Mini WordPress core server performance test suite

README.md

Mini WordPress core server performance test suite

Purpose

This quick "mini test suite" allows you to easily collect server-side performance metrics for WordPress core development. It does so by utilizing the Server-Timing header.

Usage

1. Paste the code from main.php into pretty much anywhere in WordPress core, e.g. into wp-includes/default-filters.php.
2. Use code like the one in example.com around any code or a specific function that you want to record metrics for.
   • All timing metrics should be float, in seconds. They will automatically be converted to milliseconds for output.
   • Other metrics (e.g. function or method call counts) should be integer.
3. You can test that the metrics show up correctly by loading WordPress in the browser and using performance.getEntries()[0].serverTiming in the Developer Console.
4. Use the GoogleChromeLabs/wpp-research repository, specifically its benchmark-url command, to trigger a number of requests against the URL, and return the median Server-Timing values for all requests made. For example like this (for 10 requests, and output as CSV): npm run research -- benchmark-url -u http://localhost:8889 -n 10 -o csv
5. You can copy the CSV output into a spreadsheet to easily share it with other people.

example.php

<?php

function demo_func() {
	// Add this to the top of code to record performance timing for.
	global $server_timing_values;

	if ( ! is_array( $server_timing_values ) ) {
		$server_timing_values = array();
	}

	$start_time = microtime( true );

	// Here should be the code of the function itself.
	sleep( 1 );

	// This is an example of how to add a Server-Timing metric for the total execution time _and_ call count of the function.
	if ( ! isset( $server_timing_values['demo-func-time'] ) ) {
		$server_timing_values['demo-func-time'] = 0.0;
	}
	if ( ! isset( $server_timing_values['demo-func-count'] ) ) {
		$server_timing_values['demo-func-count'] = 0;
	}
	$server_timing_values['demo-func-time'] += microtime( true ) - $start_time;
	$server_timing_values['demo-func-count']++;

main.php

<?php

// Add this pretty much anywhere in WordPress core, e.g. into the `wp-includes/default-filters.php` file.
add_action(
	'template_redirect',
	function() {
		ob_start();
		add_action(
			'shutdown',
			function() {
				global $server_timing_values, $timestart;

				if ( ! is_array( $server_timing_values ) ) {
					$server_timing_values = array();
				}

				$server_timing_values['total-time'] = microtime( true ) - $timestart;

				$output = ob_get_clean();

				$header_values = array();
				foreach ( $server_timing_values as $slug => $value ) {
					if ( is_float( $value ) ) {
						$value = round( $value * 1000.0, 2 );
					}
					$header_values[] = sprintf( 'wp-%1$s;dur=%2$s', $slug, $value );
				}
				header( 'Server-Timing: ' . implode( ', ', $header_values ) );

				echo $output;
			},
			-9999
		);
	}
);