Detailed explanation of Http request processing in Go language

Go language is an efficient programming language. Its advantages such as simplicity, efficiency, safety and reliability have been widely recognized and applied. Among them, the reason why it is widely used is also inseparable from the powerful network library it supports. This article will focus on Http request processing in Go language.

1. Basics of Http request processing
Http request processing is an essential part of Web back-end development, and the processing of Http requests in the Go language can be said to be extremely simple and easy to use. Let's take a look at the related APIs.

1. http.ListenAndServe()
   can be understood as an Http server, which can directly listen to the local port and wait for the arrival of Http requests.

func ListenAndServe(addr string, handler Handler) error

Among them, addr is used to specify the network address, the general form is "IP address or domain name: port number", but if the port When the number is 0, the operating system will automatically allocate an unused port; handler is a function used to process http requests.

2. http.HandleFunc()
   is an API that registers http request callback functions. Its definition is as follows:

func HandleFunc(pattern string, handler func( ResponseWriter, *Request))

Among them, pattern is the path of the registration request, and handler is the callback function of the http request. The structure of the callback function is as follows:

type HandlerFunc func(ResponseWriter, * Request)

You can see that the formal parameters of the Http request callback function are http.ResponseWriter and *http.Request.

3. http.ResponseWriter
   is the type of Http response returned to the client. Commonly used methods are:

1) ResponseWriter.Header(), used to set Http response header;

2) ResponseWriter.Write(), used to write the Http response body to the client.

4. http.Request
   represents the structure of the Http request, which contains the details of all Http requests, such as the header, body, method, etc. of the http request.
5. Http request processing example
   The following code snippet shows how to handle Http GET request in Go language, which calls http.HandleFunc() to register a callback function:

func main() {

http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
    fmt.Fprintf(w, "Hello, World!")
})

http.ListenAndServe(":8080", nil)

}

Note: When the interface of the Http request is defined as "/", the path that needs to be registered by http.HandleFunc() should be written as "/".

2. Http request processing method

1. http.Get()
   is used to obtain the response of the remote Http request. If the return status code of the request is not 2xx, then return Error message, the data type returned by this method is *http.Response, which belongs to a structure and contains many attributes. The more important one is its Body attribute. The Body attribute represents the content of the body of the Http request response. You can use ioutil The .ReadAll() function reads the contents of the Body's body.

func (c Client) Get(url string) (resp Response, err error)

2. http.PostForm()
   Use For submitting Http form data, such as submitting a login form, the most commonly used ContentType is the application/x-www-form-urlencoded type. The return type of this method is *http.Response. It should be noted that this method only supports POST requests, and the url.Values.Encode() method should be called to encode the form data before submitting the form.

func PostForm(url string, data url.Values) (resp *Response, err error)

3. http.Post()
   This method is the same as http. PostForm() is similar, but supports more types of network requests, that is, the ContentType type is not limited to application/x-www-form-urlencoded.

func (c Client) Post(url string, bodyType string, body io.Reader) (resp Response, err error)

where bodyType is Content-Type of the request, body is the request content.

4. http.Do()
   supports more network request types, and we can customize the request headers, which is the most flexible request method. It should be noted that this method will return *http.Response, and you need to close it after using the response.

func (c Client) Do(req Request) (resp *Response, err error)

3. Http request processing performance optimization
In When using multiple Goroutines to perform HTTP requests at the same time, we need to understand the performance bottleneck and be able to choose an appropriate optimization solution. The following introduces several Http request performance optimization solutions.

1. Keep-Alive
   Keep-Alive of the http connection is to optimize the resource occupation of the http connection as much as possible and avoid the performance loss caused by frequent TCP connection establishment and disconnection. By maintaining the tcp connection with the server Connecting without closing can reduce the performance loss caused by the establishment and closing of TCP and improve the efficiency of HTTP requests.
2. Idle connection pool
   If we need to request different paths for the same host, we can use an idle connection pool to manage the connection. By defining a slice to save the conn, before reusing, try to retrieve it from the slice. Get the conn and check whether it can be reused. If it cannot be reused, close the connection. If the number of connections exceeds the maximum number of connections in the pool, close the oldest connection. In this way, the number of connections can be consistent with the maximum number of connections of the operating system.
3. Long connection
   When a large number of requests need to be initiated, the optimization of long connections is very important. When the server supports Http's Keep-Alive, the client can specify the Connection:keep-alive header. , thereby establishing a long connection state, which can realize the processing of multiple requests and responses. A TCP connection can be reused, effectively reducing the establishment and closing of TCP.

4. Summary
This article mainly introduces Http request processing in Go language. In actual development, we can choose different network request methods and performance optimization solutions according to business needs. To achieve better network request results. At the same time, the network request library in the Go language is extremely simple and easy to use. It also supports a variety of HTTP request methods and optimization solutions, which provides great convenience for our back-end development.

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