Invoke vs. InvokeAsync

[joreg]

helo darkl,

thanks a lot for your work on the wamp implementation. works great here. before i come back to the topic i just wanted to quickly comment on the 2 PRs i just sent:

#16
in our application we need the possibility to dynamically register/unregister RPCs

#15
here we needed a way to be notified when a session connects/disconnects and also when an RPC call finished.

hope they work for you. let me know if you need things adapted.

back to the topic:
have you thought of a way to decide globally or per RPC whether it is invoked synchronously or asynchronously? for now it seems you default to async which doesn't work in our scenario. so for now in WampRPCServer.cs l55 we just call Invoke() instead of InvokeAsync() but of course that is not solution. any ideas?

[darkl]

I prefer not to block if possible, that's why the InvokeAsync is the preferred option. If you want to block the calling thread, you can implement InvokeAsync in your DynamicRPC class so it invokes the synchronous method and returns a suitable Task<> (use TaskCompletionSource for instance).

This behavior is subject to change in wampv2, I'm considering blocking the calling thread if the rpc method doesn't return a Task type, but this is still open for changes.

[tebjan]

thanks for this suggestion, it seems to work pretty well. just to confirm, did you had this in mind:

public Task<object> InvokeAsync(object[] parameters)
{
    var tcs = new TaskCompletionSource<object>();
    tcs.SetResult(Invoke(parameters));
    return tcs.Task;
}

from our side, this issue can be considered as closed...

[darkl]

Yeah, exactly.
You can also wrap the invoke call in a try-catch block and set the exception of the task in the catch if you like to.

[tebjan]

perfect, this should be the final code:

public Task<object> InvokeAsync(object[] parameters)
{
    var tcs = new TaskCompletionSource<object>();
    try
    {
        tcs.SetResult(Invoke(parameters));
    }
    catch (Exception e)
    {
        tcs.SetException(e);
    }
    return tcs.Task;
}