fix: kapinger use service IP instead of name

[matmerr]

Description

CoreDNS wasn't playing nice with massive bursts of service name fqdn lookups, this moves to using the ip of the service(s) directly

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[MikeZappa87]

What was the issue with CoreDNS? Have we informed the correct teams of a possible issue with CoreDNS?

[huntergregory]

why import this? Comment for future users?

[timraymond]

@huntergregory that's fairly common with pprof, but also not my most favorite thing. It uses init() to attach pprof handlers to the default net/http handler. Probably fine here, where it's for testing, but for production pprof handlers I usually like to explicitly attach those handlers to my routes. This is documented in the package docs here: https://pkg.go.dev/runtime/pprof .

[huntergregory]

non-blocking: I'm not a fan of the experimental library because it makes breaking changes all the time

[MikeZappa87]

From that repo:
Warning: Packages here are experimental and unreliable. Some may one day be promoted to the main repository or other subrepository, or they may be modified arbitrarily or even disappear altogether.

We probably should make attempts to just move away from this entirely.

[huntergregory]

What if there's a networkpolicy dropping traffic in our testing? This change would reduce that amount of traffic by 80%?

[huntergregory]

perhaps make this timeout configurable?

[huntergregory]

Are we killing the TARGET_TYPE=pod functionality? I'd remove any dead code or add comments to it to fix later

retina/hack/tools/kapinger/clients/http.go

Lines 61 to 73 in d1378d1

	switch k.targettype {
	case Service:
	k.urls, err = k.getServiceURLs()
	if err != nil {
	return nil, fmt.Errorf("error getting service URLs: %w", err)
	}
	case Pod:
	k.urls, err = k.getPodURLs()
	default:
	return nil, fmt.Errorf("env TARGET_TYPE must be \"service\" or \"pod\"")
	}