Question Commands issue when trying to use Remote Players Prediction

In my project, I've noticed an issue where commands written at a specific tick sometimes seem to disappear during the following frames. A detailed description of the problem follows, but you may want to read the rest of the post before you read that part in spoilers, because I think my real problem is a faulty prediction setup

Spoiler: Description of the problem

This is what's happening, in chronological order, on the local-owned player on Client:

• a playerCommands system in GhostInputSystemGroup updates at tick 797
  • checks if commands already existed for tick 797 by doing a GetDataAtTick(797); finds out that's not the case
  • adds commands at tick 797 to commands buffer using AddCommandData()
• a prediction system in GhostPredictionSystemGroup updates at tick 797
  • successfully does a GetDataAtTick(797) that returns commands of tick 797
  • everything working as expected so far, and we've confirmed that a command at tick 797 does exist in the commands buffer
• a playerCommands system in GhostInputSystemGroup updates at tick 797 once again (new frame, but still on same tick),
  • checks if commands already existed for tick 797 by doing a GetDataAtTick(797); but it returns commands of tick 796. This is the part I wasn't expecting. Where did the previous commands of tick 797 go? I've tried to manually iterate on the commands buffer at this point to find the latest tick, but even this returns 796. The commands of tick 797, that we successfully retrieved during the last prediction frame, seem to have disappeared
  • adds commands at tick 797 to commands buffer using AddCommandData()

I'm not sure why this situation happens at the moment, and why the commands added for tick 797 seem to have disappeared from the buffer during the next frame

After trying out a bunch of stuff, it looks like the problem disappears when I don't try to use Remote Player Prediction. So my guess is that the problem is simply that I haven't set this up correctly. Here's what I do

• my ICommandData buffer is built-into the Player ghost prefab instead of being added at runtime. So it's always present regardless of if we're the local player or not, and regardless of if we're on Client or Server.
• my ICommandData ghost is set up as described here; It has a regular [GhostComponent()] without params, and all fields have a [GhostField] without params
• my Player prefab has "Support Auto Commands Target" and ghost mode is "Predicted"

 

I'm pretty sure if you're sending commands to remote clients, you need to use:

Code (CSharp):

1. [GhostComponent(OwnerSendType = SendToOwnerType.SendToNonOwner)]

To prevent commands being incorrectly overwritten

 

Tried this, and it makes a lot of sense, but it seems to not have solved the problem. I think I'll have to try to debug this more carefully and see if our local player commands still receive anything from server

 

@PhilSA these forum posts help me so much, I'm very grateful that you take the time to write up your findings in a public forum. Also very grateful to the Unity team for their presence on the forum.

This topic of input prediction seems to be one of the biggest sticking points in Netcode.
It's not that the API is bad, the documentation probably just require a few more examples of these more advanced topics.