Implement logic to measure specific hook execution time with Server-Timing controlled by a WP Admin screen

admin/server-timing.php

@@ -0,0 +1,131 @@
+<?php
+/**
+ * Server-Timing API admin integration file.
+ *
+ * @package performance-lab
+ */
+
+/**
+ * Adds the Server-Timing page to the Tools menu.
+ *
+ * @since n.e.x.t
+ */
+function perflab_add_server_timing_page() {
+	$hook_suffix = add_management_page(
+		__( 'Server-Timing', 'performance-lab' ),
+		__( 'Server-Timing', 'performance-lab' ),
+		'manage_options',
+		PERFLAB_SERVER_TIMING_SCREEN,
+		'perflab_render_server_timing_page'
+	);
+
+	// Add the following hooks only if the screen was successfully added.
+	if ( false !== $hook_suffix ) {
+		add_action( "load-{$hook_suffix}", 'perflab_load_server_timing_page' );
+	}
+
+	return $hook_suffix;
+}
+add_action( 'admin_menu', 'perflab_add_server_timing_page' );
+
+/**
+ * Initializes settings sections and fields for the Server-Timing page.
+ *
+ * @since n.e.x.t
+ */
+function perflab_load_server_timing_page() {
+	add_settings_section(
+		'benchmarking',
+		__( 'Benchmarking', 'performance-lab' ),
+		static function() {
+			?>
+			<p>
+				<?php esc_html_e( 'In this section, you can provide hook names to include measurements for them in the Server-Timing header.', 'performance-lab' ); ?>
+			</p>
+			<?php
+		},
+		PERFLAB_SERVER_TIMING_SCREEN
+	);
+
+	/*
+	 * For all settings fields, the field slug, option sub key, and label
+	 * suffix have to match for the rendering in the callback to be
+	 * semantically correct.
+	 */
+	add_settings_field(
+		'benchmarking_actions',
+		__( 'Actions', 'performance-lab' ),
+		static function() {
+			perflab_render_server_timing_page_field( 'benchmarking_actions' );
+		},
+		PERFLAB_SERVER_TIMING_SCREEN,
+		'benchmarking',
+		array( 'label_for' => 'server_timing_benchmarking_actions' )
+	);
+	add_settings_field(
+		'benchmarking_filters',
+		__( 'Filters', 'performance-lab' ),
+		static function() {
+			perflab_render_server_timing_page_field( 'benchmarking_filters' );
+		},
+		PERFLAB_SERVER_TIMING_SCREEN,
+		'benchmarking',
+		array( 'label_for' => 'server_timing_benchmarking_filters' )
+	);
+}
+
+/**
+ * Renders the Server-Timing page.
+ *
+ * @since n.e.x.t
+ */
+function perflab_render_server_timing_page() {
+	?>
+	<div class="wrap">
+		<?php settings_errors(); ?>
+		<h1>
+			<?php esc_html_e( 'Server-Timing', 'performance-lab' ); ?>
+		</h1>
+
+		<form action="options.php" method="post" novalidate="novalidate">
+			<?php settings_fields( PERFLAB_SERVER_TIMING_SCREEN ); ?>
+			<?php do_settings_sections( PERFLAB_SERVER_TIMING_SCREEN ); ?>
+			<?php submit_button(); ?>
+		</form>
+	</div>
+	<?php
+}
+
+/**
+ * Renders a field for the given Server-Timing option.
+ *
+ * @since n.e.x.t
+ *
+ * @param string $slug Slug of the field and sub-key in the Server-Timing option.
+ */
+function perflab_render_server_timing_page_field( $slug ) {
+	$options = (array) get_option( PERFLAB_SERVER_TIMING_SETTING, array() );
+
+	// Value for the sub-key is an array of hook names.
+	$value = '';
+	if ( isset( $options[ $slug ] ) ) {
+		$value = implode( "\n", $options[ $slug ] );
+	}
+
+	$field_id       = "server_timing_{$slug}";
+	$field_name     = PERFLAB_SERVER_TIMING_SETTING . '[' . $slug . ']';
+	$description_id = "{$field_id}_description";
+
+	?>
+	<textarea
+		id="<?php echo esc_attr( $field_id ); ?>"
+		name="<?php echo esc_attr( $field_name ); ?>"
+		aria-describedby="<?php echo esc_attr( $description_id ); ?>"
+		class="large-text code"
+		rows="8"
+	><?php echo esc_textarea( $value ); ?></textarea>
+	<p id="<?php echo esc_attr( $description_id ); ?>" class="description">
+		<?php esc_html_e( 'Enter a single hook name per line.', 'performance-lab' ); ?>
+	</p>
+	<?php
+}

load.php

@@ -431,6 +431,7 @@ function perflab_maybe_remove_object_cache_dropin() {
 // Only load admin integration when in admin.
 if ( is_admin() ) {
 	require_once PERFLAB_PLUGIN_DIR_PATH . 'admin/load.php';
+	require_once PERFLAB_PLUGIN_DIR_PATH . 'admin/server-timing.php';
 }
 
 /**

server-timing/defaults.php

@@ -207,3 +207,86 @@ static function( $acc, $query ) {
 	}
 }
 add_action( 'wp_loaded', 'perflab_register_default_server_timing_template_metrics' );
+
+/**
+ * Registers additional Server-Timing metrics as configured in the setting.
+ *
+ * These metrics should be registered as soon as possible. They can be added
+ * and modified in the "Tools > Server-Timing" screen.
+ *
+ * @since n.e.x.t
+ */
+function perflab_register_additional_server_timing_metrics_from_setting() {
+	$options = (array) get_option( PERFLAB_SERVER_TIMING_SETTING, array() );
+
+	if ( isset( $options['benchmarking_actions'] ) ) {
+		foreach ( $options['benchmarking_actions'] as $action ) {
+			$metric_slug = 'action-' . $action;
+
+			$measure_callback = static function( $metric ) use ( $action ) {
+				$metric->measure_before();
+				add_action( $action, array( $metric, 'measure_after' ), PHP_INT_MAX, 0 );
+			};
+
+			add_action(
+				$action,
+				static function() use ( $metric_slug, $measure_callback ) {
+					perflab_server_timing_register_metric(
+						$metric_slug,
+						array(
+							'measure_callback' => $measure_callback,
+							'access_cap'       => 'exist',
+						)
+					);
+				},
+				// phpcs:ignore PHPCompatibility.Constants.NewConstants.php_int_minFound
+				defined( 'PHP_INT_MIN' ) ? PHP_INT_MIN : ~PHP_INT_MAX
+			);
+		}
+	}
+
+	if ( isset( $options['benchmarking_filters'] ) ) {
+		foreach ( $options['benchmarking_filters'] as $filter ) {
+			$metric_slug = 'filter-' . $filter;
+
+			$measure_callback = static function( $metric ) use ( $filter ) {
+				$metric->measure_before();
+				add_filter(
+					$filter,
+					static function( $passthrough ) use ( $metric ) {
+						$metric->measure_after();
+						return $passthrough;
+					},
+					PHP_INT_MAX
+				);
+			};
+
+			add_filter(
+				$filter,
+				static function( $passthrough ) use ( $metric_slug, $measure_callback ) {
+					perflab_server_timing_register_metric(
+						$metric_slug,
+						array(
+							'measure_callback' => $measure_callback,
+							'access_cap'       => 'exist',
+						)
+					);
+					return $passthrough;
+				},
+				// phpcs:ignore PHPCompatibility.Constants.NewConstants.php_int_minFound
+				defined( 'PHP_INT_MIN' ) ? PHP_INT_MIN : ~PHP_INT_MAX
+			);
+		}
+	}
+}
+
+/*
+ * If this file is loaded from the Server-Timing logic in the object-cache.php
+ * drop-in, it must not call this function right away since otherwise the cache
+ * will not be loaded yet.
+ */
+if ( ! did_action( 'muplugins_loaded' ) ) {
+	add_action( 'muplugins_loaded', 'perflab_register_additional_server_timing_metrics_from_setting' );
+} else {
+	perflab_register_additional_server_timing_metrics_from_setting();
+}

server-timing/load.php

@@ -6,6 +6,54 @@
  * @since 1.8.0
  */
 
+define( 'PERFLAB_SERVER_TIMING_SETTING', 'perflab_server_timing_settings' );
+define( 'PERFLAB_SERVER_TIMING_SCREEN', 'perflab-server-timing' );
+
+/**
+ * Registers the Server-Timing setting.
+ *
+ * @since n.e.x.t
+ */
+function perflab_register_server_timing_setting() {
+	register_setting(
+		PERFLAB_SERVER_TIMING_SCREEN,
+		PERFLAB_SERVER_TIMING_SETTING,
+		array(
+			'type'              => 'object',
+			'sanitize_callback' => 'perflab_sanitize_server_timing_setting',
+			'default'           => array(),
+		)
+	);
+}
+add_action( 'init', 'perflab_register_server_timing_setting' );
+
+/**
+ * Sanitizes the Server-Timing setting.
+ *
+ * @since n.e.x.t
+ *
+ * @param mixed $value Server-Timing setting value.
+ * @return array Sanitized Server-Timing setting value.
+ */
+function perflab_sanitize_server_timing_setting( $value ) {
+	if ( ! is_array( $value ) ) {
+		return array();
+	}
+
+	// Ensure that every element is an indexed array of hook names.
+	return array_filter(
+		array_map(
+			static function( $hooks ) {
+				if ( ! is_array( $hooks ) ) {
+					$hooks = explode( "\n", $hooks );
+				}
+				return array_filter( array_map( 'sanitize_key', $hooks ) );
+			},
+			$value
+		)
+	);
+}
+
 /**
  * Provides access the Server-Timing API.
  *