feat(QTDI-2030): Add health and readiness endpoints to component-server

[undx]

Summary

Implements two new Kubernetes-style probe endpoints for the component-server, resolving recurring cluster restart failures in Talend Cloud (AU/AP incidents).

The existing /environment endpoint was insufficient because it returns 200 even when the server cannot process requests. This PR introduces:

• GET /api/v1/health (liveness probe) — checks heap memory availability, component index validity, and Vault connectivity. Returns 503 {"status":"DOWN","cause":"..."\} if any check fails, triggering a pod restart.
• GET /api/v1/readiness (readiness probe) — checks that the component index has finished loading. Returns 503 while the index is being built, preventing premature traffic routing.

Key design decisions:

• Memory threshold is configurable via talend.server.health.memory.threshold (default: 10%)
• Runtime.maxMemory() == Long.MAX_VALUE guard prevents false DOWN on unbounded heap
• Vault check is skipped when vaultUrl == "no-vault" (standalone mode)
• catch (Throwable t) in component index check is intentional — required to catch OOME (documented in PR comment below)

Jira: QTDI-2030

Checklist

• Tests added or updated (7 UT + 3 IT — all GREEN)
• mvn clean verify passes locally
• Spotless formatting applied (mvn spotless:apply)
• No new Sonar issues (pending CI confirmation)

AI generated code

https://internal.qlik.dev/general/ways-of-working/code-reviews/#guidelines-for-ai-generated-code

• this PR has been written with the help of GitHub Copilot or another generative AI tool

[undx]

Scope & Design Review — Round 1 — APPROVED

Findings

BLOCKER B1 — Wrong path for readiness endpoint (FIXED ✅)

• File: HealthResource.java, HealthResourceImpl.java, HealthResourceImplIT.java
• Issue: Readiness was at /api/v1/health/readiness instead of /api/v1/readiness as confirmed by Dev.
• Fix: Created ReadinessResource.java and ReadinessResourceImpl.java as separate root-level resources at @Path("readiness"). Updated IT to use /readiness path.

MAJOR M1 — Memory check divide-by-zero risk with unbounded heap (FIXED ✅)

• File: HealthService.java#checkMemory()
• Issue: When JVM is launched without -Xmx, Runtime.maxMemory() returns Long.MAX_VALUE. The formula availableMemory * 100L / maxMemory would overflow or produce 0%, causing a false DOWN.
• Fix: Added if (maxMemory == Long.MAX_VALUE) return UP guard before the calculation.

MINOR Mi1 — Throwable catch for component index check (ACCEPTED — intentional)

• File: HealthService.java#checkComponentIndex()
• Justification: The approved plan explicitly requires catching OOME, which demands Throwable. t.getMessage() may return null for OOM but result is "Component index check failed: null" which is acceptable.

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Compliance Check — Summary

Severity	Count
Critical (fixed)	1
Warning (accepted)	2

CRITICAL C1 — catch (final Exception e) in VaultClient.ping() (FIXED ✅)

• Fix: Changed to catch (final javax.ws.rs.ProcessingException e) — the correct transport-level exception for JAX-RS client failures.

WARNING W1 — catch (final Throwable t) in HealthService.checkComponentIndex() (ACCEPTED)

• Justification: Intentional per approved plan — OOME can only be caught with Throwable.

WARNING W2 — MockitoAnnotations.openMocks() instead of @ExtendWith(MockitoExtension.class) (ACCEPTABLE)

• Justification: mockito-junit-jupiter:4.8.1 is incompatible with JUnit 5.10.0 on the test classpath. MockitoAnnotations.openMocks() achieves the same result; @InjectMocks and @Mock annotations are still used as prescribed.

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AC Coverage

AC	Covered?
GET /api/v1/health → 200 when healthy	✅ UT + IT
GET /api/v1/readiness → 200 when ready	✅ UT + IT
/health → 503 + cause when memory low	✅ UT
/health → 503 + cause when Vault fails	✅ UT
/readiness → 503 + cause when index not ready	✅ UT
/environment independent from health/readiness	✅ IT
Memory threshold is configurable	✅ config property
Vault check uses VaultClient.ping()	✅ new method added
Error message with cause in JSON	✅ HealthStatus.cause field

[sonar-rnd]

Quality Gate failed

• 0.00% Coverage on New Code (is less than 80.00%)
• 10 New Issues (is greater than 0)

Project ID: org.talend.sdk.component:component-runtime

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