AWS App Sync Subscriptions over apollo-link-ws

Question

I am trying to setup the Apollo Client without using the JavaScript AWS AppSync Client. I understand that it would be easiest to just use the JS AppSync Client since I am already using AppSync but I am trying to avoid using AWS libraries in my client. Also, it doesn't seem to work well with graphql-codegen.  
  
I can connect and start the GraphQL handshake via Apollo which produces the following messages:

```
Sent: {"type":"connection_init","payload":{}}
Sent: {"id":"1","type":"start","payload":{"variables":{"sessionID":"659d86ae-ec0c-4170-9866-b436a981ce29"},"extensions":{},"operationName":"ParticipantJoined","query":"subscription ParticipantJoined($sessionID: ID!) {
  participantJoinedSession(id: $sessionID) {
    id
    name
    participants {
      name
      vote {
        points
        abstained
        __typename
      }
      __typename
    }
    __typename
  }
}
"}}
Received: {"type":"connection_ack","payload":{"connectionTimeoutMs":300000}}
Received: {"type":"ka"}
```

But then I receive the following error:

```
{"type":"error","id":"","payload":{"errors":[{"errorType":"UnsupportedOperation","message":"unknown not supported through the realtime channel"}]}}
```

I noticed that the JS AppSync library appears to be sending the **connection_init** message without a payload, but other than that I see no other potential problem/mistake.  
  
What could this error be referring to?

Answer

I seem to have answered my own question.  
  
AWS is expecting a query payload that does not follow the shape of the **subscription-transport-ws** library. Instead, it expects something like this.

```
{"id":"1","type":"start","payload":{"variables":{"sessionID":"659d86ae-ec0c-4170-9866-b436a981ce29"},"extensions":{"authorization":{"host":"fev5xxdscnesvifqf45rj3zsl4.appsync-api.us-east-2.amazonaws.com","x-amz-user-agent":"aws-amplify/2.0.1","x-api-key":"da2-jdwemepvzbeo5okdsfokyqdmtq"}},"operationName":"ParticipantJoined","query":"subscription ParticipantJoined($sessionID: ID!) {
  participantJoinedSession(id: $sessionID) {
    id
    name
    participants {
      name
      vote {
        points
        abstained
        __typename
      }
      __typename
    }
    __typename
  }
}
","data":"{"variables":{"sessionID":"659d86ae-ec0c-4170-9866-b436a981ce29"},"extensions":{},"operationName":"ParticipantJoined","query":"subscription ParticipantJoined($sessionID: ID!) {n  participantJoinedSession(id: $sessionID) {n    idn    namen    participants {n      namen      vote {n        pointsn        abstainedn        __typenamen      }n      __typenamen    }n    __typenamen  }n}n"}"}}
```

Furthermore, app sync returns a **start_ack** message type which is not part of **subscription-transport-ws'** lifecycle events.

Answer

To get AppSync Subscriptions working with subscription-transport-ws, you need to follow the instructions in this GitHub issue:

AWS App Sync Subscriptions over apollo-link-ws

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