Factorio Forums

Whenever a player on hour server is using certain custom commands implemented by me, a certain set of players will desync. Meaning the same commands will reproducibly desync the same set of players.

I know desyncs related to user scripts won't be investigated unless proven that the dsync is not caused by the script. But I beg you to hear me out. I have several clues that make me believe the bug is in the commands API.

• 1. I have two commands (/mods and /regulars), which are implemented identically. The only difference is the variable that will be accessed. Code was actually copied, pasted and search & replaced. But /regulars caused desyncs, while /mods worked fine.
  
  2. After a server restart the commands desync behavior will change. Meaning certain other commands will cause a set of certain other placers to desync. But the scripts that would have caused the desync earlier (like /regulars) will no longer cause desyncs and work fine.
  
  3. I have found cpp exceptions in the logs. I don't know if that's relevant or not.
  
  (4. This is probably caused by one of my drivers and not factorio, but I thought mentioning won't hurt. 5 seconds after using a desyncing command I got a bluescreen. But if I have a driver issue personally, that couldn't have caused the desyncs, because the desync behavior is identical for all players on the server.)

I will do additional testing later, but can't promise results, since I can't subject a 30 player server to desync testing. The desyncs might not happen with fewer people online.


I have attacked 3 logs: The log of the client using the command causing the desync (in this case /regulars). The log of on the "victims" of the desync. And the server log.
One example of desyncs is at the following moment: (11759.674 in the client.log, 219.820 in the victim log, 718.910 in the server log)
I have also attached the files involved.

If you have any questions, need more files or want me to try/test something, i will gladly help you.

Your custom commands desync because you're not storing your data in the global table and it doesn't get persisted when someone joins in MP or through server restarts.
1. Player A joins the game
2. Player A is added to regulars
3. Player B joins the game
4. Player A runs /regulars

In this scenario player A will get his name + the default value and player B will get just the default value and it desyncs. You need to store any variables you mutate in the global table so they're persisted between save/load.

I'm going to move this to modding help.

Thank you for your quick reply on a sunday.
And sorry for wasting your time.

Have a nice day.