/cdns/capacity returns 500 error: capacity was zero

[zrhoffman]

I'm submitting a ...

• bug report
• new feature / enhancement request
• improvement request (usability, performance, tech debt, etc.)
• other

Traffic Control components affected ...

• CDN in a Box
• Documentation
• Grove
• Traffic Control Client
• Traffic Monitor
• Traffic Ops
• Traffic Ops ORT
• Traffic Portal
• Traffic Router
• Traffic Stats
• Traffic Vault
• unknown

Current behavior:

Visiting /api/3.0/cdns/capacity returns a 500 error:

{
	"alerts": [
		{
			"text": "Internal Server Error",
			"level": "error"
		}
	]
}

Expected / new behavior:

Should return a response like

{
	"response": {
		"availablePercent": 89.0939840205533,
		"unavailablePercent": 0,
		"utilizedPercent": 10.9060020300395,
		"maintenancePercent": 1.39494071146245e-05
	}
}

Minimal reproduction of the problem with instructions:

1. Start CDN-in-a-Box
2. Log into Traffic Ops
3. Visit https://trafficops.infra.ciab.test/api/3.0/cdns/capacity

Anything else:

From the error log:

ERROR: api.go:201: 2020-07-01T17:32:06.388024754Z: 192.168.48.10:55050 capacity was zero!

[ocket8888]

I think the reason it does that currently is to avoid dividing by zero. I don't remember the specifics of how it works, but it might be permissible to instead return zero values in that case.

[zrhoffman]

Do all of the structs in traffic_ops/traffic_ops_golang/cdn/capacity.go (last modified in February in c3c313f) accommodate the new interface-specific structure coming from TM? If it's not unmarshalling correctly, there won't be any data there.

[ocket8888]

Hm. Not sure. That'll need some looking-into.