Assignment solution

Problem

Build a rate limiter to limit requests per minute for a user

Solution

Let's use an incrementing pointer and expiring keys to keep track of the number of requests a user is sending per minute

• Lets use INCR <userid>:<minute_level_timestamp> every time the user sends the request
• Also while creating this key for the first time, let's put an expiry on this key at <minute_level_timestamp + 1>
• Whenever the user sends a request, you can check the value of this key to infer how many requests the user has sent. If the requests have reached 10, you can take necessary actions.
• The memory won't be an issue as at any time for any user a single key is present, because whenever a new minute begins the previous minute's key expires. So, in the worst case, the memory will be O(users), where users are the number of users sending requests.

RediSolar for Java

Introduction

This is the sample application codebase for RU102J, Redis for Java Developers at Redis University.

Solutions to the course programming challenges can be found on the solutions branch.

Prerequisites

In order to start and run this application, you will need:

• Java 8 JDK or higher
• Maven
• Access to a local or remote installation of Redis version 5 or newer (local preferred)
• If you want to try the RedisTimeSeries exercises, you'll need to make sure that your Redis installation also has the RedisTimeSeries Module installed

If you're using Windows, check out the following resources for help with running Redis:

• Redis Labs Blog - Running Redis on Windows 10
• Microsoft - Windows Subsystem for Linux Installation Guide for Windows 10

How to Start the RediSolar Application

When using Redis on localhost, port 6379 with no password:

1. Run mvn package to build your application.
2. Load the sample data: java -jar target/redisolar-1.0.jar load. If you want to erase everything in Redis before loading the data, use java -jar target/redisolar-1.0.jar load --flush true, but be aware that this will delete ALL keys in your Redis database.
3. Start the application with java -jar target/redisolar-1.0.jar server config.yml
4. To check that your application is running enter url http://localhost:8081, substituting localhost for the hostname that you're running the application on if necessary.

When using Redis on another host, port or with a password:

1. Edit config.yml, setting the values for your Redis host, port and password if needed.
2. Edit src/test/java/com/redislabs/university/RU102J/HostPort.java, setting the values for your Redis host, port, and password if needed.
3. Run mvn package to build your application.
4. Load the sample data with java -jar target/redisolar-1.0.jar load --host <hostname> --port <port> --password <password>.
5. Start application with java -jar target/redisolar-1.0.jar server config.yml.
6. To check that your application is running enter url http://localhost:8081, substituting localhost for the hostname that you're running the application on if necessary.

Tests

To run all tests:

mvn test

To run a specific test:

mvn test -Dtest=JedisBasicsTest

Building

To rebuild the application:

mvn package

To rebuild the application without running the tests:

mvn package -DskipTests 

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