reyanchaudhary / oj

For personal project.

OJ

This API Runs Code submissions in a secure environment and Passes Verdicts based on pre-saved testcases. It uses RabbitMQ for Queueing the submissions, Redis for Caching the results and Docker for Sandboxing. It is a Remote Code Execution Engine, linked to an online judge. It suppports the following Languages:

• C
• C++
• Python 3

Pre-requisites

The Following Services should be up and running:

• RabbitMQ
• Redis
• MongoDB

Apart from this You should have Docker Installed in your system

Clone the Repository

Run the following Command to clone the repository:

git clone https://github.com/vkm41101/OJ.git

Run the Server

node Server/server.js

Run The Judge

node Judge/config/rabbitMQ.js

Why Message Queueing?

The Problem Lies in the scale, This kind of API would work fine without Message Queueing with a small scale, whee at a time, the API might only face about 10-15 Submission at a time at most. However For a lager Scale, it becomes Impossible to execute all of them at once. One solution could be rate Limiting, but It would be unfair in a coding contest if your submission is held because of rate limiting, and hence Message Queueing was a Legitimate option.

Why Docker?

Let us Consider a case where a person tries to submit a malicious Code, like try to do a Fork attack or execute "rm-rf". In such Cases Docker Plays a crucial role in Containerizing the effects of such malicious code.

How to Use:

Following Header is to be used for All requests:

{"Content-type" : "application/json"}

Testcases need to be individually sent as a Post request to

http://localhost:3000/testCase/:questionID

where :questionID refers to a unique question ID for a question

The Body for Posting Testcases should be in the following format:

{
  inputSRC : "Input of the respective testcase"
  outputSRC : "Expected output for the above input"
}

To delete The Testcases, send a Delete request to:

http://localhost:3000/testCase/delete-all/:questionID

To Check a particular Testcase, send a Get request to:

http://localhost:3000/testCase/:questionID/:testcaseNumber

where :testCaseNumber refers to the testcase number of the particular Test Case you want to recieve.

Although the Testcases are posted individually, a submitted program will be tested against all the testcases.

To post a submission, send a Post request to:

http://localhost:3000/submit/

The body of the Post should include:

{
  questionID: "Question ID of the question for whom the submission is supposed to be"
  language: "Language Code of the Submission as per given below"
  timeOut: "Time Limit for Execution"
  src: "Source code of Submission"
}

The language Code of the languages are given below:

• C: 'C'
• C++: 'C++'
• Python: 'python3'

When Successfully Queued, the API Sends the Following response:

{
  status: "InQueue"
  submissionID: "The submission ID assigned by the API to the respective submission"
}

After this, the User needs to send Regular Get Requests to:

http://localhost:3000/result/:submissionID

To get updates about the Submission. Here submissionID is the Submission ID assigned to the submission by the application

Refer Below for What does each response mean:

• AC: All Correct
• WA: Wrong Answer
• CE: Compilation Error
• timeOut: Time Limit Exceeded

Applications

• Online Coding Contests
• Coding Interviews
• Online Assesments and Coding Tests

Built With

• Express - The web framework used
• RabbitMQ - Message queue
• MongoDB - Database for testcases.
• Redis - Used for caching the results.
• Docker - Used for Running the Program in a secure Environment.
• NodeJS - Used as the js runtime.

Acknowledgements:

• https://blog.remoteinterview.io/how-we-used-docker-to-compile-and-run-untrusted-code-2fafbffe2ad5
• https://medium.com/@yashbudukh/building-a-remote-code-execution-system-9e55c5b248d6