Graphql subscription?

[david-vendel]

Hello, it seems your library allows for using subscriptions-transport-ws to establish graphql subscription, which is not maintained anymore and is not recommended to be used.
Is there a way to make your library work with graphql-ws?
To be clear, I just want to use subscription next to already using query and mutation using this library. Is there an example how apollo-multi-endpoint-link can be used with graphql subscription?

Thank you for any help.

[jean9696]

Hi @justdvl, it does work. Here is an example we have

import { ApolloLink, NextLink, Operation } from '@apollo/client/link/core'
import { GraphQLWsLink } from '@apollo/client/link/subscriptions'
import { getMainDefinition, hasDirectives } from '@apollo/client/utilities'
import { createClient } from 'graphql-ws'

import { createHttpLink } from './httpLink'

export class GatewayLink extends ApolloLink {
  wsLink: ApolloLink
  httpLink: ApolloLink
  constructor(env: Envs, clientName: string) {
    super()
    this.wsLink = new GraphQLWsLink(
      createClient({
        url: YOUR URL HERE,
        lazy: true,
      })
    )
    this.httpLink = createHttpLink({
      uri:  YOUR URI HERE,
      headers: {
        'X-Request-From': clientName,
      },
    })
  }

  public request(operation: Operation, forward?: NextLink) {
    if (hasDirectives(['rest'], operation.query)) {
      return forward?.(operation) ?? null
    }
    const definition = getMainDefinition(operation.query)
    if (
      definition.kind === 'OperationDefinition' &&
      definition.operation === 'subscription'
    ) {
      return this.wsLink.request(operation, forward)
    }
    return this.httpLink.request(operation, forward)
  }
}

[simxn1]

@jean9696 It is also worth noting that it is needed to check for typeof window !== 'undefined' and only then define the wsLink, like so:

 if (typeof window !== 'undefined') {
      this.wsLink = new GraphQLWsLink(
        createClient({
          lazy: true,
          url: 'ws://localhost:8080/graphql',
        }),
      )
   }

Otherwise I get this:

Error: WebSocket implementation missing; on Node you can `import WebSocket from 'ws';` and pass `webSocketImpl: WebSocket` to `createClient`

[david-vendel]

Thank you @jean9696. I assume I need to create 2 instances of GatewayLink, one for each BE service I connect to (as I need to maintain websocket with both services)?
How do I then use these instances with MultiAPILink? I am missing this last part.

Currently I have:

const httpLink = new MultiAPILink({
  createHttpLink: () => createHttpLink(),
  endpoints,
  httpSuffix: '',
  wsSuffix: '',
})
links.push(httpLink)

Thanks.