internal static Task <GraphQLResponse <TResponse> > SendRequest <TResponse>(
this GraphQLHttpWebSocket graphQlHttpWebSocket,
GraphQLRequest request,
GraphQLHttpClient client,
CancellationToken cancellationToken = default)
{
return(Observable.Create <GraphQLResponse <TResponse> >(async observer => {
await client.Options.PreprocessRequest(request, client);
var websocketRequest = new GraphQLWebSocketRequest {
Id = Guid.NewGuid().ToString("N"),
Type = GraphQLWebSocketMessageType.GQL_START,
Payload = request
};
var observable = graphQlHttpWebSocket.ResponseStream
.Where(response => response != null && response.Id == websocketRequest.Id)
.TakeUntil(response => response.Type == GraphQLWebSocketMessageType.GQL_COMPLETE)
.Select(response => {
Debug.WriteLine($"received response for request {websocketRequest.Id}");
var typedResponse =
client.Options.JsonSerializer.DeserializeToWebsocketResponse <TResponse>(
response.MessageBytes);
return typedResponse.Payload;
});
try {
// intialize websocket (completes immediately if socket is already open)
await graphQlHttpWebSocket.InitializeWebSocket().ConfigureAwait(false);
}
catch (Exception e) {
// subscribe observer to failed observable
return Observable.Throw <GraphQLResponse <TResponse> >(e).Subscribe(observer);
}
var disposable = new CompositeDisposable(
observable.Subscribe(observer)
);
Debug.WriteLine($"submitting request {websocketRequest.Id}");
// send request
try {
await graphQlHttpWebSocket.SendWebSocketRequest(websocketRequest).ConfigureAwait(false);
}
catch (Exception e) {
Console.WriteLine(e);
throw;
}
return disposable;
})
// complete sequence on OperationCanceledException, this is triggered by the cancellation token
.Catch <GraphQLResponse <TResponse>, OperationCanceledException>(exception =>
Observable.Empty <GraphQLResponse <TResponse> >())
.FirstOrDefaultAsync()
.ToTask(cancellationToken));
}
internal static IObservable <GraphQLResponse <TResponse> > CreateSubscriptionStream <TResponse>(
this GraphQLHttpWebSocket graphQlHttpWebSocket,
GraphQLRequest request,
GraphQLHttpClient client,
Action <Exception> exceptionHandler = null,
CancellationToken cancellationToken = default)
{
return(Observable.Defer(() =>
Observable.Create <GraphQLResponse <TResponse> >(async observer => {
await client.Options.PreprocessRequest(request, client);
var startRequest = new GraphQLWebSocketRequest {
Id = Guid.NewGuid().ToString("N"),
Type = GraphQLWebSocketMessageType.GQL_START,
Payload = request
};
var closeRequest = new GraphQLWebSocketRequest {
Id = startRequest.Id,
Type = GraphQLWebSocketMessageType.GQL_STOP
};
var initRequest = new GraphQLWebSocketRequest {
Id = startRequest.Id,
Type = GraphQLWebSocketMessageType.GQL_CONNECTION_INIT,
};
var observable = Observable.Create <GraphQLResponse <TResponse> >(o =>
graphQlHttpWebSocket.ResponseStream
// ignore null values and messages for other requests
.Where(response => response != null && response.Id == startRequest.Id)
.Subscribe(response => {
// terminate the sequence when a 'complete' message is received
if (response.Type == GraphQLWebSocketMessageType.GQL_COMPLETE)
{
Debug.WriteLine($"received 'complete' message on subscription {startRequest.Id}");
o.OnCompleted();
return;
}
// post the GraphQLResponse to the stream (even if a GraphQL error occurred)
Debug.WriteLine($"received payload on subscription {startRequest.Id}");
var typedResponse =
client.Options.JsonSerializer.DeserializeToWebsocketResponse <TResponse>(
response.MessageBytes);
o.OnNext(typedResponse.Payload);
// in case of a GraphQL error, terminate the sequence after the response has been posted
if (response.Type == GraphQLWebSocketMessageType.GQL_ERROR)
{
Debug.WriteLine($"terminating subscription {startRequest.Id} because of a GraphQL error");
o.OnCompleted();
}
},
o.OnError,
o.OnCompleted)
);
try {
// initialize websocket (completes immediately if socket is already open)
await graphQlHttpWebSocket.InitializeWebSocket().ConfigureAwait(false);
}
catch (Exception e) {
// subscribe observer to failed observable
return Observable.Throw <GraphQLResponse <TResponse> >(e).Subscribe(observer);
}
var disposable = new CompositeDisposable(
observable.Subscribe(observer),
Disposable.Create(async() => {
// only try to send close request on open websocket
if (graphQlHttpWebSocket.WebSocketState != WebSocketState.Open)
{
return;
}
try {
Debug.WriteLine($"sending close message on subscription {startRequest.Id}");
await graphQlHttpWebSocket.SendWebSocketRequest(closeRequest).ConfigureAwait(false);
}
// do not break on disposing
catch (OperationCanceledException) { }
})
);
// send connection init
Debug.WriteLine($"sending connection init on subscription {startRequest.Id}");
try {
await graphQlHttpWebSocket.SendWebSocketRequest(initRequest).ConfigureAwait(false);
}
catch (Exception e) {
Console.WriteLine(e);
throw;
}
Debug.WriteLine($"sending initial message on subscription {startRequest.Id}");
// send subscription request
try {
await graphQlHttpWebSocket.SendWebSocketRequest(startRequest).ConfigureAwait(false);
}
catch (Exception e) {
Console.WriteLine(e);
throw;
}
return disposable;
}))
// complete sequence on OperationCanceledException, this is triggered by the cancellation token
.Catch <GraphQLResponse <TResponse>, OperationCanceledException>(exception =>
Observable.Empty <GraphQLResponse <TResponse> >())
// wrap results
.Select(response => new Tuple <GraphQLResponse <TResponse>, Exception>(response, null))
// do exception handling
.Catch <Tuple <GraphQLResponse <TResponse>, Exception>, Exception>(e => {
try {
if (exceptionHandler == null)
{
// if the external handler is not set, propagate all exceptions except WebSocketExceptions
// this will ensure that the client tries to re-establish subscriptions on connection loss
if (!(e is WebSocketException))
{
throw e;
}
}
else
{
// exceptions thrown by the handler will propagate to OnError()
exceptionHandler?.Invoke(e);
}
// throw exception on the observable to be caught by Retry() or complete sequence if cancellation was requested
return cancellationToken.IsCancellationRequested
? Observable.Empty <Tuple <GraphQLResponse <TResponse>, Exception> >()
: Observable.Throw <Tuple <GraphQLResponse <TResponse>, Exception> >(e);
}
catch (Exception exception) {
// wrap all other exceptions to be propagated behind retry
return Observable.Return(new Tuple <GraphQLResponse <TResponse>, Exception>(null, exception));
}
})
// attempt to recreate the websocket for rethrown exceptions
.Retry()
// unwrap and push results or throw wrapped exceptions
.SelectMany(t => {
// if the result contains an exception, throw it on the observable
if (t.Item2 != null)
{
return Observable.Throw <GraphQLResponse <TResponse> >(t.Item2);
}
return t.Item1 == null
? Observable.Empty <GraphQLResponse <TResponse> >()
: Observable.Return(t.Item1);
})
// transform to hot observable and auto-connect
.Publish().RefCount());
}
