How do large platforms like Facebook utilize long polling for their messaging services and what can be learned from their approach?

Large platforms like Facebook utilize long polling for their messaging services by having clients send a request to the server, which waits for a response. If there are no new messages, the server delays its response until a new message is available. This allows for real-time updates without the need for constant polling. 

// Example of long polling implementation in PHP

// Client-side code
function getMessage() {
    $.ajax({
        url: 'get_messages.php',
        success: function(data) {
            // Handle received message
            // Call getMessage() again to continue long polling
        },
        error: function() {
            // Handle error
            // Call getMessage() again to continue long polling
        },
        timeout: 30000 // Timeout after 30 seconds and call getMessage() again
    });
}

// Server-side code (get_messages.php)
// Check for new messages and return response if available
// If no new messages, delay response until a new message is available

Keywords

long polling messaging services Facebook scalability real-time communication

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