Add graph button throws Handlebar Exeception

[medyagh]

What did you do?

Click on Add Graph

What did you expect to see?
Anything to happen (a graph to be added or aything)

What did you see instead? Under which circumstances?
Nothing. and I get these exceptions in chrome inspect:

in chrome's inspect I see

Uncaught ReferenceError: Handlebars is not defined
    at graph.js:6

that line is

Handlebars.registerHelper('pathPrefix', function() { return PATH_PREFIX; });

Environment
Mac OS, Chrome, and I used prometheus-1.5.0.darwin-amd64 version.

• System information:

  Darwin 15.6.0 x86_64

• Prometheus version:

	prometheus, version 1.5.0 (branch: master, revision: d840f2c400629a846b210cf58d65b9fbae0f1d5c)
  build user:       root@a04ed5b536e3
  build date:       20170123-13:59:53
  go version:       go1.7.4

screenshots

[bvis]

I've found this same issue when Prometheus is deployed under a path. For example:

• https://prometheus.domain.com/ <- OK
• https://my.domain.com/prometheus <- KO

It could be related with this line:

prometheus/web/ui/static/js/graph.js

Line 823 in 7daa21e

url: PATH_PREFIX + "/static/js/graph_template.handlebar",

Where PATH_PREFIX wouldn't have any value.

[h0tbird]

Same thing exposing via Kubernetes API server + kubectl proxy:

[0] ~ >> kubectl cluster-info --namespace monitoring | grep Prometheus
Prometheus is running at https://104.155.8.87/api/v1/proxy/namespaces/monitoring/services/prometheus

[h0tbird]

Setting -web.external-url to the value below makes the WebUI unreachable.

-web.external-url=http://127.0.0.1:8001/api/v1/proxy/namespaces/monitoring/services/prometheus

However, I managed to reach the /graph endpoint by setting PATH_PREFIX='http://127.0.0.1:8001/api/v1/proxy/namespaces/monitoring/services/prometheus'

[brian-brazil]

This might be a bug, this might be the kubeproxy doing something that's fundamentally unsupportable. Requires investigation.