Refactor loggers with Slog

[jan-law]

Related #1170
Depends on dbason/opentelemetry-collector-contrib#1
Depends on kralicky/totem#5

Replaces zap with slog. According to docs, this should eliminate any allocations for logging strings and numbers. Benchmark test results for slog handlers: https://gist.github.com/jan-law/bfb4db82ba05dbcb551e0de1ed36f8c1

How to rebase branches ahead of main

In general, logging calls are identical with a few exceptions:

• Format string logs eg Infof, Errorf -> replace with Info(fmt.Sprintf(...)), Error(fmt.Sprintf(...))
• logger.New().Named("some-name") -> replace with logger.New().WithGroup("some-name")
• When you need to create a logr.Logr, you can use logger.NewLogr(options...)
• To create a new logger, see pkg/logger/logger.go for available options

This script will help you refactor existing zap logs with the slog equivalents.

Disclaimer: gofmt can only refactor logging calls that have a fixed number of arguments and is also case sensitive. If you created a log message with a different number of key/val pairs than what already exists in the codebase, the script may not format that log message.

Notes

• log messages of the form logger.With(args...).Info("blah") are still valid, but may cost extra memory allocations. You can replace them with logger.Info("blah", args...)
• Slog doesn't enforce an even number of args when you're logging loosely typed key/value pairs. It will log the last odd-numbered arg as !BADKEY=<value>. Docs recommend using https://pkg.go.dev/cmd/vet to check your code

[jan-law]

Note: branches rancher/opni:slog and jan-law:slog are the same. Lmk if you'd like me to make a PR with the upstream branch instead of my fork

[jan-law]

Note: I still need to update go.mod with the updated commit hash once dbason/opentelemetry-collector-contrib#1 is merged

[kralicky]

Some of the log messages that look like this:

a.logger.With(
	zap.Error(err),
	zap.String("group", ruleGroup.Name),
).Error("failed to marshal rule group")

seem to have been rewritten as

a.logger.Error("failed to marshal rule group", logger.Err(err),
	"group", ruleGroup.Name)

Is there a way we can have the format match? i.e.

a.logger.With(
	logger.Err(err),
	"group", ruleGroup.Name,
).Error("failed to marshal rule group")

[jan-law]

Is there a way we can have the format match?

Yes, your last example is valid slog syntax. The reason why I changed the format is because the original format causes an extra allocation per line, and you mentioned you wanted to reduce allocations by moving to slog.

I can revert the format of the logger.With calls so that they match if you'd prefer the same format?

[kralicky]

Ah, yeah I think for most cases the extra memory allocation isn't a big deal, but in performance oriented code that is good to keep in mind. we should keep the old format in places where it's originally written like that.

[kralicky]

LGTM

[jan-law]

Rebased onto main, no other changes

[jan-law]

@kralicky This PR is using my fork of Dan's copy of opentelemetry-collector-contrib. Dan mentioned his copy is outdated and needed time to think about how to update the rancher sandbox fork here.

Should we merge this PR and then update the fork later? How do you want to handle this?

[kralicky]

Yeah that sounds fine to me, we can merge this PR first.