Alertmanager webUI "Failed to load CSS from..."

[Moses Moore]

Alertmanager 0.22, and this showed up today on a half-dozen separate instances that haven't been rebooted in 2-7 days each.

Go to the web UI and see red text at the top of the page:

> Failed to load CSS from: //lib/bootstrap-4.0.0-alpha.6-dist/css/bootstrap.min.css

When I type https://alertmanager-us-east-1.[redacted]//lib/bootstrap-4.0.0-alpha.6-dist/css/bootstrap.min.css into my browser address bar, I successfully get the CSS sheet.

Check the browser console and I see the following error messages. 

Uncaught DOMException: Failed to execute 'pushState' on 'History': A history state object with URL 'https:/#/alerts' cannot be created in a document with origin 'https://alertmanager-us-east-1.[redacted]' and URL 'https://alertmanager-us-east-1.[redacted]//#'.

    at Object.b (https://alertmanager-us-east-1.[redacted]//script.js:1:21485)

    at https://alertmanager-us-east-1.[redacted]//script.js:1:10002

    at Nn (https://alertmanager-us-east-1.[redacted]//script.js:1:10137)

    at _n (https://alertmanager-us-east-1.[redacted]//script.js:1:9699)

    at Zn (https://alertmanager-us-east-1.[redacted]//script.js:1:11063)

    at Un (https://alertmanager-us-east-1.[redacted]//script.js:1:10709)

    at https://alertmanager-us-east-1.[redacted]//script.js:1:20847

    at Object.init (https://alertmanager-us-east-1.[redacted]//script.js:1:341)

    at https://alertmanager-us-east-1.[redacted]//:20:32

script.js:1 GET https://lib/bootstrap-4.0.0-alpha.6-dist/css/bootstrap.min.css net::ERR_NAME_NOT_RESOLVED

script.js:1 GET https://lib/font-awesome-4.7.0/css/font-awesome.min.css net::ERR_NAME_NOT_RESOLVED

script.js:1 GET https://lib/elm-datepicker/css/elm-datepicker.css net::ERR_NAME_NOT_RESOLVED

Looks like some javascript is not able to sense the hostname part of the window.address, and making URLs with a broken netloc part?  

Startup arguments are:

      --web.listen-address=0.0.0.0:9093

      --config.file=/etc/config/alertmanager.yml

      --storage.path=/data

      --cluster.listen-address=0.0.0.0:9094

      --cluster.gossip-interval=100ms

      --cluster.peer=prometheus-stack-prometheus-alertmanager-headless:9094

      --web.external-url=https://alertmanager-us-east-1.[redacted]

I tried re-launching without the "--web.external-url" part, does not fix it.  Tried changing browsers, and used someone else's computer, still the "Failed to load CSS from" error.

What boggles my mind is I viewed three of these websites yesterday and they were fine.  Time to make a bug report, or is there something screwy with my (and my co-workers's) web browsers that's confusing the alertmanager javascript?

[Moses Moore]

I found it -- there's a '//' in the path part of the URL, and that's screwing up the javascript in script.js somehow that tries to get the hostname part out of the window.location.href.