Memcached Add in Golang (Detailed Guide w/ Code Examples)

Use Case(s)

In Golang, the 'Add' function of the Memcached client is commonly used when you want to set a new key-value pair only if the key does not already exist in the cache. This can be useful when preventing overwrites of existing data or ensuring uniqueness.

Code Examples

Here's an example of how to use it:

package main

import (
    "fmt"
    "github.com/bradfitz/gomemcache/memcache"
)

func main() {
    mc := memcache.New("127.0.0.1:11211")

    err := mc.Add(&memcache.Item{Key: "Hello", Value: []byte("World")})

    if err != nil {
        fmt.Println(err)
    } else {
        it, _ := mc.Get("Hello")
        fmt.Println(string(it.Value))
    }
}

In this code, we first instantiate a Memcached client that connects to a local Memcached server. Then, we attempt to add a key-value pair ("Hello": "World") to the cache using the Add function. If the key already exists, it will return an error. If the operation was successful, it retrieves the value associated with the key "Hello" and prints it out.

Best Practices

• Always handle errors returned by the Add function. It will return an error if the key already exists in the cache.
• Use keys that are descriptive and consistent for easier debugging and maintenance.
• Be aware of the maximum size allowed for keys and values in Memcached. As of 2021, the key length limit is 250 bytes, and the value size can't exceed 1MB by default.

Common Mistakes

• One common mistake is not checking if the Add operation was successful. Always check the error returned by the Add function.
• Overusing Memcached for data that isn't frequently accessed. Memcached is best used for data that needs to be retrieved quickly and frequently.

FAQs

Q: What happens if I try to add a key-value pair that already exists in Memcached?

A: The Add function will return an error if you try to add a key that already exists. You can use the Set function if you want to overwrite the value of an existing key.

Q: Can I increase the maximum size of the keys and values in Memcached?

A: Yes, you can configure these limits when starting up your Memcached server, but it's generally recommended to stay within the defaults as increasing them may lead to inefficient usage of memory.