Allow BatchSpanProcessor to send early when a full batch is ready

[RafalSumislawski]

Which problem is this PR solving?

The BatchSpanProcessor waits scheduledDelayMillis (5000 by default) since the arrival of the first span, or since the last export before exporting. It never exports more than one batch of maxExportBatchSize (512 by default). If there's more than 512 spans produced per 5000 seconds the surplus starts building up in the queue, until it overflows and starts dropping spans. Which is observable though these logs: Dropped 2576 spans because maxQueueSize reached

Short description of the changes

In comparision Java's BatchSpanProcessor also uses a configured delay and batch size, but will send the batch as soon as sufficient number of spans is enqueued (https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk/trace/src/main/java/io/opentelemetry/sdk/trace/export/BatchSpanProcessor.java#L244). Therefore the delay doesn't limit the maximum throughput.

This PR implements similar logic in JS's BatchSpanProcessor.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• I've adapted all the relevant unit tests to this new behaviour
• I've run a nodejs lambda which produces ~10k spans in ~20s and observed spans dropped before the changes and no spans dropped after the changes.

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: RafalSumislawski / name: Rafał Sumisławski (6cbbce3)

[Flarna]

There seem to be a related issue #3094 and some similar PRs: #3458 #3828

fyi @seemk @dyladan

[codecov]

Codecov Report

Merging #4164 (13c66b8) into main (2499708) will increase coverage by 1.73%.
The diff coverage is 93.54%.

❗ Current head 13c66b8 differs from pull request most recent head 6cbbce3. Consider uploading reports for the commit 6cbbce3 to get more accurate results

@@            Coverage Diff             @@
##             main    #4164      +/-   ##
==========================================
+ Coverage   90.52%   92.25%   +1.73%     
==========================================
  Files         159      329     +170     
  Lines        3757     9388    +5631     
  Branches      835     1997    +1162     
==========================================
+ Hits         3401     8661    +5260     
- Misses        356      727     +371     

Files	Coverage Δ
...dk-trace-base/src/export/BatchSpanProcessorBase.ts	92.36% <93.54%> (-0.56%)	⬇️

... and 176 files with indirect coverage changes

[github-actions]

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[github-actions]

This PR was closed because it has been stale for 14 days with no activity.