fix: only show enabled backends in /health response

[koriyoshi2041]

Summary

Resolves #6750. The /health endpoint previously always included all backends (ClickHouse, Postgres, Valkey, Valkey cache) in its response, even when they were disabled. This made the response noisy and potentially confusing for operators.

Changes:

• Added is_clickhouse_enabled(), is_postgres_enabled(), is_valkey_enabled() helpers that check concrete connection types
• Changed health_check_inner() to accept concrete types instead of dyn HealthCheckable, enabling compile-time backend state inspection
• Only includes a backend in the JSON response when it is actually configured
• Replaced futures::join! with tokio::join! (removes an unnecessary dependency)

Before:

{"gateway": "ok", "clickhouse": "ok", "postgres": "ok", "valkey": "ok", "valkey_cache": "ok"}

After (e.g., only ClickHouse + Postgres configured):

{"gateway": "ok", "clickhouse": "ok", "postgres": "ok"}

Test plan

• Updated existing tests to use concrete types instead of mocks
• Added test_health_handler_all_disabled — verifies only "gateway" appears when all backends are disabled
• cargo check -p tensorzero-core passes

[koriyoshi2041]

I have read the Contributor License Agreement (CLA) and hereby sign the CLA.

[shuyangli]

these tests will fail.

[koriyoshi2041]

Could you clarify which tests you expect to fail? The unit tests in endpoints::status::tests all pass locally (4/4):

test endpoints::status::tests::test_health_handler_all_disabled ... ok
test endpoints::status::tests::should_report_error_for_unhealthy_postgres ... ok
test endpoints::status::tests::test_health_handler_all_enabled_and_healthy ... ok
test endpoints::status::tests::should_report_error_for_unhealthy_clickhouse ... ok

Are you referring to specific E2E tests that assert on the health response format? Happy to update those as well.

[shuyangli]

I thought we had e2e tests that assert on the full shape of the response but it should be fine.

/check-fork

[shuyangli]

/check-fork

[github-actions]

🚀 General Checks workflow triggered on new branch external-contributor/pr-6769!

View the run: https://github.com/tensorzero/tensorzero/actions/runs/23214904673