[Bug] Socket connection keeps dropping when deployed in Azure

[frankcorneliusmartin]

Describe the bug
The websocket connection in the UI is not working. In the console I can retrieve the following:

Request URL: https://blueberry.vantage6.ai/socket.io/?EIO=4&transport=polling&t=****
Request Method: POST
Status Code: 400 BAD REQUEST
Remote Address: ****
Referrer Policy: strict-origin-when-cross-origin

Response headers:

HTTP/1.1 400 BAD REQUEST
Content-Type: text/plain
Date: Thu, 01 Feb 2024 09:54:46 GMT
Access-Control-Allow-Credentials: true
Access-Control-Allow-Origin: https://portal.blueberry.vantage6.ai
Set-Cookie: ARRAffinity=7101dfab990a2cbc29fbd6aac7283eac2eee64f0475fd413223cec5239511076;Path=/;HttpOnly;Secure;Domain=blueberry.vantage6.ai
Set-Cookie: ARRAffinitySameSite=7101dfab990a2cbc29fbd6aac7283eac2eee64f0475fd413223cec5239511076;Path=/;HttpOnly;SameSite=None;Secure;Domain=blueberry.vantage6.ai
Transfer-Encoding: chunked

Request headers:

POST /socket.io/?EIO=4&transport=polling&t=*****&sid=***** HTTP/1.1
Accept: */*
Accept-Encoding: gzip, deflate, br
Accept-Language: en,nl;q=0.9,en-GB;q=0.8,en-US;q=0.7
Authorization: Bearer ***************
Connection: keep-alive
Content-Length: 9
Content-type: text/plain;charset=UTF-8
Host: blueberry.vantage6.ai
Origin: https://portal.blueberry.vantage6.ai
Referer: https://portal.blueberry.vantage6.ai/
Sec-Fetch-Dest: empty
Sec-Fetch-Mode: cors
Sec-Fetch-Site: same-site
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36 Edg/121.0.0.0
sec-ch-ua: "Not A(Brand";v="99", "Microsoft Edge";v="121", "Chromium";v="121"
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: "Windows"

To Reproduce
Start the UI in an Azure environment

Details

• UI version: 4.3.0b3
• server version: 4.3.0b3

Additional context
It seems this post describes the same problem: https://stackoverflow.com/questions/63038955/flask-socket-io-400-error-code-on-azure-app-services

[bartvanb]

This issue only occurs if we use horizontal scaling. With a single App Service instance, there are no issues (even when RabbitMQ is used). Only when using multiple instances I can observe these issues (despite using RabbitMQ)

In app service we see:

2024-02-06T10:19:43.931809458Z 2024-02-06 10:19:43 - engineio.server - ERROR    - 
Invalid session pNbKGKPv-v2SrVD8AAAC (further occurrences of this error will be logged with level INFO)

[bartvanb]

Fixed in 4.3.0b4 by #229