Why does the one _blazor.js call take 1.5 minutes?

Question

Hi all;

I am load testing my blazor app. As the load test was running I loaded a page myself with F12 displaying in my browser and see this (it consistently happens):

2OOS0jM6[1]

Why does this one call to blazor.server.js take 1.5 minutes? And is there anything I can do to speed it up?

As to could something in my Blazor app be causing this? Possibly. But I have no idea what and therefore have no idea if there's anything specific in my code that is causing this.
thanks - dave

Accepted Answer

Hi @David Thielen ,

It's a normal behavior in your project, we don't need to speed it up.

I found you are using LongPolling in your blazor project, that why we can see a lot of (fetch) http requests like [https://localhost:7043/_blazor?id=Iwns6](https://localhost:7043/_blazor?id=Iwns6IpNs2UkqNaIq6Xe_Q&_=1719383611048)_[pNs2UkqNaIq6Xe_Q&_=1719383611048](https://localhost:7043/_blazor?id=Iwns6IpNs2UkqNaIq6Xe_Q&_=1719383611048)_.

User's image

Blazor Server applications use SignalR to manage real-time communication between the client and the server, enabling efficient data exchange and state synchronization.

In SignalR, there are three protocols: WebSocket（Default）, LongPolling, and ServerSentEvents.

If we are using websocket, we can find the behavior like below. You can verify it by creating a brand new project.

User's image

_blazor?id=Iwns6IpNs2UkqNaIq6Xe_Q&_= *** It means that the front-end and back-end keep communicating, and 1.5min should be the browser's default behavior or configuration for LongPolling.

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Best regards,

Jason

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