Unable to run in a single-threaded PHP server

[akirk]

Quick summary

The ActivityPub plugin depends on the webserver being multi-worker or multi-threaded.

Steps to reproduce

1. Use php -S localhost:8080 in the root of a WordPress install that has the ActivityPub plugin.
2. Navigate to wp-admin/options-general.php?page=activitypub
3. Hangs until the CLI server errors out with Fatal error: Maximum execution time of 30+2 seconds exceeded (terminated) in wp-includes/Requests/src/Transport/Curl.php on line 204

Site owner impact

Fewer than 20% of the total website/platform users

Severity

Minor

What other impact(s) does this issue have?

No response

If a workaround is available, please outline it here.

It works if you set the timeout to a low value like this:

add_filter( 'activitypub_remote_get_timeout', function() { return 1; } );

The reason for this is that the author page availability is checked (is_author_url_accessible) with a blocking HTTP request in the same request and the built-in php webserver is single-threaded. See this backtrace:

(
    [0] => Array
        (
            [file] => wp-includes/Requests/src/Requests.php
            [line] => 469
            [function] => request
            [class] => WpOrg\Requests\Transport\Curl
            [type] => ->
        )

    [1] => Array
        (
            [file] => wp-includes/class-wp-http.php
            [line] => 420
            [function] => request
            [class] => WpOrg\Requests\Requests
            [type] => ::
        )

    [2] => Array
        (
            [file] => wp-includes/class-wp-http.php
            [line] => 658
            [function] => request
            [class] => WP_Http
            [type] => ->
        )

    [3] => Array
        (
            [file] => wp-includes/http.php
            [line] => 68
            [function] => get
            [class] => WP_Http
            [type] => ->
        )

    [4] => Array
        (
            [file] => wp-content/plugins/activitypub/includes/class-http.php
            [line] => 157
            [function] => wp_safe_remote_get
        )

    [5] => Array
        (
            [file] => wp-content/plugins/activitypub/includes/class-http.php
            [line] => 290
            [function] => get
            [class] => Activitypub\Http
            [type] => ::
        )

    [6] => Array
        (
            [file] => wp-content/plugins/activitypub/includes/wp-admin/class-health-check.php
            [line] => 195
            [function] => get_remote_object
            [class] => Activitypub\Http
            [type] => ::
        )

    [7] => Array
        (
            [file] => wp-content/plugins/activitypub/includes/wp-admin/class-health-check.php
            [line] => 131
            [function] => is_author_url_accessible
            [class] => Activitypub\WP_Admin\Health_Check
            [type] => ::
        )

    [8] => Array
        (
            [function] => test_author_url
            [class] => Activitypub\WP_Admin\Health_Check
            [type] => ::
        )

    [9] => Array
        (
            [file] => wp-content/plugins/activitypub/includes/wp-admin/class-health-check.php
            [line] => 49
            [function] => call_user_func
        )

    [10] => Array
        (
            [file] => wp-content/plugins/activitypub/includes/wp-admin/class-welcome-fields.php
            [line] => 72
            [function] => count_results
            [class] => Activitypub\WP_Admin\Health_Check
            [type] => ::
        )

[akirk]

While I don't think this needs to be fixed, I wonder if the author page could be checked client-side using JavaScript, like Health Check does it for its checks. This could be generally good for performance.

[Jiwoon-Kim]

I don't really use a CLI PHP server for development, but I'm just curious — why does the WordPress Playground (live preview) seem to work fine, even though it's also running in a limited environment?

[akirk]

Well the problem is being single-threaded. If the php script uses HTTP to fetch a URL on the same single-threaded HTTP server and blocks until it receives a response, it will timeout because the HTTP server (with the single thread) is occupied by the first request.

[obenland]

I spent some time on this today, but admittedly have not made much progress.

There doesn't seem to be a Core-provided API to handle client side health checks and append their results and I'm not entirely convinced this is even really necessary?

If anyone feels like they want to continue this work, a first pass can be found on https://github.com/Automattic/wordpress-activitypub/compare/fix/client-side-health-check