Total crash of my VPS server

Jim Zim

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« on: March 25, 2008, 07:38:54 PM »

I noticed the phpBB forum on my web site was acting very sluggish this evening, and then a few minutes later there was a total crash of the VPS server. The following error message was displayed when trying to view my site:

Quote

General Error
SQL ERROR [ mysql4 ]

Can't create a new thread (errno 12); if you are not out of available memory, you can consult the manual for a possible OS-dependent bug [1135]

I immediately went to Plesk and upon clicking on the SERVER icon, I got the exact same message from Plesk. So, I did a re-boot of the server... and then everything started to work fine again.

Just prior to the crash, I noticed that the forum indicated that 59 people had been viewing the forum in the last five-minute period. That's a fair amount of people all accessing the forum at one time... but certainly not a huge amount. On shared hosting, I had as many as 120 people access the forum in a five-minute period.

One other thing...
Around the same time last evening, the server didn't actually crash but I couldn't get my forum to respond at all... so I did a re-boot then, too. So, that's twice in about 24 hours that I had to re-boot.

I'm fairly new to VPS... just a few weeks since we moved up from shared hosting. It seems like the VPS server is unable to handle a moderately active web site and forum. Is this what I should expect from VPS hosting? Or do I need to tweak a setting somewhere?

By the way, the first day after we upgraded from shared hosting to the VPS, I noticed some performance issues and sent an email to VPS@lunarpages.com asking about it. Never heard a single thing back from them. Should I be calling instead of emailing if I run in to VPS problems or have questions?


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perestrelka

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Jedi

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Posts: 980

Re: Total crash of my VPS server

« Reply #1 on: March 25, 2008, 11:55:25 PM »

Hello Jim Zim,

When you emailed vps@lunarpages.com, did you receive a notification from the helpdesk about ticket created? If your issues or questions are not urgent (i.e. sites are not down), the better way would be to open a ticket by emailing vps@lunarpages.com or via web interface at https://support.lunarpages.com/

As for the issues you are experiencing. From the errors you posted it appears that your server reached the memory limit of 512 MB. To confirm this, you would review QoS Alerts in Plesk under System > Virtuozzo > QoS alerts. Black zone even for privvmpages means the scripts and programs have consumed all available memory on the server. To avoid this from happening again, you need to ensure your scripts and databases are optimized for memory usage and there is no unnecessary services running on the server and consuming its memory and CPU. Some time of caching configuration would be also helpful.

Finally, please note that although your site could use some more resources whilst being on a shared server, it won't be allowed to do so continuously. So, if there were load spikes on it, there should also be much longer periods of rather calmness on it to be suitable for shared server and of course the load spikes shouldn't be too high due to the site. On VPS plan, your scripts can use all the resources available for the VPS server and their performance is the only restriction for the amount of users the site can serve instantly.

I hope this helps. Please respond if you have any further questions or concerns.


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Kind Regards,
Vlad Artamonov

Jim Zim

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Posts: 5

Re: Total crash of my VPS server

« Reply #2 on: March 26, 2008, 06:11:04 PM »

Could you elaborate on how to set up a cache on the VPS? I think that sounds like a good idea. As I am simply running a straight phpBB installation, there is no way for me to optimize scripts or databases. It is what it is. If you could give me some idea of how to set up a cache so the VPS has a way to deal with things when it runs out of RAM, I think that might really help.


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hairboy

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Posts: 39

If I were a jockey..??

Re: Total crash of my VPS server

« Reply #3 on: March 28, 2008, 06:31:55 AM »

Interesting post - disappointed that there are no replies.

I've got the opposite problem. Have just moved to a VPS and my pages are now suddenly BEING cached where they weren't being cached on basic hosting.

I Don't want them to be cached but I can't seem to stop it - I've currently got this in my php scripts for the header:

Code:

header('Expires: Mon, 26 Jul 1997 05:00:00 GMT');
header('Cache-Control: no-store, no-cache, must-revalidate');
header('Cache-Control: post-check=0, pre-check=0', FALSE);
header('Pragma: no-cache');

which should prevente EVERYTHING!! But the headers turning up in web pages is:

Quote

HTTP/1.x 200 OK
Date: Fri, 28 Mar 2008 13:18:41 GMT
Server: Apache/2.0.52 (CentOS)
X-Powered-By: PHP/4.3.9
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: max-age=600
Pragma: no-cache
Connection: close
Transfer-Encoding: chunked
Content-Type: text/html

which is CLEARLY different?!?! Anyone able to help here? Can we swap problems there JimZim?! ;-)


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Jim Zim

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Re: Total crash of my VPS server

« Reply #4 on: March 28, 2008, 08:34:24 PM »

Someone please correct me if I am wrong, but I think we are talking about two different kinds of caches now.

I think what perestrelka was suggesting was to do some disk caching so that when the server ran out of RAM it would cache to disk. You are tricking the system in to storing data on to a hard disk when there is no more RAM available to store it in.

I think the situation that hairboy is talking about is page caching... where a server can save the trouble of having to re-create some data by just serving up a saved version of the data from the last time someone asked for it.

Please do correct me if I am wrong!


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perestrelka

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Jedi

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Posts: 980

Re: Total crash of my VPS server

« Reply #5 on: March 28, 2008, 11:32:33 PM »

Hi,

Yeah that's correct, these two issues are different. I would recommend Hairboy to open a new thread about this issue to not create confusion in this one.

Unfortunately, Jim Zim also got me wrong. It is not possible to have VPS server to use disk cache if it runs out of RAM limit like a physical server does. Your main problem appears to be memory consumption of programs running on the server. So you need to stop the services you don't use and optimize programs and scripts that should be running for your site to function. You mentioned forums on phpBB as the main part of it. So you need to work on optimizing parameters of MySQL server and phpBB resource utilization. I'm not sure if phpBB can cache pages to reduce the amount of resources required to generate each page. You can ask about any extension for that on phpBB support forums. If it does not have such feature, you can use the modules mentioned below as they work as PHP extenssion and cache PHP results directly. Also, you can consider migrating to another forums script such as SMF that runs on this site.

Under the caching I mean such solutions as the ones mentioned http://www.lunarforums.com/lunarpages_vps_hosting/zend_eaccelerator_other_accelerators-t46950.0.html They are helpful for the scripts that don't have their own caching mechanisms implemented.

I hope this was helpful.


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Kind Regards,
Vlad Artamonov

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