docs: graceful shutdown runs the drain and then the hooks on every engine; say what the deadline does (celeris#703, celeris#738) - #77
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…gine; say what the deadline does (celeris#703, celeris#738) The pages described the pre-#703 order per engine (hooks during the drain on epoll and io_uring), said a cancel behaves identically on every engine, called ShutdownTimeout the hook phase's budget, and cited the engine contract that remaining connections are closed at the deadline. Rewritten for celeris v1.6.0 from measurements: one order everywhere, one deadline for the drain and the hooks, nothing interrupts a handler at the deadline, std's cancel path does not keep to ShutdownTimeout (celeris#753). The readiness flip moves to the SIGTERM handler, calling Shutdown from a handler gets a pitfall, the listener is closed on a failed start (celeris#737), and graceful-shutdown.md cites server.go symbols instead of stale line numbers.
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. 📝 SummarySummary by CodeRabbit
WalkthroughThe documentation updates describe shutdown ordering, shared deadlines, HTTP/2 drain exceptions and deployment steps. They also revise listener ownership guidance and replace source line references with method names. ChangesGraceful shutdown guidance
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~20 minutes Change: Other Merge Risk: 🟡 Moderate · up to The shutdown guidance can mislead readers about unfinished requests, HTTP/2 responses, and how long std shutdown may take. The Kubernetes formula may allow the process to be force-stopped before a handler or hook finishes; correct these caveats before merging. Architecture SummaryArchitecture risk: 🔵 Low · up to The change affects 1 system. Changed systems: Architecture concerns Review detailsSystems and components
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…Shutdown that stopped it (celeris#703, celeris#738) Round 2 of the docs#77 review, for celeris#746's head 3d2ab72: - The rule "the hooks start after the requests in flight have finished" is scoped on every page. The drain does not wait for HTTP/2 streams on async routes (native engines) or for h2c on std (celeris#759), and epoll closes without flushing (celeris#760). A new section, "What the drain waits for", has the measurements. - Start and StartWithListener: the call returns after the Shutdown that stopped it, hooks included (celeris#746 round 2). The entry-point table, the Shutdown section, the hook rule and the pitfalls say so. The pitfalls add "wait for Shutdown" for older versions. - The FAQ's deadline answer is re-measured, with every call's return read as it happens. Round 1's probe read Start after Shutdown had returned, which made std look like it returned at the deadline. It also says epoll can cut a large response. - The quoted StartWithContext and OnShutdown godocs follow the new text.
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Review comments at @src/content/docs/deployment.md:
- Line 537: Update the source citation in the deployment documentation to point
to repository-root server.go instead of celeris/server.go, retaining the
StartWithContext symbol reference.
- Line 620: Update the shutdown sequence in the deployment documentation to
describe draining as an attempt bounded by ShutdownTimeout, not a guarantee:
requests still active when the deadline expires may not finish, and excluded
HTTP/2 streams are not awaited. Preserve the sequence in which OnShutdown hooks
run and the process exits.
- Line 622: Qualify the grace-period formula near ShutdownTimeout: state that
readiness delay plus ShutdownTimeout is sufficient only when every OnShutdown
hook honours ctx.Done(). For hooks that may continue afterward, include their
bounded completion time; require unbounded hooks to honour ctx.Done().
- Line 622: Qualify the shutdown sequence and terminationGracePeriodSeconds
formula in the deployment documentation for the std engine: note that a
cancelled StartWithContext may wait beyond ShutdownTimeout for active handlers,
and advise allowing additional grace-period time for them.
Review comments at @src/content/docs/getting-started.md:
- Around line 191-192: Update the shutdown comment around ctx and OnShutdown to
say hooks run after the request drain completes or its deadline expires, without
promising that all in-flight requests have drained.
- Around line 201-203: Update each shared-budget description for
Config.ShutdownTimeout to qualify that, on the std cancellation path, Listen may
wait for a handler beyond the timeout, allowing hooks and StartWithContext to
complete later.
Review comments at @src/content/docs/graceful-shutdown.md:
- Around line 661-662: Update the c.Context() cancellation statement in “What
the drain waits for” to distinguish engine behavior: on std, Engine.Shutdown
cancels the base context at the shutdown deadline, so handlers can observe
cancellation through c.Context().Done(); retain any limitation only for engines
where it applies.
- Around line 658-660: Qualify the response guarantee in the graceful-shutdown
documentation: async HTTP/2 streams on the native engines can have their
connections closed before the handler finishes, resulting in an unexpected EOF.
Preserve the existing description of other handlers and the epoll socket-buffer
limitation.
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These pages document the Celeris framework (goceleris/celeris, linked below).
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src/content/docs/configuration.mdsrc/content/docs/getting-started.mdsrc/content/docs/core-concepts.mdsrc/content/docs/deployment.mdsrc/content/docs/graceful-shutdown.md
🪛 LanguageTool
src/content/docs/graceful-shutdown.md
[typographical] ~72-~72: Conjunctions like ‘and’ should not follow semicolons. Consider using a comma, or removing the conjunction.
Context: ...not run it, or your hooks, a second time; and a Shutdown your code calls after the ca...
(CONJUNCTION_AFTER_SEMICOLON)
[uncategorized] ~81-~81: Loose punctuation mark.
Context: ...is/issues/673)): > StartWithContext: "When the context is canceled, the se...
(UNLIKELY_OPENING_PUNCTUATION)
[uncategorized] ~87-~87: Loose punctuation mark.
Context: ...[Server.OnShutdown]." > > OnShutdown: "The hooks run before the Start* call...
(UNLIKELY_OPENING_PUNCTUATION)
[grammar] ~215-~215: It looks like there is a word missing here. Did you mean “listen to context”?
Context: ...s at once: those engines drain as their listen context is cancelled (the next step). 3. **C...
(LISTEN_TO_ME)
[uncategorized] ~216-~216: Do not mix variants of the same word (‘cancelled’ and ‘canceled’) within a single text.
Context: ...nes drain as their listen context is cancelled (the next step). 3. **Cancel the listen...
(EN_EXACT_COHERENCY_RULE)
[grammar] ~217-~217: It looks like there is a word missing here. Did you mean “listen to context”?
Context: ...celled (the next step). 3. Cancel the listen context and wait for the drain. Cancelling it...
(LISTEN_TO_ME)
[uncategorized] ~236-~236: Do not mix variants of the same word (‘cancelled’ and ‘canceled’) within a single text.
Context: ...g when the deadline expires?](#faq)). A cancelled StartWithContext returns only after b...
(EN_EXACT_COHERENCY_RULE)
[misspelling] ~262-~262: Use “a” instead of ‘an’ if the following word doesn’t start with a vowel sound, e.g. ‘a sentence’, ‘a university’.
Context: ...`, every h2c stream. net/http hands an h2c connection to the HTTP/2 server a...
(EN_A_VS_AN)
[misspelling] ~273-~273: Use “A” instead of ‘An’ if the following word doesn’t start with a vowel sound, e.g. ‘a sentence’, ‘a university’.
Context: ... one request in flight at the shutdown. An h2c request on an .Async() route got ...
(EN_A_VS_AN)
[uncategorized] ~661-~661: Do not mix variants of the same word (‘cancelled’ and ‘canceled’) within a single text.
Context: ...drain-waits-for)). c.Context() is not cancelled at the deadline, so a handler cannot se...
(EN_EXACT_COHERENCY_RULE)
[uncategorized] ~668-~668: Do not mix variants of the same word (‘cancelled’ and ‘canceled’) within a single text.
Context: .... Start, StartWithListenerand a cancelledStartWithContext` all return after the...
(EN_EXACT_COHERENCY_RULE)
[uncategorized] ~677-~677: Use a comma before “and” if it connects two independent clauses (unless they are closely connected and short).
Context: ...ed with a 500 ms deadline, a 100 ms hook and a request held 2 s, reading each call's...
(COMMA_COMPOUND_SENTENCE_2)
[uncategorized] ~686-~686: Do not mix variants of the same word (‘cancelled’ and ‘canceled’) within a single text.
Context: ...y engine, and c.Context() was never cancelled.) Keep handlers shorter than the budge...
(EN_EXACT_COHERENCY_RULE)
🪛 markdownlint-cli2 (0.23.2)
src/content/docs/graceful-shutdown.md
[warning] 87-87: Spaces inside emphasis markers
(MD037, no-space-in-emphasis)
🔀 Multi-repo context goceleris/celeris, goceleris/probatorium, goceleris/loadgen
Linked repositories findings
celeris
Server.Shutdowndocuments drain-before-hook ordering, shared context deadlines, HTTP/2 async-stream exceptions, andStart*waiting for shutdown completion (server.go:514-575). This directly supports the PR’s revised claims. [::goceleris/celeris::]Config.ShutdownTimeoutis explicitly one budget for draining requests and then runningOnShutdownhooks, defaulting to 30 seconds (config.go:109-113). [::goceleris/celeris::]- Native engines perform their drain during
Listencancellation, whilestduseshttp.Server.Shutdown; the server waits forListenbefore running hooks (engine/epoll/engine.go:211-217,engine/iouring/engine.go:454-461,engine/std/engine.go:213+). The docs’ engine caveats therefore need to remain precise. [::goceleris/celeris::] - Regression tests cover all engines, direct shutdown, cancellation, async handlers, and h2c, including the requirement that hooks and
Start*do not return before the drain completes (shutdown_drain_order_linux_test.go:21-39,350-405). [::goceleris/celeris::]
probatorium
- The benchmark’s Celeris adapter configures
ShutdownTimeout: 10s, usesStart(), and invokes directsrv.Shutdownfrom its SIGTERM handler (servers/celeris/server.go:112-156). The revised docs should preserve guidance for directStartusers, not only context-based entry points. [::goceleris/probatorium::] - The adapter enables
AsyncHandlersfor several configurations and marks database routes.Async(); itsAutoconfigurations also exercise h2c (servers/celeris/server.go:44-100,servers/celeris/driver_handlers.go:140+). The PR’s HTTP/2 async/h2c drain exceptions are directly relevant to these benchmark consumers. [::goceleris/probatorium::] - The adapter currently pins a Celeris v1.5.12 pseudo-version (
servers/celeris/go.mod:6), while this documentation describes v1.6.0 behavior. Version scope should remain explicit so users of the pinned older dependency do not assume identical shutdown semantics. [::goceleris/probatorium::]
loadgen
- The broad search found no references to Celeris shutdown APIs or
ShutdownTimeout; its relevant role is exercising HTTP/1.1, h2c, and HTTP/2 request/stream behavior. [::goceleris/loadgen::]
1 participant
Makes the graceful-shutdown pages true for celeris v1.6.0 once goceleris/celeris#746 (celeris#703) merges, and settles goceleris/celeris#738.
Merge order: after goceleris/celeris#746, at or after its round-2 head
3d2ab72. The pages describe #746's behaviour: on every engine the hooks run after the drain, and aStart*call returns after theShutdownthat stopped it. On celeris main before it they would be wrong. One sentence (listener ownership on a failed start) describes goceleris/celeris#747 (celeris#737), so that PR should be merged before this one too.celeris#738:
Fixesdoes not work across repositories, so this PR does not close it. Close goceleris/celeris#738 by hand once this PR and goceleris/celeris#746 have both merged.What changes
celeris#738's three items:
Shutdownsection, the "preferStartWithContext" note, the entry-point table, the shutdown sequence and its summary, the shared-context note, theOnShutdownsection, the pitfalls), getting-started, core-concepts and deployment.ShutdownTimeout"applied to the hook phase", and getting-started's promise that every request finishes. Now: one deadline for the drain and then the hooks (table, watcher paragraph, getting-started, configuration). What happens at the deadline is a new FAQ answer, measured (below).celeris/server.goline locators. Everyserver.go:NNNon graceful-shutdown.md now cites the symbol instead (Shutdown,PauseAccept,InheritListener, ...), as the rest of the page does. So do the paragraphs this PR edits on deployment and configuration. The line locators elsewhere on those pages are Follow-ups from docs#77: stale line locators next to the edited shutdown text, and the uncommitted docs probe celeris#779.Also, from the same fix:
OnShutdownhook, which ran as the drain began only onepollandio_uring. With the hooks after the drain on every engine, the example now flips readiness in theSIGTERMhandler, waits a probe period, then cancels. The Kubernetes sequence and the grace-period advice follow.Shutdownfrom a handler.Shutdownnow waits for the requests in flight on every engine, the handler's own included. A pitfall and a paragraph say to run it on its own goroutine.stda cancel does not keep toShutdownTimeout: the hooks and the call wait for a handler that outlives it. Filed as std: a cancel of StartWithContext's context ignores Config.ShutdownTimeout; the drain, the OnShutdown hooks and Start wait for every handler celeris#753 and stated where the page promises the deadline.Round 2 (head
5b463a1)The review of
4ce08f5found four blocking errors. All are fixed here:epoll,io_uringandadaptive, which loses its response, nor for any h2c stream onstd(HTTP/2 streams on the shared H2 worker pool are not drained at shutdown: an async-route stream loses its response on epoll, io_uring and adaptive, and std waits for no h2c stream celeris#759). A new section, What the drain waits for, says what the drain covers and what it does not, with the measurement. Every page that stated the rule links to it: graceful-shutdown intro, shutdown sequence step 3 and summary,OnShutdownsection, pitfalls; getting-started; core-concepts; deployment.Shutdownsynchronously and readStart's return only after it, soStartcould never look earlier thanShutdown. At76c205cstd'sStartin fact returned whenShutdownbegan. celeris#746 round 2 now makes everyStart*call wait for the directShutdownthat stopped it. The round-2 probe reads every call's return as it happens. The FAQ says what it measured: on std,Startreturns whenShutdowndoes, at the deadline and after the hooks, while the handler keeps running.Startusers when they may exit. TheStartandStartWithListenerrows of the entry-point table, theShutdownsection (with the net/http-style example) and the pitfalls now say that theStart*call returns after theShutdownthat stopped it, hooks included, since v1.6.0. They also say what that means on std whenctxexpires. On earlier versions, wait forShutdownto return, as net/http teaches.The quoted
StartWithContextandOnShutdowngodocs follow celeris#746's round-2 text; a script checks that each quote is a substring of the godoc at3d2ab72. The minor and nit findings are in goceleris/celeris#779.Measured (what the new text says)
celeris#746's head
3d2ab72, linux/arm64 Docker, unconstrained memlock. A 100 msOnShutdownhook, one request held 2 s in its handler (or untilc.Context()is done). Every call's return is stamped by its own goroutine, in ms since the shutdown began. 54 cases (round2/738/run-docs-probe.sh, summarised byround2/738/docs-table.py):ShutdownreturnedStart*returnedc.Context()doneStartorStartWithContext+ directShutdownShutdownShutdownStartorStartWithContext+ directShutdownThe net/http-style
main(go func(){ <-sig; s.Shutdown(10s) }(); s.Start(); exit, with a 200 ms hook that writes a marker file and one request held 500 ms), run in a child process 5 times per engine: the hook finished before the process exited in 5/5 on std, epoll, io_uring and adaptive. With the same script (round2/738/run-mainexit.sh), the hook was lost in 5/5 runs on every engine at celeris#746's round-1 head76c205c, and at celeris main5936dd8in 5/5 on std and adaptive and 0/5 on epoll and io_uring, where the hooks ran at t=0, before the drain.The drain gaps in "What the drain waits for" were measured on celeris
3d2ab72and main698bed6byround2/repro/run-repro.sh(the numbers are also in goceleris/celeris#759 and #760).The order statements (hooks after the drain,
Shutdownafter the hooks,Start*afterShutdown) are what celeris#746's tests assert on all four engines, over HTTP/1.1 and h2c; that PR has the numbers.Scripts and logs:
evidence/lanes-20260927/LIFECYCLE/round2/(738/,repro/,logs/) in the maintainer's probatorium evidence root. The probe is not committed anywhere public (goceleris/celeris#779).