How to get webscoket context in onClose

[alucardu]

I want to notify users (and clean up my database) when a user disconnects from the websocket:

const serverCleanup = useServer(
  {
    schema,
    onConnect: async () => {
      console.log('User connected')
    },
    onClose() {
      console.log('User disconnected')
      userResolvers.Mutation.deleteUser({
        name: 'John'
      })
    },
  },
  wsServer
)

In my server log I do see User disconnected { name: 'jan' } but I of course need the user id to correctly remove the user from the database. I'm using Apollo client and server as my graphql solution.

I do have a websocket connection running, and I'm also happy with it:

So what I would like to know is how do I get (all) websocket information in the onClose() function so I can delete the user that has closed the connection.

[enisdenjo]

You can use the context extra field which is shared between the hooks for distinct connections:

const serverCleanup = useServer(
  {
    schema,
-   onConnect: async () => {
+   onConnect: async (ctx) => {
+     ctx.extra.userName = getUserName()
      console.log('User connected')
    },
-   onClose() {
+   onClose(ctx)
      console.log('User disconnected')
      userResolvers.Mutation.deleteUser({
-       name: 'John'
+       name: ctx.extra.userName
      })
    },
  },
  wsServer
)

[alucardu]

Thank you for the suggestion @enisdenjo. In my app users can create a username and connect that to a session. So initially there's no information available.

Should I then add the created user to the websocket and extract it like so:

private subscribeToUsers(user: User): void {
  this.apollo.subscribe({
    query: USER_CREATED,
    variables: {
      ...user
    },
  }).subscribe(({
    next: (data) => {
      console.log(data);
    }
  }));
}

const serverCleanup = useServer(
  {
    schema,
    onConnect: async () => {
      console.log('User connected')
    },
    onClose(ctx) {
      console.log('onClose', ctx.extra.userId)
    },
    context(ctx, msg, args) {
      if (msg?.payload?.operationName === 'userCreated') {
        ctx.extra.userId = msg.payload.variables.id
      }
    }
  },
  wsServer
)

When I create a new user I subscribe to it, then I can extract it from the msg argument in the context() and use that value to put it in the extra context. Seems to work.

[enisdenjo]

This behaviour will overwrite the current use in the context for each userCreated operation, can be quite unsafe. If you can guarantee that userCreated will be ran just once - then fine; otherwise I'd rethink this if I were you.