Live Coding Task: Anonymous Comment Board

Services in docker-compose

The repository includes a docker-compose.yml with the following pre-configured services:

• test-task: the main service you will implement. It contains a Dockerfile and a starter Rust application using actix-web.
• nginx: reverse proxy.
• mongodb
• redis

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Goal

Build a REST-based service that allows posting and reading anonymous comments grouped by topic. Each topic is identified by a UUID. The service stores comments and maintains an in-memory list of the most recently updated topics.

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Task Description

Implement an HTTP service with the following features:

1. Post a comment

Endpoint:

POST /comments

Input:

{
  "topic_id": "uuid-string",
  "sender": "anon123",
  "text": "hello world"
}

Behavior:

• Adds the comment under the specified topic.
• Sets a server-side timestamp (DateTime<Utc>).
• Updates an in-memory list of 10 most recently updated topics (most recent first).
• Logs the sender and topic ID.
• Returns 201 Created with the full comment (including timestamp).

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2. Get comments for a topic

Endpoint:

GET /comments/{topic_id}

Behavior:

• Returns all comments for the specified topic.
• JSON array format, ordered by timestamp ascending.

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3. Get recently updated topics

Endpoint:

GET /topics/recent

Behavior:

• Returns up to 10 most recently updated topic UUIDs.
• This list is stored and updated in memory only, not in the database.

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Data model

{
  "topic_id": "uuid",
  "sender": "string",
  "text": "string",
  "timestamp": "RFC3339 datetime"
}

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Constraints

• Comments must be stored persistently in database.
• Only the list of recent topics should be kept in memory.
• No authentication.
• Fully async using tokio and actix-web.
• Use uuid for topic IDs.
• Use chrono for timestamps.

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Building and Running the Project

To build the Docker image:

./build-image.sh

To start the project with all services:

docker compose up

The test-task service will be accessible at:

http://0.0.0.0:8080/test-task/

To rebuild the image and apply changes:

./build-image.sh && docker compose up -d

To shut everything down and remove volumes:

docker compose down -v