Add logs sampler

[oliver-zhang]

Sometimes we don't want to collect all the logs, we only need the logs associated with the call chain. The goal of this PR is to provide a mechanism for users to customize the log sampling rules to meet custom requirements.Add logs sampler

[jkwatson]

Do you have a link to the relevant specification that includes this feature? We'd need to have it merged into the spec before we could include it here.

[oliver-zhang]

Do you have a link to the relevant specification that includes this feature? We'd need to have it merged into the spec before we could include it here.

No,I don't know if the specification has this implementation plan

[jack-berg]

No,I don't know if the specification has this implementation plan

This repo is limited in scope to components which implement concepts defined in the spec.

I do think this is a useful concept, particularly the ability to only retain logs if they have an associated span which is sampled.

Your options include:

• Use this PR / branch as a prototype and try to update the spec to include this concept.
• Move to opentelemetry-java-contrib and refactor to work as a LogRecordProcessor. For example, you could have a FilteringLogRecordProcessor which accepts a Predicate<LogRecordData> and a delegate LogRecordProcessor as arguments. When FilteringLogRecordProcessor#onEmit is called, the implementation would: call delegate.onEmit(..) if predicate.test(logRecord) == true. The normal use would be be to pair FilteringLogRecordProcessor with a BatchLogRecordProcessor. I believe this would achieve the same effect as what you've shown in this PR.