[8.4.x]: SQLStore: Prevent concurrent migrations (#44101) (#45447)

* SQLStore: Prevent concurrent migrations (#44101)

* SQLStore: Prevent concurrent migrations

* Hide behind a feature toggle

* Configurable locking attempt timeout

* Update docs/sources/administration/configuration.md

Co-authored-by: Igor Suleymanov <radiohead@users.noreply.github.com>
Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>
(cherry picked from commit d718ee1918)

* Resolve dependency cycle (#45427)

(cherry picked from commit 6a38ce2307)

pkg/services/featuremgmt/registry.go

@@ -121,5 +121,10 @@ var (
 			Description: "Highlight Enterprise features",
 			State:       FeatureStateStable,
 		},
+		{
+			Name:        "migrationLocking",
+			Description: "Lock database during migrations",
+			State:       FeatureStateBeta,
+		},
 	}
 )

pkg/services/featuremgmt/toggles_gen.go

@@ -90,4 +90,8 @@ const (
 	// FlagFeatureHighlights
 	// Highlight Enterprise features
 	FlagFeatureHighlights = "featureHighlights"
+
+	// FlagMigrationLocking
+	// Lock database during migrations
+	FlagMigrationLocking = "migrationLocking"
 )