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Why SQL error

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7 replies to this topic

#1 polyfrag   Crossbones+   -  Reputation: 2061

Posted 28 April 2013 - 11:24 PM

Why is the site always broken and saying there's SQL errors?


#2 slicer4ever   Crossbones+   -  Reputation: 4255

Posted 29 April 2013 - 05:47 AM



There was a more recent discussion on the topic, but I can't seem to locate it now.  But yes, depending on your time zone(for me it's midnight), ~15-30 mins every day the site is down.

Check out https://www.facebook.com/LiquidGames for some great games made by me on the Playstation Mobile market.

#3 Hodgman   Moderators   -  Reputation: 36290

Posted 29 April 2013 - 06:22 AM

~2:30pm every day for me...

#4 jbadams   Senior Staff   -  Reputation: 21505

Posted 29 April 2013 - 07:08 AM

We are investigating, but so far we've been unable to find the cause of this one -- seems to be some regular task carried out by our provider, but so far it's been non-obvious.

#5 Michael Tanczos   Senior Staff   -  Reputation: 5520

Posted 29 April 2013 - 07:40 AM

Here is a brief synopsis of what happens:


There is a period of about 5-10 minutes where our final system activity suddenly spikes and we see a HUGE IO load that pretty much brings most of the system to a halt.    During this time the SQL server cannot answer all queries and gets about 250 queries backed up and waiting to be answered.    For a brief time the IO fluctuates up and down enough to make it possible to answer some of the queries but very few of them.   What happens is that the HTTP part of the request is answered by our reverse proxy (that's the part that says the "Site is down") and sometimes by our site software (that's the part that says SQL Error).   When it's our site software the reason for the SQL Error is "Too Many Connections".   Largely the effect is caused by the reverse proxy cache being invalidated for being down more than a few minutes, the queries getting backed up in the SQL server, and the shear number of people hitting the "WTF is going on.. refresh this shit.. damn why isn't it working?!" button.    That last button slams our server because so many of the queries used to build the page aren't even being used because the page request gets abandoned.


TL;DR - It's caused by an as-of-yet unknown high disk IO problem (which we think may be our ISP backing up the server to be honest) caused by a period of people rapidly refreshing their browser in an attempt to help us fix the problem (while also overloading the server with too many database queries too quickly).


#6 JTippetts   Moderators   -  Reputation: 9308

Posted 29 April 2013 - 08:10 AM

Did you try turning it off then back on? Check to make sure the cable is plugged in. Maybe the intarweb hamsters need faster hamster wheels. I have three goats; do you want to try sacrificing one of them?

#7 Bacterius   Crossbones+   -  Reputation: 9981

Posted 29 April 2013 - 09:17 AM

~ 4:30pm here.

The slowsort algorithm is a perfect illustration of the multiply and surrender paradigm, which is perhaps the single most important paradigm in the development of reluctant algorithms. The basic multiply and surrender strategy consists in replacing the problem at hand by two or more subproblems, each slightly simpler than the original, and continue multiplying subproblems and subsubproblems recursively in this fashion as long as possible. At some point the subproblems will all become so simple that their solution can no longer be postponed, and we will have to surrender. Experience shows that, in most cases, by the time this point is reached the total work will be substantially higher than what could have been wasted by a more direct approach.


- Pessimal Algorithms and Simplexity Analysis

#8 polyfrag   Crossbones+   -  Reputation: 2061

Posted 30 April 2013 - 11:16 PM

Just happened to me. Started ~10:10 PM -8:00 (pacific time).

Edited by polyfrag, 30 April 2013 - 11:16 PM.

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