Prometheus 0.18.0 fails to start with short version of Alertmanger URL

[xbglowx]

I am trying to upgrade from Prometheus 0.17.0 to 0.18.0 and noticed that Prometheus is failing to start due to:

2016-04-22_23:43:36.52662 time="2016-04-22T23:43:36Z" level=error msg="invalid Alertmanager URL: http://prometheus-alertmanager.service.q:9093" source="main.go:65"

I first thought Prometheus couldn't resolve the URL, but after doing some straces, I didn't even see Prometheus trying to resolve the name. Prometheus 0.18.0 currently doesn't like it when there is a single character after the last . of the URL. Maybe there is regex in Prometheus which is assuming that all URLs will be FQDN and there are no single character TLDs?

Works:
http://prometheus-alertmanager.t.te

Doesn't work:
http://prometheus-alertmanager.t.t

[juliusv]

0.18.0 introduced #1456, which uses govalidator.IsURL() to validate the Alertmanager URL. And this is the regex it uses: https://github.com/asaskevich/govalidator/blob/master/patterns.go#L33

The {2,} in the end seems to point to the fact that it requires at least two letters in the TLD, if there is one. Not sure if some standard somewhere says that it has to be at least 2 chars (couldn't find it immediately), or if it should be fixed in govalidator. Certainly there is no public 1-letter TLD in existence today.

[matthiasr]

But requiring a TLD at all implies that relative domains can't be used. This would make e.g. using it in Kubernetes unnecessarily hard, so I think this should be relaxed a bit.

[juliusv]

@matthiasr So it allows having no TLD at all (just http://f validates fine), but if the last component is dot-something, it needs to be at least 2 chars long. Of course, you could still have relative URLs where there are more than 2 name components, but the last one should not be the TLD yet.

All for relaxing this.

[juliusv]

I filed an issue with govalidator, let's see: asaskevich/govalidator#125

[juliusv]

It's fixed upstream.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.