What are the advantages/disadvantages? (gRPC vs TCP/IP vs HTTPS)

Short answer: If possible, use gRPC as it is a future-proof connection protocol.

Longer answer: gRPC should be used when possible, but setting up a gRPC environment when there's a proxy server in front of the M-Files application server requires expertise in that particular proxy solution. We don't currently have extensive documentation on setting up such an environment and some details are of course dependent on the used proxy solution. gRPC works over HTTP/2 so IIS cannot currently be used as a proxy as it lacks this support as far as I know. That's why RPC over HTTPS is still used also in some new on-premises environments. Vaults on the new M-Files Cloud will always use gRPC for the communication.

At least in theory gRPC can provide performance benefits over the other protocols but I haven't yet seen any data from real-world setups. My gut feeling is that there isn't a noticeable difference currently.

On the recent partner conference it was mentioned that some upcoming functions will only work with gRPC. I did not notice exactly what it was, but apparently that is the way we are headed. Have included gRPC settings on all installations that last year just to be prepared but have not seen any noticeable difference so far. Have been lucky not to encounter situations with proxy servers in front so far (except for my own, where I am not able to forward gRPC calls to other than the primary server.)

On the recent partner conference it was mentioned that some upcoming functions will only work with gRPC. I did not notice exactly what it was, but apparently that is the way we are headed. Have included gRPC settings on all installations that last year just to be prepared but have not seen any noticeable difference so far. Have been lucky not to encounter situations with proxy servers in front so far (except for my own, where I am not able to forward gRPC calls to other than the primary server.)

That the other connection methods will not have feature parity with gRPC going forward, or sometime in the future, was also my understanding. This is obviously not great in cases where gRPC is not an option, like as Joonas Linkola mentions when IIS is used as a proxy, which is a very common sight. Some more transparency on what will happen feature-wise would be ideal.

I am hoping one day to understand how to set up HAProxy myself to allow for M-Files to run on gRPC and to gain a better understanding of the performance and so on compared to the other methods.

Perhaps the gRPC setup instructions on the KB could also do with an update. In my opinion, it is not clear what should go into the certificate and private key sections. Would that be from the certificate used in IIS for HTTPS or something separate?

I've sent a note to our documentation team to check if the setup instructions could be clarified.

With recent advances to IIS and its support for gRPC and HTTP/2, has there been any updates on setting up IIS as a proxy server for gRPC communication between M-Files desktop and M-Files application server?

See gRPC on .NET supported platforms | Microsoft Learn for more information about Microsoft support.

Our understanding is that the "Application Request Routing" IIS extension still does not support HTTP/2, and that would be required to be able to use IIS as a proxy server with M-Files gRPC traffic. So it's not possible until Microsoft implements better support.

For what it's worth, we have tested Traefik for proxy connections. There's also some information for HAProxy settings on the support portal: HAProxy Settings for Secured M-Files gRPC Connections

Awesome to see a help article for gRPC configuration! Will attempt a grpc configuration with our proxy in the near future hopefully.