Make sure panel id is unique since some datasources (Graphite) will cancel ongoing requests with the same panel id

public/app/features/explore/Explore.tsx

@@ -608,9 +608,11 @@ export class Explore extends React.PureComponent<ExploreProps, ExploreState> {
     // Clone range for query request
     // const queryRange: RawTimeRange = { ...range };
     // const { from, to, raw } = this.timeSrv.timeRange();
-    // Datasource is using `panelId + query.refId` for cancellation logic.
+    // Most datasource is using `panelId + query.refId` for cancellation logic.
     // Using `format` here because it relates to the view panel that the request is for.
-    const panelId = queryOptions.format;
+    // However, some datasources don't use `panelId + query.refId`, but only `panelId`.
+    // Therefore panel id has to be unique.
+    const panelId = `${queryOptions.format}-${query.key}`;
 
     return {
       interval,