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Auction system

The goal of the system is to serve offers to users. Using the Ports and Adaptors pattern to illustrate how a service can be easily developed and tested in isolation before being deployed as microservices.

The project is a POC that supporting the concepts outlined in the associated BLOG post.

Requirements

  • Return offers filtered by credit score.
  • Return user with eligible offers based on the following rules:
    • (a) The user's credit score is within the offer's range
    • (b) The user's current outstanding loan is less than or equal to the auto loan offer's high limit (maximumAmount).
  • Design the eligibility system to be easily extended with new rules.
  • Deserialize the sample data in an asynchronous manor and service the appropriate offers from step

Data

The json data used for validation is included in the data.json file in the fixtures folder. This data should be deserialized and processed by type.

Getting started

Starting the Partner Service

sbt 'runMain krs.partner.service.PartnerServer -admin.port=:9990'

Starting the User Service

sbt 'runMain krs.user.service.UserServer -admin.port=:9991'

Starting the API Service

sbt 'runMain rest.APIServer -admin.port=:9992'

Testing

Confirm the services are working with the REST services:

Getting offers by credit score

curl http://localhost:8080/offers/550

Getting user with offers

curl http://localhost:8080/user/1

Load Testing

brew install wrk
wrk -t12 -c400 -d30s http://127.0.0.1:8080/user/2

Architecture

System architecture:

Item service

Manages the description and auction status (created, auction, completed, cancelled) of an item.

Queries handled

  • getItem - Gets an item by an ID.
  • getItemsForUser - Gets a list of items in a provided status that are owned by a given user.

Events emitted

  • AuctionStarted (public) - When the auction is started, in response to startAuction.
  • ItemUpdated (private) - When user editable fields on an item are updated in response to createItem.
  • AuctionCancelled (private) - When the auction is cancelled, in response to cancelAuction.
  • AuctionFinished (private) - When the auction is finished, in response to BiddingFinished.

Event emitted publically are published via a broker topic named item-ItemEvent.

Commands handled

External (user)

  • createItem - Creates an item - emits ItemUpdated.
  • updateItem - Updates user editable properties of an item, if allowed in the current state (eg, currency can't be updated after auction is started), emits ItemUpdated.
  • startAuction - Starts the auction if current state allows it, emits AuctionStarted.
  • cancelAuction (not supported) - Cancels the auction if current state allows it, emits AuctionCancelled.

Events consumed

Bidding service

  • BidPlaced - Updates the current price of the item.
  • BiddingFinished - Completes the auction if current state allows, emits AuctionFinished.

Bidding service

Manages bids on items.

Queries handled

  • getBids - Gets all the bids for an item.

Events emitted

  • BidPlaced - When a bid is placed, in response to placeBid.
  • BiddingFinished - When bidding has finished, in response to finishBidding.

Commands handled

External (user)

  • placeBid - Places a bid, if the bid is greater than the current bid, emits BidPlaced.

Internal

  • finishBidding - Triggered by scheduled task that polls a read side view of auctions to finish, emits BiddingFinished

Events consumed

Item service

  • AuctionStarted - Creates a new auction for the item
  • AuctionCancelled - Completes an auction prematurely

Search service

Handles all item searching.

Queries handled

  • search - Search for items currently under auction matching a given criteria.
  • getUserAuctions - Gets a list of all current auctions that a user is participating in by user ID.

Events consumed

Item service

  • ItemUpdated - Creates or updates the details for an item in the search index
  • AuctionStarted - Updates the status for an item to started
  • AuctionFinished - Deletes an item from the search index
  • AuctionCancelled - Deletes an item from the search index

Bidding service

  • BidPlaced - Updates the current price for an item, if it exists in the index

Transaction service

Handles the transaction of negotiating delivery info and making payment of an item that has completed an auction.

Queries handled

  • getTransaction - Gets a transaction by an items ID.
  • getTransactionsForUser - Gets a list of all transactions that a given user is involved with.

Events emitted

  • DeliveryByNegotiation - When the buyer has selected by negotiation, in response to submitDeliveryDetails.
  • DeliveryPriceUpdated - When the seller has updated the delivery price, in response to setDeliveryPrice.
  • PaymentDetailsSubmitted - When payment details are submitted, in response to submitPaymentDetails.
  • PaymentConfirmed - When payment has been confirmed, in response to payment service ReceivedPayment.
  • PaymentFailed - When payment has failed, in response to payment service FailedPayment.
  • ItemDispatched - When the item has been dispatched, in response to dispatchItem.
  • ItemReceived - When the item has been received, in response to receiveItem.
  • MessageSent - When a user has sent a message, in response to sendMessage.
  • RefundInitiated - When the seller has initiated a refund, in response to initiateRefund.
  • RefundConfirmed - When a refund has been confirmed.

Commands handled

External (user)

  • sendMessage - Send a message to the other user, emits MessageSent.
  • submitDeliveryDetails - Used by the buyer to submit delivery details, emits DeliveryDetailsSubmitted.
  • setDeliveryPrice - Used by the seller to set the delivery price when delivery option is by negotiation, emits DeliveryPriceUpdated.
  • submitPaymentDetails - Used by the buyer to submit payment details.
  • dispatchItem - Used by the seller to say they have dispatched the item.
  • receiveItem - Used by the buyer to say they have received the item.
  • initiateRefund - Used by the seller to initiate a refund.

Events consumed

Item service

  • AuctionFinished - Creates the transaction.

Payment service

  • ReceivedPayment - Indicates the payment has been made, emits PaymentConfirmed.
  • FailedPayment - Indicates payment failed, emits PaymentFailed.
  • MadeRefund - Indicates a refund was made, emits RefundConfirmed.