WebListener RC2: 503 Service Unavailable when hosted in Azure Service Fabric

[alecor191]

I'm having an issue when using WebListener RC2 together with Azure Service Fabric: I have a very simple ASP.NET Core RC2 app that works fine when hosted using WebListener as standalone app.

However, as soon as I host this app in Azure Service Fabric (repro both on local cluster as well as Azure-hosted cluster), the following happens:

• The app starts up without issues (i.e. webHost.Run() doesn't throw any exception and blocks the thread - expected)

• As soon as a request is sent to the app, 503 Service Unavailable is returned (expected would be a 200).

• I took http.sys logs, but all I see there is that it returns a 503, no indication about what the reason could be.

• I looked at the logs produced by the WebListener, but there are also no error entries; it just shows that it started up successfully:

  Microsoft.AspNetCore.Hosting.Internal.WebHost: Debug: Hosting starting
  Microsoft.Net.Http.Server.WebListener: Information: Start
  Microsoft.Net.Http.Server.WebListener: Information: Listening on prefix: http://localhost:8082/aspnetcorerc2/
  Microsoft.AspNetCore.Hosting.Internal.WebHost: Debug: Hosting started
  

• If I just replace .UseWebListener() with .UseKestrel() it works fine on both local cluster as well as Azure-hosted cluster.

Here the code that shows how I host the ASP.NET app in Azure Service Fabric:

var webHost = new WebHostBuilder()
    .UseContentRoot(Directory.GetCurrentDirectory())
    .UseStartup<Startup>()
    .UseWebListener()
    .UseServiceFabricEndpoint("ServiceEndpoint")
    .Build();

ServiceRuntime
    .RegisterServiceAsync(
        "AspCoreRC2StatelessType", 
        serviceContext => new AspCoreRC2StatelessService(serviceContext, webHost))
    .Wait();

webHost.Run();

where UseServiceFabricEndpoint is implemented as follows:

public static IWebHostBuilder UseServiceFabricEndpoint(this IWebHostBuilder webHostBuilder, string endpointName)
{
    var endpoint = FabricRuntime.GetActivationContext().GetEndpoint(endpointName);

    string serverUrl = $"{endpoint.Protocol}://{FabricRuntime.GetNodeContext().IPAddressOrFQDN}:{endpoint.Port}/aspnetcorerc2/";

    webHostBuilder.UseUrls(serverUrl);

    return webHostBuilder;
}

I'm using Microsoft.AspNetCore.Server.WebListener/0.1.0-rc2-20901

BTW the reason I'm using WebListener instead of Kestrel is that I have multiple Service Fabric-hosted apps that all listen on the same port (but different paths). But for troubleshooting I made sure that only the service described above listens on the configured port.

Any idea what I could do to further troubleshoot the root cause of that 503 error?

[Tratcher]

WebListener strictly enforces the host name match. You registered it on localhost. What host name are you using to contact it?

[alecor191]

I tried both http://localhost:8082/aspnetcorerc2/ and http://<mylocalmachinename>:8082/aspnetcorerc2/. Neither worked.

When running the app using WebListener and dotnet run I can connect using http://localhost:8082/aspnetcorerc2/.

One difference that I noticed between running the app using dotnet run and using ASF is that in the latter case it runs as Network Service. Could the issue be related to permissions?

[alecor191]

I just got it working by having WebListener listen on wildcard host name: http://+:8080/aspnetcorerc2/.

What I don't understand yet is why WebListener listening on http://localhost:8080/aspnetcorerc2/ works fine when launching the selfhost app using dotnet run, but it doesn't when hosted in ASF.

Thanks @Tratcher for your input, as it led me to the working solution.

[Tratcher]

ASF isn't running on the same machine, it's running in a VM or emulator.

[cwe1ss]

ASF isn't running on the same machine, it's running in a VM or emulator

If you run the local DEV cluster of ASF, there's no emulator or VM involved. ASF acts like there are multiple nodes but all processes are just regular processes on your machine.

[pharring]

I ran into the same problem when moving from Kestrel to WebListener because the sample code I used (which came from the Visual Studio template for a new Service Fabric ASP.Net Core app) used
FabricRuntime.GetNodeContext().IPAddressOrFQDN for the host name (in WebHostingService.OpenAsync in program.cs). Replacing that expression with '+' made it work for both localhost (debugging in a SF dev cluster on the same box) and a real SF cluster in Azure.

[vikashsingh009]

Angular2 Apps getting 503 as main.js not loading

[Tratcher]

@vikashsingh005 check your address registrations. #749 (comment)

[vikashsingh009]

I have Followed the same Pattern like this

 Task<string> ICommunicationListener.OpenAsync(CancellationToken cancellationToken)
            {
                var endpoint = FabricRuntime.GetActivationContext().GetEndpoint(_endpointName);

                string serverUrl = $"{endpoint.Protocol}://+:{endpoint.Port}/company";
                //  string serverUrl = $"{endpoint.Protocol}://{FabricRuntime.GetNodeContext().IPAddressOrFQDN}:{endpoint.Port}/company";
                 _webHost = new WebHostBuilder().UseWebListener()
                                               .UseContentRoot(Directory.GetCurrentDirectory())
                                               .UseStartup<Startup>()
                                               .UseUrls(serverUrl)
                                               .Build();

                _webHost.Start();

                return Task.FromResult(serverUrl);
            }

But , Angular2

[Tratcher]

I don't see any obvious problems, you'll have to ask Service Fabric for help.

[Tratcher]

Actually, I see you registered /company, but angualr is requesting /app/main.js. Shouldn't that be /company/app/main.js?

[vikashsingh009]

yes, after changed /app/main.js to /company/app/main.js in Angular2 Apps ,Now Context Path not working like if i hit on browser https://localhost:9999/company Angular2 Page will load but after that it Redirect back to https://localhost:9999 , my goal is to run 2 Fabric Application Internal using Angular2 on same port like 9999 so that i can access 2 application on context path like

https://localhost:9999/company
https://localhost:9999/management

[Tratcher]

Context Path? You mean HttpContext.Path? What are you doing with it?

When generating redirect urls remember to include HttpContext.PathBase.

[vikashsingh009]

Where i will use in service fabric ,i have asp.net core Application

my requirement is based on above Discussion like how to access application on same port like 80 based on Application context path,Can you guide me the Steps or sample on fabric to achieve that

[awcab]

Same here. Changing to + works fine, but localhost results in a 503.