AuthTicketCanceled

Hey, sorry for the late response! This error basically means that the authentication ticket of the client was cancelled by the user - i.e. the ticket became invalid before the server was able to authenticate it. This could happen if a user cancels the loading process, or if there is an issue with the Steam servers.
However, what do you mean exactly with "the server stopped working"? Did it crash?

Quote from yahwho

Hi Red hope you had a good holiday
Yes the server stopped accepting connections from any client including me locally. So, it sounds to me at least that it was a issue with the Steam servers. A reboot of the server fixed the issue. It happened 2-3 times during the space of a few days, hence I thought I would mention it here. Not had a problem for a while now *touch wood* so maybe it was just glorious Steam having a few hiccups.

had a similar problem 2 times this weekend. On my side it is related to a mysql exception timeout occurred while another program ran a rsync backup that already had 450+ folders. The disk IO is too high while backup is running so mysql throws that lock timeout and after that my server hung up in a zombie state where even my restart plugin doesnt work and i have to kill the process. I knew this problem but forgot to check backup directory recently...

Hey @yahwho and @Devidian, have you considered assigning cpu affinity to the backup's process? In short you can force applications to use specific cores by adding /affinity to the start parameters for your backups application. Another trick is the /abovenormal /belownormal tags so the cpu knows which is mission critical and which is background processes.

does not matter in my case 16 cores are not very busy only the storage is! The reason is that its some sort of network-shared-storage in my case.