Alerting: Dry-run legacy upgrade on startup (#82835)

Adds a feature flag (alertingUpgradeDryrunOnStart) that will dry-run the legacy 
alert upgrade on startup. It is enabled by default.

When on legacy alerting, this feature flag will log the results of the legacy 
alerting upgrade on startup and draw attention to anything in the current legacy 
alerting configuration that will cause issues when the upgrade is eventually 
performed. It acts as a log warning for those where action is required before 
upgrading to Grafana v11 where legacy alerting will be removed.

pkg/services/featuremgmt/registry.go

@@ -1214,6 +1214,15 @@ var (
 			HideFromDocs:      true,
 			HideFromAdminPage: true,
 		},
+		{
+			Name:            "alertingUpgradeDryrunOnStart",
+			Description:     "When activated in legacy alerting mode, this initiates a dry-run of the Unified Alerting upgrade during each startup. It logs any issues detected without implementing any actual changes.",
+			FrontendOnly:    false,
+			Stage:           FeatureStageGeneralAvailability,
+			Owner:           grafanaAlertingSquad,
+			RequiresRestart: true,
+			Expression:      "true", // enabled by default
+		},
 	}
 )
 

pkg/services/featuremgmt/toggles_gen.csv

@@ -162,3 +162,4 @@ groupToNestedTableTransformation,preview,@grafana/dataviz-squad,false,false,true
 newPDFRendering,experimental,@grafana/sharing-squad,false,false,false
 kubernetesAggregator,experimental,@grafana/grafana-app-platform-squad,false,true,false
 groupByVariable,experimental,@grafana/dashboards-squad,false,false,false
+alertingUpgradeDryrunOnStart,GA,@grafana/alerting-squad,false,true,false

pkg/services/featuremgmt/toggles_gen.go

@@ -658,4 +658,8 @@ const (
 	// FlagGroupByVariable
 	// Enable groupBy variable support in scenes dashboards
 	FlagGroupByVariable = "groupByVariable"
+
+	// FlagAlertingUpgradeDryrunOnStart
+	// When activated in legacy alerting mode, this initiates a dry-run of the Unified Alerting upgrade during each startup. It logs any issues detected without implementing any actual changes.
+	FlagAlertingUpgradeDryrunOnStart = "alertingUpgradeDryrunOnStart"
 )

pkg/services/featuremgmt/toggles_gen.json

@@ -2124,6 +2124,22 @@
         "codeowner": "@grafana/plugins-platform-backend",
         "requiresRestart": true
       }
+    },
+    {
+      "metadata": {
+        "name": "alertingUpgradeDryrunOnStart",
+        "resourceVersion": "1708098586429",
+        "creationTimestamp": "2024-02-15T21:01:16Z",
+        "annotations": {
+          "grafana.app/updatedTimestamp": "2024-02-16 15:49:46.429030423 +0000 UTC"
+        }
+      },
+      "spec": {
+        "description": "When activated in legacy alerting mode, this initiates a dry-run of the Unified Alerting upgrade during each startup. It logs any issues detected without implementing any actual changes.",
+        "stage": "GA",
+        "codeowner": "@grafana/alerting-squad",
+        "requiresRestart": true
+      }
     }
   ]
 }