Question Confusion about what entities are associated with certain components

In the below ServerSystem, OnUpdate() method I am confused about what entities are associated with certain components. I understand that an entity is created by a code-generated system when an RPC is received, and that entity has the <ReceiveRpcCommandRequest> component, but it also has a <GoInGameRequest> component?

Code (CSharp):

1. // When the rpc is received, an entity that you can filter on is created by a code-generated system
2. foreach (var (reqSrc, reqEntity) in SystemAPI.Query<RefRO<ReceiveRpcCommandRequest>>().WithAll<GoInGameRequest>().WithEntityAccess())

On the ClientSystem a GoInGameRequest component was added to the RPC entity before sending it to the server side so I'm abit confused about why it would be added to a new entity created on the server side.

I thought the .SourceConnnection value was the "connnection" entity from the ClientWorld with the <NetworkStreamInGame> component. But the entity index and versions do not match up in the debugger.

Code (CSharp):

1. // reqSrc.ValueRO.SourceConnection is an entity;
2. commandBuffer.AddComponent<NetworkStreamInGame>(reqSrc.ValueRO.SourceConnection);
3. var networkId = networkIdFromEntity[reqSrc.ValueRO.SourceConnection];

Apologies for the excessive code comments in advance...

Code (CSharp):

1. //[BurstCompile]
2.     public void OnUpdate(ref SystemState state)
3.     {
4.         var prefab = SystemAPI.GetSingleton<CubeSpawner>().Cube;
5.         // GetName()
6.         state.EntityManager.GetName(prefab, out var prefabName);
7.         var worldName = state.WorldUnmanaged.Name;
8.  
9.         var commandBuffer = new EntityCommandBuffer(Allocator.Temp);
10.         // This ComponentLookup<T> is cached by a system across multiple system updates, .Update() performs the minimal updates to make the type handle safe.
11.         networkIdFromEntity.Update(ref state);
12.  
13.         // When the rpc is received, an entity that you can filter on is created by a code-generated system
14.         foreach (var (reqSrc, reqEntity) in SystemAPI.Query<RefRO<ReceiveRpcCommandRequest>>().WithAll<GoInGameRequest>().WithEntityAccess())
15.         {
16.             // reqSrc.ValueRO.SourceConnection is an entity;
17.             commandBuffer.AddComponent<NetworkStreamInGame>(reqSrc.ValueRO.SourceConnection);
18.             var networkId = networkIdFromEntity[reqSrc.ValueRO.SourceConnection];
19.  
20.             Debug.Log($"'{worldName}' setting connection '{networkId.Value}' to in game, spawning a Ghost '{prefabName}' for them!");
21.  
22.             var player = commandBuffer.Instantiate(prefab);
23.  
24.             // GhostOwner
25.             commandBuffer.SetComponent(player, new GhostOwner { NetworkId = networkId.Value });
26.  
27.             // Add the player to the linked entity group so it is destroyed automatically on disconnect
28.             commandBuffer.AppendToBuffer(reqSrc.ValueRO.SourceConnection, new LinkedEntityGroup { Value = player });
29.  
30.            
31.             commandBuffer.DestroyEntity(reqEntity);
32.         }
33.         commandBuffer.Playback(state.EntityManager);
34.     }

 

Thank you very much for taking your time to explain these details! I have gotten over a hump in understanding the communication portion of the NetworkedCube example.

In the GoInGameServerSystem OnCreate() method, why exactly is this EntityQuery cached?:

Code (CSharp):

1. var builder = new EntityQueryBuilder(Allocator.Temp)
2.             .WithAll<GoInGameRequest>()
3.             .WithAll<ReceiveRpcCommandRequest>();
4.  
5. state.RequireForUpdate(state.GetEntityQuery(builder));

Is it so that the SystemAPI.Query in the OnUpdate() method will return faster?:

Code (CSharp):

1. foreach (var (reqSrc, reqEntity) in SystemAPI.Query<RefRO<ReceiveRpcCommandRequest>>().WithAll<GoInGameRequest>().WithEntityAccess())

 

Thank you, I think I understand, is it correct to say that?:

The RequireForUpdate() method will override any other queries cached by a system including a [RequireMatchingQueriesForUpdate] attribute. And since we are using the RequireForUpdate() method for the cube spawner, we must add another RequireForUpdate() that matches the entity with <GoInGameRequest> and <ReceiveRpcCommandRequest> components.

While I did find [RequireMatchingQueriesForUpdate] in the API, I have not been able to find general documentation for system attributes in the manual. Does this exist for the current version 1.0.10?

 

Sadly the documentation is somewhat lacking in clarity on what actually breaks RequireMatchingQueriesForUpdate (I've submitted the issues through the respective "report a problem" options in the docs).

Does RequireForUpdate<SomeSingleton>() also break RequireMatchingQueriesForUpdate? If I'm not mistaken, usually when dealing with RPCs you also need access to EndSimulationEntityCommandBufferSystem.Singleton to destroy the entity containing the ReceiveRpcCommandRequest component.
Does that mean I should always specify

Code (CSharp):

1. var rpcQuery = new EntityQueryBuilder(Allocator.Temp)
2.                       .WithAll<SomeRpcCommand>()
3.                       .WithAll<ReceiveRpcCommandRequest>();
4. state.RequireForUpdate(state.GetEntityQuery(rpcQuery));
5. state.RequireForUpdate<EndSimulationEntityCommandBufferSystem.Singleton>();