lib/promscrape/discovery/kubernetes: do not drop pod meta-labels even if the corresponding node objects are missing

This reflects the logic used in Prometheus.

See https://github.com/prometheus/prometheus/pull/10080

lib/promscrape/discovery/kubernetes/endpoints.go

@@ -132,11 +132,7 @@ func (eps *Endpoints) getTargetLabels(gw *groupWatcher) []map[string]string {
 				m := map[string]string{
 					"__address__": addr,
 				}
-				if !p.appendCommonLabels(m, gw) {
+				p.appendCommonLabels(m, gw)
-					// The corresponding node is filtered out with label or field selectors.
-					// Do not generate endpoint labels in this case.
-					continue
-				}
 				p.appendContainerLabels(m, c, &cp)
 				if svc != nil {
 					svc.appendCommonLabels(m)
@@ -158,10 +154,8 @@ func appendEndpointLabelsForAddresses(ms []map[string]string, gw *groupWatcher,
 			}
 		}
 		m := getEndpointLabelsForAddressAndPort(gw, podPortsSeen, eps, ea, epp, p, svc, ready)
-		if m != nil {
 		ms = append(ms, m)
 	}
-	}
 	return ms
 }
 
@@ -176,11 +170,7 @@ func getEndpointLabelsForAddressAndPort(gw *groupWatcher, podPortsSeen map[*Pod]
 	if ea.TargetRef.Kind != "Pod" || p == nil {
 		return m
 	}
-	if !p.appendCommonLabels(m, gw) {
+	p.appendCommonLabels(m, gw)
-		// The corresponding node is filtered out with label or field selectors.
-		// Do not generate endpoint labels in this case.
-		return nil
-	}
 	// always add pod targetRef, even if epp port doesn't match container port
 	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2134
 	if _, ok := podPortsSeen[p]; !ok {

lib/promscrape/discovery/kubernetes/endpointslice.go

@@ -52,10 +52,8 @@ func (eps *EndpointSlice) getTargetLabels(gw *groupWatcher) []map[string]string
 		for _, epp := range eps.Ports {
 			for _, addr := range ess.Addresses {
 				m := getEndpointSliceLabelsForAddressAndPort(gw, podPortsSeen, addr, eps, ess, epp, p, svc)
-				if m != nil {
 				ms = append(ms, m)
 			}
-			}
 
 		}
 	}
@@ -79,11 +77,7 @@ func (eps *EndpointSlice) getTargetLabels(gw *groupWatcher) []map[string]string
 				m := map[string]string{
 					"__address__": addr,
 				}
-				if !p.appendCommonLabels(m, gw) {
+				p.appendCommonLabels(m, gw)
-					// The corresponding node is filtered out with label or field selectors.
-					// Do not generate endpointslice labels in this case.
-					continue
-				}
 				p.appendContainerLabels(m, c, &cp)
 				if svc != nil {
 					svc.appendCommonLabels(m)
@@ -116,11 +110,7 @@ func getEndpointSliceLabelsForAddressAndPort(gw *groupWatcher, podPortsSeen map[
 	if _, ok := podPortsSeen[p]; !ok {
 		podPortsSeen[p] = []int{}
 	}
-	if !p.appendCommonLabels(m, gw) {
+	p.appendCommonLabels(m, gw)
-		// The corresponding node is filtered out with label or field selectors.
-		// Do not generate endpointslice labels in this case.
-		return nil
-	}
 	for _, c := range p.Spec.Containers {
 		for _, cp := range c.Ports {
 			if cp.ContainerPort == epp.Port {

lib/promscrape/discovery/kubernetes/pod.go

@@ -129,11 +129,7 @@ func appendPodLabelsInternal(ms []map[string]string, gw *groupWatcher, p *Pod, c
 		"__address__":                          addr,
 		"__meta_kubernetes_pod_container_init": isInit,
 	}
-	if !p.appendCommonLabels(m, gw) {
+	p.appendCommonLabels(m, gw)
-		// The corresponding node is filtered out with label or field selectors.
-		// Do not generate pod labels in this case.
-		return ms
-	}
 	p.appendContainerLabels(m, c, cp)
 	return append(ms, m)
 }
@@ -147,18 +143,15 @@ func (p *Pod) appendContainerLabels(m map[string]string, c Container, cp *Contai
 	}
 }
 
-func (p *Pod) appendCommonLabels(m map[string]string, gw *groupWatcher) bool {
+func (p *Pod) appendCommonLabels(m map[string]string, gw *groupWatcher) {
 	if gw.attachNodeMetadata {
-		o := gw.getObjectByRoleLocked("node", p.Metadata.Namespace, p.Spec.NodeName)
-		if o == nil {
-			// The node associated with the pod is filtered out with label or field selectors,
-			// so do not generate labels for the pod.
-			return false
-		}
-		n := o.(*Node)
 		m["__meta_kubernetes_node_name"] = p.Spec.NodeName
+		o := gw.getObjectByRoleLocked("node", p.Metadata.Namespace, p.Spec.NodeName)
+		if o != nil {
+			n := o.(*Node)
 			n.Metadata.registerLabelsAndAnnotations("__meta_kubernetes_node", m)
 		}
+	}
 	m["__meta_kubernetes_pod_name"] = p.Metadata.Name
 	m["__meta_kubernetes_pod_ip"] = p.Status.PodIP
 	m["__meta_kubernetes_pod_ready"] = getPodReadyStatus(p.Status.Conditions)
@@ -176,7 +169,6 @@ func (p *Pod) appendCommonLabels(m map[string]string, gw *groupWatcher) bool {
 		}
 	}
 	p.Metadata.registerLabelsAndAnnotations("__meta_kubernetes_pod", m)
-	return true
 }
 
 func getPodController(ors []OwnerReference) *OwnerReference {