Refactor tracing interceptor

[XSAM]

Split from #312. I will create the remaining parts of #312 once this PR gets merged.

@bwplotka @yashrsharma44 PTAL

[codecov-commenter]

Codecov Report

Merging #450 (7e04286) into v2 (6e2c2ac) will decrease coverage by 25.42%.
The diff coverage is 50.64%.

@@             Coverage Diff             @@
##               v2     #450       +/-   ##
===========================================
- Coverage   84.01%   58.59%   -25.43%     
===========================================
  Files          30       31        +1     
  Lines         932     1577      +645     
===========================================
+ Hits          783      924      +141     
- Misses        110      590      +480     
- Partials       39       63       +24     

Impacted Files	Coverage Δ
chain.go	0.00% <ø> (-90.91%)	⬇️
interceptors/auth/auth.go	100.00% <ø> (ø)
interceptors/ratelimit/ratelimit.go	60.00% <0.00%> (-40.00%)	⬇️
interceptors/recovery/options.go	78.57% <ø> (ø)
metadata/single_key.go	60.00% <ø> (ø)
testing/testpb/interceptor_suite.go	0.00% <0.00%> (ø)
testing/testpb/test.manual_validator.pb.go	0.00% <0.00%> (ø)
util/backoffutils/backoff.go	60.00% <ø> (ø)
wrappers.go	66.66% <ø> (-33.34%)	⬇️
interceptors/reporter.go	45.45% <20.00%> (-17.05%)	⬇️
... and 25 more

---

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[yashrsharma44]

Since #394 has been merged, there have been some changes in the structuring of tags(which are removed, replaced with logging.Fields) and tracing package has been removed.

Please rebase the changes.

[yashrsharma44]

Looks good to me, I will have another round of review, particularly the kv package, seems like a lot of chunk for tracing is present there :)

[bwplotka]

Nice work! Did very quick pass with initial questions. Generally looks amazing! 💪🏽

[bwplotka]

Not a fan of this package. Looks very low value to maintain another type system. Can we avoid it?

[XSAM]

OTel uses a type-safe way to describe the type of attributes, I am afraid we will lose type information if we don't implement a type system.

[yashrsharma44]

Everything looks good to me! Regarding the kv package, I don't have any solid suggestions, but do you think we can define the interface for the kv helper methods, and let the providers implement the kv implementation?

[yashrsharma44]

This looks neat!

[XSAM]

do you think we can define the interface for the kv helper methods, and let the providers implement the kv implementation.

Sounds good. @bwplotka WDYT?

[bwplotka]

Just doing pass on this, sorry for lag. Feel free to ping me on Go/CNCF slack next time. Do you wish to move forward with this @XSAM ? We need that (:

[XSAM]

yeah, i can still work on this.

[bwplotka]

Sweet, let me review this unless you want to change something

[bwplotka]

Nice, some comment first.

Good work 💪🏽

[bwplotka]

Suggested change

	func (s *mockSpan) AddEvent(name string, attrs ...kv.KeyValue) {
	func (s *mockSpan) AddEvent(name string, attrs ...any) {

How bad would be to operate on interfaces (any) and expect implementation to deal with types?

NOTE: I know we could use generics, but in practice they have still some overhead, plus not everyone moved to Go 1.18, so we can add generic type of implementation later on (maybe even in non braking compatibility manner)

[bwplotka]

If we would move to interfaces, we won't be needing kv package - Otel implementation can then use "go.opentelemetry.io/otel/attribute"

[bwplotka]

This looks amzing, LGTM. Just one comment. Do you have the OTLP side handy somewhere?

[bwplotka]

Amazing idea to use gRPC codes here, love it!

[bwplotka]

Idea: Remove kv and use keyvals ...any as in go-kit logger https://github.com/go-kit/kit/tree/master/log ? (:

[bwplotka]

well ..interface{}, since we can't just support Go 1.18 yet

[bwplotka]

Then we can use something like

// borrowed from https://github.com/go-logfmt/logfmt/blob/main/encode.go#L75
func kvToAttr(keyvals ...interface{}) []attribute.KeyValue {
	if len(keyvals) == 0 {
		return nil
	}
	if len(keyvals)%2 == 1 {
		keyvals = append(keyvals, nil)
	}

	j := 0
	ret := make([]attribute.KeyValue, len(keyvals)/2)
	for i := 0; i < len(keyvals); i += 2 {
		k, ok := anyToString(keyvals[i])
		if !ok {
			k = "<unsupported key type>"
		}
		
		v, ok := anyToString(keyvals[i+1])
		if !ok {
			v = "<unsupported value type>"
		}
		
		ret[j] = attribute.String(k, v)
		j++
	}
	return ret
}

func anyToString(value interface{}) (string, bool) {
	switch v := value.(type) {
	case nil:
		return "nil", true
	case string:
		return v, true
	case []byte:
		return string(v), true
	case error:
		return v.Error(), true
	case fmt.Stringer:
		return v.String(), true
	default:
		rvalue := reflect.ValueOf(value)
		switch rvalue.Kind() {
		case reflect.Array, reflect.Chan, reflect.Func, reflect.Map, reflect.Slice, reflect.Struct:
			return "", false
		case reflect.Ptr:
			if rvalue.IsNil() {
				return "nil", true
			}
			return anyToString(rvalue.Elem().Interface())
		}
		return fmt.Sprint(v), true
	}
}

[bwplotka]

Ping (:

[bwplotka]

Amazing, work thanks! Let's go!