A backend worker died under load after a notifying POST (blocking calls in async handlers?) #841
Closed
opened 2026-09-26 14:38:45 +00:00 by claude-bot
·
7 comments
No Branch/Tag specified
main
feat/1328-fill-it-in
feat/1328-fill-frontend
feat/1328-fill-backend
feat/9-foundry-push
fix/9-foundry-live
feat/9-foundry-push-frontend
renovate/celery-5.x
feat/5-foundry-connect
feat/9-foundry-push-backend
feat/9-foundry-push-module
feat/5-foundry-frontend
feat/5-foundry-backend
feat/5-foundry-module
release/v4.8.0-rc1
docs/d341-convert-draft
feat/958-update-to-version
feat/958-convert-sheet
feat/958-pathbuilder-import-frontend
fix/1360-heading-order
feat/958-pathbuilder-import-backend
feat/11-weekly-digest
feat/1341-auto-update
docs/d332-superseded
chore/1345-names-cleanup
feat/1342-mentioned-pages
feat/1328-recipes
fix/1346-pgdg-key
perf/1247-shared-recording-stream
chore/132-gitleaks-allowlist
release/v4.7.1
spike/foundry-module
release/v4.7.1-rc1
docs/decisions-d332-d337
fix/bot-certifi
chore/release-4.7.0
chore/release-4.7.0-rc4
chore/deps-4.7.0
chore/release-4.7.0-rc3
fix/1280-quote-must-say-it
fix/1257-names-row-squeeze
chore/release-4.7.0-rc2
fix/1245-pg-upgrade-count
chore/release-4.7.0-rc1
feat/1257-names-in-prep
feat/1257-be
feat/1257-fe
feat/1257-rating-fixes
design/1328-fill-it-in
feat/1257-name-splits
fix/1326-redis-503
feat/1280-fact-suggestions
feat/1280-be
feat/1280-fe
design/1280-fact-suggestions
feat/1279-infobox
feat/1279-be
feat/1279-fe
feat/1321-shelf-copies
design/1279-infobox
feat/1243-table-find
feat/1257-who-rated
feat/1243-prep-drawer
feat/1243-sheet-pickers
design/1243-browse-in-place
feat/1315-hotwords-default
feat/1242-system-filters
feat/1257-more-name-styles
feat/506-leg3-hotwords
design/1242-system-filters
fix/1302-packs-polish
feat/1241-rules-library
design/1241-rules-library
feat/1245-postgres-18
integ/4.6.2
fix/1263-map-ui-2
fix/1263-map-server
fix/1263-map-ui-1
fix/1261-editor-link-menu
fix/1229-axe-4.14-name-mismatch
renovate/axllent-mailpit-1.x
renovate/eslint-monorepo
renovate/authlib-1.x
chore/release-4.6.0
chore/release-4.6.0-rc2
fix/460-rc2-screens
fix/460-rc2-server
fix/release-prerelease-exit
chore/release-4.6.0-rc1
feat/125-campaign-templates
feat/126-calendar
feat/1181-pictures-and-files
feat/1190-event-people
integ/4.6.0
feat/1191-line-of-the-night
feat/1200-starter-packs
chore/bot-multidict-and-playwright-group
fix/1202-this-week-answered-count
fix/122-124-leftovers
fix/1178-get-routes-that-write
fix/1203-journeys-check-names
design/125-campaign-templates
feat/126-calendar-engine
design/126-in-world-calendar
fix/1189-cited-stamp-in-range
fix/1189-v4-looser-check
fix/1189-richer-beats
fix/1113-export-bind-lists
fix/1154-release-notes-by-file
chore/release-4.5.0
chore/release-4.5.0-rc12
fix/1135-wiki-markup-as-text
fix/demo-usage-cost-in-window
chore/release-4.5.0-rc11
fix/1121-sheet-consistency
fix/1121-sheet-5e-terms-and-card-hp
copy/1122-busiest-pages
fix/1121-relevant-choices
fix/1121-wiki-create-npc-save-sheet-links
fix/1029-menu-stays-on-screen
docs/prototype-transcript-bin-wording
fix/1023-editor-save-row-back-scroll
fix/1020-search-exact-first
fix/1020-table-prep
fix/1020-shell-wordmark-footer-bell
fix/1020-wiki-article-party
fix/872-admin-kept-until-phone-tables
feat/l13-milestone-level-waiting
fix/1000-1001-bell-older-setup-context
fix/999-pronouns-in-prompts
fix/l19-other-class-feats
fix/1010-transcript-window-ordinary-confirm
docs/d254-d269-decisions
fix/702-member-search
fix/680-transcript-bin
fix/993-unidentified-prompts
fix/841-redis-timeouts
fix/990-binned-not-exported
fix/830-export-prep-shelf
fix/deps-audit-2026-10-01
fix/877-title-reads
fix/798-audio-received-at
build/lane11-17-j7
build/lane11-16-levelup
build/lane11-14-seams
build/lane11-14-seed
build/lane11-15-start
build/lane11-13-old-block-out
fix/980-review-r3
build/lane11-12-block
build/lane11-8-packs
fix/demo-seed-canonical-names
build/lane11-11-hot-half
docs/l11-decisions
build/lane11-7-convert
build/lane11-10-editing
fix/npm-audit-brace-expansion
build/lane11-9-sheet-page
fix/bot-pyjwt
build/lane11-6-content
fix/lane11-rank-names
build/lane11-2b-language
build/lane11-4-js-evaluator
build/lane11-3-server
build/lane11-5a-pf2e
build/lane11-5b-5e
feat/design-admin
build/lane11-2-evaluator
build/lane11-1-sheet-pieces
build/lane11-0-drawing
fix/943-quest-objectives-fk
fix/prepsheet-shelf-flake
fix/945-leftovers
build/demo-gm-copy
fix/901-email-landings
build/lane10-8-journeys
build/demo-seed-lanes-8-10
fix/887-gm-own-confirmation
build/lane9-5-j1-admin
fix/918-audience-click
fix/useasync-overtaken
ci/939-critical-path
test/937-backend-suite-speed
chore/claude-orchestration
fix/924-xp-gm-only
fix/session-stale-poll
docs/decisions-d239-d242
fix/930-pypdf
build/lane8-journeys
build/925-quest-editor
fix/894-private-page-pictures
build/lane8-p4-drafts
build/lane8-p7-map
build/lane8-p6-handouts-rules
fix/wiki-fixture-names
build/lane10-d227-test-usage
fix/rsvp-horizon-test-tuesday
fix/media-volume-owner
build/lane8-p3-editor
fix/912-unidentified-rename
build/lane8-p5-party-quests
build/lane8-handout-takeback
build/lane10-pickers
build/lane8-p2-article
build/lane8-6-map
build/lane10-7b-email-pages
build/lane8-5-handouts
build/lane10-7a-test-the-bot-pages
build/lane8-p1-pages
build/lane8-4-quests
build/lane8-2b-feeds
build/lane8-3-parties
build/lane8-2a-links
build/lane10-5-commands
build/lane9-6-seed
build/lane10-4b-reactions
build/lane9-4d-pages
build/lane9-4c-pages
build/lane10-4a-posts
build/lane10-3-email
fix/891-web-fonts
build/lane9-4b-pages
build/lane10-6-test-the-bot
build/lane10-2-notify-out
build/lane8-1-wiki-text
build/lane9-4a-frame
design/lane10-drawings
fix/j6-budget
fix/j5-phone-flake
fix/869-test-leaks
fix/843-record-start-followups
build/lane7-all
build/lane6-all
build/lane9-b2-server
chore/changelog-fragments
docs/decisions-d218
build/lane9-a-owner-overview
fix/rule-card-level-label
fix/834-retention-semantics
fix/o3c-record-without-announcement
docs/decisions-d179
docs/decisions-d131-d170
fix/851-commit-before-response
build/lane6-j3-seed
build/lane9-b1-d67-identity
fix/841-blocking-loop
build/lane9-c-backups-audit
fix/vote-race-and-start-commit
fix/recording-announcement
fix/proposal-read-leak
fix/last-admin-guard
build/lane6-p4c-planning
build/lane6-p4b-margin
build/lane6-p4a-sheet
build/lane5-j4-seed
build/lane6-base
build/lane7-pages-talk
build/lane5-pages
build/lane7-pages-safety
build/lane7-p3-safety
build/lane7-p2-notify
build/lane6-p3-planning
build/lane6-p2-history
build/lane6-p1b-items
build/lane7-p1-threads
build/lane5-p6-faces
build/lane6-p1a-sheet
build/lane5-p5-find
build/lane5-p4a-board
build/lane5-p4b-scenes
build/lane5-p3-live
build/lane5-base
build/lane5-p2-cards
docs/lane5-decisions
build/review-r2-wide
fix/review-r1
build/lane5-p1-scenes
build/demo-seed
build/lane4-journeys-j5
build/lane4-page-review-b
build/lane4-page-review-a
build/lane4-page-read
build/lane4-journeys
build/lane4-page-sess2
build/lane4-page-sess1
build/lane4-notes
build/lane4-discord-on-approval
build/lane4-scheduling
build/lane4-versions
build/760-session-number
build/lane4-decisions
build/797-erase-no-regenerate
build/test-race-audit
build/lane3-completions
build/794-dark-only
build/796-titles-scroll
build/791-retention-anchor
build/a11y-sweep
build/shell-followups
build/retention-preview
build/753-backup-readback
docs/d91-d93
build/lane3-j1
build/ci-harness-paths-selftest
fix/useauth-test-race
build/ci-harness-paths
build/777-ai-settings-read
build/lane3-settings-c
build/lane3-settings-b
build/lane3-j6
build/lane3-sessionform
build/lane3-settings-a
build/lane3-members
build/lane3-thisweek
build/lane3-story
chore/87-align-python-3.12
v4.8.0-rc1
v4.7.1
v4.7.1-rc1
v4.7.0
v4.7.0-rc4
v4.7.0-rc3
v4.7.0-rc2
v4.7.0-rc1
v4.6.2
v4.6.2-rc4
v4.6.2-rc3
v4.6.2-rc2
v4.6.2-rc1
v4.6.1
v4.6.1-rc1
v4.6.0
v4.6.0-rc2
v4.6.0-rc1
v4.5.3
v4.5.3-rc1
v4.5.2
v4.5.2-rc1
v4.5.1
v4.5.1-rc2
v4.5.1-rc1
v4.5.0
v4.5.0-rc12
v4.5.0-rc11
v4.5.0-rc10
v4.5.0-rc9
v4.5.0-rc8
v4.5.0-rc7
v4.5.0-rc6
v4.5.0-rc5
v4.5.0-rc4
v4.5.0-rc3
v4.5.0-rc2
v4.5.0-rc1
v4.4.1
v4.4.0
v4.3.0
v4.2.3
v4.2.2
v4.2.1
v4.2.0
v4.1.2
v4.1.1
v4.1.0
v4.0.1
v4.0.0
v3.11.4
v3.11.3
v3.11.2
v3.11.1
v3.11.0
v3.10.0
v3.9.1
v3.9.0
v3.8.0
v3.7.0
v3.6.1
v3.6.0
v3.5.0
v3.4.1
v3.4.0
v3.3.0
v3.2.0
v3.1.0
v3.0.0
v2.1.0
v2.0.0
v1.1.0
v1.0.0
v0.12.0
v0.11.0
v0.10.0
v0.9.1
v0.3.3
v0.9.0
v0.8.0
v0.3.2
v0.3.1
v0.3.0
v0.7.0
v0.6.0
v0.5.0
v0.4.0
v0.2.1
v0.2.0
v0.1.1
v0.1.0
Labels
Clear labels
backend
Issue related to the backend
bot
Issue related to the bot
bug
Something is not working
duplicate
This issue or pull request already exists
enhancement
New feature
frontend
Issue related to the frontend
help wanted
Need some help
invalid
Something is wrong
question
More information is needed
recording
Issue related to the recording system
security
Security hardening / vulnerability work
wontfix
This won't be fixed
No labels
backend
bot
bug
duplicate
enhancement
frontend
help wanted
invalid
question
recording
security
wontfix
Milestone
Clear milestone
No items
No milestone
Projects
Clear projects
No items
No project
Assignees
Clear assignees
No assignees
1 participant
Notifications
Due date
The due date is invalid or out of range. Please use the format "yyyy-mm-dd".
No due date set.
Dependencies
No dependencies set
Reference
rbrooks/Quest-Board#841
Loading…
Reference in a new issue
No description provided.
Delete branch "%!s()"
Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?
Seen twice during lane 7's journey runs (#733) on a loaded machine, where another stack was using about 2 GB of Docker's 7 GB. A backend worker died ("Child process died", then an nginx 502) right after a POST that notifies: a discussion reply, and a session confirm.
Uvicorn 0.52's 5-second worker health check killed a worker whose event loop had blocked. The suspicion is synchronous Celery
.delay()or Redis calls made inside async request handlers on the notify path. Under load, these block the loop past the health-check window.A related symptom: J1's keyboard project began losing an Enter while a page was still arriving, 2 of 5 runs after lane 7, where it had been 6 of 6 before. The test now waits for the heading, which may be hiding an app-side race.
To do:
enqueue, and Redis publishes;run_in_threadpoolor an async client;Refs #733, #726.
Seen again (2026-09-26), in J4 phone's Notes step during lane 7's integration run. Three session-page requests all came back 502 at the same moment, after about 5.5 s. That matches a worker death. Backend memory in the next run was sampled at about 345–352 MiB of the container's 512 MiB limit, so running out of memory is also possible, alongside the 5 s health check. The final run, with nothing else on Docker, was green.
Picking this up (2026-09-26) on
fix/841-blocking-loop. Evidence first:Then a single off-loop helper for Celery publishes and sync Redis, plus a regression guard.
Findings (2026-09-26). The fix for the real blocking is in #850; the worker kills are still unexplained.
1. A blocked loop can't trip uvicorn's health check.
supervisors/multiprocess.py), the health-check pong is answered by a separate thread (always_pong), not the event loop. The parent polls each worker with a 5 s timeout and logs "Child process [pid] died" when it kills one. That same line is logged for any death.--workers 2:time.sleep(12)in anasync deffreezes the loop but releases the GIL. It was not killed.2. The best hypothesis for the kills (medium confidence, not reproduced): memory stalls in the Docker VM.
oom_kill 0since boot.fullat 657 s.Follow-ups, not done:
UVICORN_TIMEOUT_WORKER_HEALTHCHECK=15and/or moremem_limitfor the backend (it's 512m). Sampledocker statsand/proc/pressure/memoryduring a journeys run to confirm.app/redis_pool.py, the ad-hocaioredis.from_urlcalls) have no socket timeouts. A paused Redis hangs that request indefinitely (not the loop).notify()could stop enqueueing further recipients after the first broker failure. Each one still costs up to ~8 s during an outage, now off the loop.Leaving this open for the kill hypothesis and the follow-ups.
Picking up two of the follow-ups (1 Oct), on
fix/841-redis-timeouts:app/redis_pool.py, with every ad-hocfrom_urlsite converted. Blocking reads (pub/sub, stream consumers) keep no read timeout or a longer one, and a timeout takes the same path a Redis outage already does at each site.notify()stops enqueueing after the first broker failure in one call, while still writing every in-app row and without letting one bad payload stop the others.Not doing, because they are the owner's call: the backend's
mem_limit(512m indocker-compose.yml) and uvicorn's worker health-check timeout. The worker kills have not been seen since the CI runner's capacity was raised on 29 Sep; today's eight full CI runs were all green. If they stay away, the remaining hypothesis (memory stalls in a contended Docker VM) is an environment matter, and this issue can close when these two land.Correction to my last comment: "eight full CI runs, all green" overstated it. Today's count, checked: four PR runs green (#986, #987, #989, #992) and two of main's push runs green (after #987 and #989); main's run after #986 was cancelled when the next push superseded it, and one is running now. No worker deaths in any of them. The scheduled Dependency Audit did fail this morning, for unrelated reasons (#995).
The two code follow-ups are merged in #1002 (1 Oct, main
c95fe032):app/redis_pool.py): 2 s to connect, 10 s for a reply. Ten and not two because on an async client the wait is measured on the event loop, so a loop stall would otherwise fail session lookups. The live recording-status stream, the one blocking reader, keeps no read timeout. A guard test fails if a module builds a Redis client without them.notify()stops enqueueing after the first broker connectivity failure in a call, still writes every in-app row, and doesn't let one bad payload stop the others.What is left is the owner's: whether to raise the backend's
mem_limit(512m indocker-compose.yml) or uvicorn's worker health-check timeout. The kills this issue was opened for haven't been seen since the CI runner's capacity was raised on 29 Sep. Leaving this open for that call.Closing, by the owner's answer to Q160 (O35), 2026-10-05: "Close it: it has not come back."
Reopen if a backend worker dies under load again.