An Important Update

Dear Followers Of This Blog ...

If you did not use a Blogger / Google account when you Followed this blog, years ago, you are probably not Following now . During the past...

Wednesday, November 26, 2014

Clearing Cache Won't Always Solve Problems

Sometimes, when diagnosing a problem which involves cache, you may be advised to "clear cache" - or possibly, "clear cache, cookies, and sessions".

Instructions, to do either, may vary according to the problem being diagnosed. Unfortunately, clearing "cache" or clearing "cache, cookies, and sessions", for problems which involve cache, may not always solve the problem at hand.

If you have a problem when viewing your blog - or if you wish to immediately refresh your personal view of your blog, you might clear "cache". If you have a problem with your Blogger dashboard - maybe when switching between Draft and Production Blogger, on the other hand, you would want to clear "cookies". Whenever you clear cookies, you should clear cache, also - so, if you have a problem when maintaining or publishing your blog, you will be advised to clear "cache, cookies, and sessions".

Not all problems involving "cache" will always be solved by "clearing cache" - or even "clearing cache, cookies, and sessions". Clearing browser cache won't help, if the problem involves
  • cache outside the browser being used
  • cookie or script filtering

Clearing browser cache won't help, if the problem involves cache outside the browser being used. When you clear cache, you are clearing cache in one individual browser.
  • If you have other browsers, or other computers, you may have to clear cache there, also.
  • You cannot control cache, outside your computer.
  • You cannot control cache, on your reader's computers.


There is no permanent solution, for upstream cache. But, there may be a diagnostic step, that helps us understand what is going on.

This is the URL of this blog.
http://blogging.nitecruzr.net/
If I need to access the main page, without refreshing the browser, or clearing cache, I can retrieve the updated content, on a temporary basis.
http://blogging.nitecruzr.net?
A URL containing a "?" is normally used for retrieving a web page, dynamically, with extra settings embedded in the URL.
http://blogging.nitecruzr.net?something
A dynamic retrieval is evaluated immediately, using the Blogger server (in this case) - and without any interference from any caches.

Even without a real need to have the URL evaluated by the server, we can still make the URL dynamic, just by adding the "?" at the end. And this bypasses any cache - including cache upstream from the browser.
http://blogging.nitecruzr.net?
Just remember - this is a temporary solution.

Clearing cache won't help, if the problem involves cookie or script filtering. If you clear cache when diagnosing a problem with the Blogger dashboard, a problem with commenting, or any other problem which requires logging in to Blogger, you will need to clear cookies and sessions, at the same time. This won't always be successful, even so. If a problem starts from improper filtering of private data, you won't solve anything by clearing private data.

Cookies, needed when viewing a Blogger blog, are vulnerable to "third party" cookie filters.
  • A preference cookie (aka "cookie") is created under "blogger.com", where an interstitial display runs.
  • A session cookie (aka "session") is created under "google.com", where you login.
Both types of cookies are read under "blogspot.com" - or under whatever custom domain, or whatever country code alias, is being used by the blog, as displayed.

Whether a cookie is needed, but non existent - or needed, but can't be read - the result is the same. The reader is unable to continue, and does not get to view the blog, when necessary.

If a problem which appears to be caused by out of date cache is actually caused by a cookie filter, and you clear cache, cookies, and sessions, you won't solve anything. A cookie, wrongly filtered, will continue to be a problem, even with cache cleared.

If a reader is subject to a filter that blocks "third party" cookies, and a preference or session cookie is needed, the reader will be unable to continue. This is a condition that Blogger Engineers cannot program around, because it is part of the security code, in the browser - and helps to protect us from malicious activity, when we surf dodgy websites.

The bottom line is you need to know when to clear cache (and cookies and sessions), in your browser - when you need to clear cache, elsewhere - and when you need to check your cookie and script filters. None of the 3 makes either of the other 2 redundant - advice given in Google - Blogger Help: Fix a Blogger error notwithstanding.

Dude, hit me with a comment!