Cannot use IPv6 address in Alertmanager URL

[thedirtycolumbia]

What did you do?
Tried to set -alertmanager.url=http://[IPV6ADDRESS]:PORT/

What did you expect to see?
Prometheus able to send alerts to an IPv6 Alertmanager.

What did you see instead? Under which circumstances?
It appears that govalidator.IsURL does not properly handle IPv6 address (w/ or w/o brackets).

Environment

• System information:

  Linux 3.14.33-4.el6.pharos.x86_64 x86_64

• Prometheus version:

  prometheus, version 0.18.0 (branch: release-0.18, revision: f12ebd6)
  build user: root@ebaf628123aa
  build date: 20160418-08:20:43
  go version: go1.5.4

• Alertmanager version:

  alertmanager, version 0.4.2 (branch: master, revision: 9a5ab2fa63dd7951f4f202b0846d4f4d8e9615b0)
  build user: root@2811d2f42616
  build date: 20160902-15:33:13
  go version: go1.6.3

• Prometheus configuration file:
  https://gist.github.com/shore/8761b976a0f2a68e366772c4033b62b3

• Alertmanager configuration file:
  https://gist.github.com/shore/bfa3def3beb8b83f86e48b8a72b86d3c

• Logs:

time="2016-09-23T00:08:32Z" level=error msg="invalid Alertmanager URL: http://[::1]:9093" source="main.go:65"

[juliusv]

@thedirtycolumbia Thanks! Hmm, govalidator has bitten us a number of times already now. I wonder if we should keep using it or just let the occasional wrong URL through.

For now I filed a bug there: asaskevich/govalidator#150

The fix doesn't seem totally trivial if one wanted to fix the rxURL regex there. Regexing IPv6 correctly apparently gets quite long. Maybe the correct solution there is to restructure the code and move away from a URL regex altogether.

[thedirtycolumbia]

@juliusv Thanks for the quick response and the bug filed upstream! I have subscribed to that issue as well. It may be that moving away from the URL regex is a good solution if it is a recurring problem. We'll keep an eye on how things go in asaskevich/govalidator#150.

[juliusv]

@thedirtycolumbia Yeah, sorry about that. The workaround for now would be to use a DNS name (or even just an /etc/hosts entry) that resolves only to a v6 address. Still, we should fix this soon ourselves if govalidator doesn't do so.

[brian-brazil]

Looks like we just need to update our vendoring now.

[thedirtycolumbia]

@brian-brazil Thanks! We're looking forward to this fix.

[lock]

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