feat(server): keep serving through a drain window before closing the listener - #995
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…listener
A load balancer learns that an instance is withdrawing on its next health
check, not the moment the instance decides to. Between those two points it
keeps routing new connections. The gateway closed its listener about a
second after SIGTERM, so every connection routed inside that interval was
refused and callers saw gateway errors during an ordinary rolling update
or scale-down.
Separate the two events. On the shutdown signal the gateway now:
- answers /readyz and /livez with 503 immediately, as before;
- keeps accepting new connections for at least `shutdown.min_drain_secs`
(new, defaults to 30s);
- adds `Connection: close` to HTTP/1.1 responses, so a pooling client
retires its connections as it uses them instead of holding idle ones
open until the listener disappears — a request dispatched onto one of
those in the closing instant dies with no response, which is how a
graceful shutdown still surfaces as an upstream reset at the caller;
- stops accepting only once that window has elapsed AND nothing is left
in flight, so a balancer slower than configured cannot make it close
under live traffic;
- drains the remaining in-flight requests without a deadline of its own,
as before, leaving `terminationGracePeriodSeconds` / `TimeoutStopSec`
as the one hard bound.
The in-flight count is a new process-wide counter raised by the telemetry
middleware's RAII guard. The `aisix_proxy_in_flight_requests` gauge next to
it is sliced by endpoint and protocol and lives behind the metrics
registry's lock — the right shape for a dashboard, the wrong one for a
drain gate.
The e2e harness pins `min_drain_secs: 0`: no balancer fronts a spawned test
binary, and paying the window on every teardown would cost 30s per app and
lose the clean-exit path the specs rely on.
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📝 WalkthroughWalkthroughThe gateway adds configurable graceful shutdown. It withdraws readiness after SIGINT or SIGTERM, accepts connections during the minimum drain window, tracks in-flight requests, retires HTTP/1.x connections, and closes listeners after all requests finish. ChangesGraceful shutdown
Estimated code review effort: 4 (Complex) | ~45 minutes Merge Risk: 🟡 Moderate · up to The new drain window can still close listeners while streaming response bodies are active and may leave connections reusable when shutdown begins, which can truncate responses or cause failed follow-up requests during termination. The lifecycle handling and its end-to-end synchronization should be fixed before merge. Sequence Diagram(s)sequenceDiagram
participant SignalTask
participant LivezState
participant GatewayListener
participant InFlightGuard
SignalTask->>LivezState: Mark readiness as 503
SignalTask->>GatewayListener: Wait through minimum drain window
GatewayListener->>InFlightGuard: Create guard for each request
InFlightGuard->>LivezState: Enter and leave request count
SignalTask->>LivezState: Poll in-flight count
SignalTask->>GatewayListener: Close listeners when count reaches zero
Possibly related PRs
Suggested reviewers: 🚥 Pre-merge checks | ✅ 5 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (5 passed)
✨ Finishing Touches📝 Generate docstrings
🧪 Generate unit tests (beta)
Comment |
The gateway keeps accepting for shutdown.min_drain_secs after SIGTERM (30s by default, api7/aisix#995) so a balancer that polls a health check can withdraw it before the listener closes. preStop covers the other case - a balancer that watches the Kubernetes API - and is raised to 30s to match. Both count against terminationGracePeriodSeconds, which the kubelet starts before the preStop hook runs, so 120 would have left only 60s for the in-flight drain the value exists to protect. Raised to 180 to keep that budget where it was. README regenerated with helm-docs v1.13.1 per AGENTS.md.
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Inline comments:
In `@crates/aisix-proxy/src/lib.rs`:
- Around line 511-524: Update the middleware around InFlightGuard and
attribution::scope so the guard remains owned by a wrapper response body until
streaming completes, including during SSE. Evaluate
state.livez.is_shutting_down() after the request future resolves so in-progress
HTTP/1.1 responses receive the required drain behavior, and add an SSE test
covering body completion during shutdown.
Apply the same fix in `@crates/aisix-proxy/src/lib.rs` around lines 517 - 522.
In `@tests/e2e/src/cases/graceful-drain-e2e.test.ts`:
- Around line 146-151: Update the graceful-drain test around the inFlight chat
request to poll upstream.receivedRequests until the request is recorded before
capturing signalledAt and sending SIGTERM. Replace the fixed 300 ms delay with a
bounded wait using the test’s existing polling or timeout utilities, while
preserving the subsequent signal and drain assertions.
- Around line 135-139: Update the graceful-drain test so the unavailable-etcd
setup calls ctx.skip() rather than returning normally, and replace the fixed 300
ms delay with an assertion or polling wait that confirms
upstream.receivedRequests contains the in-flight request before sending SIGTERM.
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📒 Files selected for processing (8)
config.example.yamlconfig.managed.yamlcrates/aisix-core/src/config.rscrates/aisix-proxy/src/health.rscrates/aisix-proxy/src/lib.rscrates/aisix-server/src/main.rstests/e2e/src/cases/graceful-drain-e2e.test.tstests/e2e/src/harness/app.ts
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Axum polls a response body after the middleware that produced it returns, so a drain gate released there reads zero while an SSE stream is still running. The shutdown coordinator would then close the listener as soon as the minimum window elapsed — under the traffic shape an AI gateway carries most of, and for exactly the balancer the window exists to outlast: one slower to withdraw the instance than the window is long. Split the count off from `InFlightGuard` into its own guard moved into the response body, so it falls only when the body is fully written or dropped. `InFlightGuard` keeps feeding `aisix_proxy_in_flight_requests` with its established semantics; folding the body into that published gauge would shift what every existing dashboard reads. Also sample the draining flag AFTER the handler rather than before it: a request that arrived just ahead of the signal and finished inside the window rides one of the pooled connections that most needs retiring, and was missing its `Connection: close`. Tests: a second spec drives a live SSE stream across the signal and pins that the listener still accepts well past the window. The first spec now gates on the upstream having received the slow request instead of sleeping 300ms, and both use the suite's `ctx.skip()` idiom for an unreachable etcd.
Problem
A load balancer learns that an instance is withdrawing on its next health check, not the moment the instance decides to. Between those two points it keeps routing new connections.
The gateway closed its proxy listener about a second after
SIGTERM— a hardcodedsleep(1)between flipping readiness and cancelling the listeners. Every connection a balancer routed inside its own detection window was therefore refused, and callers saw gateway errors during an ordinary rolling update or scale-down. Measured on a stock build:/readyzwent 503 at +0.03s and the listener stopped accepting at +1.06s, while a Kubernetes readiness probe at the chart's defaults needs up to 9s to withdraw the pod and an external health check commonly needs longer still.A second, quieter path produced the same symptom: the graceful shutdown closes idle connections at once, so a client that pools upstream connections could dispatch a request onto one in the instant it was being closed and get no response at all.
Change
The shutdown signal and the listener close are now separate events.
On
SIGTERM/SIGINTthe gateway:/readyzand/livezwith 503 immediately — unchanged;shutdown.min_drain_secs, a new config knob defaulting to 30s;Connection: closeto HTTP/1.1 responses, so a pooling client retires connections as it uses them and nothing idle is left to lose when the listener does close (HTTP/2 keeps itsGOAWAY);terminationGracePeriodSeconds/TimeoutStopSecas the one hard bound.The in-flight count is a new process-wide counter raised by the telemetry middleware's existing RAII guard. The
aisix_proxy_in_flight_requestsgauge beside it is sliced by endpoint and protocol and lives behind the metrics registry's lock — the right shape for a dashboard, the wrong one for a hot-path drain gate.Behavior change
Termination now takes at least 30s by default where it previously took ~1s. In-flight drain is unaffected. Deployments that front the gateway with nothing that health-checks it can set
min_drain_secs: 0.The e2e harness pins
min_drain_secs: 0for spawned binaries: no balancer fronts a test process, and paying the window on every teardown would add 30s per app and push the harness into theSHUTDOWN_GRACE_MSSIGKILL path, losing the clean-exit behaviour the specs rely on.Tests
tests/e2e/src/cases/graceful-drain-e2e.test.tsdrives a real binary with a 5s window and a mock upstream that answers one request slowly enough to outlive it:/readyzreports 503 within milliseconds of the signal;Connection: close;Verified to fail on the pre-change binary and pass after.
Summary by CodeRabbit
Fixes api7/AISIX-Cloud#1342