Request Threshold Blocker

Welcome to the Express.js coding lab! In this lab, your task is to implement a simple Express.js application that includes a /get-time route. This route will return the current time in Unix timestamp format, but with some specific requirements and constraints.

Objectives

• Implement a route /get-time that returns the current time in Unix timestamp format.
• Ensure the route only responds if a custom request header x-sent-from is present and has a valid string value.
• Implement rate limiting to restrict the number of requests per user to a maximum of 10 requests.

Instructions

1. Create the Express App:

   • Set up an Express.js application.
   • Implement the /get-time route.

2. Implement JSON Response:

   • When a request is made to /get-time with a valid x-sent-from header, the response should be a JSON object with the current Unix timestamp.
   • Example response: { "time": 1631810967 }.

3. Validate Custom Header:

   • Ensure that the /get-time route responds with a 400 status code if the x-sent-from header is missing or its value is not a valid string.
   • Example error response: 400 Bad Request.

4. Implement Rate Limiting:

   • Track the number of requests made by each user based on the x-sent-from header.
   • Allow a maximum of 10 requests per user. If a user exceeds this limit, respond with a 400 status code.
   • Example error response after exceeding the limit: 400 Bad Request.

Constraints

• Use port number 1337, but you can reference it using process.env.PUBLIC_PORT.
• Always use process.env.PUBLIC_HOSTNAME to get the URL of the backend server.
• Utilize the axios library for making network requests.
• Log errors using console.error in try-catch blocks.
• Implement the solution in a single file for simplicity.
• Use ESM syntax exclusively (no CommonJS).

Example

Here’s an example of how you might structure your response:

{
  "time": 1631810967
}

Challenges Information

Challenge 1: /get-time returns proper JSON response

Objective: Ensure that the /get-time route returns the current time in Unix timestamp format.

Details:

• When a request is made to /get-time with a valid x-sent-from header, the response should include a JSON object.
• The JSON object should have a single key time with the value being the current Unix timestamp.
• Example response: { "time": 1631810967 }

Instructions:

1. Implement the /get-time route in your Express app.
2. Ensure the route responds with a JSON object containing the current Unix timestamp when a valid x-sent-from header is present.
3. Use res.json() to send the JSON response.

Challenge 2: /get-time returns 400 in absence of custom request header

Objective: Validate that the route correctly handles missing or invalid custom request headers.

Details:

• When a request is made to /get-time without the x-sent-from header, the server should respond with a 400 status code indicating a bad request.
• Similarly, if the x-sent-from header is present but its value is not a valid string, the server should also respond with a 400 status code.
• Example response: 400 Bad Request

Instructions:

1. Check for the presence of the x-sent-from header in the request.
2. If the header is missing or its value is not a valid string, respond with a 400 status code.
3. Use res.status(400).send() to send the error response.

Challenge 3: /get-time returns 400 when exceeds 10 requests per id threshold

Objective: Implement and verify rate limiting based on the x-sent-from header.

Details:

• Each unique value of the x-sent-from header represents a unique user.
• Track the number of requests made by each user.
• Allow up to 10 requests per user. If a user exceeds this limit, the server should respond with a 400 status code.
• Example response after exceeding limit: 400 Bad Request

Instructions:

1. Create an in-memory data structure (e.g., an object) to track the number of requests per user.
2. Increment the request count for each request made by a user.
3. If the request count exceeds 10 for a user, respond with a 400 status code.
4. Use res.status(400).send() to send the error response.