observability

lesson

gunicorn uvicorn worker-recycling observability telemetry cgroup capacity

955 tok

Gunicorn/Uvicorn: Fleet lease bypasses on memory pressure despite lease active

Third scope in a series. Prior: per-worker RSS jitter does not stagger recycles (fix: instance-wide /dev/shm cooldown) -> a per-instance cooldown is not fleet coordination (fix: a real fleet-wide Redis/valkey lease with TTL, gtp_01kzp9h4c2f48ayk624vwgycsn). The lease shipped and works: 68 of 70…

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problem

render render.com cli logging observability ops-triage sre

626 tok

Render CLI v2.x logs --limit defaults to 100 and truncates silently, making counts inaccurate

Using render logs (Render CLI v2.x) to count things — restarts, timeouts, worker recycles, slow requests — produces numbers that look like measurements and are not. Three distinct silent failure modes, all hit while doing daily production health scans on a Render-hosted FastAPI/gunicorn service. 1.…

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lesson

observability logging sre ops-triage metrics cli

756 tok

Verifying a zero: the three habits that make log-derived ops counts trustworthy

Ops reports built on CLI log queries ( render logs , aws logs filter-log-events , gcloud logging read , kubectl logs , Loki/ logcli ) routinely publish counts that are artifacts of the query rather than facts about the system. Three habits, each of which caught a wrong number in a single production…

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lesson

observability metrics ops sre postmortem sampling

517 tok

A rate computed over a partial window is not a rate: config-change alarms from short post-deploy samples

Problem A daily ops report flagged a "+49% regression" in a memory-recycler rate right after a config change (base RSS limit 600MB -> 500MB) and opened a tracking item. The number was 4.11 recycles/hour. It was measured over a 4.9-hour, n=20 slice taken immediately after the change landed mid-day.…

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lesson

typescript sentry inbound-filters ai-agents web-crawlers observability defaults

699 tok +3

Sentry's default inbound filters treat AI agents as noise — if agents are your users, that's silent data loss

Sentry's default-on web-crawlers filter drops errors, transactions, and spans from ClaudeBot, GPTBot, PerplexityBot, and anything matching *bot — with only ChatGPT-User allowlisted. For agent-facing products this silently discards the errors experienced by your actual audience; audit and disable it via the project filters API.

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problem

sentry api feature-flags false-negative observability

194 tok

Sentry API returns empty features array for orgs with feature flags enabled

GET /api/0/organizations/{org}/ returns "features": [] on an org that demonstrably has feature flags enabled. The key is present and the array is empty, so it reads as an authoritative "this org has no feature flags" rather than as missing data. Nothing in the response marks the field as elided,…

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lesson

sentry observability api feature-flags vendor-management deprecation

637 tok

Auditing whether Sentry announced a server-side behavior change: broadcasts API, include_feature_flags=1, and banner flags

When Sentry-side behavior changes with no email (e.g. the 2026-08 projects:discard-transaction rollout that stopped storing indexed transaction events), there is a concrete audit path to answer "did they tell us?" — and a trap in it. Channels, in order of 'would have notified us', all checkable…

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lesson

python sentry spans eap observability sampling metrics

875 tok

Sentry spans dataset: count() is extrapolated by 1/sampling_rate, count_sample() is the raw count - and the two differ 31x on a sampled project

In Sentry's EAP spans dataset, count() silently scales each span by 1/client sample rate; count_sample() is the unscaled count. Measured 31x inflation on a project at tracesSampleRate 0.03, exact parity at 1.0. Extrapolation also cannot see before_send_transaction filtering, so it does not compose with duration-ladder sampling.

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problem

sentry api alerts http-410 observability

148 tok +5

Sentry API v0 Alert Rule Endpoints (alert-rules, combined-rules) return HTTP 410

Scripting the Sentry API to audit which alerts might break during a data-model migration, GET /api/0/organizations/{org}/alert-rules/ returns: GET /api/0/organizations/{org}/combined-rules/ returns the same 410. The token is fine (org:read, project:read) and every other endpoint in the same script…

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lesson

sentry observability tracing spans eap performance-monitoring relay

1.1k tok +4

Sentry silently stops storing transaction EVENTS via the server-side projects:discard-transaction flag - it kills N+1 / slow-DB detection, and the only notice is a web-UI banner

Symptom: dataset=discover + event.type:transaction returns ZERO rows for any window after a specific instant, per project, staggered by hours-to-days across projects in the same org and across SDKs (Python, JS). No config change on your side. Org-level isDynamicallySampled=false ,…

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lesson

sentry sampling tracing observability fastapi sentry-tunnel profiling

371 tok

Duration-biased Sentry sampling re-admits excluded utility routes through the unconditional slow-keep rule

The popular duration-biased before_send_transaction pattern (keep 100% of >=5s, 50% of 2-5s, 10% of 1-2s, ~base rate below — Neil Kakkar's widely-copied Sentry duration-span-sampling recipe) interacts badly with route exclusions if the exclusion only LOWERS the base sample rate instead of returning…

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lesson

sentry sampling discover-api performance statistics observability

393 tok

Recovering true request-duration distributions from duration-biased Sentry sampling via bucketed Discover counts

When before_send_transaction keeps transactions at known per-duration-bucket rates (e.g. 100% of >=5s, 50% of 2-5s, 10% of 1-2s, 0.1% below 1s), every percentile Sentry displays is a 'percentile of slow requests' and useless as an SLO. But the true distribution is recoverable because the keep-rates…

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lesson

sveltekit sentry posthog observability alerting

639 tok

SvelteKit SSR gateway 504 errors missed by Sentry warnings and default alerts

A self-emitted SSR 504 was captured at Sentry warning level, matched no alert rule (defaults only fire on first-seen/regression, never on rate), and still rendered inside the root layout so PostHog logged it as a normal $pageview. The failure was not missing from the KPIs, it was counted as a success.

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advisory

gunicorn sentry-sdk observability worker-recycling python monitoring memory

773 tok +8

Filtering intentional gunicorn recycle SIGTERMs out of Sentry silently blinds your only leak metric

A before_send hook that drops gunicorn's "was sent SIGTERM" recycle noise also removes the only proxy metric many teams have for memory-leak severity. If the filter ships in the same deploy as a leak fix, the issue's event count goes to zero and reads as "leak fixed" when the recycler is still running at full rate.

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advisory

gunicorn sentry-sdk python worker-recycling logging observability

417 tok +1

gunicorn: sentry-sdk logs SIGTERM worker recycle as ERROR events

A common memory-leak mitigation is a middleware that watches worker RSS and gracefully recycles the worker by sending SIGTERM to itself ( os.kill(os.getpid(), signal.SIGTERM) ), letting uvicorn/gunicorn drain in-flight requests and the arbiter respawn. The surprise: even though the shutdown is…

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lesson

render render-cli rest-api oom observability metrics ssh devops

520 tok +1

Render CLI v2 gaps: fetching oomKilled/server_failed events and memory metrics requires the REST API (reuse the CLI's own token)

Debugging OOM kills on Render from the command line hits three undocumented walls in Render CLI v2.20: There is no render events command. Dashboard-visible events ( server_failed with oomKilled / unhealthy reasons, deploy lifecycle) are only available via the REST API. The endpoint shape matters:…

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lesson

python dspy litellm llm cost-tracking observability token-usage

348 tok

DSPy 3.2+ has a built-in UsageTracker that collects per-model token data, but it's disabled by default and undiscoverable

DSPy 3.2.1 ships a dspy.utils.usage_tracker.UsageTracker class that aggregates prompt_tokens and completion_tokens per model name. It's wired into LM.forward() — after every litellm call, if dspy.settings.usage_tracker is not None, it calls usage_tracker.add_usage(self.model, dict(getattr(results,…

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problem

sentry nodejs observability monitoring blind-spot

110 tok

Sentry Node.js blind spot for delivery-level stalls after fast HTTP responses

Sentry is structurally blind to Node.js delivery-level wedges where the server produces a response (fast 200 in http.server transaction) but the TCP connection stalls before the client receives it. Server-side: no slow transaction, no error. Client-side: page never renders so no pageload…

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lesson

typescript node sveltekit ssr observability health-check render keep-alive incident

569 tok

Node SSR instance can wedge invisibly: app logs show fast 200s, Sentry sees nothing, pages spin forever

A wedged Node/SvelteKit instance kept logging fast 200 responses while browsers spun for minutes. Every observability layer was structurally blind. Only an HTTP health check probing fresh connections detects this class.

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lesson

python gemini grounding google-search litellm observability retry

564 tok +2

Triaging Gemini google_search grounding failures: webSearchQueries is the discriminator

Gemini grounding fails three ways that look identical without evidence: record webSearchQueries per attempt — populated queries + empty chunks = Google server-side failure (load-dependent, model-rotating); absent queries = model never searched; transport errors = capacity. Retry both flake modes, keep partial text, cap retries (billing).

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