Prevent deleting upstream that is use

backend/internal/api/handler/upstreams.go

@@ -9,6 +9,7 @@ import (
 	c "npm/internal/api/context"
 	h "npm/internal/api/http"
 	"npm/internal/api/middleware"
+	"npm/internal/entity/host"
 	"npm/internal/entity/upstream"
 	"npm/internal/jobqueue"
 	"npm/internal/logger"
@@ -151,6 +152,12 @@ func DeleteUpstream() func(http.ResponseWriter, *http.Request) {
 		case sql.ErrNoRows:
 			h.ResultErrorJSON(w, r, http.StatusNotFound, "Not found", nil)
 		case nil:
+			// Ensure that this upstream isn't in use by a host
+			cnt := host.GetUpstreamUseCount(upstreamID)
+			if cnt > 0 {
+				h.ResultErrorJSON(w, r, http.StatusBadRequest, "Cannot delete upstream that is in use by at least 1 host", nil)
+				return
+			}
 			h.ResultResponseJSON(w, r, http.StatusOK, item.Delete())
 			configureUpstream(item)
 		default:

backend/internal/entity/host/methods.go

@@ -29,7 +29,7 @@ func create(host *Model) (int, error) {
 
 	db := database.GetInstance()
 	// nolint: gosec
-	result, err := db.NamedExec(`INSERT INTO `+fmt.Sprintf("`%s`", tableName)+` (
+	result, err := db.NamedExec(`INSERT INTO `+tableName+` (
 		created_on,
 		modified_on,
 		user_id,
@@ -198,6 +198,21 @@ func List(pageInfo model.PageInfo, filters []model.Filter, expand []string) (Lis
 	return result, nil
 }
 
+// GetUpstreamUseCount returns the number of hosts that are using
+// an upstream, and have not been deleted.
+func GetUpstreamUseCount(upstreamID int) int {
+	db := database.GetInstance()
+	query := fmt.Sprintf("SELECT COUNT(*) FROM %s WHERE upstream_id = ? AND is_deleted = ?", tableName)
+	countRow := db.QueryRowx(query, upstreamID, 0)
+	var totalRows int
+	queryErr := countRow.Scan(&totalRows)
+	if queryErr != nil && queryErr != sql.ErrNoRows {
+		logger.Debug("%s", query)
+		return 0
+	}
+	return totalRows
+}
+
 // AddPendingJobs is intended to be used at startup to add
 // anything pending to the JobQueue just once, based on
 // the database row status