Support subscriptions

[smyrick]

GraphQL Java can support subscriptions: https://www.graphql-java.com/documentation/v11/subscriptions/

We just need to come up with a good way to represent the different type in the schema.

This may be able to be done without a breaking change. Can we just add a @GraphQLSubscription?

[smyrick]

FYI I have a WIP branch here: https://github.com/smyrick/graphql-kotlin/tree/subscribtions

I think we should update the example first to use the webflux as a demo, this can be done without supporting subscriptions but add them after will be much easier and help split up all the example changes I need to do to show how to use a publisher

[shahabio]

Whats the status of this? 🙄

[smyrick]

@shahabio I had started working on the update but had trouble getting the example app working with spring websockets. If you want to pick up from my branch you can pull from here: https://github.com/smyrick/graphql-kotlin/tree/subscribtions

[camuthig]

@smyrick I looked into your branch a bit. At least in my testing, it looks like the issue might be with the headers coming back from the server. I'm getting this error and noticing that the headers are missing on the server response.

Error during WebSocket handshake: Sent non-empty 'Sec-WebSocket-Protocol' header but no response was received

I'm still new to the Spring Boot environment, and largely to Kotlin, so I'm a bit stuck at that point. Looking at the graphql-java spring starter, it looks like they are modifying the handshake specifically to handle this. I'm not sure if there is an easier way to accomplish this or not.

[smyrick]

@camuthig When I run a subscription query through the playground and I put a breakpoint at the top of SubscriptionHandler.handle() I can see the value for session.handshakeInfo.headers["Sec-WebSocket-Protocol"] is graphql-ws so that is still being sent

[camuthig]

@smyrick I added the same breakpoint and agree that the header is there. However, when I use the dev console on Chromium to look at the response, I don't see it coming back on the response.

The headers using graphql-spring-boot-autoconfigure look something like

Connection: upgrade
Date: Tue, 23 Apr 2019 08:55:26 GMT
Sec-WebSocket-Accept: <token>
Sec-WebSocket-Extensions: permessage-deflate;client_max_window_bits=15
Sec-WebSocket-Protocol: graphql-ws
Upgrade: websocket

But with your branch I'm seeing

connection: upgrade
sec-websocket-accept: <token>
upgrade: websocket

[smyrick]

With my latest branch I have successfully connected using the following Websocket client:

https://chrome.google.com/webstore/detail/simple-websocket-client/pfdhoblngboilpfeibdedpjgfnlcodoo

It looks like there is an issue with GraphQL Playground and Spring Webflux Websockets, specifically the graphql-ws protocol used by Apollo

• https://github.com/graphql-java-kickstart/graphql-java-servlet/blob/b8c567abfdab7bd8ac2b36839be9c0382928539d/src/main/java/graphql/servlet/internal/ApolloSubscriptionProtocolHandler.java#L31
• https://github.com/graphql-java-kickstart/graphql-java-servlet/blob/b8c567abfdab7bd8ac2b36839be9c0382928539d/src/main/java/graphql/servlet/internal/ApolloSubscriptionProtocolFactory.java#L15
• Apollo subscriptions on the reactive stack leangen/graphql-spqr-spring-boot-starter#24
• https://spectrum.chat/graphql-java/general/graphql-java-and-apollo-client-subscriptions~75da047e-a30b-40e1-ac94-5035f5447946

[hinterdupfinger]

putting

override fun getSubProtocols(): List<String> {
    return listOf("graphql-ws")
}

in SubscriptionHandler(private val graphQL: GraphQL) : WebSocketHandler

should fix the the protocol issue as org.springframework.web.reactive.socket.server.support.HandshakeWebSocketService is checking for supported protocols in the handler