Styjun

I have a flask application using bokeh that is running in a Docker container, and it works when I use it on local machines.

However, when I deploy it to a GCP instance, even though I can reach the server, I have some AjaxDataSource() objects which are failing to connect.

Some details,

• All the machines, local and gcp vm are running Ubuntu 18.04


• 
  

  The flask app is started like this,

  
  
  

  app.run(host="0.0.0.0", port=6600, debug=False)

  
  


• 
  

  The Ajax route looks like this,

  
  
  

  http://127.0.0.1:6600/land/tmidemo/data_rate?name=ResultBaseKeysV1

  
  


• 
  

  The GCP firewall rules look like,

  
  
  

  Name Type Targets Filters Protocols / ports Action Priority Network
  tmiserver-egress Egress Apply to all IP ranges: 0.0.0.0/0 tcp:6600 udp:6600 Allow 1000 default
  tmiserver-ingress Ingress Apply to all IP ranges: 0.0.0.0/0 tcp:6600 udp:6600 Allow 1000 default
  

  
  


• 
  

  The docker container is run like this,

  
  
  

  docker run --net tminet --hostname=TEST -p 6600:6600 -v $(pwd):/app/public --name myserver --rm myserver
  

  
  



• I am not using a Bokeh server. The AjaxDataSource() calls point back to the flask application, not another (bokeh) server

There is a lot that works,

• able to use the GCP external ip address and reach the server


• going from web page to web page works, so flask routing is working

Whats NOT working is that Ajax() call which uses 127.0.0.1, although this DOES work when I run the container on a local machine.

The error I see in the inspect window is ERR_CONNECTION_REFUSED

The GCP instance hosts.conf DOES include a line for 127.0.0.1 localhost

I tried (from here) on the GCP VM instance, same result,

 iptables -A INPUT -i docker0 -j ACCEPT

I also tried (from here) changing the Docker run network to --net="host" and the result is identical.

I also tried adding --add-host localhost:127.0.0.1 to the Docker run command, same result.

I think the problem is configuring the GCP to know how to route a request to 127.0.0.1, but I don't know where to check, configure this, beyond what I have already done.

I wasn't able to specifically resolve the issue I was having, but I tried a different approach to the URL for the AjaxDataSource() and it worked and I think a better approach...

I used Flask url_for() function to create a link to the route that the AjaxDataSource() needs and this worked. The resulting link looks something like,

 /land/tmidemo/data_rate/ResultBaseKeysV1

ie, no http://127.0.0.1, and this seems to work in all cases, my dev environment and GCP.

I think I tried this a long time ago and it didn't work, because I use "flask" URLs all over the place, but for some reason I thought I needed "http://127.0.0.1" for the Ajax stuff. Its works now.... moving on!