[0.16.18] Repeated and reproducable desync

[oracleguy]

Loaded up 0.16.18 and connected to my server. The save was previously on 0.16.16. I just started walking around the map and the game desynced. I tried re-connecting and the game immediately desynced. I tried restarting the server and the problem persisted. I rolled back to the previous save and I was able to connect again however then it desynced again. It seems to keep happening.

Here is the report from the original desync: https://drive.google.com/open?id=1vyxOu ... EXIPaq7LP8
I have more reports if needed.

And I have attached the last map save before upgrading.

I am using vanilla -- no mods were ever installed.

[Loewchen]

After you restart the server, what are the steps to reproduce this?

[oracleguy]

You just need to run the save and walk around and look at the map for about 20-30 seconds total, you don't have to build or remove anything. The server was running the Linux headless version and I was using the Windows build from Steam. I was the only player on the server.

[Rseding91]

Thanks for the report. I'll look into it.

Every one of these save files that are "reproducible" end up being > 30 MB which makes testing them reallllly slooooow.. :\

[oracleguy]

Thanks for the report. I'll look into it.

Every one of these save files that are "reproducible" end up being > 30 MB which makes testing them reallllly slooooow.. :\

You have my sympathies, I know how you feel. Let me know if you have any more questions or if there is any other data I can provide.

[Sarsey]

Thanks for the report. I'll look into it.

Every one of these save files that are "reproducible" end up being > 30 MB which makes testing them reallllly slooooow.. :\

I'm glad to see you look into it, i've got the same desync problems on 0.16.18 with two desync-reports of 103MB and 104MB each

[elderdakkar]

Same here.
Step to reproduce: Login, wait some time, use the map and thats it.

vanilla. Server restarts don't fix that problem.

[Starfish34]

i got the same issue on a dedicated server. Everybody disconnects after like max. 1 minute of playing.

Reconnecting, uninstall install did not help.
Pure vanilla, no mods ever installed

and thx btw. awsome game

[Rseding91]

We can't reproduce *any* of these desyncs on our end which means we can't fix it as it is.

I need someone to give me a *small* save file - not one that's 30+ MB - that shows the desync with an exact series of steps that reproduces it. "Start the server, join, and wait some time" is not going to cut it with this

My current theory is the linux headless/client is broken and connecting to it with other game versions triggers the desync. So if anyone can confirm that - that would be great. I personally can't because I only have access to a windows machine and it never desyncs for me on any save I test no matter how long I wait.

[oracleguy]

with an exact series of steps that reproduces it. "Start the server, join, and wait some time" is not going to cut it with this .

That's the thing, the steps are literally that simple. I'll make a recording of it tonight.

My current theory is the linux headless/client is broken and connecting to it with other game versions triggers the desync. So if anyone can confirm that - that would be great. I personally can't because I only have access to a windows machine and it never desyncs for me on any save I test no matter how long I wait.

By "other versions" do you mean other platforms? I can run a small test tonight with a new map on the Linux headless server and see if it happens right away. Alternatively if there is a debug flag I can launch Factorio with on the client or server, I can do that. I can also send you the password to my headless server if you want to connect to it with your debugger attached to your client.

Out of fellow software developer curiosity, is your concern with the file size of the save related to how many entities in the map have to stay in sync? If your Windows machine is version 10, Microsoft's Hyper-V is pretty a decent for running VMs if you ever want/need to install a Linux system.

I will run some tests in a couple hours and will get back to you.

[Rseding91]

Out of fellow software developer curiosity, is your concern with the file size of the save related to how many entities in the map have to stay in sync? If your Windows machine is version 10, Microsoft's Hyper-V is pretty a decent for running VMs if you ever want/need to install a Linux system.

I will run some tests in a couple hours and will get back to you.

The issue is I can't run the save with the desync-detection flags turned on without 60 seconds of game simulation taking 10+ hours when the save sizes are so large. So "run it for a few minutes and it will maybe desync" becomes "run it for a few days/a week and it will maybe desync" which simply isn't viable.

[oracleguy]

The issue is I can't run the save with the desync-detection flags turned on without 60 seconds of game simulation taking 10+ hours when the save sizes are so large. So "run it for a few minutes and it will maybe desync" becomes "run it for a few days/a week and it will maybe desync" which simply isn't viable.

Gotcha makes sense. Thanks for indulging me.

[oracleguy]

So I ran a test with a new blank map and couldn't reproduce the problem. I'm guessing it needs more content than a blank map. However I can still easily reproduce it with the save file I sent.

Here is a video of me reproducing it with the save I posted: https://drive.google.com/open?id=1stvN7 ... GKgPb7PsLC

EDIT: I should say that with all my reproductions the time for it to happen is about the same.

[Rseding91]

So I ran a test with a new blank map and couldn't reproduce the problem. I'm guessing it needs more content than a blank map. However I can still easily reproduce it with the save file I sent.

Here is a video of me reproducing it with the save I posted: https://drive.google.com/open?id=1stvN7 ... GKgPb7PsLC

EDIT: I should say that with all my reproductions the time for it to happen is about the same.

The desync involves biters so you'll need at least some of them for it to happen.

[silvervest]

The desync involves biters so you'll need at least some of them for it to happen.

I've been able to make this small map (~5mb), generating a small amount of pollution and with biter evolution set to 1, and have had a couple of desyncs now between linux headless and macos client. Desync is still completely random though, I can't seem to get it to trigger in any reliable manner - one time I was placing concrete, another I was just idle watching an attack, etc.

[oracleguy]

With 0.16.19 the desync happens instantly when I join the server. Let me know if you want to desync report from 0.16.19.

[Oxyd]

Thanks for all the reports, this should be fixed in 0.16.20.