How to implement long connection multiplexing and curl_upkeep()

M66 2025-05-26

When using PHP for network requests, the cURL library is a very powerful tool, especially when dealing with scenarios that require a large number of HTTP requests. To improve performance, Keep-Alive is a very important technology that can avoid re-establishing connections for every request, significantly reducing request latency and resource consumption. In this article, we will explain in detail how to use curl_upkeep() to achieve long connection multiplexing and provide some connection maintenance tips.

1. What is a long connection?

Long connections are a mechanism for HTTP connection multiplexing, which allows a TCP connection to remain open between multiple HTTP requests instead of re-establishing a new connection for each request. This can significantly reduce the time and resource overhead of connection establishment and improve performance, especially in high concurrency scenarios.

2. What is curl_upkeep() ?

curl_upkeep() is a custom function in PHP that is commonly used to manage and maintain persistent connections to cURL sessions. It is not a built-in function in PHP, but is based on the encapsulation of the cURL library, providing the function of connection multiplexing. Through reasonable configuration, each HTTP request can use the same TCP connection to avoid repeated connection establishment.

3. How to use curl_upkeep() to achieve long connection multiplexing?

To better understand how to implement long connection multiplexing using curl_upkeep() , we first need to understand the basic cURL configuration and how to keep the connection active.

Here is a PHP code example that implements long connection multiplexing:

 function curl_upkeep($url, $headers = array(), $timeout = 30) {
    static $ch = null;  // Static variable savingcURLSession
    
    // 如果Session不存在，则初始化一个新的Session
    if ($ch === null) {
        $ch = curl_init();
        
        // Set up the basicscURLOptions
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
        curl_setopt($ch, CURLOPT_TIMEOUT, $timeout);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
        
        // set upKeep-Alivehead，Make sure the connection remains active
        curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);  // useHTTP/1.1
        curl_setopt($ch, CURLOPT_FORBID_REUSE, false);  // Allow connection multiplexing
        curl_setopt($ch, CURLOPT_TCP_KEEPALIVE, 1);  // EnableTCP Keep-Alive
    }
    
    // Execute a request
    curl_setopt($ch, CURLOPT_URL, $url);
    $response = curl_exec($ch);
    
    // Check if the request is successful
    if ($response === false) {
        echo "cURL Error: " . curl_error($ch);
    }
    
    return $response;
}

// Example usage
$url = "http://m66.net/api/v1/resource";
$response = curl_upkeep($url);
echo $response;

Code explanation:

The curl_upkeep() function uses a static variable $ch to save the cURL session. In this way, in subsequent calls, this session can be reused to avoid reinitialization every time.
curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1) enforces the use of HTTP/1.1 protocol, which is a prerequisite for long connection multiplexing.
curl_setopt($ch, CURLOPT_TCP_KEEPALIVE, 1) Enable TCP's Keep-Alive function to ensure that the connection remains active between multiple requests.

4. Connection maintenance skills

When using curl_upkeep() , in addition to enabling Keep-Alive, the following connection maintenance tips can also help improve the stability and efficiency of long connections:

4.1 Set a reasonable timeout

Long-term connections may time out due to network fluctuations or server problems. Setting the timeout time reasonably can prevent the connection from being forced to be closed.

 curl_setopt($ch, CURLOPT_TIMEOUT, 30);  // set up连接超时为30Second

4.2 Handling connection loss

In some special cases, the connection may be unexpectedly interrupted. To avoid re-establishing the connection every request, you can check the connection status before each request is executed and re-initialize the session.

 if (!is_resource($ch)) {
    $ch = curl_init();  // 重新初始化Session
}

4.3 Using persistent connection pools

If you have multiple URLs that require frequent requests, you can use a connection pool to manage multiple cURL sessions. By multiplexing different connections, it is possible to avoid creating new connections for each request, thereby improving efficiency.

 $ch1 = curl_init("http://m66.net/api/v1/resource1");
$ch2 = curl_init("http://m66.net/api/v1/resource2");

// set up其他Options并Execute a request

5. Things to note

Server support : Not all servers support Keep-Alive connections, and it is necessary to ensure that the server side is configured to support HTTP/1.1 and Keep-Alive.
Maximum number of connections : Too many long connections may consume a large amount of system resources, ensuring a reasonable configuration of the maximum number of connections to avoid resource exhaustion of servers or clients.
Connection Close : Although long connections can improve performance, for some requests, too long connections can also lead to waste of resources. Therefore, it is very important to manage the life cycle of a connection reasonably.

curl_upkeep