services can enhance security. For example, you might want to separate sensitive pet health data.

• Microservices can make it easier to maintain and update specific components of the application without affecting the entire system. This can be advantageous for a long-term project.

• If you need to integrate with external systems like governmental services or payments, having independent microservices can make it easier to manage these integrations without affecting the entire system.

Service boundaries

Technology Stack and Communication Patterns

The services will be written in C# and will use SQL server as a database. The API Gateway, Service Discovery and Load Balancers will be written in Go. Additionally, the API Gateway will have a cache in Redis.

The communication between client and API Gateway will be done using REST while the communication between services will be done via gRPC.

Data Management

The Owner Service and Veterinary service will have their own databases. The Gateway will have a Redis Cache to return some cached requests. All messages wil be in JSON format.

Deployment and Scaling

Containerization (Docker) and orchestration (Kubernetes) will be used for Deployment and Scaling.

References

1. Example. ”Microservice Architecture”.

2. AWS. ”What is an API”.

3. ”API health check”.

4. ”408 Request Timeout”.

5. Mark Smallcombe. ”SQL vs NoSQL: 5 Critical Differences”.

6. ”About maximum concurrent tasks”.

7. ”What is a Gateway and What Does it Do?”.

8. Julien Le Coupanec. ”Redis Cheatsheet - Basic Commands You Must Know”.

9. Simone Cusimano. ”Service Discovery in Microservices”.

10. ”Load Balancing As A Service (LBaaS)”.

11. Martin Fowler. ”CircuitBreaker”.

12. Thomas Hamilton. ”Unit Testing Tutorial – What is, Types and Test Example”.

13. Thomas Hamilton. ”Integration Testing: What is, Types with Example”.

14. Phil Sturgeon. ”Understanding RPC Vs REST For HTTP APIs”.

15. ”Pattern: Health Check API”.

16. Keyang Xiang. “Patterns for distributed transactions within a microservices architecture.

17. Ben Lutkevich. “database replication”.

18. Elasticsearch. “What is the ELK Stack?”.

19. Cloud Native Computing Foundation. “Prometheus”.

20. Grafana Labs. “Grafana”.

21. Redis. “Replication”.

22. Juan Pablo Carzolio. “The Ultimate Guide to Consistent Hashing”.

23. l3a0. “Distributing a Cache”.

24. “What is a data warehouse”.