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Critical Database Error

 
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dansut
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Joined: 02 Apr 2004
Posts: 1488
Location: Lakes Region, NH

PostPosted: Mon Feb 28, 2005 10:11 am    Post subject: Critical Database Error Reply with quote

As this seems to be happening more often Sad I just thought I'd open a topic here so that people know the cause of this.

This error is caused by the database software getting overloaded and refusing any more connections. It's not really a crash because if left alone the connections will time out and normal service will resume.

The error does not happen under normal usage - what appears to happen is that certain companies caching proxies can occasionally go wild and start spidering the sites entire contents with no regard for moderating the speed they do this at. When Google and the other big search engines spider out content they do it at a nice moderated speed and so it never causes a problem. Whoever sets up these companies caching proxies is not doing things nicely and if I could just have a quiet word with them in the server room... Twisted Evil

I don't really want to increase the number of connections the database will allow because this will just move the bottleneck to a potentially more critical resource Sad I'd really like to work out some way of moderating this access speed to the server - if anyone has any ideas/clues then drop me a PM or something and I'll try to find time to do some research myself.

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Daniel Sutcliffe
91 GVR4 1743/2000 - DD, undergoing engine rebuild
92 GSX - one day it may run again ... RallyX goals
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dansut
Site Admin


Joined: 02 Apr 2004
Posts: 1488
Location: Lakes Region, NH

PostPosted: Thu Mar 17, 2005 9:17 pm    Post subject: mod_choke Reply with quote

In an attempt to stop the database being flooded by the aforementioned proxies I've installed a Web server module that limits the number of concurrent connections from individual IPs. This is called mod_choke and the current limit is set at 25 connections.

When the limit is reached the Web server will return HTTP 503 - Service Unavailable. If you see this error (or the previous Critical Database Error) then please report this in the User Feedback forum.

Thanks

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Daniel Sutcliffe
91 GVR4 1743/2000 - DD, undergoing engine rebuild
92 GSX - one day it may run again ... RallyX goals
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dansut
Site Admin


Joined: 02 Apr 2004
Posts: 1488
Location: Lakes Region, NH

PostPosted: Mon Oct 02, 2006 7:18 am    Post subject: Reply with quote

This morning I woke up to find a new Critical Database Error!

This one is not the same as this old one though - apparently the database table used for sessions had become totally corrupted and unreadable. As this table is vital for all use of the site things were dead for a while, sorry. Doing a table repair fixed the damage though and we were up and running just as soon as I'd realized what had happened Smile Although I wish I knew what caused it Confused

Things might be a bit slow for a while - running a number of diagnostics and such ...

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Daniel Sutcliffe
91 GVR4 1743/2000 - DD, undergoing engine rebuild
92 GSX - one day it may run again ... RallyX goals
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dansut
Site Admin


Joined: 02 Apr 2004
Posts: 1488
Location: Lakes Region, NH

PostPosted: Mon Oct 02, 2006 3:02 pm    Post subject: Reply with quote

OK - it's not good news Sad The corruption is widespread, this site apparently got off lightly, and the hard drive is logging errors like crazy Confused

It looks like the server that this site is hosted on is not long for this world - I had planned on upgrading it radically anyway but this is really forcing my hand, looks like we'll be getting hardware as well as software upgrades. Although I haven't decided exactly what I'm going to do yet ...

I'm posting this note as early as possible because, hardware failures being what they are, we could lose the server at any point in time ... if it happens suddenly and unexpectedly the site could be down for a couple of days. If I can keep things under control then hopefully any switchover will be almost seamless.

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Daniel Sutcliffe
91 GVR4 1743/2000 - DD, undergoing engine rebuild
92 GSX - one day it may run again ... RallyX goals
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View user's profile Send private message Visit poster's website
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