another misAdventure

"We are all of us living in the shadow of Manhattan."

Sunday, December 10, 2006

A Puzzle, and a Weekend away from Work

OK, here's your puzzle, a puzzle I solved on Friday at work (yes, it was actual work). Answer will be at the end of the post.

There is one central computer, and it has to fetch a file every day from several remote computers. The files is generated every day on the remote site, and the central computer is supposed t fetch from each remote site once a day a half hour after the file is generated.

We got a report that for a few sites the file wasn't getting fetched when it was supposed to. The central computer was getting the previous day's file from some of the remote sites. It always got the file, but a day late.

The central computer is in Phoenix. The remote sites that were having the problem are in Albuquerque and Denver.

I told the person who was starting to investigate this what the problem was, and I told her that it probably started happening about six weeks ago or so, though it hadn't been noticed right away. What was the problem?

You may have the answer already, but I'll do my weekend update first.

I got a few more Christmas lights up outside, though I couldn't do the lights along the gutters. There's too much snow/ice in the gutter from the Friday before last to actually get the clips onto the gutter. However, I did put up the spiral-light trees, and will put up the plastic penguin at the end tomorrow, after I buy a new 25-watt bulb.

Oh, that's very exciting!

Oh and I got my tools organized again and stuff out of the way in the garage. However, I still need to get some things moved to the attic, but I need to patch the attic ladder first. The foot of the ladder on one side has come loose, so it can't be climbed properly. I need to get some steel braces to stabilize it from a hardware store, hopefully tomorrow.

I spent the afternoon and early evening with my brother, Bob. He fixed dinner and we hung out watching football.

And that's pretty much the weekend. Exciting, eh?

The good news that I managed to not worry about work for the weekend. Well, that may just mean I have some things to be sure to do right away in the morning, but that's fine.

OK, here's the puzzle answer, one that the UK part of our team may have had more problem with: the fetch of the file from Denver and Albuquerque was happening an hour early, i.e. a half hour before the file was generated. The time for the fetch was first set up over the summer. At that time, Phoenix time was an hour ahead of Albuquerque and Denver. However, Arizona does not do daylight saving time. As of the end of October, Phoenix was on the same time as Denver and Albuquerque (and everywhere else in the Mountain time zone). It'd be good, but complex, if the system recognized daylight time differences between sites so that it would always get the file a half hour after it was generated. I suggested that it should be OK, though, if they just moved the fetch an hour later so it would get the right file each day, even though it would fetch it an hour and a half after it was generated in the summer. That really wouldn't be a problem. The customer was annoyed that it was getting data that was 23 hours old.


  • Yay, I actually (sort of) figured it out! I mentally guessed that it was something to do with time zones and/or daylight savings time. And I actually came up with that before your "six weeks ago" clue, and without knowing that Arizona didn't do daylight savings time. I had no idea what the actual problem was, but I figured that had to be what was causing it.

    By Blogger Kamie, at 12/10/2006 11:32 PM  

  • Yeah, I got it pretty much right as you started describing the problem, mostly because I listen to a few podcasts by people that live in Phoenix.

    By Blogger Matt, at 12/11/2006 9:12 AM  

  • I figured that it was the computers in Denver & Albuquerque that were off by an hour or so. I didn't think it'd be time zones or DST. Especially since I didn't know Phoenix neglects to care about DST.

    My coworker said you should just convert to UTC.

    By Anonymous narf, at 12/11/2006 3:02 PM  

  • I agree with converting everything to UTC. Unfortunately, the operating companies don't agree.

    And, as we were going over some other things last week, I remarked to a co-worker that it must be a design criterion that no two log files use the same format to print time stamps.

    He took a moment to realize I was being sarcastic.

    By Blogger Tim Tjarks, at 12/11/2006 4:47 PM  

  • By the way, I think Arizona is now alone among the 48 contiguous states in not doing daylight savings time. All of Indiana now does DST, though some parts are Eastern time and some are Central.

    I know Hawaii does not do DST, and I don't think Alaska does either. It's pointless for both, because Hawaii has so little variation on the length of its day, and Alaska has extreme variation (it's daylight deep into the night anyway in the summer).

    And in Arizona, they'd rather have sundown come a bit earlier and have people enjoy some more time without the burning sun, so DST wouldn't work well for them either.

    By Blogger Tim Tjarks, at 12/11/2006 4:57 PM  

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