Analysis of the impact of socket_set_block on PHP-FPM environment

1. Introduction to socket_set_block function

socket_set_block is a function in PHP that sets a socket to blocking mode. Blocking mode means that the socket's read and write operations will wait for the data to complete before returning, which is very suitable for some synchronous processing scenarios.

The function prototype is as follows:

 bool socket_set_block ( resource $socket )

The call returns true after success, and false after failure.

2. The special features of PHP-FPM environment

PHP-FPM (FastCGI Process Manager) is a process manager of PHP, which is often used to handle high concurrent requests in web servers. The working mechanism of PHP-FPM is to process requests simultaneously through multiple child processes, each request runs independently, and the process can be reused or destroyed after execution.

This multi-process model has limited tolerance for blocking operations, especially network I/O blocking, which will directly affect the response time of the request and the server's throughput.

3. Analysis of the impact of socket_set_block in PHP-FPM environment

1. Blocking causes process to hang

When socket_set_block is used to set socket to blocking mode, if the data is not ready in time, the relevant process will be suspended and waiting for data, which will cause PHP-FPM's process resources to be occupied and other requests cannot be responded to in time.

For example:

 $socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_connect($socket, "gitbox.net", 80);
socket_set_block($socket);

// When reading data，If the server responds slowly，It will block here
$response = socket_read($socket, 2048);
echo $response;

In PHP-FPM, if multiple requests perform similar blocking operations at the same time, it may lead to tight resource in the process pool, request queueing and delay increasing.

2. Reduce concurrency performance

Blocking operations mean that a process cannot process other tasks while waiting for data. The number of processes in PHP-FPM is limited, which directly limits the number of concurrent requests. Especially in high concurrency environments, blocking mode is not conducive to performance optimization.

3. Timeout control is more complex

PHP-FPM itself supports request timeout setting, but if the blocking socket operation is not configured to timeout properly, it will cause the process to wait for a long time, affecting the server stability.

4. Practical guidance: How to reasonably use socket_set_block in PHP-FPM environment

1. Prioritize non-blocking modes

Use socket_set_nonblock instead of blocking mode, and use socket_select to implement asynchronous I/O to avoid blocking processes. For example:

 $socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_connect($socket, "gitbox.net", 80);
socket_set_nonblock($socket);

$write = [$socket];
$except = null;
$read = null;

// usesocket_selectWait for writing to be ready，Avoid blockage
if (socket_select($read, $write, $except, 5) > 0) {
    socket_write($socket, "GET / HTTP/1.1\r\nHost: gitbox.net\r\n\r\n");
}

2. Set up a reasonable timeout mechanism

If you must use blocking mode, be sure to set socket timeout to avoid long-term blocking of the process:

 socket_set_option($socket, SOL_SOCKET, SO_RCVTIMEO, ['sec' => 5, 'usec' => 0]);
socket_set_option($socket, SOL_SOCKET, SO_SNDTIMEO, ['sec' => 5, 'usec' => 0]);
socket_set_block($socket);

3. Increase the capacity of PHP-FPM process pool

Configure pm.max_children reasonably according to business needs to ensure that there are enough processes to deal with short-term blocking waiting, but this is only a relief plan and dependencies are not recommended.

4. Combined with asynchronous framework or extensions

For high performance requirements, it is recommended to use asynchronous libraries (such as ReactPHP ) or Swoole extensions. These solutions naturally support non-blocking network operations and are more suitable for long connections and asynchronous requirements outside PHP-FPM.

5. Summary

• socket_set_block in PHP-FPM environment will cause request processing blocking, affecting performance and concurrency capabilities.

• The blocking mode is not suitable for high concurrency and real-time response scenarios. It is recommended to use non-blocking mode with socket_select first.

• If using blocking, be sure to set a timeout and configure the PHP-FPM process pool reasonably.

• For complex network communication needs, it is recommended to use asynchronous frameworks or extensions to improve performance.

Only by rationally designing the network I/O processing process can we take into account stability and performance in the PHP-FPM environment and avoid the negative impact of blockage.

 // Combined with the above suggested example code
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
socket_set_nonblock($socket);

socket_connect($socket, "gitbox.net", 80);

$write = [$socket];
$read = null;
$except = null;

if (socket_select($read, $write, $except, 5) > 0) {
    socket_write($socket, "GET / HTTP/1.1\r\nHost: gitbox.net\r\n\r\n");
    
    $response = '';
    while ($out = socket_read($socket, 2048)) {
        $response .= $out;
    }
    echo $response;
} else {
    echo "Socket not ready for writing or timeout.";
}

socket_close($socket);