Wednesday, September 15, 2010

Confusion Caused By Use Of The Post Editor "Preview" Button

The new "Preview" mode in Blogger Post Editor is a considerable improvement over what we used to have - but it still can cause confusion, if the details are not understood. Lately, we see occasional glimpses of confusion, about it's use.
I changed my blog, and the changes were visible when I hit Preview - but the blog was unchanged when I Published, and then viewed my changes.

When you view your blog in Preview mode, you're viewing a private copy of the blog, that nobody else gets to see. This copy is dynamically generated, as you edit. Use Preview, and observe the URL shown in the browser address window. Here's what I see, as an example.


This is a nice view of the blog - as it was a few minutes ago, anyway.



The picture is nice, and it's reassuring when I see it. Can anybody tell me what's wrong with the picture, though?

You might get a clue from looking at the URL, in the address window.
http://blogging.nitecruzr.net/b/post-preview?token=-gItGCsBAAA.ySUB0XKSvMXVATQkgsbJpQ.L6EH7oqCazo3giFxW7Y6vg&postId=1001987166631748251&type=POST
That's a mouthful, isn't it?

The important part of the URL is the "?".
http://blogging.nitecruzr.net/b/post-preview?token=
That makes this a dynamically generated page, which is not subject to caching. Any browser, retrieving that URL, will go straight to the Blogger server, and retrieve the page, as specified.

After you decide that you like what you see, you hit "Publish Post", and your post is published. And now, the confusion starts. If you just published a new post, when you retrieve the home page of the blog, you'll see the blog, as cached in your browser (or in any caching proxy that is upstream from the browser). Depending upon what's in cache right now, you may or may not see the new post in the blog main page display.

The confusion compounds itself when you edit the published post. If you edit, then Preview the edited post, you'll see the post immediately updated. After you publish the edited changes, and view the blog, you may or may not see the changes. If you're viewing the main page display, you may or may not see the post at all. If you do see the post, you may see the initial copy of the post, or the post with any of the changes applied, since the post was originally published.

This confusion can be so easily avoided, if you clear or refresh cache, after you make changes. Here again, I'll advise you to be aware of the options for clearing or refreshing cache, and the different possible results from employing either choice.

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2 comments:

Matt said...

Is there a reason Blogger doesn't employ cache control headers to help alleviate this problem?

Chuck said...

Is there a reason Blogger doesn't employ cache control headers to help alleviate this problem?

This is Blogger that we are talking about, so I'll pass on repeating my allusion to their unpredictability.

Actually, I'm guessing that they have been using cache control headers for some time - at least, since before I wrote Your Browser and Upstream Caches, when the problem that we were seeing was possibly being aggravated by Blogger's varied "caching aggressiveness" policy (which they alluded to, in a few forum posts). I've always suspected that their policy involved cache control technique.

I'm not sure that "cache control headers" are going to be a 100% predictable solution, on all caching proxy servers - and this lack of predictability may have fueled the observed capriciousness, in the original problem.