fix(stargate): back off discovery and recover registration safely

[barrygreengus]

TL;DR

Back off Kubernetes discovery failures and make pylon registration recovery observable without exposing credential-bearing diagnostic data. Persistent API permission errors otherwise repoll immediately, while non-certificate registration failures are silent and response-stream loss reconnects without delay.

Additional Details

• Apply kube's default watcher backoff, tested against a fake API returning repeated HTTP 403 responses.
• Warn on every non-certificate discovery or registration failure. Preserve classified certificate ERROR diagnostics and duplicate suppression; generic WARN events do not bypass that suppression.
• Report response EOF/errors, wait one cancelable second before reopening registration, and clear connected metrics before cleanup and the reconnect delay.
• Format endpoints without userinfo, paths, or queries. Preserve safe JSON failure categories and positions. Omit token-file excerpts, credential-bearing HTTP URLs, and remote gRPC messages, metadata, and binary details. Keep error chains intact for callers and retain safe local transport causes and gRPC codes in logs.
• Strip URL userinfo, paths and queries from diagnostic router metric labels and reverse-tunnel log context. Preserve ordinary labels and the request endpoint. A live-stream regression reproduces token-query exposure in all three metric families on archived pre-merge main, including after disconnect.
• Update the existing registration flow diagram. No public API, CLI, metrics names, or configuration changes.

The token-file I/O cause preservation described in earlier revisions is already on current main. This layer adds safe diagnostic rendering and registration context.

For the Reviewer

Focus on registration/discovery retry boundaries, typed certificate suppression, error rendering, and metric cleanup before reconnect. #1818 and #1820 are merged. This PR targets main and contains only the registration/discovery layer.

For QA

Affected Cargo suites passed 653 tests: 533 pylon-lib unit tests, 2 public API tests, 24 forwarding tests, 74 router library tests, and 20 router binary tests. Three existing router performance tests were ignored. All-target Clippy passed for pylon-lib, stargate-k8s-router, and stargate-forwarding with warnings denied. New regressions cover real TLS failure retries, refused connections, remote-message redaction, EOF/error reconnect timing, connected metrics during retry, and cancellation.

The watcher regression fails against archived pre-merge main with immediate API repolling. New TLS warning and remote-message assertions failed before their fixes; the stream metric assertion also failed before explicit tracker cleanup. Archived pre-merge main also fails the refused-connection warning regression, stream-close diagnostic assertion, and active-stream reconnect timing regression: two connection attempts occur within the first 100 ms instead of one. The server consumes the initial registration before ending its response stream, and timing observes attempts before TLS handshake latency.

Whitespace and skill-fanout checks passed. Touched Rust formatting is checked separately; workspace formatting reports inherited changes outside this layer. Local Bazel is blocked before test execution in Zig toolchain setup. Pinned TruffleHog 3.95.2 scanned the complete main-to-head range without findings. Synthetic credential URLs are constructed at runtime so the secret scanner does not treat redaction fixtures as credential leaks. All relevant final-head checks passed on0580dc3c against pre-merge main0e622212, including Linux root/Stargate Bazel, Rust CodeQL, secret scanning and dependency checks. All seven merge-group workflows passed on actual merge commitc9421f88. No live cluster or GPU campaign was run; local fixtures cover this change.

Issues

Relates to #1817

Customer Release Notes

Discovery backs off during Kubernetes API errors. Registration reports safe failure diagnostics, omits sensitive endpoint URL components from metric labels, and retries closed streams with a cancelable delay.

Plan Summary

Not applicable.

Usage

Warnings identify the operation, sanitized endpoint, safe cause or gRPC code, and registration cluster ID. Repeated certificate failures retain the existing single diagnostic with corrective guidance.

Related Pull Requests

Predecessors #1818 and #1820 are merged. Downstream layer: #1826.

Dependencies

No new or upgraded dependency versions. The existing Tokio test-util feature is enabled for deterministic watcher tests, with matching Bazel metadata. No license or NOTICE changes.

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• src/libraries/rust/stargate/crates/pylon-lib/src/registration/tests.rs

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📝 Walkthrough

Walkthrough

The change adds structured gRPC diagnostics with sanitized error details, updates registration-stream termination and reconnect handling, and applies backoff to EndpointSlice watcher errors.

Changes

gRPC registration and reconnection

Layer / File(s)	Summary
Endpoint formatting and error-chain handling src/libraries/rust/stargate/crates/pylon-lib/src/registration/grpc_endpoint.rs, src/libraries/rust/stargate/crates/pylon-lib/src/registration/tests.rs	Endpoint display uses normalized scheme, host, and port values, and shows <invalid endpoint> when parsing fails. Connection events use structured logging. grpc_error_chain formats selected errors with reduced details. Tests cover endpoint display, sensitive-detail handling, token-resolution error chains, and certificate-failure classification.
Registration diagnostics and stream handling src/libraries/rust/stargate/crates/pylon-lib/src/registration/discovery.rs, src/libraries/rust/stargate/crates/pylon-lib/src/registration/router_stream.rs, src/libraries/rust/stargate/crates/pylon-lib/src/registration/tests.rs, src/libraries/rust/stargate/docs/diagrams/registration-and-quic-flow.puml	Discovery and registration paths distinguish certificate failures from other gRPC failures. Registration stream termination is logged, and reconnect waits up to one second unless shutdown cancels the wait. Tests cover warning events, terminal responses, delayed retries, metrics, and cancellation. The diagram note describes stream termination and reconnect behavior.
EndpointSlice watch retry backoff src/libraries/rust/stargate/crates/stargate-k8s-router/src/watcher.rs, src/libraries/rust/stargate/crates/stargate-k8s-router/Cargo.toml	The watcher applies kube’s default backoff after watch errors. Tokio test support and a paused-time test verify that repeated HTTP 403 responses do not cause an immediate second request.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Suggested reviewers: mikeyrcamp

Merge Risk: ⚪ Minimal · up to 7292b

The registration lifecycle tests exercise actual stream termination and reconnect timing. No actionable merge-blocking issue remains in the reviewed changes.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 46.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 30 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title follows Conventional Commits syntax and accurately describes the primary changes: discovery backoff and safe registration recovery.

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🛡️ CodeQL Analysis

🚨 Found 5 issue(s)

Severity Breakdown:

• 🔴 Errors: 0
• 🟡 Warnings: 0
• 🔵 Notes: 0

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_{🕐 Last updated: 2026-09-11 22:27:59 UTC | Commit: b4c0176}

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Inline comments:
In `@src/libraries/rust/stargate/crates/pylon-lib/src/registration/discovery.rs`:
- Around line 188-193: Guard the generic gRPC warning emissions so they are
skipped when log_stargate_grpc_certificate_failure classifies the error as a
suppressed repeated TLS certificate failure. Apply this at both failure branches
in discovery.rs and the connection-failure branch in router_stream.rs, while
preserving the existing warning for non-classified failures.

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• MODULE.bazel.lock is excluded by !**/*.lock, !**/MODULE.bazel.lock

📒 Files selected for processing (6)

• src/libraries/rust/stargate/crates/pylon-lib/src/registration/discovery.rs
• src/libraries/rust/stargate/crates/pylon-lib/src/registration/grpc_endpoint.rs
• src/libraries/rust/stargate/crates/pylon-lib/src/registration/router_stream.rs
• src/libraries/rust/stargate/crates/pylon-lib/src/registration/tests.rs
• src/libraries/rust/stargate/crates/stargate-k8s-router/Cargo.toml
• src/libraries/rust/stargate/crates/stargate-k8s-router/src/watcher.rs

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[FamousDirector]

Correction to the earlier scanner diagnosis: the identical-base/head message came from the initial attempt. The action then scanned broader history and reported two unverified fixture matches, with zero verified secrets. The failure therefore was not only a scanner-ref problem: https://github.com/NVIDIA/nvcf/actions/runs/36787965616/job/110133814839 .

The registration owner has corrected the synthetic fixture constructions on new head 7292b6b. Fresh exact-head CI is running. #1826 will preserve the corrected predecessor changes when reconciling its benchmark layer, then validate its complete history scan and final main CI. It remains stacked pending this layer's review and landing.

[along-2017]

LGTM

[FamousDirector]

Ada approved 7292b6b. A follow-up independent redaction probe found a remaining defect on current main: an advertised router URL's token query appears in registration connectivity, reverse connectivity and model-status metric labels, including after disconnect. The live-stream regression fails on main and the prior PR head.

A minimal fix strips URL userinfo, paths and queries from diagnostic router addresses while preserving ordinary labels and the endpoint used for requests. All 653 affected Cargo tests and all-target Clippy pass. I am pushing this additional fix; final-head CI and fresh Ada review are required before merge. #1817 remains open.

[FamousDirector]

Independent cross-layer verification for #1817 confirms the metric-label finding is valid. The metric construction and authority-string method match current main 0b1640a. An isolated native TLS fixture reaches the credential assertion and shows the query retained after disconnect in all three families: pylon_model_advertised_status, pylon_registration_stream_connected and pylon_reverse_tunnel_connected.

With the three changed registration files from d319a49, the live credential regression passes. The separate ordinary-label preservation regression also passes. These are targeted native probes, not a claim of a full main workspace test run. I will include this domain in the shared issue closeout once all surviving layers have actually merged.

[balajinvda]

🎉 This PR is included in src/libraries/rust/stargate/v0.19.7 🎉

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[FamousDirector]

Merged through the standard queue as c9421f8 at 2026-10-01 19:44:59 UTC. Ada approved exact final head 0580dc3: #1823 (review) .

All relevant final-head/current-base checks passed. All seven merge-group workflows passed on the actual merge commit, including root/Stargate Bazel, dependency documentation, licenses, secret scanning and build validation: https://github.com/NVIDIA/nvcf/actions/runs/36915058886 . Affected Cargo suites passed 653 tests, with three existing performance tests ignored; all-target Clippy passed with warnings denied.

Only this eight-file registration/discovery layer landed. No new dependency versions, license or NOTICE changes. #1826 may now reconcile its own benchmark layer with main; shared #1817 remains open for that owner's final verification. The worktree and assigned branch are retained.

[balajinvda]

This PR is included in version 1.29.1.

The release is available on GitHub release.

[balajinvda]

This PR is included in version 1.69.1.

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[balajinvda]

This PR is included in version 1.14.2.

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[balajinvda]

This PR is included in version 0.5.1.

The release is available on GitHub release.