About

App with 1 GET endpoint. Originally a take home assignment for an internship, expanding on this just for fun.

Tech Stack

• React (not updated)
• Spring Boot
  • actuator, aop, cache
• Docker
• Redis
• Prometheus / Grafana
• AWS (not updated)
• Github Actions (not updated)

---

Configuration

application.yml to change coin denominations. CoinChangeServiceFactory will set coinChangeService to either Greedy or DP service on application run.

Running the Project

On aarch64 (Apple Silicon Macs)

chmod +x docker-buildx-aarch64.sh 
./docker-buildx-aarch64.sh

On windows

idk

---

API

Swagger Documentation: http://localhost:8080/swagger-ui.html

api-docs.yml: https://github.com/Arabasta/Mini-Coin/blob/master/api-docs.yaml

Request

POST: http://localhost:8080/api/v1/coin-change

{
    "amount": 7.01,
    "denominations": [0.1, 0.5, 0.01, 1, 5, 10]
}

Response

API will respond with the smallest list of coins needed to make the given amount.

{
  "coins": [
    0.01,
    1.0,
    1.0,
    5.0
  ]
}

---

AOP

todo: add docs

---

Cache

Redis is used for caching the results of the coin change calculation. Cache is evicted when DenominationsConfig.setDenominations() is called. Docker compose file will run the Redis instance.

Sample logs of cache hit:

spring-backend-1  | 2025-03-10T19:45:49.024Z  INFO 1 --- [spring_backend] [nio-8080-exec-1] c.k.s.controller.CoinChangeControllerV1  : Received request to calculate minimum coins for amount: 10
spring-backend-1  | 2025-03-10T19:45:49.052Z TRACE 1 --- [spring_backend] [nio-8080-exec-1] o.s.cache.interceptor.CacheInterceptor   : Computed cache key '10-341' for operation Builder[public java.util.Deque com.keiyam.spring_backend.service.GreedyCoinChangeService.calculateMinCoinChange(com.keiyam.spring_backend.dto.CoinChangeRequest)] caches=[coinChangeResults] | key='#request.amount.toString() + '-' + #request.denominations.hashCode()' | keyGenerator='' | cacheManager='' | cacheResolver='' | condition='' | unless='' | sync='false'
spring-backend-1  | 2025-03-10T19:45:50.254Z TRACE 1 --- [spring_backend] [nio-8080-exec-1] o.s.cache.interceptor.CacheInterceptor   : No cache entry for key '10-341' in cache(s) [coinChangeResults]
spring-backend-1  | 2025-03-10T19:45:50.256Z  INFO 1 --- [spring_backend] [nio-8080-exec-1] c.k.s.service.GreedyCoinChangeService    : Calculating minimum coins for amount: 10
spring-backend-1  | 2025-03-10T19:45:50.277Z  INFO 1 --- [spring_backend] [nio-8080-exec-1] c.k.s.service.GreedyCoinChangeService    : Calculated minimum coins: [10]
spring-backend-1  | 2025-03-10T19:45:50.278Z TRACE 1 --- [spring_backend] [nio-8080-exec-1] o.s.cache.interceptor.CacheInterceptor   : Creating cache entry for key '10-341' in cache(s) [coinChangeResults]
spring-backend-1  | 2025-03-10T19:45:50.317Z  INFO 1 --- [spring_backend] [nio-8080-exec-1] c.k.s.controller.CoinChangeControllerV1  : Successfully calculated coins: [10]
spring-backend-1  | 2025-03-10T19:46:13.332Z  INFO 1 --- [spring_backend] [nio-8080-exec-3] c.k.s.controller.CoinChangeControllerV1  : Received request to calculate minimum coins for amount: 10
spring-backend-1  | 2025-03-10T19:46:13.375Z TRACE 1 --- [spring_backend] [nio-8080-exec-3] o.s.cache.interceptor.CacheInterceptor   : Computed cache key '10-341' for operation Builder[public java.util.Deque com.keiyam.spring_backend.service.GreedyCoinChangeService.calculateMinCoinChange(com.keiyam.spring_backend.dto.CoinChangeRequest)] caches=[coinChangeResults] | key='#request.amount.toString() + '-' + #request.denominations.hashCode()' | keyGenerator='' | cacheManager='' | cacheResolver='' | condition='' | unless='' | sync='false'
spring-backend-1  | 2025-03-10T19:46:13.756Z TRACE 1 --- [spring_backend] [nio-8080-exec-3] o.s.cache.interceptor.CacheInterceptor   : Cache entry for key '10-341' found in cache(s) [coinChangeResults]
spring-backend-1  | 2025-03-10T19:46:13.757Z  INFO 1 --- [spring_backend] [nio-8080-exec-3] c.k.s.controller.CoinChangeControllerV1  : Successfully calculated coins: [10]

Metrics

Prometheus

URL: http://localhost:9090

Metrics:

Total requests:

api_requests_total{application="spring-backend"}

Average request duration:

rate(api_request_duration_seconds_sum{application="coin-change-service"}[5m]) / rate(api_request_duration_seconds_count{application="coin-change-service"}[5m])

Error rate (%) sum(rate(api_requests_failure_total[5m])) / sum(rate(api_requests_total[5m])) * 100

Throughput rate(api_requests_total{application="spring-backend"}[5m])

CPU Usage rate(api_requests_total{application="spring-backend"}[5m])

Heap jvm_memory_used_bytes{application="spring-backend", area="heap"}

Garbage collection jvm_gc_pause_seconds_sum{application="spring-backend"}

Threads jvm_threads_live_threads{application="spring-backend"}

Grafana

URL: http://localhost:3000

Credentials: admin/admin

1. Add Prometheus as a data source: http://prometheus:9090
2. Create dashboard

Deployment

Frontend (gonnna delete FE)

No

Backend

Workflow update in progress...

Todo

• Add AOP
• Add ELK
• Finish DPService
• Add Terraform
• Add k8s
• Update deployment workflow
• Add sonarqube
• Add tests