fix: handle missing description key in MN+1 DB span detector#119488
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billyvg wants to merge 1 commit into
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fix: handle missing description key in MN+1 DB span detector#119488billyvg wants to merge 1 commit into
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Downsampled spans do not always include a 'description' field, causing KeyError crashes (335K occurrences, Fixes SENTRY-5QVD). Co-Authored-By: Claude <noreply@anthropic.com>
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Scope: Backend
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Problem
ContinuingMNPlusOne._maybe_performance_problem()crashes withKeyError: 'description'when processing downsampled spans that don't include adescriptionfield.This has been firing at high volume in production: 335K total occurrences (44K in the past 24h), all from
spans.consumers.process_segments.process_segment. Sentry issue: SENTRY-5QVD.The error manifests as a logged exception ("Failed to detect performance problems") caught in
performance_detection.py:141, so it silently skips performance problem detection for affected spans.Root cause
The event data from the local variables in the Sentry issue shows spans with
"downsampled_retention_days"set but nodescriptionkey — evidence that downsampled spans may omit optional fields. Two call sites accesseddb_span["description"]directly:desc=db_span["description"](line 258)get_notification_attachment_body("db", db_span["description"])(line 283)Fix
Switch both accesses to
.get("description", ""). All other span dict accesses in this file already use.get()safely.Evidence / Reasoning
From the Sentry event's local variables:
The
descriptionfield is missing from downsampled spans, confirming this is a data-shape issue rather than a logic bug. The fix is minimal and defensive.Claude session: https://claude.ai/code/session_014nmqRhMsbDqY6YwD21UA8e
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Look, I get it. The entity doing business as "Sentry" was incorporated in the State of Delaware in 2015 as Functional Software, Inc. and is gonna need some rights from me in order to utilize my contributions in this here PR. So here's the deal: I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Sentry can use, modify, copy, and redistribute my contributions, under Sentry's choice of terms.
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