Blazor Server Side. JS doesn't start after a long downtime on mobile browsers.

[rburnashev85]

#23039 # Describe the bug

Blazor doesn't start after a long downtime on mobile browsers.

To Reproduce

1. Open any blazor server side site on chrome or firefox on android. For instance you can open this page https://demos.devexpress.com/blazor/ChartSeriesTypes
2. Minimize your browser and wait a few hours
3. Open the browser and with high propability you will see only prerendered page. All JS dynamic stuff doesn' work. No messages that you should update the page. If you follow some link on the page and then return back the page will still not work. The only way to restore its functionality is to refresh it manualy by clicking appropriate button in the browser.

P.S. Blazor Web Assembly sites restore without the issue.

Further technical details

• ASP.NET Core version 3.1

[captainsafia]

Thanks for reporting this issue, @rburnashev85.

This is expected behavior. When the user has navigated away from the application, we disconnect the Blazor server circuit to conserve resources.

To resolve this issue, you can implement JavaScript to detect that a user has returned to the web page and reconnect.

@danroth27 Can you share the docs link to this?

[danroth27]

I don't think we ever officially documented this, but a suggested approach for doing this here: #10325 (comment).

[rburnashev85]

Thank you for the answers. I understand that after some time Blazor server closes the connection. I use the script from #10325 on my site. It works as expected when the reconnect button appears. But the issue I have writen about is not the same. After few hours of downtime on mobile browsers the reconnect button doesn't appear. It seems like JS doesn't work at all. I see only prerendered page. Maybe it is because mobile browsers use some tricky cache mechanism or because JS crashes at an early stage of page initialization. It is hard to investigate because the browsers don't have console.

I tried to host my site on Nginx and on Kestrel without any reverse proxy. Nothing changed. Then I opened different sites on internet which made with blazor server side on the same mobile browsers. And I see the same problem there.

It is interesting that blazor web assembly sites after the same downtime are reloaded. Mobile browsers seems to reset those tabs that have not been opened for a long time.

[mkArtakMSFT]

Thanks for contacting us.
We're moving this issue to the Next sprint planning milestone for future evaluation / consideration. We will evaluate the request when we will planning the work for the next milestone. To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.