Allow 0.0 to be set on tracesSampleRate.

[maciejwalkowiak]

📜 Description

Allow 0.0 to be set on tracesSampleRate.

💡 Motivation and Context

Fixes #1326.

💚 How did you test it?

📝 Checklist

• I reviewed the submitted code
• I added tests to verify the changes
• I updated the docs if needed
• No breaking changes

[maciejwalkowiak]

The question is what's the point of having null on tracesSampleRate? Shouldn't we default it to 0.0? Or this is actually a bug, and having null on tracesSampleRate should make all startTransaction calls return no-op?

[marandaneto]

The question is what's the point of having null on tracesSampleRate? Shouldn't we default it to 0.0? Or this is actually a bug, and having null on tracesSampleRate should make all startTransaction calls return no-op?

@maciejwalkowiak that was the point.

@bruno-garcia to confirm but if I understood correctly means:

tracesSampleRate and tracesSampler == null -> Tracing is fully disabled, we could do NoOp IMO as discussed in the meeting.

tracesSampleRate == 0.0, means no transaction will be created by this SDK unless an incoming trace has been sampled

[marandaneto]

missing @tests and changelog, let's wait @bruno-garcia to confirm though

[marandaneto]

@bruno-garcia thats all we need right?
@maciejwalkowiak could u work on that, so I can cut a release with it :)

[bruno-garcia]

Other than the note from @marandaneto LGTM.
As Manoel already wrote on this PR: null means no transactions should be emitted.

But 0.0 means no chance of random sampling creating transactions, but if an incoming request is sampled, the SDK will honor that decision.

[bruno-garcia]

Looks like we're missing docs too: https://docs.sentry.io/platforms/java/configuration/filtering/#using-sampling-to-filter-transaction-events

[maciejwalkowiak]

@bruno-garcia docs updated: getsentry/sentry-docs#3277

Disabling performance feature when tracesSampleRate is null will come in subsequent PR.