Enable otlp logs by default

[jack-berg]

Related to #5340.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (47ee573) 91.30% compared to head (63dcadc) 91.31%.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #5433   +/-   ##
=========================================
  Coverage     91.30%   91.31%           
- Complexity     4887     4889    +2     
=========================================
  Files           548      548           
  Lines         14404    14409    +5     
  Branches       1353     1354    +1     
=========================================
+ Hits          13152    13158    +6     
+ Misses          867      866    -1     
  Partials        385      385           

Impacted Files	Coverage Δ
.../autoconfigure/LogRecordExporterConfiguration.java	100.00% <100.00%> (+6.06%)	⬆️

... and 1 file with indirect coverage changes

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[jkwatson]

This is an interesting one. My guess is, that most people already have existing logging solutions that are already working, that they won't want to have to manually disable OTLP logs on their apps. This will only be a good experience for people who have a collector/backend that has log ingest enabled. We should be ready to revert this, based on user feedback.

[jack-berg]

I think this should be enabled by default because:

• The spec says we should and that section of the spec is stable.
• Enabling otlp by default just means that log records passed through the SdkLoggerProvider are exported by default. A user of autoconfigure still has to wire SdkLoggerProvider into their log appender.
• Its users of the agent that may already have log solutions and therefore not want OTLP logs by default. The agent is one of the main consumers of autoconfigure so maybe its typical use cases should influence the defaults of autoconfigure? I don't think so. If we find that most agent users don't want otel logs, we could change its behavior to not install the log appenders by default. So keep otlp as the default for SdkLoggerProvider, but stop application logs from flowing into SdkLoggerProvider.
• Events also flow through SdkLoggerProvider.

[Izzzu]

Hi!
I just came across this PR looking for an explanation why OTEL_LOGS_EXPORTER is not by default "otlp" as mentioned on this documentation page. It appears as one of the first in the search. Since this documentation does not mention any specific sdk it seems to be a contract description for any sdk, including java.

So from the user experience I think it would be helpful to have the default logs exporter set to "otlp" as it's consistent with the metrics and traces exporters and aligned across the docs.