Question: How to get server to send ping messages on subscriptions?

[hzargar2]

How can I make the server send ping messages with axum when the client is using subscriptions? I know I can use the client to send ping messages but then the client can choose the keep-alive value and so they may set it very short and increase data transmission and server load. I would like the ping messages to come from the server and the client to respond with pong as opposed to vice versa.

I have tried many options on the axum server to no luck. Is this the right place to put it or do I have to yield ping messages in he actual subscription resolver itself?

axum::Server::bind(&"0.0.0.0:3000".parse().unwrap())
      .http1_keepalive(true)
      .tcp_keepalive_retries(Some(1))
      .tcp_keepalive_interval(Some(core::time::Duration::from_secs(30)))
      .tcp_keepalive(Some(core::time::Duration::from_secs(30)))
      .http2_keep_alive_timeout(core::time::Duration::from_secs(60))
      .http2_keep_alive_interval(Some(core::time::Duration::from_secs(30)))
      .serve(app.into_make_service())
      .await
      .expect("Starting server failed.");

Here is a rough example of the stream my subscription resolver returns. If I need to put the code in here, how do I do so witohut actually returning a ping Object

return Ok(async_stream::stream! {

    // some vode to get our output object
    yield Ok(my_output_object);
}

This is my Graphql subscription service struct that creates and adds a Credentials struct from the api-key that is received in the on_connection_init(). Do I have to add the ping in here?

use std::{borrow::Cow, convert::Infallible, future::Future, str::FromStr};
use std::borrow::Borrow;

use async_graphql::{
    Data,
    Executor,
    futures_util,
    futures_util::task::{Context, Poll}, http::{ALL_WEBSOCKET_PROTOCOLS, WebSocketProtocols, WsMessage}, Result,
};
use axum::{
    body::{BoxBody, boxed, HttpBody},
    Error,
    extract::{
        FromRequestParts,
        WebSocketUpgrade, ws::{CloseFrame, Message},
    },
    http::{self, Request, request::Parts, Response, StatusCode},
    RequestExt, response::IntoResponse,
};
use axum::extract::FromRequest;
use futures_util::{
    future,
    future::{BoxFuture, Ready},
    Sink,
    SinkExt, stream::{SplitSink, SplitStream}, Stream, StreamExt,
};
use tower::Service;

use crate::data::credentials::Credentials;

/// A GraphQL protocol extractor.
///
/// It extract GraphQL protocol from `SEC_WEBSOCKET_PROTOCOL` header.
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub struct GraphQLProtocol(WebSocketProtocols);

#[async_trait::async_trait]
impl<S> FromRequestParts<S> for GraphQLProtocol
    where
        S: Send + Sync,
{
    type Rejection = StatusCode;

    async fn from_request_parts(parts: &mut Parts, _state: &S) -> Result<Self, Self::Rejection> {
        parts
            .headers
            .get(http::header::SEC_WEBSOCKET_PROTOCOL)
            .and_then(|value| value.to_str().ok())
            .and_then(|protocols| {
                protocols
                    .split(',')
                    .find_map(|p| WebSocketProtocols::from_str(p.trim()).ok())
            })
            .map(Self)
            .ok_or(StatusCode::BAD_REQUEST)
    }
}

/// A GraphQL subscription service.
pub struct CustomGraphQLSubscription<E> {
    executor: E,
}

impl<E> Clone for CustomGraphQLSubscription<E>
    where
        E: Executor,
{
    fn clone(&self) -> Self {
        Self {
            executor: self.executor.clone(),
        }
    }
}

impl<E> CustomGraphQLSubscription<E>
    where
        E: Executor,
{
    /// Create a GraphQL subscription service.
    pub fn new(executor: E) -> Self {
        Self { executor }
    }
}

impl<B, E> Service<Request<B>> for CustomGraphQLSubscription<E>
    where
        B: HttpBody + Send + 'static,
        E: Executor,
{
    type Response = Response<BoxBody>;
    type Error = Infallible;
    type Future = BoxFuture<'static, Result<Self::Response, Self::Error>>;

    fn poll_ready(&mut self, _cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        Poll::Ready(Ok(()))
    }

    fn call(&mut self, req: Request<B>) -> Self::Future {
        let executor = self.executor.clone();

        Box::pin(async move {
            let (mut parts, mut body) = req.into_parts();

            let protocol = match GraphQLProtocol::from_request_parts(&mut parts, &()).await {
                Ok(protocol) => protocol,
                Err(err) => return Ok(err.into_response().map(boxed)),
            };
            let upgrade = match WebSocketUpgrade::from_request_parts(&mut parts, &()).await {
                Ok(protocol) => protocol,
                Err(err) => return Ok(err.into_response().map(boxed)),
            };

            let executor = executor.clone();

            let resp = upgrade
                .protocols(ALL_WEBSOCKET_PROTOCOLS)
                .on_upgrade(move |stream| {
                    GraphQLWebSocket::new(stream, executor, protocol)
                        .on_connection_init(|x: serde_json::Value| {
                            // on connection init, the headers are sent as a payload in a websocket connection.
                            // Extract api-key value, create struct and pass to resolvers, any data here is appended
                            // to existing data when calling with_data() on GraphQlWebSocket

                            let mut data = Data::default();
                            if let Some(api_key) = x.get("api-key").and_then(|x| x.as_str()).clone()
                            {
                                data.insert(Credentials {
                                    api_key: api_key.to_string(),
                                });
                                futures_util::future::ready(Ok(data))
                            } else {
                                futures_util::future::ready(Err(async_graphql::Error::new(
                                    "Missing `api-key` header.",
                                )))
                            }
                        })
                        .serve()
                });

            Ok(resp.into_response().map(boxed))
        })
    }
}

type DefaultOnConnInitType = fn(serde_json::Value) -> Ready<async_graphql::Result<Data>>;

fn default_on_connection_init(x: serde_json::Value) -> Ready<async_graphql::Result<Data>> {
    futures_util::future::ready(Ok(Data::default()))
}

/// A Websocket connection for GraphQL subscription.
pub struct GraphQLWebSocket<Sink, Stream, E, OnConnInit> {
    sink: Sink,
    stream: Stream,
    executor: E,
    data: Data,
    on_connection_init: OnConnInit,
    protocol: GraphQLProtocol,
}

impl<S, E> GraphQLWebSocket<SplitSink<S, Message>, SplitStream<S>, E, DefaultOnConnInitType>
    where
        S: Stream<Item = Result<Message, Error>> + Sink<Message>,
        E: Executor,
{
    /// Create a [`GraphQLWebSocket`] object.
    pub fn new(stream: S, executor: E, protocol: GraphQLProtocol) -> Self {
        let (sink, stream) = stream.split();
        GraphQLWebSocket::new_with_pair(sink, stream, executor, protocol)
    }
}

impl<Sink, Stream, E> GraphQLWebSocket<Sink, Stream, E, DefaultOnConnInitType>
    where
        Sink: futures_util::sink::Sink<Message>,
        Stream: futures_util::stream::Stream<Item = Result<Message, Error>>,
        E: Executor,
{
    /// Create a [`GraphQLWebSocket`] object with sink and stream objects.
    pub fn new_with_pair(
        sink: Sink,
        stream: Stream,
        executor: E,
        protocol: GraphQLProtocol,
    ) -> Self {
        GraphQLWebSocket {
            sink,
            stream,
            executor,
            data: Data::default(),
            on_connection_init: default_on_connection_init,
            protocol,
        }
    }
}

impl<Sink, Stream, E, OnConnInit, OnConnInitFut> GraphQLWebSocket<Sink, Stream, E, OnConnInit>
    where
        Sink: futures_util::sink::Sink<Message>,
        Stream: futures_util::stream::Stream<Item = Result<Message, Error>>,
        E: Executor,
        OnConnInit: FnOnce(serde_json::Value) -> OnConnInitFut + Send + 'static,
        OnConnInitFut: Future<Output = async_graphql::Result<Data>> + Send + 'static,
{
    /// Specify the initial subscription context data, usually you can get
    /// something from the incoming request to create it.
    #[must_use]
    pub fn with_data(self, data: Data) -> Self {
        Self { data, ..self }
    }

    /// Specify a callback function to be called when the connection is
    /// initialized.
    ///
    /// You can get something from the payload of [`GQL_CONNECTION_INIT` message](https://github.com/apollographql/subscriptions-transport-ws/blob/master/PROTOCOL.md#gql_connection_init) to create [`Data`].
    /// The data returned by this callback function will be merged with the data
    /// specified by [`with_data`].
    pub fn on_connection_init<OnConnInit2, Fut>(
        self,
        callback: OnConnInit2,
    ) -> GraphQLWebSocket<Sink, Stream, E, OnConnInit2>
        where
            OnConnInit2: FnOnce(serde_json::Value) -> Fut + Send + 'static,
            Fut: Future<Output = async_graphql::Result<Data>> + Send + 'static,
    {
        GraphQLWebSocket {
            sink: self.sink,
            stream: self.stream,
            executor: self.executor,
            data: self.data,
            on_connection_init: callback,
            protocol: self.protocol,
        }
    }

    /// Processing subscription requests.
    pub async fn serve(self) {
        let input = self
            .stream
            .take_while(|res| future::ready(res.is_ok()))
            .map(Result::unwrap)
            .filter_map(|msg| {
                if let Message::Text(_) | Message::Binary(_) = msg {
                    future::ready(Some(msg))
                } else {
                    future::ready(None)
                }
            })
            .map(Message::into_data);

        let stream =
            async_graphql::http::WebSocket::new(self.executor.clone(), input, self.protocol.0)
                .connection_data(self.data)
                .on_connection_init(self.on_connection_init)
                .map(|msg| match msg {
                    WsMessage::Text(text) => Message::Text(text),
                    WsMessage::Close(code, status) => Message::Close(Some(CloseFrame {
                        code,
                        reason: Cow::from(status),
                    })),
                });

        let sink = self.sink;
        futures_util::pin_mut!(stream, sink);

        while let Some(item) = stream.next().await {
            let _ = sink.send(item).await;
        }
    }
}

[sunli829]

Not currently, I will consider adding this.

[hzargar2]

Not currently, I will consider adding this.

Oh okay, great! Not to be pushy since you're probably busy, but do you know how long feature requests like this usually take? :) thanks again.