Does Azure SignalR All.SendAsync send messages to ALL clients, or just clients with given method name?

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Problem: To minimize per-message charges, I'd like to restrict messages by method name. Per the picture below, I need to know to which clients SignalR will send a message in the following case:

1.) Create Hub "/MyHub"

2.) 3 users (on Angular clients) register with the Hub, with a method named "Post_A"

3.) Then 2 different users register with the same Hub with a method named "Post_B"

4.) If the API server sends an update via Clients.All.SendAsync("post_B", dto) will it only go to users 3 & 4? Or will that message go to all five users?

Bonus! If the answer is that all messages go to all users, is there an option without using groups? I don't think groups will work w/o a lot of additional overhead each time a user views a new post (there will be thousands of posts).

Thank you!

enter image description here

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azuresignalrazure-signalr
Why using groups is a problem for you? They exists exactly to cases like yours... Microsoft even recommend that you can have even 1 user per group... - Kiril1512
I think it would add unnecessary load on my API. Unnecessary, that is, if #4 above is correct. - Jason
In order to route messages, you'll can store connectionId's in some form of static dictionary or list (if you want to cache them, you can use redis), then you can send a message to that dictionary/list if you want. - Rav
Thanks @Rav. That doesn't really work w/ my current architecture, but might be useful later. - Jason

1 Answers

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Did some testing.

SignalR's Clients.All.SendAsync(MethodName, object) does send a message to all clients, even if they haven't registered with the method MethodName.

enter image description here

As you can see in the client-side logs above (after turning on SignalR's logging to console), the client throws a warning when it receives a message for which it has no method registered.

So groups are the only option for restricting messages.