Server-Timing with wp-before-template is always sent

[szepeviktor]

Bug Description

Sending of this HTTP header cannot be disabled in the plugin.
It is sent unconditionally.

performance/server-timing/defaults.php

Line 122 in b09405b

perflab_register_default_server_timing_before_template_metrics();

What do you recommend? How to stop sending this header?

Steps to reproduce

1. Just activate the plugin

[mukeshpanchal27]

@szepeviktor Thank you for bringing up this issue. I fully concur with your observation that the plugin lacks an option to disable the Server-Timing API. Your input is valuable in ensuring the plugin's flexibility and user-friendliness.

I would like to loop in @felixarntz and @joemcgill to gather their insights on this matter. Should we consider adding an option somewhere in the plugin settings to allow users to disable the Server-Timing API as per your suggestion?

Looking forward to hearing from both of you.

[szepeviktor]

Thank you.
I have a process called plugin castration bomb defusing where I remove things in my special ways.
This is the evidence warehouse: https://github.com/szepeviktor/wordpress-website-lifecycle/tree/master/mu-plugins

Currently the shortest path to remove that HTTP header is

add_filter(
    'get_header',
    static function () {
        header_remove('Server-Timing');
    },
    10,
    0
);

[felixarntz]

Thanks for opening the issue @szepeviktor! Allowing to disable Server-Timing makes sense. It would fall under rather advanced customization, so I think this should be limited to using a code approach (rather than e.g. a UI option).

Given that the Server-Timing logic may be initiated extra early (even before plugins are loaded), I think the most reliable and simplest solution would be to allow disabling it via a new constant that could be defined in wp-config.php, e.g. PERFLAB_DISABLE_SERVER_TIMING.