Upstream sent too big header while reading response header

  • Hello

    Not sure if this error is related only with Query Monitor but when I try to clear WP Rocket cache when QM is enabled I am getting the following error
    upstream sent too big header while reading response header on PHP 8.0 and 8.1 (Nginx v1.24.0). No issues with 7.4

    Cache is cleared with no errors if QM is de-activated.

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  • Plugin Author John Blackbourn

    (@johnbillion)

    WordPress Core Developer

    This might be related to PHP warnings being triggered on PHP 8 which QM adds to the HTTP headers of the response. Can you check your PHP error logs for any errors that occur during the request to clear the cache?

    You need to identify where the request producing the original error was processed. ‘Upstream’ might be a lot of different things (proxy, fastcgi, uwsgi).

    You need to tweak the proper upstream *_buffers and *_buffer_size to make the proper buffer(s) bigger.

    You can set the following values and test if it works. If it doesn’t work you can manually increase the value to 64k, 128k, 256k, and 512k. And then reload nginx.

    *_buffers 16 32k;
*_buffer_size 64k;
*_busy_buffers_size 64k;
Viewing 2 replies - 1 through 2 (of 2 total)
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