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Comparison Page works in Mac browsers, blank content in PC browsers

This topic contains 8 replies, has 2 voices, and was last updated by  Steve Truman 3 years, 3 months ago.

Bug Report
  • Author
  • #14588


    This is interesting…Regardless of whether I use a popup or “new window” for the Comparison Page, the contents show fine for Mac users (OSX Mavericks, Safari and/or Chrome), but I get blank contents (with only header content) when using a PC (Windows 8.1, Chrome or IE) to view the Comparison Page.

    Adding products to compare works fine—the issue is simply when pressing the “Compare” button and viewing the results in the Comparison Page.

    I’ve disabled/re-enabled plugins but the problem, seems to persist. Any help would be appreciated.

    Thanks in advance.

    Site/page: http://www.copierguide.com/product-category/multifunction-printers/mfps-color/

  • #14659

    Steve Truman

    Hello Timothy

    Thanks for the explanation and the link. I tested it and yes there is something on your site that is blocking the results showing in the Compare Window – You can see that if you add items to the Compare widget – Then refresh the page – no products show in the compare widget – they are there because it you add another item then all of the products that have been added show.

    Timothy I cannot tell what is causing that from the front end but will take a look at it for you if you set me up a wp-admin account and ftp access account. Please post the wp-admin creds and the ftp access creds in a Private reply (so only you and i can see those).

    Timothy please do that and i will take a look at it for you as soon as possible – Steve

  • #14747

    Steve Truman

    Hello Clint – thanks for the wp-admin and ftp access creds, I have removed them from your private post now i have them – as double security.

    Clint the issue is not a bug with the plugin – it is your caching CDN that is causing that. I tested the site in Chrome, Firefox and IE as a logged in user and it works fine. Then logged out and test again in all 3 browsers and no products show in the comparison pop-up. We did this on 3 separate machines in varying sequence and always get the same results.

    It seems that the CDN you have configed for the site does not cache for logged in users, but serves cache for not logged in users.

    I could see no caching plugins and it took a while to find it – then see this in the wp-config.php file


    and see the CDN from WP Engine.

    $wpe_cdn_uris=array ();
    $wpe_no_cdn_uris=array ();

    So we then added this to your wp-config file to try and exclude the Compare window / pop-up urls from the CDN cache.

    $wpe_no_cdn_uris=array ( 'http://www.copierguide.com/product-comparison', 'http://copierguide.com/product-comparison' );

    But I do not know if that will work because I do not know when the CDN cache is refreshed.

    I could see that the caching comes from this


    Tried Purging the caches – that did not work.

    Tried turning off the Object/Transient Cache but still no joy, because I think that the cache is from the CDN and we cannot clear it.

    Clint unless you know how to do that you will need to contact the WP Engine folks and ask them how you can exclude the /product-comparison/ url from their CDN caching.

    I have left all of the caching settings as I found them – but the snippet we wrote to tell the CDN to exclude the plugins URL from the cache is still in the wp-config file.

    Hope all of that helps you a bit – and please let me know what know or find out about how to exclude the plugin from the WP Engine CDN. It will be very handy to know that. Steve

  • #14760


    Steve, this is way above and beyond. Thanks so much for all the troubleshooting you did! I’m following up now with the folks from WP Engine, and I’ll report back here on the solution in as much detail as possible.

  • #14794

    Steve Truman

    Thanks Clint, only possible to do that kind of trouble shooting because of the wp-admin and most importantly ftp access. It will be really handy to know from the WP Engine folks how to exclude it from the WP Engine CDN. Steve

  • #14845

    Steve Truman

    Hey Clint – thanks for the feedback – will add that to the troubleshooting section of the plugins docs. Will also change this thread status to Closed as between us ( and the WP Engine crew) we have been able to resolve the issue. If you have further issues please start a new topic. Good working with you on this – Steve

  • #14847

    Steve Truman

    Hi Clint – Just thought i’d let you know that we just added that to the plugins docs – Troubleshooting section.

  • #14687

    This reply has been marked as private.
  • #14842


    So here’s the report from WP Engine (they fixed it per your instructions):

    I’ve gotten /product-comparison/ excluded from caching for you. I went to the site to test it out and I was able to successfully compare products in the popup window.

    Just to be clear, I see that the plugin developer brought up CDN several times, but the CDN is not currently active, nor do I see that it has been. So this wasn’t CDN caching, but caching on our Varnish layer. I just wanted to make that distinction in case you needed to bring a similar issue up with us again 🙂

    Additionally, pages are not able to be excluded from caching by adding to the wp-config.php, but rather by adding to the nginx configuration, which we control from our end.

    I hope that this has been helpful, but please do not hesitate to let me know if you have additional questions or if I may assist you further! I am updating the status of this ticket to solved. If you find it to not be resolved, please reopen it.”

    – – – –

    So it looks like you would need to tell future plug-in clients to request WP Engine exclude caching on /product-comparison/ in their nginx configuration.

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