feat(batcher): Add global flush trigger based on summed size estimates

[alexander-alderman-webb]

Description

Add a global size limit to trigger a batcher flush. This mirrors the per-bucket logic.

Adapt the test_weight_based_flushing() test which tests the per-bucket bytes limit to a test which tests the global bytes limit. Also add the test_capture_after_length_based_flushing() to ensure accurate bookkeeping to track the total estimated size of spans in the batcher.

Issues

Closes #7137

Reminders

• Please add tests to validate your changes, and lint your code using uv run ruff.
• Add GH Issue ID & Linear ID (if applicable)
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community

[github-actions]

Codecov Results 📊

✅ 99536 passed | ⏭️ 6623 skipped | Total: 106159 | Pass Rate: 93.76% | Execution Time: 348m 56s

📊 Comparison with Base Branch

Metric	Change
Total Tests	📈 +30
Passed Tests	📈 +30
Failed Tests	—
Skipped Tests	—

All tests are passing successfully.

✅ Patch coverage is 88.89%. Project has 2500 uncovered lines.
❌ Project coverage is 90.01%. Comparing base (base) to head (head).

Files with missing lines (1)

File	Patch %	Lines
sentry_sdk/_span_batcher.py	88.89%	⚠️ 1 Missing

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
- Coverage    90.02%    90.01%    -0.01%
==========================================
  Files          193       193         —
  Lines        25014     25020        +6
  Branches      9032      9032         —
==========================================
+ Hits         22516     22520        +4
- Misses        2498      2500        +2
- Partials      1435      1436        +1

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[sentry-warden]

Global byte limit tests hardcode span size assumption without dynamic measurement

Hardcoding GLOBAL_MAX_BYTES_BEFORE_FLUSH = 2_000 relies on a specific bare span size that varies with runtime environment; the test should dynamically compute span size like the adjacent test_weight_based_flushing_by_attribute_size.

Evidence

• SpanBatcher._estimate_size() computes size from runtime attributes such as sys.argv length, installed integrations, and span metadata, making a bare span's size environment-dependent.
• The neighboring test_weight_based_flushing_by_attribute_size avoids this exact fragility by calling SpanBatcher._estimate_size(bare_span._to_json()) before setting the flush limit.
• Both test_global_length_based_flushing (line 344) and test_total_size_reset_after_length_based_flushing (line 379) assume a span size between 1,000 and 2,000 bytes. If the actual estimate falls outside this range, the global flush will not trigger as expected and the assertions will fail.

_{Identified by Warden · find-bugs · GYU-MGF}