I’m not an expert on nginx, but you might simplify the config in this case by removing the upstream section and just using 127.0.0.1:5100 directly in:
proxy_pass http://127.0.0.1:5100;
I could be wrong, but I think upstream requires an nginx module to be installed, so I just thought in case that is causing a problem. In general, it would be worth looking at the nginx logs to see if it has any complaints.
Another thing that I noticed, which isn’t your current problem but you could encounter when you fix this first stage…:
bokeh serve sliders/ --allow-websocket-origin=10.73.162.4:5100 --port 5100
The web traffic will originate from port 80, so you would probably need that as the web origin instead of the local port 5100 (or 80 is the default anyway):
bokeh serve sliders/ --allow-websocket-origin=10.73.162.4 --port 5100
Hopefully someone with better nginx experience will have more to add, but in the meantime please do check your logs and ensure the config is being loaded too - maybe introduce a deliberate error just to show that problems are being discovered and reported in the logs.