api: enforce Connect stream lifecycle policies

[siavashs]

Bound stream idle time and lifetime, track active RPC cancellation, and cancel long-lived handlers during shutdown so every admission slot is eventually released.

Part of #5478

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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Review profile: CHILL

Plan: Team

Run ID: 2b859a5b-d8cc-457c-8e5e-a7d24c83373c

📥 Commits

Reviewing files that changed from the base of the PR and between 7935b44 and 774f1a1.

📒 Files selected for processing (12)

• api/api.go
• api/api_test.go
• api/connect/connect.go
• api/connect/connect_suite_test.go
• api/connect/health_test.go
• api/connect/status_test.go
• app/app.go
• app/lifecycle.go
• app/options.go
• app/options_test.go
• cmd/alertmanager/main.go
• test/e2e/status_test.go

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📝 Walkthrough

Walkthrough

The Connect API now supports configurable concurrency, timeouts, message-size limits, metrics, exact procedure matching, and shutdown cancellation. Application flags and options expose these settings, and tests cover unary, stream, metric, and shutdown behavior.

Changes

Connect RPC lifecycle

Layer / File(s)	Summary
Configuration and API initialization api/connect/connect.go, api/api.go, app/options.go, cmd/alertmanager/main.go, app/app.go	Connect settings flow from command-line flags and application options into API construction. NewAPI initializes descriptors and metrics and can return initialization errors.
Admission, registration, and shutdown api/connect/connect.go, api/api.go, app/app.go, app/lifecycle.go	Handlers enforce concurrency, deadlines, request-size, and stream limits. Metrics record RPC outcomes. Instrumentation matches exact procedures. Shutdown rejects new RPCs and cancels active RPCs.
Lifecycle and limit validation api/connect/*_test.go, api/api_test.go, app/options_test.go, test/e2e/status_test.go	Tests cover procedure labels, API initialization, request limits, unary and stream admission, metrics, defaults, and shutdown cancellation.

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: 🟡 Moderate · up to 774f1

The PR adds shared stream admission limits and optional idle/lifetime expiration, but production defaults leave both expirations disabled. A reachable client can occupy all stream slots indefinitely, causing ResourceExhausted responses for other Connect users; merge should wait for finite defaults or explicit owner acceptance.

Sequence Diagram(s)

sequenceDiagram
  participant HTTPServer
  participant ConnectAPI
  participant ConnectControlHandler
  participant PrometheusMetrics
  HTTPServer->>ConnectAPI: invoke Shutdown()
  ConnectAPI->>ConnectControlHandler: reject new RPCs and cancel active RPCs
  ConnectControlHandler->>PrometheusMetrics: record terminal RPC outcomes

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🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description accurately summarizes the primary change and references issue #5478, but it omits the required checklist, release-notes entry, applicable test and performance details, breaking-change …	Complete the repository description template. Add the checklist responses, include the applicable unit/e2e test and performance information, state whether the change is breaking, confirm documentation and commit sign-off, and add a release-…
Docstring Coverage	⚠️ Warning	Docstring coverage is 27.27% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 11 functions across 12 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title is concise, follows the required area: short description format, and accurately describes the main Connect stream lifecycle changes.
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.

Full details: Description check

Explanation

The description accurately summarizes the primary change and references issue #5478, but it omits the required checklist, release-notes entry, applicable test and performance details, breaking-change status, documentation status, and sign-off confirmation.

Resolution

Complete the repository description template. Add the checklist responses, include the applicable unit/e2e test and performance information, state whether the change is breaking, confirm documentation and commit sign-off, and add a release-notes entry or NONE.

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✨ Finishing Touches

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