When having ApplicationSet that uses shared clsuterDecisionResource, if a cluster is not found to apply one of them, it will not apply any of the application.

The applicationSet has these.

~~~
  generators:
  - clusterDecisionResource:
      configMapRef: acm-placement
      labelSelector:
        matchLabels:
          cluster.open-cluster-management.io/placement: cluster-common-dev
      requeueAfterSeconds: 180
      values:
        targetRef: feature-vishaltest
  - clusterDecisionResource:
      configMapRef: acm-placement
      labelSelector:
        matchLabels:
          cluster.open-cluster-management.io/placement: cluster-infra-dev
      requeueAfterSeconds: 180
      values:
        targetRef: develop
~~~

What this means is that look for the resource kind defined in configMapRef: acm-placement that has label cluster.open-cluster-management.io/placement: cluster-infra-dev. The resource is PlacementDecision.

When you remove the label cluster-infra=dev from the clustername cluster, the cluster-infra-dev placement cannot make any decision because there is no cluster matching the placement criteria so it removes the PlacementDecision. You can check using oc get placementdecision -n openshift-gitops --show-labels

Since the application set has a reference to a clusterDecisionResource 

~~~
  - clusterDecisionResource:
      configMapRef: acm-placement
      labelSelector:
        matchLabels:
          cluster.open-cluster-management.io/placement: cluster-infra-dev
~~~

which does not exist any more, the application set controller throws this error and cannot re-generate applicaitons.
time="2022-10-26T17:25:24Z" level=info msg="Kind.Group/Version Reference" kind.apiVersion=placementdecisions.cluster.open-cluster-management.io/v1beta1
time="2022-10-26T17:25:24Z" level=info msg="selection type" listOptions.LabelSelector="cluster.open-cluster-management.io/placement=cluster-infra-dev"
time="2022-10-26T17:25:24Z" level=warning msg="no resource found, make sure you clusterDecisionResource is defined correctly"
time="2022-10-26T17:25:24Z" level=error msg="error generating params" error="no clusterDecisionResources found" generator="&{0xc00005c058 0xc000812280 0xc0012d5e00 openshift-gitops 0xc00089e240}"
time="2022-10-26T17:25:24Z" level=error msg="error generating application from params" error="no clusterDecisionResources found" generator="{<nil> <nil> <nil> <nil> 0xc000a7e600 <nil> <nil> <nil>}"

In addition, if you change log level to debug you'll see that the generator actually generates the application for one cluster which is in the existing placement decision, but just does not apply it because of the error on the missing placement decision

gitops operator1.5.x and 1.6.1

Always

1.
2.
3.

No applications generated / applied

Application with found target cluster get generated