Use structured logging

[uablrek]

Use structured logging in json format if -logging-format=json is specified. The same setup functions as for K8s core packages are used (component-base).

Also, contextual logging is used (beta in 1.30, so no feature-gateway is needed).

Fixes #48

This PR will be a draft until all code is changed to use structured/contextual logging.

[uablrek]

/cc @pohly

@pohly Can you please review the updates in main() in the first commit? I don't want to do any fundamental mistakes. The rest I think I can manage.

[uablrek]

Example output:

# kubectl logs -n kube-system   kube-network-policies-8hb7p | jq
...
{
  "ts": 1720002972865.8306,
  "caller": "cache/reflector.go:359",
  "msg": "Caches populated for *v1.Pod from pkg/mod/k8s.io/client-go@v0.30.2/tools/cache/reflector.go:232",
  "v": 2
}
{
  "ts": 1720002972953.2607,
  "caller": "cache/shared_informer.go:320",
  "msg": "Caches are synced for kube-network-policies",
  "v": 0
}
{
  "ts": 1720002972953.3674,
  "caller": "networkpolicy/metrics.go:61",
  "msg": "Registering metrics",
  "v": 0
}
{
  "ts": 1720002972953.4724,
  "caller": "networkpolicy/controller.go:344",
  "msg": "Syncing nftables rules",
  "v": 0
}

[uablrek]

Lint complaints:

Error: cmd/main.go:81:3: exitAfterDefer: os.Exit will exit, and `defer cancel()` will not run (gocritic)

This is just as bad with klog.Fatalf, but lint misses that. A pattern seem to be:

func main() {
  os.Exit(run())
}
func run() int {
  return errorCode
}

Shall we use it? Else I restore klog.Fatalf in main()

I will call cancel() explicitly. (but since it's right before exit, it will not really matter)

[aojea]

func main() {
  os.Exit(run())
}
func run() int {
  return errorCode
}

that sounds like the right way to do it

[aojea]

@uablrek what is missing here? it lgtms

/lgtm
/approve

[k8s-ci-robot]

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[uablrek]

@uablrek what is missing here? it lgtms

Lots and lots of Infof(), and friends, should be changed to InfoS().

Also i was planning to introduce contextual logging, but I think that can wait.

[k8s-ci-robot]

New changes are detected. LGTM label has been removed.

[uablrek]

Structured logging allows a nice optimization possibility. Without this p.String() is always called, regardless of verbosity.

	// evaluatePacket() should be fast unless trace logging is enabled.
	// Logging optimization: We check if V(2) is enabled before hand,
	// rather than evaluating the all parameters make an unnecessary logger call
	tlogger := logger.V(2)
	if tlogger.Enabled() {
		tlogger.Info("Evaluating packet", "packet", p)
		tlogger = tlogger.WithValues("id", p.id)
	}

[uablrek]

Logging like this exist at several places. I am unsure how to handle them. A general recommendation is to not log errors if you return them (let the caller decide). And normally logger.Error(err, ...) is used for logging errors, but then it will be at a higher log-level. I made a compromise by keeping the log at Info level.

[uablrek]

A way to keep info about what caused the error is to wrap them:

return fmt.Errorf("could not open nfqueue socket %w", err)

(ref: recent discussion on slack)

[uablrek]

Example packet log in JSON format:

{
  "ts": 1720777151838.3552,
  "caller": "networkpolicy/controller.go:461",
  "msg": "Evaluating packet",
  "v": 2,
  "packet": {
    "Id": 9,
    "Family": "IPv4",
    "SrcIP": "11.0.3.3",
    "DstIP": "11.0.2.2",
    "Proto": "TCP",
    "SrcPort": 33803,
    "DstPort": 6000
  }
}

Text output is not altered:

I0712 09:53:52.257809       1 controller.go:461] "Evaluating packet" packet=<
        [8] 11.0.1.3:40243 11.0.2.2:6000 TCP
        00000000  00 00 a0 02 fa f0 19 33  00 00 02 04 05 b4 04 02  |.......3........|
        00000010  08 0a c1 d9 c1 bd 00 00  00 00 01 03 03 07        |..............|
 >

[uablrek]

I will squash commits later

[aojea]

let me know once is ready for merging

[pohly]

This shouldn't be needed and might never give you a JSON logger.

Leave the context as it is. A klog.FromContext will then get the global default prepared by logsapi.ValidateAndApply.

Suggested change

	logger := klog.NewKlogr()
	logger := klog.FromContext(ctx)

[pohly]

Delete this.

[uablrek]

Rebased, updated after review, and use klog.KObj. Ready for review.

Please note that payload is empty for TCP/SYN, which is the only TCP packets we see:

I0721 08:56:53.060501       1 controller.go:491] "Evaluating packet" packet=<
        [10] 11.0.4.3:34751 11.0.4.2:6000 TCP
 >

[uablrek]

let me know once is ready for merging

@aojea Ready for review at least. I hope for merging. No logic is altered (except in main()), but very many log printouts

[k8s-ci-robot]

PR needs rebase.

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