Gateway System with Rate Limiting

This project implements a gateway system that manages client connections, processes requests, and enforces rate limiting using a token bucket algorithm. The system is designed to handle multiple clients concurrently while ensuring that each client adheres to a specified request rate limit.

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Overall Functionality

The system works as follows:

1. Client Connection:

   • A client connects to the gateway using the connect method.
   • The gateway tracks the client's connection state and sets a refresh time.

2. Request Submission:

   • A client submits a request using the submit method.
   • The gateway checks if the client is connected, if the request is within the rate limit, and if the connection has expired.
   • If all checks pass, the request is processed, and the status is logged.

3. Rate Limiting:

   • The RateLimiter enforces a limit on the number of requests a client can make within a specified time window.
   • If a client exceeds the limit, the request is throttled (Status.THROTTLED).

4. Client Disconnection:

   • A client disconnects using the disconnect method.
   • The gateway updates the client's connection state.

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Classes Overview

1. Gateway

• Interface: Gateway.java
• Implementation: GatewayImpl.java
• Description: Defines the contract for the gateway system, including methods for connecting clients, submitting requests, and disconnecting clients.
• Methods:
  • connect(String client): Establishes a connection for a client.
  • submit(String client, Object request): Submits a request from a client and returns the status (OK, ERROR, or THROTTLED).
  • disconnect(String client): Disconnects a client.

2. RateLimiter

• Class: RateLimiter.java
• Description: Implements a token bucket rate-limiting algorithm to control the rate of requests per client.
• Key Components:
  • TokenBucket: Represents the token bucket for each client.
  • canConsume(String key): Checks if a client can make a request based on available tokens.

3. ClientState

• Class: ClientState.java
• Description: Tracks the state of a client connection, including connection status and the last refresh time.
• Key Methods:
  • isConnectionExpired(): Checks if the client's connection has expired based on the configured timeout.

4. RequestProcessor

• Interface: RequestProcessor.java
• Implementation: RequestProcessorImpl.java
• Description: Defines the contract for processing client requests.
• Method:
  • onRequest(String client, Object request, Status status): Processes a request and logs its status.

5. App

• Class: App.java
• Description: A simple application to demonstrate the gateway system. Connects a client, submits requests, and logs the results.

Steps to Build and Test

Prerequisites

• Java Development Kit (JDK) 8 or higher.
• Maven (for building and testing).

1. Build the Project

Using Maven:

mvn clean install

2. Run the Application

The App class demonstrates the functionality of the gateway system. Run it using the following command:

Using Maven:

mvn exec:java -Dexec.mainClass="org.galaxy.App"