Welcome back! 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 explore streams in Redis and how they can be used to handle continuous data flows. You'll learn how to create streams, add events to them, and read events from them.

Streams in Redis are data structures that follow the FIFO (First In, First Out) principle. Each entry in a stream is stored with a unique ID, which by default includes the current timestamp, but can be customized when adding events. Streams can efficiently handle continuous flows of data, making them ideal for use cases like chat applications, monitoring systems, or user activity tracking.

Redis Streams are particularly valuable in concurrent scenarios, where multiple consumers need to efficiently process real-time data. While we don't cover concurrent consumption in detail in this lesson, it's important to understand this crucial aspect of streams. Consider these real-world scenarios where Redis Streams can be beneficial:

• Chat Applications: Ideal for real-time message handling.
• Monitoring Systems: Useful for processing logs and events.
• User Activity Tracking: Tracks user actions in real-time.

Let's dive into the details!

To add an event to a stream, use the XAdd command.
To read events from a stream, use the XRange command.

Let's see how these commands work in practice using Go.

Go
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1package main
2
3import (
4    "context"
5    "fmt"
6    "github.com/redis/go-redis/v9"
7)
8
9func main() {
10    ctx := context.Background()
11    client := redis.NewClient(&redis.Options{
12        Addr: "localhost:6379",
13    })
14
15    defer client.Close()
16
17    // Adding events to the stream
18    client.XAdd(ctx, &redis.XAddArgs{
19        Stream: "mystream",  // Name of the stream where the event will be added
20        Values: map[string]interface{}{"event": "login", "user": "Alice"},  // Key-value pairs representing the event data
21        ID:     "*",  // Unique identifier for the entry, "*" auto-generates based on the timestamp
22    })
23    client.XAdd(ctx, &redis.XAddArgs{
24        Stream: "mystream",
25        Values: map[string]interface{}{"event": "purchase", "user": "Bob", "amount": "100"},
26        ID:     "*",
27    })
28    client.XAdd(ctx, &redis.XAddArgs{
29        Stream: "mystream",
30        Values: map[string]interface{}{"event": "add_to_cart", "user": "Alice", "product": "laptop"},
31        ID:     "*",
32    })
33
34    // Reading events from the stream
35    messages, err := client.XRange(ctx, "mystream", "-", "+").Result()
36    if err != nil {
37        fmt.Println("Error reading stream:", err)
38        return
39    }
40
41    fmt.Printf("Stream messages: %v\n", messages)
42
43    if len(messages) > 0 {
44        firstMessage := messages[0].Values
45        fmt.Printf("First message: %v\n", firstMessage) // {"event": "login", "user": "Alice"}
46    }
47}

The above code snippet demonstrates how to add events to a Redis stream called mystream using XAdd. Each event contains key-value pairs representing different actions by users.

The code reads messages from mystream and prints them. The "-" and "+" arguments to XRange indicate reading messages from the beginning to the end of the stream.

Notice that to access a single message from the events slice, you can use the messages[i].Values property, which contains the actual event data. In the example above, we access the first message and print it to the console.

In addition to the XAdd and XRange commands, the XRead command is another essential function for working with Redis Streams. It allows you to read entries from one or more streams. XRead is particularly useful for blocking reads, which are used in consumer applications to wait for new data to arrive. The command can be configured to read from the last point seen, making it highly effective in applications with multiple consumers.

Here's an example of using the XRead command in Go:

Go
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1// Reading latest events from the stream
2xReadArgs := &redis.XReadArgs{
3    Streams: []string{"mystream", "0"},  // Stream names and starting point for reading. "0" means from the beginning
4    Count:   0,  // Specifies the maximum number of entries to return. "0" reads all available messages
5    Block:   0,  // Block indefinitely until events are available
6}
7
8messages, err := client.XRead(ctx, xReadArgs).Result()
9if err != nil {
10    fmt.Println("Error reading stream with XRead:", err)
11    return
12}
13
14for _, stream := range messages {
15    for _, message := range stream.Messages {
16        fmt.Printf("Message: %v\n", message.Values)
17    }
18}

The above code snippet demonstrates how to use XRead to retrieve messages from mystream. XReadArgs specifies the parameters for reading, including stream names, message count, and blocking behavior, thus efficiently handling new data as it becomes available.

Understanding Redis Streams is crucial for applications that need to process a large volume of real-time data efficiently. Whether you are building a chat application, a monitoring system, or handling user activities and logs, Redis Streams can manage it all.

Through this lesson, you have seen how to handle streams using Redis with Go. Are you excited to see how Redis Streams can elevate your application? Let's move on to the practice section to get some hands-on experience!