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Date: Mon, 29 Jul 2024 12:20:45 +0200
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Subject: Re: [PHP-DEV] Deprecate ext/curl `CURLOPT_DNS_USE_GLOBAL_CACHE`?
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To: Ayesh Karunaratne <ayesh@php.watch>,
 PHP internals <internals@lists.php.net>
References: <CANLbj-rn9kfQGzx=g0LP5AkRLeEWx3XDYNQ8FKf=uMDrRWLGAw@mail.gmail.com>
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From: cmbecker69@gmx.de ("Christoph M. Becker")

On 28.07.2024 at 19:26, Ayesh Karunaratne wrote:

> We recently bumped[^1] the minimum required libcurl version supported
> by the PHP Curl extension to 7.61.0. This aligned with the recent
> CentOS/RHEL 7, along with other major Linux distros that have already
> updated to a more recent version of libcurl. I'm writing to the
> Internals to get some feedback on deprecating a Curl option (a
> `CURLOPT` constant) that we support in PHP, but is removed on Curl
> 7.62 and later.
>
> Curl supported an option called `CURLOPT_DNS_USE_GLOBAL_CACHE`[^2]
> that enabled Curl to use a global cache for DNS queries. It was added
> in Curl 7.9.3 (2002 Jan), marked as obsolete soon after, deprecated in
> 7.11.1, and removed in Curl 7.62.0[^3] (2018 Oct). The reason is that
> this functionality was not thread-safe, and was not functional after a
> few releases. Users can still share DNS caches by reusing Curl handles
> or by copying the Curl handles.
>
> The PHP Curl extension does support this constant, and if PHP is built
> with thread-safety enabled, setting this option emits a warning with
> the text "CURLOPT_DNS_USE_GLOBAL_CACHE cannot be activated when thread
> safety is enabled".
>
> I would like to propose to either deprecate this constant, or no-op it.
>
> [^1]: https://github.com/php/php-src/pull/13259
> [^2]: https://curl.se/libcurl/c/CURLOPT_DNS_USE_GLOBAL_CACHE.html
> [^3]: https://curl.se/mail/lib-2018-09/0010.html

I'm somewhat torn about this.  Generally, as a user I prefer to be
notified about a feature which will not work; a deprecation notice would
do.  On the other hand, this is "only" a caching functionality, so it's
probably not much of an issue if it doesn't work.

Actually deprecating the constant might require the RFC process, so
maybe it's best to make it a no-op for now (and to deprecate for PHP
8.5/9.0 whatever is next).

But regardless of deprecation or no-op'ing, we should document the
behavior, and tell users about alternatives to accomplish the same goal.

Cheers,
Christoph