C#•5mo ago

Async await in minimal API

Hey guys, I have a minimal API app which also hosts a client which has a websocket connection. The websocket gets in a disconnect state a lot so I reconnect if I can't get the data I want. However, it seems like the await for the reconnect isn't properly awaited, is there some special async/await mechanics in these minimal API routed calls? Code:

app.MapGet("/account", async Task<Results<Ok<AccountOverview>, NoContent>>
    () =>
    {
        try
        {
            await _client.GetAccount();
        }
        catch
        {
            _client.Reconnect().Wait();
            await _client.Authenticate();
            await _client.GetAccount();
        }
    ...
    }
);

app.MapGet("/account", async Task<Results<Ok<AccountOverview>, NoContent>>
    () =>
    {
        try
        {
            await _client.GetAccount();
        }
        catch
        {
            _client.Reconnect().Wait();
            await _client.Authenticate();
            await _client.GetAccount();
        }
    ...
    }
);

I've tried with both .Wait and await for the reconnect call.

31 Replies

Pannekoekje•5mo ago

Traceback:

mtreit•5mo ago

I don't know anything about web sockets but you definitely should not be putting a synchronous Wait in there. What is the type of _client ?

Pannekoekje•5mo ago

I've tried both await and .Wait() 🙂 The _client is a client which I wrote myself, the reconnect logic for the websocket is as such:

public async Task Reconnect()
{
    while (_websocket.State != WebSocketState.Open)
    {
        await Task.Delay(_reconnectDelay);
        try
        {
            await OpenSocket();
        }
        catch
        {
            // Error opening socket, double delay and try again.
            _reconnectDelay *= 2;
        }
    }

    _reconnectDelay = 100;
}

private async Task OpenSocket()
{
    try
    {
        _websocket = new ClientWebSocket();
        await _websocket.ConnectAsync(new Uri(_WSUrl), _cancelToken);
    }
    catch (Exception exception)
    {
        throw new Exception($"Issue connecting to websocket, error {exception}");
    }
}

public async Task Reconnect()
{
    while (_websocket.State != WebSocketState.Open)
    {
        await Task.Delay(_reconnectDelay);
        try
        {
            await OpenSocket();
        }
        catch
        {
            // Error opening socket, double delay and try again.
            _reconnectDelay *= 2;
        }
    }

    _reconnectDelay = 100;
}

private async Task OpenSocket()
{
    try
    {
        _websocket = new ClientWebSocket();
        await _websocket.ConnectAsync(new Uri(_WSUrl), _cancelToken);
    }
    catch (Exception exception)
    {
        throw new Exception($"Issue connecting to websocket, error {exception}");
    }
}

mtreit•5mo ago

Why aren't you using an off the shelf solution for web sockets?

Pannekoekje•5mo ago

it uses the off the shelf websocket

mtreit•5mo ago

Also, those blind try-catch of any exception type without tracing out the exceptions seems like a bad idea.

Pannekoekje•5mo ago

The client is just a library for an API, the _client inside the lib is just a ClientWebSocket;

mtreit•5mo ago

Also an unbounded exponential backoff is a bad idea. When do you dispose the existing _websocket instance? That's probably another bug.

Pannekoekje•5mo ago

but none of those are relevant for the question, no?

mtreit•5mo ago

I don't know.

Pannekoekje•5mo ago

Like I said, the reconnect logic works in other places but I can't get it to work in the routed API call

mtreit•5mo ago

Is it throwing an error? You didn't say what wasn't working.

Pannekoekje•5mo ago

Yes, can't paste it fully since its more than 2000 chars

mtreit•5mo ago

$paste

MODiX•5mo ago

If your code is too long, you can post to https://paste.mod.gg/ and copy the link into chat for others to see your shared code!

Pannekoekje•5mo ago

Thx 🙂 Ah then I can share the full stack trace, sec

Pannekoekje•5mo ago

https://paste.mod.gg/hkzedgtrzztu/0

BlazeBin - hkzedgtrzztu

A tool for sharing your source code with the world!

Pannekoekje•5mo ago

2nd link has the full stack trace if I recall correctly the behaviour is the same with both .Wait() and await

mtreit•5mo ago

That exception is in the Authenticate call, which implies the Reconnect method already returned successfully.

Pannekoekje•5mo ago

which would mean the socket has been improperly closed between the 2 calls?

mtreit•5mo ago

That part is unclear. I'm not sure if your Reconnect concept is valid if the remote server has terminated the connection. You might ask someone in #web to take a look at what you're doing because as I said I've never worked with web sockets. But I would probably start by making sure you correctly dispose of things, that you don't let your backoff delays get too high, that you properly set a KeepAlive value, add some tracing in the code to make sure you know exactly what exceptions are happening and where, etc. That should help eliminate possible issues and help track down why it's failing. I doubt it has anything to do with Minimal APIs but maybe there's something there I don't understand.

Pannekoekje•5mo ago

Hmm, I'll check the #web channel, the reconnect logic is working fine in other places like I said Thanks 🙂 !

mtreit•5mo ago

Hmm, that didn't seem to elicit much of a response did it?

Pannekoekje•5mo ago

No it doesn't 😛 I'm logging the websocket state now in between the calls to see if it is actually open or not here is hoping it breaks 🙂 ofc it doesn't break when you're staring at it 🙂 I'll try again tomorrow, thx

mtreit•5mo ago

Heisenbug

life grinder•5mo ago

tbh it would be wise to create a small example to reproduce the issue it could help you too

Pannekoekje•4mo ago

Hmmm It seems the websocket state is still in "open" but it isn't ?

                    try
                    {
                        await _client.GetAccount();
                    }
                    catch
                    {
                        await LogAsync($"Failed, state: {_client.WebsocketState}");
                        await _client.Reconnect();
                        await LogAsync($"Reconnected, state: {_client.WebsocketState}");
                        await _client.Authenticate();
                        await _client.GetAccount();
                    }

                    try
                    {
                        await _client.GetAccount();
                    }
                    catch
                    {
                        await LogAsync($"Failed, state: {_client.WebsocketState}");
                        await _client.Reconnect();
                        await LogAsync($"Reconnected, state: {_client.WebsocketState}");
                        await _client.Authenticate();
                        await _client.GetAccount();
                    }

Gives

[02-14-2024 19:17:18.668226] Main Program - Failed, state: Open
[02-14-2024 19:17:18.668610] Main Program - Reconnected, state: Open

[02-14-2024 19:17:18.668226] Main Program - Failed, state: Open
[02-14-2024 19:17:18.668610] Main Program - Reconnected, state: Open

Pannekoekje•4mo ago

https://stackoverflow.com/questions/47552652/websocketexception-0x80004005-the-remote-party-closed-the-websocket-connectio

Stack Overflow

WebSocketException (0x80004005): The remote party closed the WebSoc...

I have a Xamarin app that communicates using WebSocket. On the client side, I am referencing the ClientWebSocket. code: using (var client = new ClientWebSocket() { Options = { KeepAliveInterval =...

Pannekoekje•4mo ago

Seems like it's half open; I'll just create an exception case for this. Wondering why this doesn't happen in the other reconnect logic however thinking about it, the other reconnect scenarios have very active websockets, this one can just be idle for hours on end. I'll fix this thx for thinking with me 🙂 !

life grinder•4mo ago

maybe the other side is not fully adehering to the websocket standard? i've had issues like this

Pannekoekje•4mo ago

Their implementation seems quite fucky indeed, but its fine, I'll just check for this specific error: WebSocketError.ConnectionClosedPrematurely

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Async await in minimal API