feat: derive k8s.node from OTLP resource attributes (#9002)

The k8s.pod runs_on k8s.node rule can only fire from kube_pod_info: it is
the only table declaring both endpoints, and co-declared edges require
both on the same row. A deployment sending only OTLP has no
kube-state-metrics tables, so its node layer is invisible and that rule
has no source at all, even though the resource attributes carry
k8s.node.name.

Declare k8s.node in otlp_trace_entities and in the synthesized resource
descriptor, and project k8s.node.name in the descriptor writer so the
column the declaration needs exists. Identity is the name rather than
k8s.node.uid: kube-state-metrics carries no node UID, so the name is the
only identity both sources can agree on.

Signed-off-by: Dennis Zhuang <killme2008@gmail.com>

src/frontend/src/instance/entity_graph.rs

@@ -905,6 +905,7 @@ mod tests {
                 "resource_attributes.service.instance.id",
                 "resource_attributes.k8s.pod.uid",
                 "resource_attributes.k8s.pod.name",
+                "resource_attributes.k8s.node.name",
             ],
             &[(TABLE_DATA_MODEL, TABLE_DATA_MODEL_TRACE_V1)],
         );
@@ -913,20 +914,27 @@ mod tests {
             .iter()
             .map(|d| d.entity_type.as_str())
             .collect();
-        assert_eq!(types, vec!["k8s.pod", "service", "service.instance"]);
+        assert_eq!(
+            types,
+            vec!["k8s.node", "k8s.pod", "service", "service.instance"]
+        );
         assert_eq!(
             declarations[0].id_columns,
+            vec!["resource_attributes.k8s.node.name"]
+        );
+        assert_eq!(
+            declarations[1].id_columns,
             vec!["resource_attributes.k8s.pod.uid"]
         );
         assert_eq!(
-            declarations[0].descriptive_columns,
+            declarations[1].descriptive_columns,
             vec!["resource_attributes.k8s.pod.name"]
         );
         assert_eq!(
-            declarations[2].id_columns,
+            declarations[3].id_columns,
             vec!["service_name", "resource_attributes.service.instance.id"]
         );
-        assert_eq!(declarations[1].id_qualifier, None);
+        assert_eq!(declarations[2].id_qualifier, None);
 
         let namespaced = table_info(
             &[
@@ -1113,6 +1121,7 @@ mod tests {
                 "k8s.pod.name",
                 "k8s.container.name",
                 "k8s.namespace.name",
+                "k8s.node.name",
             ],
             OTEL_STAMPS,
         );
@@ -1127,6 +1136,7 @@ mod tests {
                 "container",
                 "host",
                 "k8s.container",
+                "k8s.node",
                 "k8s.pod",
                 "service",
                 "service.instance"
@@ -1145,13 +1155,14 @@ mod tests {
         );
         assert_eq!(declarations[1].id_columns, vec!["host.id"]);
         assert_eq!(declarations[1].descriptive_columns, vec!["host.name"]);
-        assert_eq!(declarations[4].id_columns, vec!["job"]);
+        assert_eq!(declarations[3].id_columns, vec!["k8s.node.name"]);
+        assert_eq!(declarations[5].id_columns, vec!["job"]);
         assert_eq!(
-            declarations[4].descriptive_columns,
+            declarations[5].descriptive_columns,
             vec!["service.name", "service.namespace"]
         );
-        assert_eq!(declarations[5].id_columns, vec!["job", "instance"]);
-        assert!(declarations[5].descriptive_columns.is_empty());
+        assert_eq!(declarations[6].id_columns, vec!["job", "instance"]);
+        assert!(declarations[6].descriptive_columns.is_empty());
 
         // Nothing here can produce a k8s.container, so the generic one must
         // stand or the container disappears instead of changing type.

src/operator/src/statement/semantic_graph/conventions.yaml

@@ -75,6 +75,11 @@ otlp_trace_entities:
     descriptive:
       - resource_attributes.k8s.pod.name
       - resource_attributes.k8s.namespace.name
+  # Named, not k8s.node.uid: kube-state-metrics carries no node UID, so the
+  # name is the only identity both sources can agree on. Same-named nodes in
+  # different clusters therefore merge.
+  - entity: k8s.node
+    id: [resource_attributes.k8s.node.name]
 
 # Implicit declarations for Prometheus entity-descriptor metrics, keyed by
 # table name. Pod and service identities are the UIDs (names stay
@@ -184,3 +189,6 @@ otel_info_metrics:
       descriptive:
         - k8s.pod.name
         - k8s.namespace.name
+    # Named for the same reason as on the trace side above.
+    - entity: k8s.node
+      id: [k8s.node.name]

src/servers/src/otlp/metrics/resource_info.rs

@@ -37,7 +37,7 @@ use crate::otlp::metrics::{
 };
 use crate::otlp::trace::{
     KEY_CONTAINER_ID, KEY_CONTAINER_NAME, KEY_HOST_ID, KEY_HOST_NAME, KEY_K8S_CONTAINER_NAME,
-    KEY_K8S_NAMESPACE_NAME, KEY_K8S_POD_NAME, KEY_K8S_POD_UID, KEY_SERVICE_NAME,
+    KEY_K8S_NAMESPACE_NAME, KEY_K8S_NODE_NAME, KEY_K8S_POD_NAME, KEY_K8S_POD_UID, KEY_SERVICE_NAME,
     KEY_SERVICE_NAMESPACE,
 };
 use crate::row_writer::{self, MultiTableData};
@@ -64,12 +64,13 @@ fn is_projected_attr(key: &str) -> bool {
             | KEY_K8S_POD_NAME
             | KEY_K8S_CONTAINER_NAME
             | KEY_K8S_NAMESPACE_NAME
+            | KEY_K8S_NODE_NAME
     )
 }
 
 /// Upper bound of [`is_projected_attr`] plus the derived `job`/`instance`,
 /// used to size the per-row buffers.
-const MAX_PROJECTED_TAGS: usize = 12;
+const MAX_PROJECTED_TAGS: usize = 13;
 
 /// Projected attributes (sorted `(name, value)` pairs) -> graph window ->
 /// the newest data-point time seen in that window, which is what the row for
@@ -264,6 +265,7 @@ mod tests {
             kv("service.namespace", "shop"),
             kv("service.instance.id", "inst-1"),
             kv("host.id", "h-1"),
+            kv("k8s.node.name", "node-a"),
             kv("os.type", "linux"),
         ];
         data.observe(&attrs, &gauge_at(&[100, 50]), &OtlpMetricCtx::default());
@@ -273,6 +275,7 @@ mod tests {
         assert!(tags.contains(&("job".to_string(), "shop/api".to_string())));
         assert!(tags.contains(&("instance".to_string(), "inst-1".to_string())));
         assert!(tags.contains(&("service.name".to_string(), "api".to_string())));
+        assert!(tags.contains(&("k8s.node.name".to_string(), "node-a".to_string())));
         assert!(
             tags.iter()
                 .all(|(k, _)| k != "os.type" && k != "service.instance.id")

src/servers/src/otlp/trace.rs

@@ -56,6 +56,7 @@ pub const KEY_K8S_POD_UID: &str = "k8s.pod.uid";
 pub const KEY_K8S_POD_NAME: &str = "k8s.pod.name";
 pub const KEY_K8S_CONTAINER_NAME: &str = "k8s.container.name";
 pub const KEY_K8S_NAMESPACE_NAME: &str = "k8s.namespace.name";
+pub const KEY_K8S_NODE_NAME: &str = "k8s.node.name";
 pub const KEY_SPAN_KIND: &str = "span.kind";
 
 // jaeger const keys, not sure if they are general