I work on a ASP.NET 5 (ASP.NET vNext) website. I use SignalR server (1.0 Beta 3) for some processing. It it is correctly set up because I can successfully invoke server methods from a Javascript browser client.
But when a I use .NET client (.NET 4.5 with SignalR 2.2.0), the method invoke fail with the generic "error 500".
I have downloaded both SignalR server and client sources to be able to debug them. I have seen that DefaultHttpClient.Post() client method is called with valid "postData" parameter, but the server PersistentConnectionMiddleware.Invoke() method has a http context without any "Form" value inside the request. And it makes SignalR server side failing in the ForeverTransport.ProcessSendRequest() method.
The post form seems to be forgotten during the transfer between the client and the server (I use the default IIS Express server).
Any idea? Thank you...
I saw the issue you opened and have committed a fix/workaround.
At the moment it doesn't look like SignalR 3 works with the client due to the fact it expects all requests to be form encoded. The workaround is to update ProcessSendRequest() so it can get the non-form-encoded data from the 2.2 .NET client;
protected virtual async Task ProcessSendRequest()
{
var data = await GetData().PreserveCulture();
if (Received != null)
{
await Received(data).PreserveCulture();
}
}
private async Task<string> GetData()
{
if (Context.Request.HasFormContentType)
{
var form = await Context.Request.ReadFormAsync().PreserveCulture();
return form["data"];
}
else
{
var stream = new System.IO.StreamReader(Context.Request.Body);
var output = await stream.ReadToEndAsync().PreserveCulture();
var decoded = UrlDecoder.UrlDecode(output);
return decoded.Replace("data=", "");
}
}
Related
I've scoured stackoverflow looking for ways to make synchronous API calls in Blazor WASM, and come up empty. The rest is a fairly length explanation of why I think I want to achieve this, but since Blazor WASM runs single-threaded, all of the ways I can find to achieve this are out of scope. If I've missed something or someone spots a better approach, I sincerely appreciate the effort to read through the rest of this...
I'm working on a Blazor WASM application that targets a GraphQL endpoint. Access to the GraphQL endpoint is granted by passing an appropriate Authorization JWT which has to be refreshed at least every 30 minutes from a login API. I'm using a 3rd party GraphQL library (strawberry-shake) which utilizes the singleton pattern to wrap an HttpClient that is used to make all of the calls to the GraphQL endpoint. I can configure the HttpClient using code like this:
builder.Services
.AddFxClient() // strawberry-shake client
.ConfigureHttpClient((sp, client) =>
{
client.BaseAddress =
new Uri(
"https://[application url]/graphql"); // GraphQL endpoint
var token = "[api token]"; // token retrieved from login API
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
});
The trick now is getting the API token from the login API at least every 30 minutes. To accomplish this, I created a service that tracks the age of the token and gets a new token from the login API when necessary. Pared down, the essential bits of the code to get a token look like this:
public async Task<string> GetAccessToken()
{
if ((_expirationDateTime ?? DateTime.Now).AddSeconds(-300) < DateTime.Now)
{
try
{
var jwt = new
{
token =
"[custom JWT for login API validation]"
};
var payload = JsonSerializer.Serialize(jwt);
var content = new StringContent(payload, Encoding.UTF8, "application/json");
var postResponse = await _httpClient.PostAsync("https://[login API url]/login", content);
var responseString = await postResponse.Content.ReadAsStringAsync();
_accessToken = JsonSerializer.Deserialize<AuthenticationResponse>(responseString).access_token;
_expirationDateTime = DateTime.Now.AddSeconds(1800);
}
catch (Exception e)
{
Console.WriteLine(e);
throw;
}
}
return _accessToken;
}
So, now I need to wire this up to the code which configures the HttpClient used by the GraphQL service. This is where I'm running into trouble. I started with code that looks like this:
// Add login service
builder.Services.AddSingleton<FxAuthClient>();
// Wire up GraphQL client
builder.Services
.AddFxClient()
.ConfigureHttpClient(async (sp, client) =>
{
client.BaseAddress =
new Uri(
"https://[application url]/graphql");
var token = await sp.GetRequiredService<FxAuthClient>().GetAccessToken();
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
});
This "works" when the application is loaded [somewhat surprisingly, since notice I'm not "await"ing the GetAccessToken()]. But the behavior if I let the 30 minute timer run out is that the first attempt I make to access the GraphQL endpoint uses the expired token and not the new token. I can see that GetAccessToken() refreshes expired token properly, and is getting called every time I utilize the FxClient, but except for the first usage of FxClient, the GetAccessToken() code actually runs after the GraphQL request. So in essence, it always uses the previous token.
I can't seem to find anyway to ensure that GetAccessToken() happens first, since in Blazor WASM you are confined to a single thread, so all of the normal ways of enforcing synchronous behavior fails, and there isn't an asynchronous way to configure the FxClient's HttpClient.
Can anyone see a way to get this to work? I'm thinking I may need to resort to writing a wrapper around the strawberry FxClient, or perhaps an asynchronous extension method that wraps the ConfigureHttpClient() function, but so far I've tried to avoid this [mostly because I kept feeling like there must be an "easier" way to do this]. I'm wondering if anyone knows away to force synchronous behavior of the call to the login API in Blazor WASM, sees another approach that would work, or can offer any other suggestion?
Lastly, it occurs to me that it might be useful to see a little more detail of the ConfigureHttpClient method. It is autogenerated, so I can't really change it, but here it is:
public static IClientBuilder<T> ConfigureHttpClient<T>(
this IClientBuilder<T> clientBuilder,
Action<IServiceProvider, HttpClient> configureClient,
Action<IHttpClientBuilder>? configureClientBuilder = null)
where T : IStoreAccessor
{
if (clientBuilder == null)
{
throw new ArgumentNullException(nameof(clientBuilder));
}
if (configureClient == null)
{
throw new ArgumentNullException(nameof(configureClient));
}
IHttpClientBuilder builder = clientBuilder.Services
.AddHttpClient(clientBuilder.ClientName, (sp, client) =>
{
client.DefaultRequestHeaders.UserAgent.Add(
new ProductInfoHeaderValue(
new ProductHeaderValue(
_userAgentName,
_userAgentVersion)));
configureClient(sp, client);
});
configureClientBuilder?.Invoke(builder);
return clientBuilder;
}
Hello I'm developing a Server-Client application that communicate with SignalR. What I have to implement is a mechanism that will allow my server to call method on client and get a result of that call. Both applications are developed with .Net Core.
My concept is, Server invokes a method on Client providing Id of that invocation, the client executes the method and in response calls the method on the Server with method result and provided Id so the Server can match the Invocation with the result.
Usage is looking like this:
var invocationResult = await Clients
.Client(connectionId)
.GetName(id)
.AwaitInvocationResult<string>(ClientInvocationHelper._invocationResults, id);
AwaitInvocationResult - is a extension method to Task
public static Task<TResultType> AwaitInvocationResult<TResultType>(this Task invoke, ConcurrentDictionary<string, object> lookupDirectory, InvocationId id)
{
return Task.Run(() =>
{
while (!ClientInvocationHelper._invocationResults.ContainsKey(id.Value)
|| ClientInvocationHelper._invocationResults[id.Value] == null)
{
Thread.Sleep(500);
}
try
{
object data;
var stingifyData = lookupDirectory[id.Value].ToString();
//First we should check if invocation response contains exception
if (IsClientInvocationException(stingifyData, out ClientInvocationException exception))
{
throw exception;
}
if (typeof(TResultType) == typeof(string))
{
data = lookupDirectory[id.Value].ToString();
}
else
{
data = JsonConvert.DeserializeObject<TResultType>(stingifyData);
}
var result = (TResultType)data;
return Task.FromResult(result);
}
catch (Exception e)
{
Console.WriteLine(e);
throw;
}
});
}
As you can see basically I have a dictionary where key is invocation Id and value is a result of that invocation that the client can report. In a while loop I'm checking if the result is already available for server to consume, if it is, the result is converted to specific type.
This mechanism is working pretty well but I'm observing weird behaviour that I don't understand.
If I call this method with await modifier the method in Hub that is responsible to receive a result from client is never invoked.
///This method gets called by the client to return a value of specific invocation
public Task OnInvocationResult(InvocationId invocationId, object data)
{
ClientInvocationHelper._invocationResults[invocationId.Value] = data;
return Task.CompletedTask;
}
In result the while loop of AwaitInvocationResult never ends and the Hub is blocked.
Maby someone can explain this behaviour to me so I can change my approach or improve my code.
As it was mentioned in the answer by Brennan, before ASP.NET Core 5.0 SignalR connection was only able to handle one not streaming invocation of hub method at time. And since your invocation was blocked, server wasn't able to handle next invocation.
But in this case you probably can try to handle client responses in separate hub like below.
public class InvocationResultHandlerHub : Hub
{
public Task HandleResult(int invocationId, string result)
{
InvoctionHelper.SetResult(invocationId, result);
return Task.CompletedTask;
}
}
While hub method invocation is blocked, no other hub methods can be invoked by caller connection. But since client have separate connection for each hub, he will be able to invoke methods on other hubs. Probably not the best way, because client won't be able to reach first hub until response will be posted.
Other way you can try is streaming invocations. Currently SignalR doesn't await them to handle next message, so server will handle invocations and other messages between streaming calls.
You can check this behavior here in Invoke method, invocation isn't awaited when it is stream
https://github.com/dotnet/aspnetcore/blob/c8994712d8c3c982111e4f1a09061998a81d68aa/src/SignalR/server/Core/src/Internal/DefaultHubDispatcher.cs#L371
So you can try to add some dummy streaming parameter that you will not use:
public async Task TriggerRequestWithResult(string resultToSend, IAsyncEnumerable<int> stream)
{
var invocationId = InvoctionHelper.ResolveInvocationId();
await Clients.Caller.SendAsync("returnProvidedString", invocationId, resultToSend);
var result = await InvoctionHelper.ActiveWaitForInvocationResult<string>(invocationId);
Debug.WriteLine(result);
}
and on the client side you will also need to create and populate this parameter:
var stringResult = document.getElementById("syncCallString").value;
var dummySubject = new signalR.Subject();
resultsConnection.invoke("TriggerRequestWithResult", stringResult, dummySubject);
dummySubject.complete();
More details: https://learn.microsoft.com/en-us/aspnet/core/signalr/streaming?view=aspnetcore-5.0
If you can use ASP.NET Core 5, you can try to use new MaximumParallelInvocationsPerClient hub option. It will allow several invocations to execute in parallel for one connection. But if your client will call too much hub methods without providing result, connection will hang.
More details: https://learn.microsoft.com/en-us/aspnet/core/signalr/configuration?view=aspnetcore-5.0&tabs=dotnet
Actually, since returning values from client invocations isn't implemented by SignalR, maybe you can try to look into streams to return values into hubs?
This is supported in .NET 7 now https://learn.microsoft.com/en-us/aspnet/core/signalr/hubs?view=aspnetcore-7.0#client-results
By default a client can only have one hub method running at a time on the server. This means that when you wait for a result in the first hub method, the second hub method will never run since the first hub method is blocking the processing loop.
It would be better if the OnInvocationResult method ran the logic in your AwaitInvocationResult extension and the first hub method just registers the id and calls the client.
I have 2 asp.net MVC web applications , as follow:-
ApplicationA . which is an Asp.net mvc-4 deployed under iis-8.
ApplicationB. which is an Asp.net mvc-5 deployed under iis-8.
now inside my ApplicationA i have the following method,which will call an action method (home/sync) on applicationB , as follow:-
public List<Technology> GetTechnology(int? currentfiltertype)
{
try
{
using (WebClient wc = new WebClient())
{
string url = currentURL + "home/sync?filtertype=" + currentfiltertype;
wc.Headers.Add("Authorization", token);
string json = wc.DownloadString(url);
List<Technology> result = JsonConvert.DeserializeObject<List<Technology>>(json);
return result;
}
}
catch (Exception e){}
}
now i have noted that when the WebClient calls the action method, and the method did not receive a response within around 2 minutes it will raise a timeout exception. But since the home/sync action method on web application B needs around 30 minutes to complete.. so i was searching for a solution to extend the web-client timeout period. so i tried changing my code to use async methods as follow,mainly by replacing wc.DownloadString with wc.DownloadStringTaskAsync as follow:-
public async Task<List<Technology>> GetTechnology(int? currentfiltertype)
{
try
{
using (WebClient wc = new WebClient())
{
string url = currentURL + "home/sync?filtertype=" + currentfiltertype;
wc.Headers.Add("Authorization", token);
string json = await wc.DownloadStringTaskAsync(url);
List<Technology> result = JsonConvert.DeserializeObject<List<Technology>>(json);
return result;
}
}
catch (Exception e) {}
}
and now seems the WebClient will never expired ... i tried calling the action method and the web client keep waiting for a response for more than 20 minutes without raising any timeout exception, then it received the response from web applicationB and everything worked well..
so can anyone advice why changing my code to use async methods as shown in the above code, caused the WebClient to not timeout ?? i can not understand the relation between using async logic and extending the timeout period for the web-client (not sure if the WebClient will ever timeout inside async methods!!)?
can anyone advice why changing my code to use async methods as shown in the above code, caused the WebClient to not timeout ??
The answer is a bit convoluted: WebClient is based on WebRequest, and HttpWebRequest's Timeout property is only honored for synchronous requests.
(noy sure if the WebClient will ever timeout inside async methods!!)?
It does not directly support asynchronous timeouts, but it does support (its own kind of) cancellation, which you can trigger after a timer.
I'm working an ASP.net MVC cloud service project running two roles, a web role and a worker role. One of the pages in the web role initiate a request to build an APK file, building an APK file on the server can take anywhere from 1-5 minutes. So we came up with the following flow:
The user initiate the APK building process on the page.
The request is routed to our mvc action, creating a new message on an Azure Storage Queue.
The Worker role is always polling from the queue and starts the APK building process. Now that the APK is ready we want ideally to notify the user by:
(a) sending an email, which is working now. and (b) notifying the user on the page using SignalR.
Our problem is now in the SignalR part, how can we notify the user on the page that the APK is ready and he can download it.
EDIT - Copying contents of the first comment for the sake of completeness -
I've looked the question again and I understand that you are using a worker role to poll the queue. In this case, you can make your work role a .Net SignalR client that connects to the APK signalR hub on the web role. The signlaR hub on the web role can simple forward any message it receives from the .Net client to the javascript client (browser).
I would recommend going through the below links
Hubs API Guide - Server
Hubs API Guide - Javascript Client
before going through rest of the answer.
As can be understood from the above two links, SignalR enables the server to 'push' data to the client. In order for this to happen, you require two things -
A signalR hub - this is the 'hub' to which clients can subscribe to in order to receive messages.
A client connected to the hub
Your signalR hub on the server can look something like this -
public class APKHub : Hub
{
public async Task JoinGroup(string groupName)
{
await Groups.Add(Context.ConnectionId, groupName);
Clients.Group(groupName).sendMessage(Context.User.Identity.Name + " joined.");
}
public Task LeaveGroup(string groupName)
{
return Groups.Remove(Context.ConnectionId, groupName);
}
public void NotifyUser(string userId)
{
this.Clients.Group(userId).notify();
}
}
On the client, your code might look something like this -
var notificationHandler = function () {
var url;
var user;
var init = function (notificationUrl, userId) {
url = notificationUrl;
user = userId;
connectToAPKHub();
}
var connectToAPKHub = function () {
$.connection.hub.url = url;
var apk= $.connection.apkHub;
apk.client.notifyUser = function (user) {
console.log(user);
}
apk.client.addMessage = function (message) {
console.log(message);
}
$.connection.hub.start().done(function () {
console.log('connected to apkhub');
apk.server.joinGroup(user);
})
}
return {
init: init
}
}();
The notificationUrl is the URL that the signalR server is listening to.
This sets up your basic hub on the server and you should now be able to connect your client to the signalR hub. When the APK is built, you can use the following code (place it anywhere - for ex - in a controller action) to actually push a message to the concerned client -
var apkHub = GlobalHost.ConnectionManager.GetHubContext<APKHub>();
apkHub.Clients.Group(groupName).notifyUser(groupName);
The groupName can be an identifier that uniquely identifies a user.
Hope this helps.
I have setup a SignalR hub which has the following method:
public void SomeFunction(int SomeID)
{
try
{
Thread.Sleep(600000);
Clients.Caller.sendComplete("Complete");
}
catch (Exception ex)
{
// Exception Handling
}
finally
{
// Some Actions
}
m_Logger.Trace("*****Trying To Exit*****");
}
The issue I am having is that SignalR initiates and defaults to Server Sent Events and then hangs. Even though the function/method exits minutes later (10 minutes) the method is initiated again ( > 3 minutes) even when the sendComplete and hub.stop() methods are initiated/called on the client prior. Should the user stay on the page the initial "/send?" request stays open indefinitely. Any assistance is greatly appreciated.
To avoid blocking the method for so long, you could use a Taskand call the client method asynchronously.
public void SomeFunction(Int32 id)
{
var connectionId = this.Context.ConnectionId;
Task.Delay(600000).ContinueWith(t =>
{
var message = String.Format("The operation has completed. The ID was: {0}.", id);
var context = GlobalHost.ConnectionManager.GetHubContext<SomeHub>();
context.Clients.Client(connectionId).SendComplete(message);
});
}
Hubs are created when request arrives and destroyed after response is sent down the wire, so in the continuation task, you need to create a new context for yourself to be able to work with a client by their connection identifier, since the original hub instance will no longer be around to provide you with the Clients method.
Also note that you can leverage the nicer syntax that uses async and await keywords for describing asynchronous program flow. See examples at The ASP.NET Site's SignalR Hubs API Guide.