Links: Filter data sources in derived link to tracing only (#23948)

docs/sources/features/datasources/loki.md

@@ -189,14 +189,15 @@ datasources:
     jsonData:
       maxLines: 1000
       derivedFields:
-        # Field with internal link pointing to datasource in Grafana
+        # Field with internal link pointing to data source in Grafana.
+        # Right now, Grafana supports only Jaeger and Zipkin data sources as link targets.
         - datasourceUid: my_jaeger_uid
           matcherRegex: "traceID=(\\w+)"
           name: TraceID
           # url will be interpreted as query for the datasource
           url: "$${__value.raw}"
 
-        # Field with external link
+        # Field with external link.
         - matcherRegex: "traceID=(\\w+)"
           name: TraceID
           url: "http://localhost:16686/trace/$${__value.raw}"

public/app/plugins/datasource/loki/configuration/DerivedField.test.tsx

@@ -2,12 +2,31 @@ import React from 'react';
 import { shallow } from 'enzyme';
 import { DerivedField } from './DerivedField';
 import DataSourcePicker from '../../../../core/components/Select/DataSourcePicker';
+import { DataSourceInstanceSettings } from '@grafana/data';
 
 jest.mock('app/features/plugins/datasource_srv', () => ({
   getDatasourceSrv() {
     return {
-      getExternal(): any[] {
-        return [];
+      getExternal(): DataSourceInstanceSettings[] {
+        return [
+          {
+            id: 1,
+            uid: 'metrics',
+            name: 'metrics_ds',
+            meta: {
+              tracing: false,
+            } as any,
+          } as any,
+
+          {
+            id: 2,
+            uid: 'tracing',
+            name: 'tracing_ds',
+            meta: {
+              tracing: true,
+            } as any,
+          } as any,
+        ];
       },
     };
   },
@@ -39,4 +58,21 @@ describe('DerivedField', () => {
     const wrapper = shallow(<DerivedField value={value} onChange={() => {}} onDelete={() => {}} suggestions={[]} />);
     expect(wrapper.find('DataSourceSection').length).toBe(0);
   });
+
+  it('shows only tracing datasources for internal link', () => {
+    const value = {
+      matcherRegex: '',
+      name: '',
+      datasourceUid: 'test',
+    };
+    const wrapper = shallow(<DerivedField value={value} onChange={() => {}} onDelete={() => {}} suggestions={[]} />);
+    const dsSection = wrapper.find('DataSourceSection').dive();
+    expect(dsSection.find(DataSourcePicker).props().datasources).toEqual([
+      {
+        meta: { tracing: true },
+        name: 'tracing_ds',
+        value: 'tracing',
+      },
+    ]);
+  });
 });

public/app/plugins/datasource/loki/configuration/DerivedField.tsx

@@ -152,6 +152,8 @@ const DataSourceSection = (props: DataSourceSectionProps) => {
   const { datasourceUid, onChange } = props;
   const datasources: DataSourceSelectItem[] = getDatasourceSrv()
     .getExternal()
+    // At this moment only Jaeger and Zipkin datasource is supported as the link target.
+    .filter(ds => ds.meta.tracing)
     .map(
       ds =>
         ({