Database caching?

[lat9]

I've got a client running a highly-customized Zen Cart v1.5.1 that recently transferred to bluehost (yes, I know ...) on PHP 5.4.43 and just ran into the weirdest thing:

I go to one of the configuration screens and change the first value in the list. Upon clicking the "Update" button, I'm returned to the overall configuration display ... but the value hasn't been changed. I can click the next item in the configuration screen and, like magic, the change I made to the first item now displays! This is using the built-in configuration handling in the Zen Cart admin.

I've checked the configure.php files to ensure that all the file-paths are proper (they are) and the Configuration->Sessions to make sure that the session-save-directory is the /cache folder (it is).

There are other bits of funkiness going on on this site after the move, but I believe that the above issue is a large, underlying factor.

I'd appreciate any/all clues or other pieces of information to hunt up.

[kobra]

As you know

Zen Cart v1.5.1 is compatible with PHP 5.2.14 thru PHP 5.3.x.

This is a place to start

[lat9]

Yes, the site's been kept up with the various changes so that's not it.

Edit: There was no issue when the site was on its previous host, also running a later version of PHP 5.4.

[lat9]

Arggh. Discussing the issue with the client, bluehost apparently offered them a "performance improvement" if they configured the site to act as a CDN. Working now to remove remnants of that change; it certainly would explain all the funnies I was seeing on the site.

[RodG]

Arggh. Discussing the issue with the client, bluehost apparently offered them a "performance improvement" if they configured the site to act as a CDN. Working now to remove remnants of that change; it certainly would explain all the funnies I was seeing on the site.

CDN's a generally a good thing - and yes, they can/do offer some *huge* performance benefits. I recommend using a CDN whenever possible.

Yup, there can be downsides to them - Especially during any development work (and various other changes) due to the delay caching affect, but of the few CDN services we use, they've all had a 'development' mode that temporarily bypasses the caching, and they'll all had an option to clear the cache contents - individual files, folders, or the entire site.

Just my 2cents worth,

Cheers
RodG

[lat9]

Thanks, RodG. The site in question is pretty dynamic (products added quite frequently). The client called bluehost yesterday to have them really (unlike the last time they called) turn off the CDN and now the admin and store appear to be working "better"!

[RodG]

Thanks, RodG. The site in question is pretty dynamic (products added quite frequently). The client called bluehost yesterday to have them really (unlike the last time they called) turn off the CDN and now the admin and store appear to be working "better"!

If by 'better' you mean it loads faster, I can only think of one instance where this could be the case, and this is if the store itself is hosted in Australia, and the CDN provider doesn't have a server over here.

CDN's improve performance in two ways.

1) They have multiple servers across the globe - So far less demand is placed on the host server.
2) They use a routing/addressing technology that serves the CDN content from the server in the closest proximity to the client.

Adding *new* products isn't a concern because dynamic pages aren't cached so these will be found from the moment they are activated. The *images* for the product will be automatically cached when viewed by the first customer, leading to better performance for other customers.

The only problems I've had with CDN's is where any *static* content needs to be changed. On a ZenCart site these are generally only going to be the images, and the .css content.

Even the images aren't a problem if the change involves replacing existing images with new ones. The problem only arises if the image(s) are *altered* and the original name is kept. It can take a while (sometimes what seems like eternity) before the CDN's realise that their cached copy is now different from the master copy. This is also compounded because each of the CDN servers have their own cached copy.

IOW, a CDN should never cause performance issues. Theory dictates that they can only improve performance.

Of course, I'm making an assumption here that your 'better' is relating to performance (time it takes a page to load) rather than any other issues that you may have found.

BTW, I'm not basing my comments about performance improvements based on personal observations and/or anecdotal evidence. The effect is quite measurable. Although there are many sites that will test site performance, the one I predominately use is www.webpagetest.org.

Having said that, on a smallish site with few images there aren't many gains to be made. On a site with 1000's of images the difference can be quite dramatic.

Oh, yeah, they can also save on a lot of bandwidth too - I've just 'grabbed' this from one of the CDN's we use for one of our busiests sites:

In the last 7 days 33.09 GB saved
46.23 GB total bandwidth

Not an insignificant saving eh?

Cheers
Rod.

[kobra]

they configured the site to act as a CDN

Glad you discovered this - dynamic sites do not play well with cloud services

[RodG]

Glad you discovered this - dynamic sites do not play well with cloud services

Kobra! You should be ashamed of yourself for making such a simplistic comment such as this.

You/We could also say the *exact* same thing about the caching provided by all web browsers as well as all proxy servers that are implemented (often transparently) by almost every ISP on the planet.

A CDN is just another cache, and like all caches, they only cache static content.

This very busy ZenCart site appears to be playing very nicely with the CDN. As can be clearly seen, the bulk of the content on this dynamic site are the static images. The bandwidth saved and performance gained (by not having to server the requests from the master/host server are clearly quite significant.

In what way can this be considered as 'not playing well'?

Cheers
RodG