Help with Inductive troubleshooting?

  • kjohnson_2

    (@kjohnson_2)


    7 years, 3 months ago

    I am trying to solve a problem with a site I support, and need a new approach. Detailed reasoning at the end.

    What kind of code would you need to write (or coding error would you need to make) to cause the front-end of a WordPress installation to be the Blank White page? Required conditions: no plugins enabled, 2019 theme. WP_DEBUG is enabled; no error messages in php.log, debug.log, or Apache error.log.

    Answers might help me in two ways.

    One: I could then follow my former partner’s approach (see below), and go looking for that code.

    Two: Currently, the files and database that fail on the live site work great in my test environment. So, I could try you answer in my test environment. If it fails the same way, I could work in my test environment to develop methods to get error messages that I can look at. Then move those methods to the live site, and with some luck, see some kind of fault information that would give me a clue.

    Explanation:
    25 some years ago, I had a business partner, who, like me, was at the expert level at troubleshooting O/S kernel and device driver problems in two now-obscure operating systems called VMS and RSX-11m. I leaned toward a deductive approach, working backward from the core dump toward the logical error that caused the crash. He leaned toward an inductive method, studying the symptoms and nature of the crash, and then asking himself ‘what code would I need to write that would cause this kind of failure?’. Or what coding error, if you prefer. Then he would look for that code. In partnership, we were never stumped.

    So, I have a tough ‘blank screen’ problem; you can read about it here. But that is not essential to my question. Unfortunately, at the moment, my PHP coding is just a little past ‘Hello, World’. (Most of my work is not with WordPress.) So this is a question I cannot answer on my own, at least not yet.

    Thanks for any insight you can give.

Viewing 2 replies - 1 through 2 (of 2 total)
  • Joy

    (@joyously)

    7 years, 3 months ago

    I’d say your method is unhelpful since there’s no output to work backward from.
    Yet your partner’s method is sort of the long way around.

    For WordPress, it’s a simple client/server request flow, so if there was a problem before there was any output, you get a blank screen. But a blank screen might not be totally blank (just not visible to the human). It could have headers sent, or even the beginnings of HTML (which is invisible, think <html> or <head>), and these would be clues to where the error is. You can use your browser developer tools to inspect the network traffic and browser console for errors.

    If it truly is blank, the error was before any output. You don’t say what version of WP you are on, but I saw something yesterday that the newer versions no longer output errors on the REST API. Not sure how you tell what’s what there, but the new editor uses the REST API.
    Also, there is this sticky posts for each release:
    https://ww.wp.xz.cn/support/topic/read-this-first-wordpress-5-1-master-list/

    JNashHawkins

    (@jnashhawkins)

    7 years, 3 months ago

    I smoke so when I run into something I can’t figure out I’ll go outside on the patio and have a smoke. I may stay out there for a while but I usually find the change of space, pace, and place gets things to working in my head and the solution bubbles up.

    I used to work on old IBM ATMs. They had this orderly process that you could follow to find the problem. It mostly consisted of starting at a certain spot and looking for a symptom then following the tree through to the end.

    Being taught ‘old school’ I was not able to do that easily. Too restrictive. I often wondered when you were supposed to ‘put out the fire’ but I imagine IBM expected their engineers to defer those actions to the Fire Department or had a special team to deal with that. If some subsystem is melting, smoking, or combusting that’s probably a good place to start.

    I like the ‘what code could I write to cause this approach’ but no two coders code alike all the time so you could miss something. Going from the obvious problem to the part or code that caused it seems more intuitive.

    Experience sure does help the most when it comes right down to it and you get that by tackling the problems from different directions.

Viewing 2 replies - 1 through 2 (of 2 total)

The topic ‘Help with Inductive troubleshooting?’ is closed to new replies.