feat(health): add health check for Longhorn Volume

resource_customizations/longhorn.io/Volume/health.lua

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+-- Health check for the Longhorn Volume CRD.
+-- See https://argo-cd.readthedocs.io/en/stable/operator-manual/health/ for how
+-- custom health checks work and what each status means.
+-- Maps the Volume status.state and status.robustness to an Argo CD health status:
+--   Degraded    - robustness is "faulted" (the volume's data is unavailable).
+--   Progressing - the volume is being created/attached/detached, or is attached
+--                 but rebuilding replicas ("degraded" robustness).
+--   Healthy     - the volume is attached and healthy, or cleanly detached (idle).
+local hs = { status = "Progressing", message = "Waiting for volume" }
+if obj.status ~= nil then
+  local state = obj.status.state
+  local robustness = obj.status.robustness
+
+  if robustness == "faulted" then
+    hs.status = "Degraded"
+    hs.message = "Volume is faulted"
+    return hs
+  end
+
+  if state == "attached" then
+    if robustness == "healthy" then
+      hs.status = "Healthy"
+      hs.message = "Volume is attached and healthy"
+    elseif robustness == "degraded" then
+      hs.status = "Progressing"
+      hs.message = "Volume is degraded (rebuilding replicas)"
+    else
+      hs.status = "Progressing"
+      hs.message = "Volume is attached"
+    end
+    return hs
+  elseif state == "detached" then
+    hs.status = "Healthy"
+    hs.message = "Volume is detached"
+    return hs
+  elseif state ~= nil and state ~= "" then
+    hs.status = "Progressing"
+    hs.message = "Volume is " .. state
+    return hs
+  end
+end
+return hs

resource_customizations/longhorn.io/Volume/health_test.yaml

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+tests:
+  - healthStatus:
+      status: Healthy
+      message: "Volume is attached and healthy"
+    inputPath: testdata/attached_healthy.yaml
+  - healthStatus:
+      status: Healthy
+      message: "Volume is detached"
+    inputPath: testdata/detached.yaml
+  - healthStatus:
+      status: Progressing
+      message: "Volume is degraded (rebuilding replicas)"
+    inputPath: testdata/degraded.yaml
+  - healthStatus:
+      status: Degraded
+      message: "Volume is faulted"
+    inputPath: testdata/faulted.yaml
+  - healthStatus:
+      status: Progressing
+      message: "Volume is attaching"
+    inputPath: testdata/attaching.yaml

resource_customizations/longhorn.io/Volume/testdata/attached_healthy.yaml

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+apiVersion: longhorn.io/v1beta2
+kind: Volume
+metadata:
+  name: pvc-abc123
+  namespace: longhorn-system
+spec:
+  numberOfReplicas: 3
+  size: "10737418240"
+status:
+  state: attached
+  robustness: healthy
+  currentNodeID: node-1

resource_customizations/longhorn.io/Volume/testdata/attaching.yaml

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+apiVersion: longhorn.io/v1beta2
+kind: Volume
+metadata:
+  name: pvc-abc123
+  namespace: longhorn-system
+spec:
+  numberOfReplicas: 3
+  size: "10737418240"
+status:
+  state: attaching
+  robustness: unknown

resource_customizations/longhorn.io/Volume/testdata/degraded.yaml

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+apiVersion: longhorn.io/v1beta2
+kind: Volume
+metadata:
+  name: pvc-abc123
+  namespace: longhorn-system
+spec:
+  numberOfReplicas: 3
+  size: "10737418240"
+status:
+  state: attached
+  robustness: degraded
+  currentNodeID: node-1

resource_customizations/longhorn.io/Volume/testdata/detached.yaml

@@ -0,0 +1,11 @@
+apiVersion: longhorn.io/v1beta2
+kind: Volume
+metadata:
+  name: pvc-abc123
+  namespace: longhorn-system
+spec:
+  numberOfReplicas: 3
+  size: "10737418240"
+status:
+  state: detached
+  robustness: unknown

resource_customizations/longhorn.io/Volume/testdata/faulted.yaml

@@ -0,0 +1,11 @@
+apiVersion: longhorn.io/v1beta2
+kind: Volume
+metadata:
+  name: pvc-abc123
+  namespace: longhorn-system
+spec:
+  numberOfReplicas: 3
+  size: "10737418240"
+status:
+  state: detached
+  robustness: faulted