Aggregator Service

This repo contains code for an aggregator service that

1. Takes the discovery URL, i.e. http://localhost:8080/shops as a command line argument.
2. Queries the discovery URL to find out all the shops and their flavor URLs.
3. Queries each of these per shop flavor URLs, i.e. http://localhost:8080/shops/shop1/flavors, and aggregates them.
   • Multiple shops can have the same flavor, but the aggregate list should be unique. So, if 2 shops report the rum raisin flavor, there should only be a single entry in the aggregate.
4. Exposes a local http server with a single endpoint of /flavors, which returns the aggregated list of flavors across all ice cream shops.
5. Keep this aggregated list of flavors up-to-date by repeating steps 2 and 3 every few seconds.

We have a discovery endpoint that provides us a list of ice cream shop names and URLs for flavors available at that shop:

$ curl http://localhost:8080/shops 
shop1,http://localhost:8080/shops/shop1/flavors
shop2,http://localhost:8080/shops/shop2/flavors
shop3,http://localhost:8080/shops/shop3/flavors

Each flavor URL returns a list of flavors available at that shop:

$ curl http://localhost:8080/shops/shop1/flavors
rum raisin
cherry garcia

We want to provide an aggregated endpoint to our customers which tells them all the flavors available across all the shops:

$ curl http://localhost:8081/flavors
rola cola
rum raisin
chunky monkey
mcflurry
cherry garcia

Constraints

• The aggregated /flavors endpoint should respond in less than 1s.
• The shops can be added or removed any time. The aggregator should stay up-to-date with the current list of shops within 1 minute of the list changing from the /shops url.
• The /shops url can take upto 10s to respond and can return 1-10K shops.
• The flavors for each shop can also be added or removed any time. The aggregator should stay up-to-date with the current list of flavors within 3 minutes of the flavor list changing for a shop.
• One shop can have 1-1000 flavors and can take upto 10s to respond to requests for listing its flavors.
• It is acceptable to return a partial list of flavors when the application is initializing.