feat(BA-5985): allow deployments without health_check via deployment_revisions.health_check_enabled flag

Persist a denormalized boolean on deployment_revisions indicating whether
the revision's model_definition declares service.health_check, computed at
insert time from ModelDefinition.is_health_check_enabled() and backfilled
for existing rows. Manager skips HTTP probing entirely for revisions that
omit the block — routes stay NOT_CHECKED for life and still register with
AppProxy so traffic flows.

- Schema + ORM column + Alembic backfill (handles JSON null vs SQL NULL)
- The boolean is the SQL-level filter; the in-memory RouteData carries the
  resolved ModelHealthCheck (or None) joined eagerly from
  deployment_revisions.model_definition, so no second per-revision fetch
  is needed when initialising health records
- Filter framework: RouteHealthCheckFilter dataclass; handler.health_check_filter()
  abstract classmethod; RouteTargetStatuses gains traffic_status
- Observer-dedicated repository entry: get_routes_for_health_observation()
- HealthCheckRouteHandler: skip revisions with health_check disabled
- AppProxySyncRouteHandler: include revisions with health_check disabled
  (HEALTHY OR disabled, plus traffic_status=ACTIVE) so unconfigured routes
  still register
- RouteData.session_data (replaces session_id field; session_id kept as
  property) carries SessionStatus so sync_appproxy can validate live sessions
- sync_appproxy uses input routes' replica_host/replica_port directly (same
  pattern as register_routes_now); removes the second route+kernel re-query
  via fetch_route_connection_infos and the related condition helper
- Skip routes whose session is not RUNNING/CREATING; error on missing
  session_data or replica info

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: fregataa

changes/11534.feature.md

@@ -0,0 +1 @@
+Allow model deployments to omit `service.health_check`; manager skips HTTP probing for such revisions and AppProxy receives traffic as soon as routes reach `RUNNING`.

src/ai/backend/common/config.py

@@ -489,6 +489,10 @@ def health_check_config(self) -> ModelHealthCheck | None:
                     return model.service.health_check
         return None
 
+    def is_health_check_enabled(self) -> bool:
+        """Whether any model in this definition declares a health_check block."""
+        return self.health_check_config() is not None
+
     def with_args_appended(self, args: list[str]) -> ModelDefinition:
         """Return a copy with ``args`` appended to each model's
         ``service.start_command`` as separate argv tokens.

src/ai/backend/manager/data/deployment/types.py

@@ -250,10 +250,29 @@ class DeploymentTargetStatuses:
 
 @dataclass(frozen=True)
 class RouteTargetStatuses:
-    """Target statuses for route handler filtering (lifecycle x health)."""
+    """Target statuses for route handler filtering (lifecycle x health x traffic).
+
+    ``traffic_status=None`` skips the filter; otherwise the row's
+    ``traffic_status`` must match.
+    """
 
     lifecycle: list[RouteStatus]
     health: list[RouteHealthStatus]
+    traffic_status: RouteTrafficStatus | None = None
+
+
+@dataclass(frozen=True)
+class RouteHealthCheckFilter:
+    """Revision-level ``health_check_enabled`` gating for route queries.
+
+    - ``health_check_required=None``: no filter on the flag.
+    - ``health_check_required=True/False``: AND with the flag.
+    - ``include_health_check_disabled=True``: OR-include rows where the flag
+      is ``False``, regardless of the row's ``health_status``.
+    """
+
+    health_check_required: bool | None = None
+    include_health_check_disabled: bool = False
 
 
 @dataclass(frozen=True)

src/ai/backend/manager/models/alembic/versions/d1afd38a32ee_add_health_check_enabled_to_deployment_revisions.py

@@ -0,0 +1,59 @@
+"""add health_check_enabled to deployment_revisions
+
+Revision ID: d1afd38a32ee
+Revises: fc249eccd0b2
+Create Date: 2026-05-09
+
+Denormalized boolean of whether the revision's ``model_definition``
+declares a ``service.health_check`` block. Backfilled by scanning
+existing JSONB rows.
+
+"""
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+# Part of: 26.5.0 (main)
+revision = "d1afd38a32ee"
+down_revision = "fc249eccd0b2"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "deployment_revisions",
+        sa.Column(
+            "health_check_enabled",
+            sa.Boolean(),
+            nullable=False,
+            server_default=sa.false(),
+        ),
+    )
+
+    # ``->`` returns SQL NULL only when the key is absent; an explicit
+    # JSON ``null`` (which ``PydanticColumn.process_bind_param`` produces
+    # for ``health_check=None``) is a JSONB 'null' value, not SQL NULL.
+    # Filter both forms with ``jsonb_typeof(...) != 'null'``.
+    op.execute(
+        sa.text(
+            """
+            UPDATE deployment_revisions
+            SET health_check_enabled = TRUE
+            WHERE model_definition IS NOT NULL
+              AND EXISTS (
+                SELECT 1
+                FROM jsonb_array_elements(
+                    COALESCE(model_definition->'models', '[]'::jsonb)
+                ) AS m
+                WHERE m->'service'->'health_check' IS NOT NULL
+                  AND jsonb_typeof(m->'service'->'health_check') != 'null'
+              )
+            """
+        )
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("deployment_revisions", "health_check_enabled")

src/ai/backend/manager/models/deployment_revision/row.py

@@ -139,6 +139,14 @@ class DeploymentRevisionRow(Base):  # type: ignore[misc]
     model_definition: Mapped[ModelDefinition | None] = mapped_column(
         "model_definition", PydanticColumn(ModelDefinition), nullable=True
     )
+    # Set at insert time from ``model_definition.is_health_check_enabled()``.
+    health_check_enabled: Mapped[bool] = mapped_column(
+        "health_check_enabled",
+        sa.Boolean(),
+        nullable=False,
+        default=False,
+        server_default=sa.false(),
+    )
 
     # Resource configuration
     resource_group: Mapped[str] = mapped_column(

src/ai/backend/manager/repositories/deployment/creators/revision.py

@@ -73,6 +73,9 @@ def build_row(self) -> DeploymentRevisionRow:
             model_mount_destination=self.model_mount_destination,
             model_definition_path=self.model_definition_path,
             model_definition=self.model_definition,
+            health_check_enabled=bool(
+                self.model_definition and self.model_definition.is_health_check_enabled()
+            ),
             resource_group=self.resource_group,
             resource_opts=self.resource_opts,
             cluster_mode=self.cluster_mode,