Background callback returns 502

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Describe your context
I have some high CPU/RAM efficient workflow that handling by celery and in the same time I have background callback that triggering this workflow and partially doing some CPU-related calculations too.

  • replace the result of pip list | grep dash below
│ dash                 │ 2.7.0       │                                            │
│ dash-dv2             │ 1.0.95      │                                            │
│ fef-dash             │ 4.4.4       │                                            │
│ dash-table           │ 5.0.0       │                                            │
│ dash-core-components │ 2.0.0       │                                            │
│ dash-html-components │ 2.0.0       │                                            │
  • if frontend related, tell us your Browser, Version and OS
    • OS: macOS
    • Browser Chrome
    • Version 108

Describe the bug

When I’m starting only one this loading in parallel – all is ok, when more than three (including) – I’m receiving 502 error:
The issue reproducing regularly, not one-time issue and not fixing by restarting containers (we’re using k8s: 2 pods of dash app, 2 Redis instances, 2 scalable pods of nginx-ingress).

HTTP/1.1 502 Bad Gateway
Date: Thu, 29 Dec 2022 03:15:18 GMT
Content-Type: text/html
Content-Length: 552
Connection: keep-alive
Content-Security-Policy: <HIDDEN>
Referrer-Policy: no-referrer
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
X-XSS-Protection: 1; mode=block

Expected behavior

Not receiving 502 or with described output.



Hmm, how is your load balancer working?

What does it say for the routing of these, are they going to the same backend?