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BetVictor Exchange Rate Challenge

DESIGN DECISIONS

Basic Model Class Diagram

alt text

DataSource Clients

  • The Application integrates with the clients using the abstractions of exchange-rate-client and Configuration. There is no direct reference of Client Implementations for loosely coupling.

  • The coupling point of application with client implementations is by scanning any components found under client-impl module. Therefore, if you wish to add a new client implementation, two steps are required:

    • Make it a Component (to be scanned by spring)
    • Declare its type in DataSourceClientType numeration. That enumeration is also used for configuration of the default client implementation

  • In All Operations, the client implementation can be controlled by passing x-datasource-provider header to the request. The header receives values from DataSourceClientType enum. If nothing is passed, the application uses the default client type configured via property default.application.datasource-provider.

CACHE

  • Hazelcast was selected as a call-reduction layer against the DataSources to cache responses. The in-memory data-grid of Hazelcast will have at least 1 backup (replication) across other nodes so even values fetched by node A will be accessible by node B even if traffic goes through B.

  • Retention period is configured in hazelcast.xml on each cache and affects how often the APIs might be called to fetch data (see time-to-live-seconds)

ASYNC API

  1. The implementation of async api is implemented using a RabbitMQ. Event ExchangeOperationRequest is published by all async operations to a configurable queue (exchange-operation-request).
  2. Each application node has a consumer that listens for these events and asynchronously will process them one by one.
  3. All async operations receive a mandatory callback url which will be called before the successful processing of the event finished to communicate the results to the client.
  4. If the event processing happens after 60s, the event is discarded.
  5. application.async-api.enabled controls the feature. If false, the application does not require RabbitMQ as dependency.

RUN PROJECT

To Run the Project, you can use the following options:

  • i) Using the IDEA Runner, run Main class of exchange-rate-app

  • ExampleClientMain for exhange-rate-app-client-example, the application that simulates the user for asynchronous callbacks (when application.async-api.enabled is set to true)

  • ii) mvn spring-boot:run can be used inside exchange-rate-app.

  • iii) java -jar ./target/exchange-rate-app-0.0.1-SNAPSHOT.jar in exchange-rate-app Directory

  • iv) Async-api Prerequisite: Run RabbitMQ Docker Command: docker run -it --rm --name rabbitmq -p 5672:5672 -p 15672:15672 rabbitmq:3.9-management

  • The application swagger API can be found at http://localhost:8080/swagger-ui/index.html

  • The application simulating the client swagger API can be found at http://localhost:9080/swagger-ui/index.html

  • RabbitMQ Management can be monitored at http://localhost:15672/ using guest:guest