golang cache implementation

Golang is an efficient, concise and fast programming language, which is favored by more and more developers. As Internet applications become more and more popular, some performance optimization technologies have gradually attracted attention. Caching technology is one of the commonly used performance optimization solutions in Internet applications. As a language for developing high concurrency, golang also provides a cache library for developers to use. This article will introduce the implementation of caching in golang.

1. What is cache?

Caching is a technology that improves data reading and writing performance, analogous to translation in daily life. If a person needs to translate an article but does not understand some of the new words in the article, he needs to look it up in a dictionary. If you have to look up the dictionary every time, the time spent cannot be underestimated. But if we already know the meaning of some new words, we can temporarily store these new words in our minds, and when we encounter the same words, we can directly use the meanings we have already mastered. During this process, we temporarily store the contents of the dictionary in our minds, which is what we call caching.

In Internet applications, we can temporarily store some data that is accessed frequently and does not change frequently in the cache. For example, some basic configurations can be stored in the cache to reduce the time and resources of querying the database and improve the operating efficiency of the system.

2. Cache implementation in golang

In golang, there are many open source cache libraries, including: groupcache, bigcache, redis-go, etc. Among them, groupcache is the cache library that comes with golang and is the cache library recommended by the golang official team. This article takes groupcache as an example to introduce the cache implementation in golang.

1. Installing groupcache

Using groupcache in golang is very simple and can be installed quickly. Just use the go get command:

go get -u github.com/golang/groupcache

2. Using groupcache

groupcache provides two basic cache implementations, namely stand-alone cache and distributed cache. In this article, we will focus on the use of stand-alone cache.

Single-machine cache is very convenient to use. You only need to define a groupcache object to start using it:

package main

import (
    "fmt"
    "time"

    "github.com/golang/groupcache"
)

func main() {
    group := groupcache.NewGroup("mycache", 64<<20, groupcache.GetterFunc(
        func(ctx groupcache.Context, key string, dest groupcache.Sink) error {
            time.Sleep(100 * time.Millisecond) // 模拟耗时读取操作
            value := []byte("value from db")
            dest.SetBytes(value)
            return nil
        }),
    )
    var data []byte
    ctx := groupcache.Context{}
    if err := group.Get(ctx, "key", groupcache.AllocatingByteSliceSink(&data)); err != nil {
        fmt.Println(err)
    }
    fmt.Println(string(data)) // value from db
}

In the above code, we define a groupcache object named mycache and set The cache capacity is 64MB, and a GetterFunc callback function is defined to represent the operation of reading data from the database. The GetterFunc function receives three parameters: Context, key and Sink. Among them, Context is the context information of the groupcache cache request, which can be used in GetterFunc; key is the cached key value; Sink is the target object of the groupcache cache, and the data will be read into the Sink.

Next, in the Get function, we pass in the key value and Sink to perform the cache read operation. The code execution result is: value from db.

3. Cache invalidation strategy

In an application, some data will become invalid due to time or other reasons. At this time, the data in the cache should also be deleted. In order to solve this problem, we need to set the cache invalidation policy (cache expiration time). Groupcache provides two basic expiration time strategies. The first is to set an expiration time for each key, and the second is to set an expiration time for the entire cache. In groupcache, the first strategy is implemented using the ExpireKey method of groupcache.Cache, and the second strategy is implemented using the SetExpiration method of Group.

4. Summary

This article mainly introduces the cache implementation in golang, including the concept of cache, the introduction of the cache library in golang, and the specific implementation of using golang's own cache library groupcache. In practical applications, caching is a very practical performance optimization technology that can effectively improve the operating efficiency of the system. When using cache, you need to pay attention to some caching strategies, such as data invalidation strategies. I hope this article can help readers further understand the cache implementation in golang.

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