[wp-hackers] getting the expiration value of a transient when OBJECT_CACHE is involved
Nikola Nikolov
nikolov.tmw at gmail.com
Thu Jun 26 23:22:49 UTC 2014
Nicely done! That's a very elegant solution - I like it :)
On Fri, Jun 27, 2014 at 1:10 AM, Haluk Karamete <halukkaramete at gmail.com>
wrote:
> I had kind of sensed that Nikola that it would not be easy to get that
> information - for the reasons that you eloborately explained. Thank you for
> that.
>
> Since it was way too cool to have that sort of insight displayed at the
> bottom of pages, I had to find another way.
>
> When there is a will, there is a way as they say...
>
> So what I ended up doing was this;
>
> Attach a piece of HTML like: <!--timestamp:1455454343--> right within the
> HTML I'm saving.
> Since I'm the one who sets the transient, and I'm the one who gets it
> back, this technique guarantees that the time-stamp wwould be part of the
> meal-deal, and when I retrieve the transient, then it would be a string
> extract to get what I want. :)
>
> Tested and works like a charm - no matter what the internal mechanism is...
>
> before setting:
> $expire_time = time()+$expire;
> $transient_data = $transient_data . '<!--blp:expires{' . $expire_time .
> '}-->';
> $ret_val = set_transient($id,$transient_data,$expire);
>
> after getting:
> $when_to_expire = blp_getinbetween
> ($transient_data,'<!--blp:expires{','}-->');
> $transient_data =
> blp_replace($transient_data,'<!--blp:expires{' . $when_to_expire .
> '}-->','');
>
>
>
>
>
> On Thu, Jun 26, 2014 at 12:27 PM, Nikola Nikolov <nikolov.tmw at gmail.com>
> wrote:
>
> > It's not going to be very easy to do that.
> >
> > First of all wp_cache_add() can actually be using different storage
> > mechanisms, or at least different implementations of the clients. For
> > instance the most common object cache as far as I'm aware is the
> Memcached
> > (Memcache Daemon).
> > In PHP there are two general classes that act as clients for - Memcache
> and
> > Memcached. Memcache is pretty plain and doesn't really give you a whole
> lot
> > to work with. Memcached I think has more possibilities, but I don't think
> > getting the expiration date would be one of the built-in ones.
> >
> > But then there could be a caching plugin that uses a different back-end
> to
> > store objects in memory, so unless you cover all of the possibilities,
> then
> > it's not really possible to do what you're looking to do.
> >
> > Is it really necessary to know when a transient will expire? You might
> have
> > to look for a way to avoid going that way :)
> >
> >
> > On Thu, Jun 26, 2014 at 9:21 PM, Haluk Karamete <halukkaramete at gmail.com
> >
> > wrote:
> >
> > > In the code segment that I pasted below ( which is straight from the
> > core -
> > > > option.php ), I 'm trying to understand how I can pull the
> > expire_time (
> > > the unix time stamp ) for the transient I'm after.
> > >
> > > When there is no object_cache is involved, that's a piece of ccake as
> > > *get_option(
> > > $transient_timeout )* just gets me that.
> > >
> > > <begin_snippet>
> > >
> > > if ( wp_using_ext_object_cache() ) {
> > > $value = wp_cache_get( $transient, 'transient' );
> > > } else {
> > > $transient_option = '_transient_' . $transient;
> > > if ( ! defined( 'WP_INSTALLING' ) ) {
> > > // If option is not in alloptions, it is not autoloaded and
> > > thus has a timeout
> > > $alloptions = wp_load_alloptions();
> > > if ( !isset( $alloptions[$transient_option] ) ) {
> > > $transient_timeout = '_transient_timeout_' .
> $transient;
> > > if ( get_option( $transient_timeout ) < time() ) {
> > > delete_option( $transient_option );
> > > delete_option( $transient_timeout );
> > > $value = false;
> > > }
> > > }
> > > }
> > >
> > > if ( ! isset( $value ) )
> > > $value = get_option( $transient_option );
> > > }
> > >
> > >
> > > <end_snippet>
> > >
> > > But on an object cache situation, such as total_cache, that's been a
> > uphill
> > > battle for me.
> > >
> > > All I got there for inspiration is this;
> > >
> > > $value = wp_cache_get( $transient, 'transient' );
> > >
> > > When I traced that function ( wp_cache_get() ) down to its roots, I
> end
> > up
> > > with the following which did not produce any fruits neither.
> > >
> > > /**
> > > * Retrieves the cache contents from the cache by key and group.
> > > *
> > > * @since 2.0.0
> > > * @uses $wp_object_cache Object Cache Class
> > > * @see WP_Object_Cache::get()
> > > *
> > > * @param int|string $key What the contents in the cache are called
> > > * @param string $group Where the cache contents are grouped
> > > * @param bool $force Whether to force an update of the local cache
> > > from the persistent cache (default is false)
> > > * @param &bool $found Whether key was found in the cache.
> > > Disambiguates a return of false, a storable value.
> > > * @return bool|mixed False on failure to retrieve contents or the
> > > cache
> > > * contents on success
> > > */
> > > function wp_cache_get( $key, $group = '', $force = false, &$found =
> > > null ) {
> > > global $wp_object_cache;
> > >
> > > return $wp_object_cache->get( $key, $group, $force, $found );
> > > }
> > >
> > >
> > > As you see, there is no talk on $expire there neither.
> > >
> > > Then the ball is sent to $wp_object_cache->get court... and I got lost
> > in
> > > there.
> > >
> > > Could someone shed some light where to go to get that timestamp?
> > >
> > > My goal is to be able to report back to me when the current transient
> > will
> > > expire for the current page.
> > >
> > > On my local host, I display this at the bottom of the page without
> sweat:
> > >
> > > This page's transient will expire in 0 day(s) 0 hour(s) 0 min(s) 30
> > > sec(s)
> > >
> > >
> > > But for the development server, I got nada. :(
> > > _______________________________________________
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> > >
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