Build a Chat Room Application with Redpanda and Rust

Create a basic chat room application with Redpanda and Kafka clients developed with rust-rdkafka.

This example shows you how to:

Write a client application in Rust to produce and consume chat room messages.
Build and run multiple clients to exchange chat messages streamed through Redpanda.

What is a chat room application?

A chat room application is software that enables users to engage in real-time textual communication with one another. These applications typically allow multiple users to join a chat room, where they can send messages and interact with others in a group conversation.

Chat room applications often include features such as private messaging, user profiles, and notifications. Some popular chat room applications include Slack, Discord, and WhatsApp.

Why use Redpanda?

Redpanda offers several features that make it ideal for building a fast, scalable, and robust chat room application.

Scalability: Redpanda can scale horizontally and vertically to accommodate growing chat room usage over time.
Low-latency: Redpanda is designed for minimal latency to provide a smooth user experience and fast message delivery.
Fault tolerance: Redpanda is resilient to failures, thanks to its built-in replication and partitioning capabilities. This built-in resilience ensures that the chat room application continues to serve users even if individual brokers in the cluster experience downtime.
Durability: Redpanda persists messages on disk, maintaining chat history and allowing users to read previous conversations.

Prerequisites

Download and install Rust from rustup.rs.
Complete the Redpanda Quickstart before continuing. This example expands on the quickstart. You can choose to run either one or three brokers.

Run the lab

Build the client chat application, run it from multiple client terminals, and chat between the clients.

Clone this repository:

git clone https://github.com/redpanda-data/redpanda-labs.git

Change into the example directory:
```
cd clients/chat-room/docker/rust
```

Verify that the chat-room topic exists in your cluster by listing all topics:

docker exec -it redpanda-0 rpk topic list

Output:

NAME       PARTITIONS  REPLICAS
chat-room  1           1

If the topic doesn’t exist yet, use rpk to create a chat-room topic:

docker exec -it redpanda-0 rpk topic create chat-room

Output:

TOPIC      STATUS
chat-room  OK

Open at least two terminals, and for each terminal:
Run the client application:
```
cargo run
```
When prompted with Enter user name:, enter a unique name for the chat room.
Use the chat application: enter a message in a terminal, and verify that the message is received in the other terminals.

For example:
```
Enter user name:
Alice
Connected, press Ctrl+C to exit
Alice: Hi, I'm Alice
Bob: Hi Alice, I'm Bob, nice to meet you
```

Files in the example

This example includes the following files:

admin.rs: Checks whether the chat-room topic exists and creates it if not.
producer.rs: A producer that sends strings entered by the user of the terminal to the chat-room topic. Messages are sent as JSON encoded strings.
consumer.rs: A consumer that reads all messages from the chat-room topic and prints them to the console. You can start as many consumer groups as you like, but each group reads a message only once, which is why the example is using a generated timestamp appended to the group ID. This way, each time you run the application, you see all previous messages.
main.rs: The client application that creates the topic, producer, and consumer and implements the chat logic.

The broker settings in this code are from the Redpanda Quickstart, where the external port for broker redpanda is set to port 19092.

Next steps

This is a basic example of a chat room application. You can improve this application by implementing additional features and components, such as:

A user interface to make it more interactive and user-friendly.
A user registration and login system to authenticate users before they can access the chat room.
Rate limiting and other measures to prevent spamming and abuse in the chat room.

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