Rescue Kubeclient::HttpError when generating prometheus_client

app/models/clusters/applications/prometheus.rb

@@ -49,6 +49,11 @@ module Clusters
         # ensures headers containing auth data are appended to original k8s client options
         options = kube_client.rest_client.options.merge(headers: kube_client.headers)
         RestClient::Resource.new(proxy_url, options)
+      rescue Kubeclient::HttpError
+        # If users have mistakenly set parameters or removed the depended clusters,
+        # `proxy_url` could raise an exception because gitlab can not communicate with the cluster.
+        # Since `PrometheusAdapter#can_query?` is eargely loaded on environement pages in gitlab,
+        # we need to silence the exceptions
       end
 
       private