fix: OpenTelemetryCollector health check shows 0/0 for mode: daemonset (#26391)

Signed-off-by: tank.500m <tank.500m@kakaocorp.com>

resource_customizations/opentelemetry.io/OpenTelemetryCollector/health.lua

@@ -14,8 +14,16 @@ if obj.status ~= nil then
             total = tonumber(total)
 
             if ready == 0 then
-                hs.status = "Degraded"
-                hs.message = "No replicas are ready"
+                -- DaemonSet desiredNumberScheduled is based on eligible nodes.
+                -- 0/0 is valid when no nodes match; treat as Healthy.
+                -- https://kubernetes.io/docs/concepts/workloads/controllers/daemonset/#how-daemon-pods-are-scheduled
+                if obj.spec ~= nil and obj.spec.mode == "daemonset" and total == 0 then
+                    hs.status = "Healthy"
+                    hs.message = "DaemonSet has no eligible nodes (0/0)"
+                else
+                    hs.status = "Degraded"
+                    hs.message = "No replicas are ready"
+                end
             elseif ready == total then
                 hs.status = "Healthy"
                 hs.message = "All replicas are ready"

resource_customizations/opentelemetry.io/OpenTelemetryCollector/health_test.yaml

@@ -3,6 +3,10 @@ tests:
       status: Healthy
       message: "All replicas are ready"
     inputPath: testdata/healthy.yaml
+  - healthStatus:
+      status: Healthy
+      message: "DaemonSet has no eligible nodes (0/0)"
+    inputPath: testdata/daemonset-no-eligible-node.yaml
   - healthStatus:
       status: Degraded
       message: "No replicas are ready"

resource_customizations/opentelemetry.io/OpenTelemetryCollector/testdata/daemonset-no-eligible-node.yaml

@@ -0,0 +1,14 @@
+apiVersion: opentelemetry.io/v1beta1
+kind: OpenTelemetryCollector
+metadata:
+  name: test-collector-daemonset-no-eligible-node
+  namespace: default
+spec:
+  mode: daemonset
+status:
+  image: ghcr.io/open-telemetry/opentelemetry-collector-releases/opentelemetry-collector-contrib:0.124.1
+  scale:
+    replicas: 0
+    selector: app.kubernetes.io/component=opentelemetry-collector
+    statusReplicas: 0/0
+  version: 0.124.1