[Performance] Report scale dimensions for service-map and hosts (#205607)

closes https://github.com/elastic/observability-dev/issues/3777 

## Summary

This PR provides scale dimensions for the service map and infra host
pages without introducing any additional requests.

### Global Service Map and Per-service APM Service Map 


| Metric         | Description                        |
|----------------|------------------------------------|
| `num_of_nodes` | Total number of discovered nodes (services +
dependenies |
| `num_of_traces`   | Total number of traces             |

### Infra


| Metric        | Description                     | default
|---------------|---------------------------------| -----------------
| `num_of_hosts`  | Total number of hosts          |
| `max_hosts_per_page` | Maximum number of host returne `50/100/500` |
100


| Page | Screenshot |

|-------------------------------|-------------------------------------------------------------------------------------------|
| Global Service Map | ![Screenshot 2025-01-08 at 12 54
43](https://github.com/user-attachments/assets/478b1f7b-bbd7-4ed5-8a7f-b041e6dab3b5)
|
| Per-service APM Service Map | ![Screenshot 2025-01-08 at 12 53
07](https://github.com/user-attachments/assets/62ee7852-6410-4dfc-9da2-5fc849ec18bc)
|
| Infra | !![Screenshot 2025-01-08 at 12 56
00](https://github.com/user-attachments/assets/e8b28a9c-14f7-4296-83cb-ddc25047f508)
|

 





### How to test
- Open any of the above pages
- In the network tab, look for `kibana:plugin_render_time`

x-pack/solutions/observability/plugins/apm/public/components/app/service_map/index.tsx

@@ -110,7 +110,7 @@ export function ServiceMap({
   const { onPageReady } = usePerformanceContext();
 
   const {
-    data = { elements: [] },
+    data = { elements: [], nodesCount: 0, tracesCount: 0 },
     status,
     error,
   } = useFetcher(
@@ -187,6 +187,12 @@ export function ServiceMap({
 
   if (status === FETCH_STATUS.SUCCESS) {
     onPageReady({
+      customMetrics: {
+        key1: 'num_of_nodes',
+        value1: data.nodesCount,
+        key2: 'num_of_traces',
+        value2: data.tracesCount,
+      },
       meta: { rangeFrom: start, rangeTo: end },
     });
   }

x-pack/solutions/observability/plugins/apm/server/routes/service_map/get_service_map.ts

@@ -32,6 +32,11 @@ export interface IEnvOptions {
   kuery?: string;
 }
 
+export interface ServiceMapTelemetry {
+  tracesCount: number;
+  nodesCount: number;
+}
+
 async function getConnectionData({
   config,
   apmEventClient,
@@ -63,6 +68,8 @@ async function getConnectionData({
     const init = {
       connections: [],
       discoveredServices: [],
+      tracesCount: 0,
+      servicesCount: 0,
     };
 
     if (!traceIds.length) {
@@ -99,16 +106,17 @@ async function getConnectionData({
 
     logger.debug('Merged responses');
 
-    return mergedResponses;
+    return { ...mergedResponses, tracesCount: traceIds.length };
   });
 }
 
 export type ConnectionsResponse = Awaited<ReturnType<typeof getConnectionData>>;
 export type ServicesResponse = Awaited<ReturnType<typeof getServiceStats>>;
+export type ServiceMapResponse = TransformServiceMapResponse & ServiceMapTelemetry;
 
 export function getServiceMap(
   options: IEnvOptions & { maxNumberOfServices: number }
-): Promise<TransformServiceMapResponse> {
+): Promise<ServiceMapResponse> {
   return withApmSpan('get_service_map', async () => {
     const { logger } = options;
     const anomaliesPromise = getServiceAnomalies(
@@ -137,8 +145,10 @@ export function getServiceMap(
       },
     });
 
-    logger.debug('Transformed service map response');
-
-    return transformedResponse;
+    return {
+      ...transformedResponse,
+      tracesCount: connectionData.tracesCount,
+      nodesCount: transformedResponse.nodesCount,
+    };
   });
 }

x-pack/solutions/observability/plugins/apm/server/routes/service_map/group_resource_nodes.ts

@@ -39,6 +39,7 @@ interface GroupedEdge {
 
 export interface GroupResourceNodesResponse {
   elements: Array<GroupedNode | GroupedEdge | ConnectionElement>;
+  nodesCount: number;
 }
 
 export function groupResourceNodes(responseData: {
@@ -151,5 +152,6 @@ export function groupResourceNodes(responseData: {
 
   return {
     elements: [...ungroupedNodes, ...groupedNodes, ...ungroupedEdges, ...groupedEdges],
+    nodesCount: ungroupedNodes.length,
   };
 }

x-pack/solutions/observability/plugins/apm/server/routes/service_map/route.ts

@@ -23,7 +23,7 @@ import { environmentRt, rangeRt, kueryRt } from '../default_api_types';
 import { getServiceGroup } from '../service_groups/get_service_group';
 import { offsetRt } from '../../../common/comparison_rt';
 import { getApmEventClient } from '../../lib/helpers/get_apm_event_client';
-import type { TransformServiceMapResponse } from './transform_service_map_responses';
+import type { ServiceMapResponse } from './get_service_map';
 
 const serviceMapRoute = createApmServerRoute({
   endpoint: 'GET /internal/apm/service-map',
@@ -39,7 +39,7 @@ const serviceMapRoute = createApmServerRoute({
     ]),
   }),
   security: { authz: { requiredPrivileges: ['apm'] } },
-  handler: async (resources): Promise<TransformServiceMapResponse> => {
+  handler: async (resources): Promise<ServiceMapResponse> => {
     const { config, context, params, logger } = resources;
     if (!config.serviceMapEnabled) {
       throw Boom.notFound();

x-pack/solutions/observability/plugins/apm/server/routes/service_map/transform_service_map_responses.test.ts

@@ -73,6 +73,7 @@ describe('transformServiceMapResponses', () => {
         },
       ],
       anomalies,
+      tracesCount: 10,
     };
 
     const { elements } = transformServiceMapResponses({ response });
@@ -106,6 +107,7 @@ describe('transformServiceMapResponses', () => {
         },
       ],
       anomalies,
+      tracesCount: 10,
     };
 
     const { elements } = transformServiceMapResponses({ response });
@@ -165,6 +167,7 @@ describe('transformServiceMapResponses', () => {
         },
       ],
       anomalies,
+      tracesCount: 10,
     };
 
     const { elements } = transformServiceMapResponses({ response });
@@ -203,6 +206,7 @@ describe('transformServiceMapResponses', () => {
         },
       ],
       anomalies,
+      tracesCount: 10,
     };
 
     const { elements } = transformServiceMapResponses({ response });
@@ -228,6 +232,7 @@ describe('transformServiceMapResponses', () => {
         },
       ],
       anomalies,
+      tracesCount: 10,
     };
 
     const { elements } = transformServiceMapResponses({ response });

x-pack/solutions/observability/plugins/infra/public/pages/metrics/hosts/components/hosts_table.tsx

@@ -17,10 +17,13 @@ import { useHostCountContext } from '../hooks/use_host_count';
 import { FlyoutWrapper } from './host_details_flyout/flyout_wrapper';
 import { DEFAULT_PAGE_SIZE, PAGE_SIZE_OPTIONS } from '../constants';
 import { FilterAction } from './table/filter_action';
+import { useUnifiedSearchContext } from '../hooks/use_unified_search';
 
 export const HostsTable = () => {
   const { loading } = useHostsViewContext();
-  const { loading: hostCountLoading } = useHostCountContext();
+  const { loading: hostCountLoading, count } = useHostCountContext();
+  const { searchCriteria } = useUnifiedSearchContext();
+
   const { onPageReady } = usePerformanceContext();
 
   const {
@@ -40,9 +43,16 @@ export const HostsTable = () => {
 
   useEffect(() => {
     if (!loading && !hostCountLoading) {
-      onPageReady();
+      onPageReady({
+        customMetrics: {
+          key1: 'num_of_hosts',
+          value1: count,
+          key2: `max_hosts_per_page`,
+          value2: searchCriteria.limit,
+        },
+      });
     }
-  }, [loading, hostCountLoading, onPageReady]);
+  }, [loading, hostCountLoading, onPageReady, count, searchCriteria]);
 
   return (
     <>