fix(api): restore HTTP GET /health endpoint

[pront]

Summary

Restores the HTTP GET /health endpoint on the Vector API to avoid user disruption. The endpoint is served on the same port as the gRPC API, so existing HTTP probes (AWS ALB health checks, Kubernetes HTTP liveness/readiness probes, etc.) keep working unchanged.

• Response matches the pre-0.55 shape: 200 {"ok":true} while serving, 503 {"ok":false} during drain.
• HEAD /health is also accepted for load balancers that prefer it.
• The standard gRPC health service (grpc.health.v1.Health/Check) is unchanged. Both probes share the same serving flag so they agree during shutdown.

Flagged in #25210.

No changelog fragment: no release has shipped without /health, so there is no user-visible change relative to 0.54.0. The no-changelog label applies.

Implementation

src/api/grpc_server.rs now builds the tonic Server into an axum::Router via into_router(), merges an axum router exposing GET/HEAD /health, and serves the combined router via hyper::Server over the existing TcpListener. accept_http1(true) lets plain HTTP/1.1 requests reach the axum routes while gRPC continues to use HTTP/2. set_not_serving() now flips both the gRPC HealthReporter and the shared HTTP serving flag.

Vector configuration

Any config with the API enabled works, e.g.:

api:
  enabled: true
  address: 127.0.0.1:8686

sources:
  demo:
    type: demo_logs
    format: json

sinks:
  out:
    type: blackhole
    inputs: [demo]

How did you test this PR?

• Added two integration tests in tests/vector_api/health.rs covering GET /health (200 + body) and HEAD /health (200). Existing gRPC grpc.health.v1.Health/Check test still passes.
• Manual: curl -i http://127.0.0.1:8686/health returns 200 {"ok":true}; grpcurl -plaintext 127.0.0.1:8686 grpc.health.v1.Health/Check still returns SERVING.
• Local make check-fmt, make check-clippy, make check-markdown, and website/ make cue-build all pass.

Change Type

• Bug fix
• New feature
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

• Related: Vector health endpoint in master branch #25210
• Related: chore(api)!: replace GraphQL observability API with gRPC, remove async-graphql dependencies #24364
• Related: chore(releasing): prepare v0.55.0 release #25229 (cherry-pick target for v0.55)

[thomasqueirozb]

Nice! This will make upgrading simpler 🙂. We can look into removal at a later date

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 281bbf9d3c

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

[chatgpt-codex-connector]

Keep honoring gRPC deadlines after router merge

For gRPC clients that set request deadlines via grpc-timeout metadata, converting the tonic server into an axum router and serving it directly through hyper bypasses tonic's transport MakeSvc, which is where the previous serve_with_incoming_shutdown path wrapped routes in GrpcTimeout. Those deadline-bounded API calls/streams will no longer be cancelled with a deadline-exceeded status by the server, and can keep consuming server work until they otherwise finish or the client disconnects; please preserve tonic's timeout handling when serving the merged router.

Useful? React with 👍 / 👎.