TraceID stringer prefix zeroes

[lukedirtwalker]

Requirement - what kind of business use case are you trying to solve?

Logging TraceIDs should result in the same TraceIDs that are shown in the JaegerUI.
For example if I see 0c2de5a29f1a2dff in the JaegerUI and if I log the TraceID id with id.String() I will see c2de5a29f1a2dff in the log. This makes it harder than it should be to find a trace ID in the logs.

The change of displaying the 0 prefix in the UI was introduced in Jaeger 1.16 (see https://github.com/jaegertracing/jaeger/releases/tag/v1.16.0)

Problem - what in Jaeger blocks you from solving the requirement?

I could manually address this by writing my own formatting for the logging. The question is whether it wouldn't make sense to change the String method of the TraceID

Proposal - what do you suggest to solve the problem or improve the existing situation?

Change

jaeger-client-go/span_context.go

Lines 345 to 350 in 4b20232

	func (t TraceID) String() string {
	if t.High == 0 {
	return fmt.Sprintf("%x", t.Low)
	}
	return fmt.Sprintf("%x%016x", t.High, t.Low)
	}

to use always a fixed width hex representation.
Example: https://play.golang.org/p/DyCZUMF33i9

Any open questions to address

If you think it makes sense to change the Stringer in the proposed way, I can send a PR.
If you think it doesn't make sense I would be interested in the reason.

[yurishkuro]

+1. The wire encoding was already changed in #472 to include leading zeros, and ^^^ function should be consistent with that.

Would you like to create a PR?

[lukedirtwalker]

Thanks, I created #533 , let me know if you want me to change anything.