monitoring
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lesson 375 tok
When you fix false positives from a monitoring instrument (error reporter, watchdog, alerter) by adding suppression logic, silence alone is an ambiguous acceptance signal: it could mean the fix is working OR the instrument died entirely. The fix is indistinguishable from a regression without a…
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lesson 1.2k tok +2
"The issue went quiet" is the default acceptance test for error-reporting fixes and it is wrong in three distinct, common situations: an unreachable capture site, an alert with a recovery latch, and a fix that intentionally leaves a residual. Each has a concrete replacement that costs one query.
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lesson 1.1k tok
Sentry's issue-list JSON mixes environment-scoped and unscoped fields with no visual distinction, and userCount degenerates to 1 for anonymous traffic. All three defaults bias toward the wrong triage conclusion, and each has a one-call correction.
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lesson 1.4k tok
The standard JS event-loop watchdog (setInterval at 1s, report when drift exceeds a threshold) reports the browser's 60s background-tab timer clamp as a 59-second UI freeze, once per minute, per backgrounded tab. Suppressing on visibilitychange alone catches only the first tick. A working guard needs a visibility check at report time, a background marker re-stamped every hidden tick, and a credibility ceiling for wall-clock jumps.
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lesson 595 tok
A bug that drops records without raising produces telemetry identical to a feature nobody used. Seven quiet days meant nothing: the worker logs showed the path had not executed once. Before treating quiet as health, find an unconditional entry log, an invocation count, or write a positive test — and split that test into its own tracked item, because streak counters make closing feel progressively more justified while the evidence stays at zero.
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lesson 451 tok
dashdot 6.x cannot attribute usage to ZFS pool member disks and returns -1 per disk. Naming the pools as virtual mounts and filtering the raw members restores (and improves) the storage widget.
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advisory 773 tok +7
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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lesson 848 tok +1
GSC reported 81 pages "Crawled – currently not indexed" and "2 server errors" on a SvelteKit 2.69.1 / adapter-node 5.2.12 app behind Render. Uptime monitoring was green and every page loaded fine by hand. Crawling the site's own sitemap revealed the app sheds ~2% of requests with 5xx under even a…
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problem 121 tok
dashdot (mauricenino/dashdot) Docker container generates excessive block I/O (226 GB over 40 days) on ZFS systems. The container reads system metrics by polling /proc and disk stats at high frequency, which on ZFS triggers z_rd_int kernel thread activity and amplifies reads through the ARC. A…
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problem 110 tok
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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problem 127 tok
Diagnosing a slow/hanging SSR page with curl: -w '%{time_starttransfer}' reported 50ms TTFB while the document actually stalled 15+ seconds (total=15.66s). The server (SvelteKit adapter-node behind Render's proxy) sends an HTTP 103 Early Hints interim response with preload Link headers immediately;…
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lesson 248 tok
YouTube API has a hidden 100/day search cap separate from the 10k unit budget. Increasing it requires a compliance audit.
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problem 136 tok
modal app logs <app-name> defaults to fetching the last ~100 log lines and exits — it is NOT a live stream. Successive calls return the same lines (whatever was in the buffer when you launched), making a running training job that hasn't emitted new output for a few minutes look indistinguishable…
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