feat(serve)!: graceful shutdown with a bounded drain - #124
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- serve_with_shutdown and ProxyServer::serve_with_shutdown stop on a signal future: the listener closes, connections in a TLS handshake or waiting for a max_connections slot are dropped, HTTP/2 gets a GOAWAY, HTTP/1.1 closes after the response in progress, and calls and streams in flight finish - ServeOptions::drain_timeout / listen.drain_timeout_secs (30 s by default, 0 waits for all) bounds the drain; the connections still open are closed - connections are tasks of the serve future, so dropping it closes every connection and ends every handler, HTTP/2 stream tasks included - the binary drains on SIGTERM and Ctrl-C and exits 0; the systemd unit stops a few seconds after the default drain BREAKING CHANGE: ListenConfig gains drain_timeout_secs, so a ListenConfig built as a struct literal must set it. Closes #123
- default drain timeout 25 s, below the 30 s a pod gets after SIGTERM, so the drain ends before the kill; the systemd unit keeps TimeoutStopSec=30 - the README's Rust examples compile as doc tests in every feature set; examples that read a config file at startup are no_run Part of #123
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📝 SummarySummary by CodeRabbit
WalkthroughThe proxy now accepts shutdown signals, stops accepting connections, and drains tracked connections with a configurable timeout. The binary maps Ctrl-C and Unix SIGTERM to shutdown. Tests cover HTTP/1, HTTP/2, TLS, connection limits, timeout expiry, and task cancellation. ChangesGraceful shutdown
Priority: ➖ Normal Estimated code review effort: 4 (Complex) | ~45 minutes Change: Feature · Severity of issue fixed: Medium Sequence Diagram(s)sequenceDiagram
participant Signal as Shutdown signal
participant Server as serve_with_shutdown
participant Listener as TcpListener
participant Tasks as Connection tasks
participant Clients as HTTP clients
Signal->>Server: Resolve shutdown future
Server->>Listener: Stop accepting connections
Server->>Tasks: Request graceful shutdown
Tasks->>Clients: Finish active work and send GOAWAY when applicable
Tasks-->>Server: Report connection closure
Merge Risk: 🟡 Moderate · up to HTTP/2 work may continue after shutdown reports completion. Tie stream handlers to the connection lifetime before merging, or explicitly accept that shutdown limitation. Security Architecture ReviewSecurity architecture risk: 🟡 Moderate · up to The default shutdown is bounded and stops accepting new connections, but upgraded connections need confirmation: they may outlive the new drain guarantee in embedded deployments. No authorization bypass is established. Retained concerns
Security review detailsSecurity Blast Radius
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🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 75.56% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 45 functions across 8 files. (4 skipped: 4 unsupported.) ✨ Finishing Touches 💡 1📝 Generate docstrings 💡
🧪 Generate unit tests (beta)
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Inline comments:
Review comments at @src/serve.rs:
- Around line 324-341: Tie HTTP/2 stream tasks spawned by
hyper_util::rt::TokioExecutor to each connection’s lifetime in the
serve_with_shutdown flow, using tracked tasks or a cancellation token. On forced
shutdown after drain_timeout expires, ensure connections.shutdown also cancels
and awaits those stream tasks before serve_with_shutdown returns.
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Cargo.tomlREADME.mdpackaging/config.yamlpackaging/structured-proxy.servicesrc/config.rssrc/lib.rssrc/main.rssrc/serve.rssrc/serve/tests.rstests/cli.rstests/embedded.rstests/shutdown.rs
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- The accept loop reaped finished connection tasks only when a new client arrived, so a burst that closed while the listener sat idle stayed allocated (about 190 bytes each) until the next connection. Every wait (slot, accept) now reaps as tasks finish; tests/connection_memory.rs counts live bytes after such a burst. - HTTP/2 stream tasks were spawned on the plain tokio executor, so a handler could still be running when serve_with_shutdown returned after the drain timeout. They now run under a TaskTracker the shutdown waits on; the new drain-timeout case checks the handler is gone on return. - The JWKS refresh-in-flight test measured the throttle with a 50 ms interval, shorter than the time a loaded machine takes between the held refresh starting and the second lookup checking it (2 failures in 300 runs); 500 ms leaves the margin, with no failure in 300 runs. Part of #123
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After the drain timeout the shutdown waited on the stream tasks without a bound, relying on hyper ending a stream when its connection closes. A stream that never observes that (a service or body that is never woken again, or a hyper release that does not poll for the reset) would hang the shutdown past its timeout. Stream tasks now run under a cancellation token: the drain timeout cancels them before waiting, and dropping the serve future cancels them too. The regression test stopping_the_streams_ends_one_that_never_finishes timed out on the previous code. Part of #123
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Summary
Changes
serve_with_shutdown(listener, service, options, signal)andProxyServer::serve_with_shutdown(signal);serveandserve_withrun until dropped.max_connectionsslot is dropped; HTTP/1.1 closes after the response in progress.ServeOptions::drain_timeoutandlisten.drain_timeout_secs(25 s by default, below the 30 s Kubernetes grace period; 0 waits for all): the connections still open after it are closed.JoinSet), reaped as they close; HTTP/2 stream tasks run under a tracker the shutdown waits on, and are cancelled when the drain times out or the serve future is dropped.TimeoutStopSecstays above the default drain, and the packaged config template documents the key.Testing
Formatting, clippy, the full test suite, doc tests and rustdoc pass locally; the new shutdown cases run in cleartext, behind TLS and under a connection limit, and the binary is checked to exit 0 on SIGTERM.
BREAKING CHANGE:
ListenConfiggainsdrain_timeout_secs, so aListenConfigbuilt as a struct literal must set it.Closes #123