Add instance health checks

[sjmiller609]

Summary

• add instance health_check policy and health_status response fields for http, tcp, and exec probes
• add a health check controller owned by the instance manager, with timing, thresholds, start-period handling, and runtime status persistence
• start health checks while instances are Initializing or Running, while keeping public health status starting until the instance reaches Running
• add HTTP healthcheck assertions to TestCreateInstanceWithNetwork so the VM-starting network path waits for persisted healthy status
• wire the controller into the api process and document lifecycle semantics in lib/healthcheck/README.md

Tests

• go test ./lib/healthcheck
• go test ./lib/instances -run TestCreateInstanceWithNetwork -count=0
• go test ./lib/instances -run 'TestHealthCheck|TestValidateCreateRequestHealthCheck|TestValidateUpdateInstanceRequest|TestManagerUpdateInstanceHealthCheckOnlyPublishesLifecycleUpdate|TestLifecycleEventMetrics_ObserveSubscribersQueueDepthAndDrops|TestLifecycleSubscribers'
• go test ./cmd/api/api -run 'TestCreateInstance_MapsHealthCheckPolicy|TestUpdateInstance_MapsHealthCheckPatch|TestCreateInstance_MapsAutoStandbyPolicy|TestUpdateInstance_MapsAutoStandbyPatch'
• go test ./cmd/api -run TestDoesNotExist
• go test ./lib/providers

Notes

• go test ./lib/instances -run TestCreateInstanceWithNetwork -count=1 was attempted twice; both runs failed before instance creation because the existing nginx image readiness wait still saw image status pending after 60s.
• go test ./cmd/api/api is currently blocked by Docker Hub unauthenticated pull rate limits and local network bridge permissions in existing integration tests.
• make generate-wire is currently blocked because the checked-in wire binary was built with Go 1.24 and this package now requires Go 1.25; wire_gen.go was updated in the same small shape and go test ./cmd/api -run TestDoesNotExist passes.

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Note

Medium Risk
Adds a new health-check policy surface area, background controller, and metadata persistence path; bugs could impact instance API behavior and metadata writes, but lifecycle state is intentionally unchanged.

Overview
Adds first-class instance health checks via new health_check policy (HTTP/TCP/exec) and health_status fields in the API/OpenAPI, including request validation, defaulting/normalization, and bidirectional mapping between OAPI and domain types.

Introduces a new lib/healthcheck package plus an instances.HealthCheckController that subscribes to lifecycle events, schedules probes with interval/timeout/threshold/start-period semantics, and persists per-instance runtime status; the controller is wired into the API process startup. Instance metadata now stores health_check_runtime, and saveMetadata switches to atomic temp-file + rename writes; update flows reset health runtime when the health check policy changes, and tests/integration tests are expanded to cover health-check behavior and lifecycle metrics labeling.

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[github-actions]

✱ Stainless preview builds for hypeman

This PR will update the hypeman SDKs with the following commit message.

feat: Add instance health checks

✅ hypeman-openapi studio · code

Your SDK build had at least one "note" diagnostic.
generate ✅

⚠️ hypeman-typescript studio · code

Your SDK build had a failure in the lint CI job, which is a regression from the base state.
generate ✅ → build ✅ → lint ❗ → test ✅

✅ hypeman-go studio · code

Your SDK build had at least one "note" diagnostic.
generate ✅ → build ⏭️ → lint ✅ → test ✅

go get github.com/stainless-sdks/hypeman-go@6335d0e4156a205becb27419bf593b14580fba45

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Last updated: 2026-05-18 15:04:47 UTC

[firetiger-agent]

Monitoring Plan: Instance Health Checks (PR #234)

This PR adds a new health-check subsystem to hypeman: POST /instances and PUT /instances/{id} now accept an optional health_check policy (HTTP, TCP, or exec probes), and a new HealthCheckController goroutine runs alongside the existing AutoStandbyController to drive periodic probes and persist runtime status. The GET /instances/{id} response gains health_check + health_status fields.

The main risks are: (1) validation errors in toDomainHealthCheck/NormalizePolicy surfacing as unexpected 400s on existing callers who send bodies that incidentally conflict with new fields, (2) the new controller goroutine panicking or leaking timers under high instance churn, and (3) exec probes firing guest-agent commands on instances that lack a guest-agent, triggering error log noise. API 5xx error rate baseline is 0.013–0.018% (30–35 errors/hr out of ~190K–280K req/hr); 400 error baseline is ~267 in the latest 4-hour window. Status updates will be posted automatically on this PR as monitoring progresses.

Key risks to watch:

• Spike in HTTP 400 responses on /instances endpoints (invalid_health_check errors from new validation path)
• Unhandled panics or nil pointer dereference errors in HealthCheckController.Run or timer callbacks
• API 5xx error rate exceeding 0.05% (3× normal baseline) sustained for >15 min
• Log errors: "failed to set health check runtime" or "health check controller started" absent after deploy

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