Net 6 Blazor server application::Failed to start the transport 'WebSockets': Error: WebSocket failed to connect. The connection could not be found on the server, either the endpoint may not be a SignalR endpoint, the connection ID is not present on the server, or there is a proxy blocking WebSockets. If you have multiple servers check that sticky sessions are enabled.

[rajaashutosh]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

I am running the .Net 6 Blazor server application. The application is working fine in localhost/ with a single instance. However, when I deployed to a pivotal cloud foundry with multiple instances it starts breaking.

With a single instance, its page loads look fine.

With multiple instances, the page is showing blank. please refer to the screenshot.

Error:
[2022-08-09T20:26:06.460Z] Error: Failed to start the transport 'WebSockets': Error: WebSocket failed to connect. The connection could not be found on the server, either the endpoint may not be a SignalR endpoint, the connection ID is not present on the server, or there is a proxy blocking WebSockets. If you have multiple servers check that sticky sessions are enabled.

Also after a couple of refresh pages showing up, again if I start to navigate to other links its kind of not working.

Expected Behavior

Page should up and running with multiple instances

Steps To Reproduce

No response

Exceptions (if any)

Not using any Nginx rule for now. the deployment env is Linux

.NET Version

6

Anything else?

ASP.NET Core version 6

[BrennanConroy]

From the error message:

If you have multiple servers check that sticky sessions are enabled.

Do you have sticky sessions enabled when using multiple instances?

[rajaashutosh]

for sticky sessions: Added this
...........................................................................
services.AddMemoryCache();
..............................................................................
**builderService.AddSession(options =>
{
options.IdleTimeout = TimeSpan.FromSeconds(10);
options.Cookie.HttpOnly = true;
options.Cookie.IsEssential = true;
});

.................................................................
app.UseSession();

[BrennanConroy]

Sticky sessions is done at the proxy layer.
https://github.com/cloudfoundry/routing-release/blob/develop/docs/session-affinity.md

[rajaashutosh]

@BrennanConroy , are you saying, Cloud foundry infrastructure level? I am not using any Nginx yet.

[BrennanConroy]

Yes, as the link I provided shows.

[rajaashutosh]

@BrennanConroy , let me talk to infra team and let you guys update

[javiercn]

@rajaashutosh @BrennanConroy suggestions are on point. For more information on how to deploy Blazor Server applications check-out these docs

[rajaashutosh]

Thanks, Team, It's working with multiple instances, here is the solution to add sticky_session_cookie in pivotal cloud foundry.

Mainfast.yml

applications:
- name: unifieddeals-admin-ci
  stack: cflinuxfs3
  buildpacks:
    - dicf_dotnet_core_buildpack_2343_cflinuxfs3
  instances: 2
  memory: 4G
  disk_quota: 2G
  env:
    ASPNETCORE_ENVIRONMENT: CI
    router.sticky_session_cookie_names: "JSESSIONID"
  services:
  - secrets-unifieddeals-admin

Program.cs :
In Middleware

app.Use(async (context, next) =>
                {
                    //context.Response.Headers.Add("Content-Security-Policy", "{POLICY STRING}");
                    context.Response.Cookies.Append("JSESSIONID", Guid.NewGuid().ToString(), new
                        CookieOptions()
                    {
                        Secure = true,
                        HttpOnly = true,
                        SameSite = SameSiteMode.Strict
                    });
                    await next();
                });