问题
I am trying to implement an app sync subscription similar to this python example but in .net https://aws.amazon.com/blogs/mobile/appsync-websockets-python/
I started this using the nuget package GraphQL.Client https://www.nuget.org/packages/GraphQL.Client The execution of Query/Mutation is working fine like given in the readme of https://github.com/graphql-dotnet/graphql-client But subscription is not working.
My code using the GraphQL.Client:
using var graphQLClient = new GraphQLHttpClient("https://<MY-API-PATH>.appsync-realtime-api.<AWS-region>.amazonaws.com/graphql", new NewtonsoftJsonSerializer());
graphQLClient.HttpClient.DefaultRequestHeaders.Add("host", "<API HOST without https or absolute path and 'realtime-' text in the api address>"); //As given in the python example
graphQLClient.HttpClient.DefaultRequestHeaders.Add("x-api-key", "<API KEY>");
var req= new GraphQLRequest
{
Query = @"subscription SubscribeToEventComments{ subscribeToEventComments(eventId: 'test'){ content }}",
Variables = new{}
};
IObservable<GraphQLResponse<Response>> subscriptionStream = graphQLClient.CreateSubscriptionStream<Response>(req, (Exception ex) =>
{
Console.WriteLine("Error: {0}", ex.ToString());
});
var subscription = subscriptionStream.Subscribe(response =>
{
Console.WriteLine($"Response'{Newtonsoft.Json.JsonConvert.SerializeObject(response)}' ");
},
ex =>
{
Console.WriteLine("Error{0}", ex.ToString());
});
Its giving the exception "The remote party closed the WebSocket connection without completing the close handshake."
stack trace:
at System.Net.WebSockets.ManagedWebSocket.d__662.MoveNext()
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter1.GetResult()
at GraphQL.Client.Http.Websocket.GraphQLHttpWebSocket.d__40.MoveNext() in C:\Users\UserName\Source\repos\graphql-client\src\GraphQL.Client\Websocket\GraphQLHttpWebSocket.cs:line 546
Then I tried without this nuget and using standard websocket
Code without nuget:
static public async Task CallWebsocket()
{
try
{
_client = new ClientWebSocket();
_client.Options.AddSubProtocol("graphql-ws");
_client.Options.SetRequestHeader("host", "<HOST URL without wss but now with 'realtime' text in api url because otherwise we are getting SSL error>");
_client.Options.SetRequestHeader("x-api-key", "<API KEY>");
await _client.ConnectAsync(new Uri("https://<MY-APPSYNC_API_PATH>.appsync-realtime-api.<AWS-region>.amazonaws.com/graphql"), CancellationToken.None);
await SendCommand();
var docList = await Receive();
}
catch(Exception ex)
{
}
}
static private async Task SendCommand()
{
ArraySegment<byte> outputBuffer = new ArraySegment<byte>(Encoding.UTF8.GetBytes("'query' : 'subscription SubscribeToEventComments{ subscribeToEventComments(eventId: 'test'){ content }}'"));
await _client.SendAsync(outputBuffer, WebSocketMessageType.Text, true, CancellationToken.None);
}
static private async Task<string> Receive()
{
var receiveBufferSize = 1536;
byte[] buffer = new byte[receiveBufferSize];
var result = await _client.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);
var resultJson = (new UTF8Encoding()).GetString(buffer);
return resultJson;
}
I am getting below exception:
Inner exception: "An established connection was aborted by the software in your host machine."
Inner exception message: "Unable to read data from the transport connection: An established connection was aborted by the software in your host machine.."
Message: "The remote party closed the WebSocket connection without completing the close handshake."
Could anyone please help with the correct implementation.
回答1:
Nuget won't work out of the box with AppSync subscriptions, so you will need to write your own client code for that, like you attempted in the second (non-nuget) example.
Now, for the second example, take a second look at the python example referenced in your question. There are several steps that are not included in your code. I will enumerate the required steps and try to port them to C# from the python code (note that I don't have a C# environment at hand so there might be syntax errors, but this code should be pretty close to what you need)
Step 0 - AppSync Endpoints
Assume the result of invoking aws appsync get-graphql-api --api-id example123456 for your API is:
{
"graphqlApi": {
"name": "myNewRealTimeGraphQL-API",
"authenticationType": "<API_KEY>",
"tags": {},
"apiId": "example123456",
"uris": {
"GRAPHQL": "https://abc.appsync-api.us-west-2.amazonaws.com/graphql",
"REALTIME": "wss://abc.appsync-realtime-api.us-west-2.amazonaws.com/graphql"
},
"arn": "arn:aws:appsync:us-west-2: xxxxxxxxxxxx:apis/xxxxxxxxxxxx"
}
}
Step 1 - Build the connection URL
Step 2 - Connect to WebSocket Endpoint
This includes sending a connection_init message as per the protocol mentioned in the python article
Step 3 - Wait for connection_ack as per protocol
Again, this is as per protocol
Step 4 - Register subscription
Step 5 - Send mutation
This step is not in this response, but can be done through the AWS console
Step 6 - Wait for "data" messages
These are the real-time events sent by AppSync
Step 7 - Deregister subscription
Step 8 - Disconnect
// These are declared at the same level as your _client
// This comes from the graphqlApi.uris.GRAPHQL in step 0, set as a var here for clarity
_gqlHost = "abc.appsync-api.us-west-2.amazonaws.com";
// This comes from the graphqlApi.uris.REALTIME in step 0, set as a var here for clarity
_realtimeUri = "wss://abc.appsync-realtime-api.us-west-2.amazonaws.com/graphql";
_apiKey = "<API KEY>";
static public async Task CallWebsocket()
{
// Step 1
// This is JSON needed by the server, it will be converted to base64
// (note: might be better to use something like Json.NET for this task)
var header = var test = $@"{{
""host"":""{_gqlHost}"",
""x-api-key"": ""{_apiKey}""
}}";
// Now we need to encode the previous JSON to base64
var headerB64 = System.Convert.ToBase64String(
System.Text.Encoding.UTF8.GetBytes(header));
UriBuilder connectionUriBuilder = new UriBuilder(_realtimeUri);
connectionUriBuilder.Query = $"header={headerB64}&payload=e30=";
try
{
_client = new ClientWebSocket();
_client.Options.AddSubProtocol("graphql-ws");
// Step 2
await _client.ConnectAsync(connectionUriBuilder.Uri), CancellationToken.None);
// Step 3
await SendConnectionInit();
await Receive();
}
catch(Exception ex)
{
}
}
static private async Task SendConnectionInit()
{
ArraySegment<byte> outputBuffer = new ArraySegment<byte>(Encoding.UTF8.GetBytes(@"{""type"": ""connection_init""}"));
await _client.SendAsync(outputBuffer, WebSocketMessageType.Text, true, CancellationToken.None);
}
static private async Task SendSubscription()
{
// This detail is important, note that the subscription is a stringified JSON that will be embeded in the "data" field below
var subscription = $@"{{\""query\"": \""subscription SubscribeToEventComments{{ subscribeToEventComments{{ content }} }}\"", \""variables\"": {{}} }}";
var register = $@"{{
""id"": ""<SUB_ID>"",
""payload"": {{
""data"": ""{subscription}"",
""extensions"": {{
""authorization"": {{
""host"": ""{_gqlHost}"",
""x-api-key"":""{_apiKey}""
}}
}}
}},
""type"": ""start""
}}";
// The output should look like below, note again the "data" field contains a stringified JSON that represents the subscription
/*
{
"id": "<SUB_ID>",
"payload": {
"data": "{\"query\": \"subscription SubscribeToEventComments{ subscribeToEventComments{ content}}\", \"variables\": {} }",
"extensions": {
"authorization": {
"host": "abc.appsync-api.us-west-2.amazonaws.com",
"x-api-key":"<API KEY>"
}
}
},
"type": "start"
}
*/
ArraySegment<byte> outputBuffer = new ArraySegment<byte>(Encoding.UTF8.GetBytes(register));
await _client.SendAsync(outputBuffer, WebSocketMessageType.Text, true, CancellationToken.None);
}
static private async Task Deregister()
{
var deregister = $@"{{
""type"": ""stop"",
""id"": ""<SUB_ID>""
}}"
ArraySegment<byte> outputBuffer = new ArraySegment<byte>(Encoding.UTF8.GetBytes(deregister));
await _client.SendAsync(outputBuffer, WebSocketMessageType.Text, true, CancellationToken.None);
}
static private async Task Receive()
{
while (_socket.State == WebSocketState.Open)
{
ArraySegment<Byte> buffer = new ArraySegment<byte>(new Byte[8192]);
WebSocketReceiveResult result= null;
using (var ms = new MemoryStream())
{
// This loop is needed because the server might send chunks of data that need to be assembled by the client
// see: https://stackoverflow.com/questions/23773407/a-websockets-receiveasync-method-does-not-await-the-entire-message
do
{
result = await socket.ReceiveAsync(buffer, CancellationToken.None);
ms.Write(buffer.Array, buffer.Offset, result.Count);
}
while (!result.EndOfMessage);
ms.Seek(0, SeekOrigin.Begin);
using (var reader = new StreamReader(ms, Encoding.UTF8))
{
// convert stream to string
var message = reader.ReadToEnd();
Console.WriteLine(message)
// quick and dirty way to check response
if (message.Contains("connection_ack"))
{
// Step 4
await SendSubscription();
} else if (message.Contains("data")) // Step 6
{
// Step 7
await Deregister();
// Step 8
await _client.CloseOutputAsync(WebSocketCloseStatus.NormalClosure, string.Empty, CancellationToken.None);
}
}
}
}
}
回答2:
For others who face same issues, I have created a nuget package now. https://www.nuget.org/packages/DotNetCSharp.AWS.AppSync.Client/1.1.1 You can use it as below.
//Create Client Specify eithen APIKey or AuthToken
var Client = new AppSyncClient("<Appsync URL>", new AuthOptions()
{
// APIKey = "<API Key>",
AuthToken = "<JWT Token>"
});
//To Subscribe an query
Guid newId = Guid.NewGuid();
await Client.CreateSubscriptionAsync<Message>(new QueryOptions()
{
Query = "subscription <Subscription Query>",
SubscriptionId = newId
},
(data) =>
{
});
//To unsubscribe an subscription
await Client.UnSubscribe(newId);
//To close the websocket
await Client.Close();
来源：https://stackoverflow.com/questions/62111313/aws-appsync-implementation-using-graphql-client-library-in-net