feat(span-first): Better span first estimates

[sentrivana]

We were underestimating the size of spans with particularly bulky attributes, and flushing the buffer too late as a result. Take attribute size into account for estimating.

[github-actions]

Semver Impact of This PR

🟡 Minor (new features)

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[github-actions]

Codecov Results 📊

✅ 13 passed | Total: 13 | Pass Rate: 100% | Execution Time: 7.20s

📊 Comparison with Base Branch

Metric	Change
Total Tests	—
Passed Tests	—
Failed Tests	—
Skipped Tests	—

✨ No test changes detected

All tests are passing successfully.

❌ Patch coverage is 0.00%. Project has 14775 uncovered lines.
✅ Project coverage is 29.96%. Comparing base (base) to head (head).

Files with missing lines (1)

File	Patch %	Lines
_span_batcher.py	26.51%	⚠️ 61 Missing

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    25.16%    29.96%     +4.8%
==========================================
  Files          190       190         —
  Lines        21088     21094        +6
  Branches      6884      6888        +4
==========================================
+ Hits          5306      6319     +1013
- Misses       15782     14775     -1007
- Partials       432       477       +45

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Generated by Codecov Action

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

Bugbot Autofix prepared a fix for the issue found in the latest run.

• ✅ Fixed: Estimate ignores attribute key name length entirely
  • Updated _estimate_size to iterate attribute items and include key length plus a realistic per-attribute serialization overhead, eliminating the key-name underestimation gap.

Or push these changes by commenting:

@cursor push 829ce915e2

Preview (829ce915e2)

diff --git a/sentry_sdk/_span_batcher.py b/sentry_sdk/_span_batcher.py
--- a/sentry_sdk/_span_batcher.py
+++ b/sentry_sdk/_span_batcher.py
@@ -94,8 +94,8 @@
         # 210 is the rough size of the payload without attributes, and then we
         # estimate the attributes separately.
         estimate = 210
-        for value in item._attributes.values():
-            estimate += 7
+        for key, value in item._attributes.items():
+            estimate += 40 + len(key)
 
             if isinstance(value, str):
                 estimate += len(value)

_{This Bugbot Autofix run was free. To enable autofix for future PRs, go to the Cursor dashboard.}