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Computercraft is BAD for large servers...VERY BAD.

Volgarenthor
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Volgarenthor Stone

Volgarenthor

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So, we, being Terra Novo, have been running Tekkit2 for a solid 8 days now, due to the nature of this error, i will not be able to supply any error reports on the subject. The server as a whole has had to scale its allocated memory back quite a bit because there was a gigantic memory leak that would literally cause the server to go down every 3 hours. So we setup auto-restarting for the server every 2 hours, which usually was just barely enough time to keep it from crashing. Since then, the problem has gotten worse. As of today, the server started experiencing severe issues that would take the server down in a matter of seconds.

So we whitelisted the server, thinking it might have been a machinery issue, and it wasnt. We swept through our entire backend testing things out, and finally decided to turn off computercraft to see if maybe that was an issue, IT WAS. Not only did it solve our problem, whichw as the server eating ALL of our memory in a matter of seconds and crashing, but it fixed the memory leak that would steadily over the course of several hours, kill the server. I dont know whos responsible for updating or approving mods for tekkit, but it seems that this mod was not tested, or even designed for large scale usage. Which is a huge shame....

I am including a few graphs to show the memory usage/spikes from our server, against the graph of another server in the same network:

here is a server on the same network, aside from the 2 world edit crashs you will see, the CPU usage is very stable

graphRPPUJc.png

And now here is our graph taken the same day, the two sections where it completely runs out of memory were the issues we were experienceing, but notice how our memory usage through out the day is really up and down?

graphvll2vs.png

Since removing Computercraft, our memory has been very stable and almost perfect, we could most likely support upwards of 200 players now without this issue.

If its possible, and if the author/authors had the time to actually do it, maybe look at the coding and fix the issues with it. I know not having it is going to suck for a lot of people, including me, whos entire town is rigged with computer security consoles.

Thanks guys, and keep up the good work. ^_^

agelian Grass

agelian

Posted
Posted

You do realise that computercraft allows computers to run in the game.. if i put a computer block down and then write a stupid program on it and then have it auto run on boot its going to cause issues..

So in summary unless you are able to police who can put down computer blocks and what they can run then yes it might be best to disable it for now as that its the basis of the mod itself.. computers in minecraft.

We include it for people who play tekkit with friends.. for the larger servers.. well you may need to find a way to police who can put down the block and access it or just disable it alltogether, there will likely never really be a 'fix'

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KakerMix Bedrock

KakerMix

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I only see RAM usage, unless I am missing something.

And afaik, that's how ram dumps work no? You give it 9 gigs, it will use 9 gigs.

linkthegamer Obsidian

linkthegamer

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Couldn't the issue be there because some guy purposefully made a very intensive program to try and crash the server?

it is possible, a virus would not be that hard to make, all it has is a loop of really horrible code. I made two for the command prompt in windows once, one was a loop of text (which was annoying but no big deal) and the other was a loop of launching more command prompts (which turned EVIL and ate up all the computers memory). The point of that is they where both rather simple batch scripts (No, you can not know what they were) and at least one of them had the power to eat up memory. Doing the same in Lua wouldn't be that hard if you know what commands to have it issue on loop to take up the most RAM.

hindos Gold

hindos

Posted
Posted

If you visisted the computer craft program library you'll find quite a few people made viruses... I think someone should make an anti-virus plug-in in a future update or just as a program, it might solve this server's issue.

linkthegamer Obsidian

linkthegamer

Posted
Posted

If you visisted the computer craft program library you'll find quite a few people made viruses... I think someone should make an anti-virus plug-in in a future update or just as a program, it might solve this server's issue.

In theory that wouldn't be to hard, most AVs are just programs that scan other programs for known malicious code (like the deltree c:\*.* /y command for DOS, enter that any any batch file on a windows computer and run a virus scanner on it, you AV will go off on it. Only mentioned that one because deltree is a long dead command if memory serves me right) So all one would need to do is program a lua script to read other lua scripts and remove ones that contain known malicious code.

Volgarenthor Stone

Volgarenthor

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Perhaps i didnt properly convey not only my feelings, but what i was actually trying to say. From day 1 of updating to tekkit2, the servers RAM has slowly depreciated until the server would either crash, or need a restart, this hasnt been a issue that has arose in the past 1-2 days, we had to specifically implement countermeasures just to keep the server up, that included modifying certain config files and applying a Autobackup plugin to auto restart every 2 hours to prevent a crash/rollback.

The most recent issue, was that it would crash every few seconds after coming backup, it would usually take 200-700mb a second, and dump it until there was none left, and it would just crash. Now, in no way was i attempting to blame this on code, i should have worded it better. I was merely asking if there was any possibility of the code being revisited in the future, and tweaked to be more large scale server friendly. Thats all. As for the Viri, it is very probable that someone had loaded a malicious program into their computer console, in an effort to subvert the server and take it down, as we didnt think to need to have them limited to certain ranks, something we most certainly CAN do using perms and configs. it also does not help that they are literally able to be crafted from bottom rank items, which in turn makes them extremely easy to acquire and distribute.

Kaker, in the instance of RAM usage you speak of, it would continue to take more than was allocated to it, and would sometimes not only freeze the container, but there have been atleast 4 instances where it crashed the server hardware, because it attempted to take more than was actually there. Which is not only ODD, but downright unexplainable by me, as im in NO WAY good with code and programming. Even our host, who is majoring in...whatever (insert computer course, certification, code, language here) could not figure out what was causing this issue, an therefore continued to allocate more and more memory until it reached a point where there was no more to allocate to the memory dumping.

I patiently await your wise responses.

havocx42 Iron

havocx42

Posted
Posted

I patiently ask if you posted all this on the computer craft forums, it's essential that they hear it :) !

Not sure how more clear this could be, from the CC forum:"How to Post a Bug: (Anything done on or about Bukkit is not a bug)"

They do not support the bukkit port. This is why in the other thread I suggested testing CC with a vanilla installation to see if the same problem occurred.

Please do not submit a bug report for this unless it has been confirmed to happen in the non Bukkit version.

EDIT: The only potential negative to a modpack like Tekkit is that people report bugs to the mod authors which they cannot do anything about and will waste their time looking for. Let's not make that potential a reality. Only submit bug reports to the original mod author if its confirmed to occur in the version they support.

thecodemonk Grass

thecodemonk

Posted
Posted

I can confirm that the memory issue with computer craft IS NOT because of code being run. We had one server where he simply spawned in a console and placed it simple for decoration. That seems to be the starting point of our issues. Actually, he may not have even placed one now that I think about it. The server has 8 gig of ram and all of it was being allocated for 3 minecraft servers that were only 1gig each. When stopping all servers, only 4gig of ram would free up. I had to reboot the machine to free up the remaining ram (which is definitely the sign of a memory leak). I removed computer craft and the problem seems to have completely gone away.

  • 4 months later...
TheSandwichMakr Gold

TheSandwichMakr

Posted
Posted

An easy solution for this would be to add an option for a memory and cpu cap for each computercraft device and a limit on how many 1 player can place, maybe also an automatic shutdown. If the memory or cpu cap is reached the computer would be shutdown and the owner of the computer would somehow be notified.

VideoBoy Emerald

VideoBoy

Posted
Posted

As an ex amateur virus programmer and experienced Lua programmer, I can think of at least 2 ways to crash a server with CC without even actually trying it... Thank the Gods I don't have another me on my server. ;_;

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