Infinite loop in canonical.php

[emerlen]

A site 24x7 monitor that points to a URL on our website leads to an error with infinite loops reported.

This error started after the page being pointed by the monitor received a new Slug, leading to HTTP redirection due to autocomplete to the closest URL. Still, I believe it occurs only during periods of transient availability of our shared host.

Looking at the source code [REF2] I believe there is potential for an infinite loop on line 800. Possible fix in [REF3].

By assigning the result of redirect_canonical() to a variable ($chained_redirect) before the if statement, we ensure that the same value is used throughout the if block preventing unnecessary recursive calls.

References

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[REF1]

HTTP/1.1 508 Loop Detected
Server : nginx
...

[REF2]
​https://github.com/WordPress/wordpress-develop/blob/6.2/src/wp-includes/canonical.php#L780-812

[REF3]

Protect against chained redirects.

$chained_redirect = redirect_canonical($redirect_url, false);
if (!$chained_redirect)

[emmaevy]

$chained_redirect = redirect_canonical($redirect_url, false);
if (!$chained_redirect)

It help prevent the infinite loop by ensuring that the same result of redirect_canonical() is consistently used within the if block. This approach might mitigate the recursive redirection issue and the resulting infinite loop.
Steps: You can manually check on browser developer tools to inspect network requests and redirects or use this tool Link:​redirect checker This can help you with Canonical URLs and identify the loop and detail redirection chain and its http status code.