Welcome back! In this lesson, we will explore a crucial feature of Redis: key expiration. This topic builds on our Redis knowledge and adds another tool to our kit for managing data efficiently in high-performance applications.
You will learn how to set expiration times on your Redis keys. This is useful for many situations, such as caching data, managing session lifetimes, or any scenario where you want data to automatically expire after a certain period. We will learn how to set expiration times on keys and check the remaining time-to-live (TTL) for a key.
Here's a quick preview of what you will be doing:
To set a key with an expiration time, you can use the Set method with an additional parameter for timestamp:
Go1package main 2 3import ( 4 "context" 5 "fmt" 6 "time" 7 "github.com/redis/go-redis/v9" 8) 9 10func main() { 11 client := redis.NewClient(&redis.Options{ 12 Addr: "localhost:6379", 13 }) 14 15 key := "session:12345" 16 ctx := context.Background() 17 18 // Set the key with a value and an expiration time of 2 seconds 19 err := client.Set(ctx, key, "data", 2*time.Second).Err() 20 if err != nil { 21 panic(err) // Handle any errors in setting the key 22 } 23 24 // Retrieve and print the time-to-live (TTL) for the key 25 ttl, err := client.TTL(ctx, key).Result() 26 if err != nil { 27 panic(err) // Handle any errors in getting the TTL 28 } 29 fmt.Printf("Time-to-live for session key: %v\n", ttl) 30 31 // Wait for the key to potentially expire 32 time.Sleep(3 * time.Second) 33 34 // Attempt to retrieve the value of the key after expiration time 35 value, err := client.Get(ctx, key).Result() 36 if err == redis.Nil { 37 fmt.Println("Value: None") // The key has expired as expected 38 } else if err != nil { 39 panic(err) // Handle any errors in retrieving the key 40 } else { 41 fmt.Printf("Value: %s\n", value) // Print the value if the key hasn't expired 42 } 43}
The above code snippet shows how to set a key (session:12345) with a value (data) that expires after 2 seconds.
To check the remaining time-to-live (TTL) for a key, you can use the TTL method with the key name as the parameter.
After waiting for the expiration time, you can verify that the key no longer exists. This code waits 3 seconds and then attempts to get the value of the key, which should indicate that the key has expired.
Another useful method is Expire, which allows you to set the expiration time for a key after it has been created:
Go1package main 2 3import ( 4 "context" 5 "fmt" 6 "time" 7 "github.com/redis/go-redis/v9" 8) 9 10func main() { 11 client := redis.NewClient(&redis.Options{ 12 Addr: "localhost:6379", 13 }) 14 15 key := "session:12345" 16 ctx := context.Background() 17 18 // Set the key with a value and no expiration initially 19 err := client.Set(ctx, key, "data", 0).Err() // 0 indicates no expiration for now 20 if err != nil { 21 panic(err) // Handle any errors in setting the key 22 } 23 24 // Set an expiration time of 2 seconds for the key 25 err = client.Expire(ctx, key, 2*time.Second).Err() 26 if err != nil { 27 panic(err) // Handle any errors in setting expiration 28 } 29 30 // Retrieve and print the time-to-live (TTL) for the key 31 ttl, err := client.TTL(ctx, key).Result() 32 if err != nil { 33 panic(err) // Handle any errors in getting the TTL 34 } 35 fmt.Printf("Time-to-live for the key: %v\n", ttl) 36 37 // Wait for the key to potentially expire 38 time.Sleep(3 * time.Second) 39 40 // Attempt to retrieve the value of the key after expiration time 41 value, err := client.Get(ctx, key).Result() 42 if err == redis.Nil { 43 fmt.Println("Value: None") // The key has expired as expected 44 } else if err != nil { 45 panic(err) // Handle any errors in retrieving the key 46 } else { 47 fmt.Printf("Value: %s\n", value) // Print the value if the key hasn't expired 48 } 49}
This code snippet sets the key session:12345 with a value (data) and then sets the expiration time to 2 seconds. We will explore this method in more detail in the practice section.
Key expiration is an essential feature for managing limited memory resources efficiently. By setting expiration times, you can ensure that outdated data is removed automatically without manual intervention. This can significantly improve your application's performance and reliability.
By mastering key expiration, you can build more intelligent caching mechanisms, manage user sessions effectively, and handle temporary data seamlessly. This concept is a critical aspect of maintaining high-performance applications that need to run efficiently over time.
Exciting, right? Let's move on to the practice section and start applying these concepts hands-on.