Websocket State: PINGING_SERVER Event: CONNECTION_TIMED_OUT when deploying on AWS (Cloudfront+ALB+NLB+EC2)

Using Streamlit
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Summary

Currently, I am building a website with Streamlit with the configuration below, but due to a WebSocket error, it does not transition from the “Please wait” screen.

Could you please advise me on how to handle this?

Configuration:

  1. AWS-Cloudfront -(HTTPS)-> 2. AWS-ALB -(HTTP)-> 3. AWS-NLB -(TCP)-> 4. EC2

With access to 3. NLB and 4. EC2, the WebSocket is correctly connected and the expected screen transition occurs. With 2. ALB, I am not sure what the cause is, but it cannot connect.

  1. Cloudfront, as mentioned above, displays up to Streamlit, but due to a WebSocket error, it does not transition from the “Please wait” screen.

If anyone understands how to handle this situation based on the information above, please instruct me.

Additional information

Additionally, I am path routing with /xxx/yyy on 2. ALB. The browser I am using is Chrome.

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Did you find a way to make this work? I’m using HTTPS → ALB → EC2 and my page gets stuck in the “Please wait” for a while before displaying. I get the same websocket connection timed out issue. The page itself doesn’t time out but takes a while to display. Sometimes minutes. It works intermittently though. Sometimes the upgrade to websocket happens instantly without any errors. Not sure what the issue is. Using streamlit 1.24.0 with python 3.9. Not using Nginx.

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