Airtasker Rate Limiter

Thanks for given me the opportunity to enjoy working on this challenge. As the challenge does not specify how the method should be exposed, what is the interface, and how the "return" value should be make, I tried to build a first iteration for an extensible rate limiter.

The project is divided in submodules:

core: it contains the logic of rate limiting, but it is quite generic, it does not impose any restrictions on the type of the request. This module contains one implementation of a generic RateLimiter based on SlideLog algorithm. Additionally, has a KeyBased rate limiter which uses a delegate pattern and maintains one RateLimiter for each key.
jaxrs: Contains the integration classes for adapting the core rate limiters to the JAX-RS 2.1 specification. It contains a filter and also it provides a simple annotation that can be used in resource methods in order to provide simple rate limiting by resource method.
jaxrs-sample-app: App with a sample resource URL /sample which is rate limited. It simulates a key based authentication (it actually just check if the header is in the request), and the rate limit is applied for each different key.

How to build

Requirements

JDK version 11 or later (it is tested with version 11)

Build and test

Run the command (in linux or mac):

# ./gradlew check

Run the sample application

Run the command (in linux or mac):

# ./gradlew run --args="-p 8080"

Change the number 8080 for a free port.

The application only have one endpoint /sample which is rate limited by default to 100 request per hour.

The rate limit is based on an api key which should be passed as a header Api-Key. In case the header is not present, the response returns 403.

Example request with curl:

curl -v -H 'Api-Key: testing4' http://localhost:8081/sample

JAXRS Module

This module contains a generic filter compatible with JAX-RS 2.1. It is tested with the Jerser which is the reference implementation.