GET /deliveryservice_stats limits metric types

[mitchell852]

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:

The Go version of GET /deliveryservice_stats limits the metric types to the following:

dsMetricTypes = map[string]interface{}{
	"kbps":      struct{}{},
	"tps_total": struct{}{},
	"tps_2xx":   struct{}{},
	"tps_3xx":   struct{}{},
	"tps_4xx":   struct{}{},
	"tps_5xx":   struct{}{},
}

Therefore making it impossible to fetch metricType=foo for example. The Perl version did not restrict the metric types but rather it simply added whatever metric type to the influx query.

I would suggest fixing this in 1.x and 2.x (which is already part of TC 4.1) and potentially redesigning the entire endpoint for 3.x (which is part of TC 5.0). I'll created a separate issue for that - #4741

Expected / new behavior:

GET /api/deliveryservice_stats does not limit metric types to a predefined set.

Minimal reproduction of the problem with instructions:

GET /api/1.4/deliveryservice_stats?metricType=foo will return a 400 bad request.

[ocket8888]

This was intentional. The Perl version allowed for arbitrary input without restriction, which let a read-only user destroy the entire stats database. I'd suggest that instead if there's a new type of stat you want, we just add support for that instead.