Introduction to Redis Streams

Welcome! In this lesson, we will dive into Redis Streams — a powerful feature used for processing streams of data. This lesson will guide you through the basics and show you how Redis Streams can be essential for high-performance applications.

In this lesson, we'll learn about streams in Redis and how they can be used to handle continuous data flows. We'll learn how to create streams, add events to them, and read events from them using the Boost.Redis library.

Streams are a powerful data structure that allows you to process real-time data efficiently. Here are a few real-world scenarios where Redis Streams can be useful:

• Chat Applications: Redis Streams can be used to handle messages in real time.
• Monitoring Systems: Streams can be used to process logs and events.
• User Activity Tracking: Streams can be used to track user actions in real time.

Here's a quick preview:

• To add an event to a stream, use the Redis command XADD.
• To read events from a stream, use the Redis command XREAD.

First, let's set up a connection to Redis using Boost.Redis. We'll connect to localhost:6379:

#include <boost/redis.hpp>
#include <boost/redis/src.hpp>
#include <boost/asio.hpp>
#include <iostream>

namespace net = boost::asio;
using boost::redis::connection;
using boost::redis::config;
using boost::redis::request;
using boost::redis::logger;

int main()
{
    net::io_context ioc;
    auto conn = std::make_shared<connection>(ioc);

    config cfg;
    cfg.addr.host = "127.0.0.1";
    cfg.addr.port = "6379";

    conn->async_run(cfg, logger{logger::level::disabled},
                    net::consign(net::detached, conn));

Here we create a Boost.Asio io_context and a Redis connection. The async_run method establishes and maintains the connection to Redis asynchronously.

Now let's add three events to a stream called mystream. Each event contains field-value pairs that describe the event:

    request req;
    req.push("XADD", "mystream", "*", "event", "login", "user", "Alice");
    req.push("XADD", "mystream", "*", "event", "purchase", "user", "Bob", "amount", "100");
    req.push("XADD", "mystream", "*", "event", "add_to_cart", "user", "Alice", "product", "laptop");

    boost::redis::response<std::string, std::string, std::string> xadd_resp;

    conn->async_exec(req, xadd_resp, [conn](auto ec, auto) {
        if (ec) {
            std::cerr << "XADD error: " << ec.message() << "\n";
            return;
        }

The request object allows us to pipeline multiple Redis commands. Each XADD command uses "*" as the entry ID, which tells Redis to auto-generate a unique ID based on the current timestamp.

The response type boost::redis::response<std::string, std::string, std::string> tells Boost.Redis that we expect three string responses (one for each XADD command). Each response will contain the auto-generated entry ID.