chore: Add some empty dir volume mounts for the application controller (

#19474)

Closes #19474

Kube cache couldn't be used on read-only root file system leading to errors as revealed with `--gloglevel` equal to 6.
Create an empty dir mount for `/tmp` and add a config-map-based param to override `KUBECACHEDIR`.

Signed-off-by: Andrii Korotkov <[email protected]>

docs/operator-manual/argocd-cmd-params-cm.yaml

@@ -74,6 +74,8 @@ data:
   controller.diff.server.side: "false"
   # Enables profile endpoint on the internal metrics port
   controller.profile.enabled: "false"
+  # Changes the directory for kube caching, useful when root filesystem is readonly. E.g. put it somewhere in /tmp as it's mounted as an empty dir. Defaults to $HOME/.kube/cache.
+  controller.kubecachedir:
 
   ## Server properties
   # Listen on given address for incoming connections (default "0.0.0.0")

manifests/base/application-controller/argocd-application-controller-statefulset.yaml

@@ -208,6 +208,12 @@ spec:
               name: argocd-cmd-params-cm
               key: controller.ignore.normalizer.jq.timeout
               optional: true
+        - name: KUBECACHEDIR
+          valueFrom:
+            configMapKeyRef:
+              key: controller.kubecachedir
+              name: argocd-cmd-params-cm
+              optional: true
         image: quay.io/argoproj/argocd:latest
         imagePullPolicy: Always
         name: argocd-application-controller
@@ -236,6 +242,8 @@ spec:
           mountPath: /home/argocd
         - name: argocd-cmd-params-cm
           mountPath: /home/argocd/params
+        - name: argocd-application-controller-tmp
+          mountPath: /tmp
       serviceAccountName: argocd-application-controller
       affinity:
         podAntiAffinity:
@@ -255,6 +263,8 @@ spec:
       volumes:
       - emptyDir: {}
         name: argocd-home
+      - emptyDir: {}
+        name: argocd-application-controller-tmp
       - name: argocd-repo-server-tls
         secret:
           secretName: argocd-repo-server-tls