Investigation Request: High Frequency of `hooked_block_types` Filter Calls

[mreishus]

I have identified a potential performance concern related to the hooked_block_types filter in WordPress 6.5.3, particularly regarding its scalability when a site has a large number of blocks and custom patterns.

Steps to Reproduce:

1. Environment Setup:
   • Installed a completely blank WordPress.org 6.5.3 site using the default Twenty Twenty-Four theme.

2. Customization:
   • Installed and activated a custom plugin to count the number of times the hooked_block_types filter is applied. The plugin code is as follows:

<?php
/*
Plugin Name: Hooked Block Types Counter
Description: A simple plugin to count how many times the 'hooked_block_types' filter is applied.
Version: 1.0
Author: Your Name
*/

function init_hooked_block_types_counter() {
    $GLOBALS['hooked_block_types_count'] = 0;
}
add_action('init', 'init_hooked_block_types_counter');

function increment_hooked_block_types_count($hooked_block_types, $relative_position, $anchor_block_type, $context) {
    $GLOBALS['hooked_block_types_count']++;
    return $hooked_block_types; // Returning the original list without modification
}
add_filter('hooked_block_types', 'increment_hooked_block_types_count', 10, 4);

function log_hooked_block_types_count() {
    $count = $GLOBALS['hooked_block_types_count'];
    error_log("The 'hooked_block_types' filter was run $count times.");
}
add_action('shutdown', 'log_hooked_block_types_count');
?>

3. Initial Observation:
   • Visiting the front page with the default Twenty Twenty-Four theme and no additional content shows:

     [16-May-2024 22:03:09 UTC] The 'hooked_block_types' filter was run 526 times.
     

4. Adding Content:
   • Using the Site Editor, edited the Index template by adding a Columns block, with a few Paragraph blocks in each column.
   • After saving the changes and visiting the home page again, it showed:

     [16-May-2024 22:09:02 UTC] The 'hooked_block_types' filter was run 590 times.
     

Concerns:

• While the out-of-the-box performance might be acceptable, the issue scales significantly with added content.
• On a site with extensive custom patterns, I observed the filter being applied approximately 9,800 times.
• This scalability concern implies that functions hooked to hooked_block_types could potentially run thousands of times, which can have significant performance implications.
• For example, Jetpack’s sharing-button.php hooks into this filter and runs the following check: ( new Modules() )->is_active( 'sharedaddy' ). Running such a check 10,000 times seems inefficient and could lead to performance bottlenecks. Authors writing code on this hook might be unaware it could be run thousands of times.

Reference:

Jetpack’s sharing-button.php:
​https://github.com/Automattic/jetpack/blob/3631fb251d8734d656d818ed3c52cf71a2be204c/projects/plugins/jetpack/extensions/blocks/sharing-button/sharing-button.php#L224

Request:

• Investigate why the hooked_block_types filter is being applied so many times.
• Consider optimizing the filter application to reduce redundancy and improve performance.
• Provide guidelines or best practices for plugin authors to avoid performance issues when hooking into hooked_block_types.

Thank you for looking into this matter. I believe addressing this will help improve the performance and scalability of WordPress sites, especially those with complex block structures and custom patterns.

[Bernhard Reiter]

Tangentially, we started an ​experiment a while ago that would replace the parsing/traversal/re-serialization with a streaming parser, which we hope will improve performance. We haven’t been working on this for a while but might get back to it some time after 6.6.