[Fleet] Add agents per OS telemetry (#163039)

## Summary

Querying agent operating system to add to telemetry.

How to test locally:
- enroll a few different agents running on different operating system
- wait up to 1h to see the telemetry task triggered
- check debug logs to see that the agents per version telemetry contains
the status information

x-pack/plugins/fleet/server/collectors/agent_collectors.ts

@@ -70,12 +70,18 @@ export interface AgentData {
     degraded: number;
   };
   agents_per_policy: number[];
+  agents_per_os: Array<{
+    name: string;
+    version: string;
+    count: number;
+  }>;
 }
 
 const DEFAULT_AGENT_DATA = {
   agent_checkin_status: { error: 0, degraded: 0 },
   agents_per_policy: [],
   agents_per_version: [],
+  agents_per_os: [],
 };
 
 export const getAgentData = async (
@@ -117,6 +123,18 @@ export const getAgentData = async (
           policies: {
             terms: { field: 'policy_id' },
           },
+          os: {
+            multi_terms: {
+              terms: [
+                {
+                  field: 'local_metadata.os.name.keyword',
+                },
+                {
+                  field: 'local_metadata.os.version.keyword',
+                },
+              ],
+            },
+          },
         },
       },
       { signal: abortController.signal }
@@ -166,10 +184,17 @@ export const getAgentData = async (
       (bucket: any) => bucket.doc_count
     );
 
+    const agentsPerOS = ((response?.aggregations?.os as any).buckets ?? []).map((bucket: any) => ({
+      name: bucket.key[0],
+      version: bucket.key[1],
+      count: bucket.doc_count,
+    }));
+
     return {
       agent_checkin_status: statuses,
       agents_per_policy: agentsPerPolicy,
       agents_per_version: agentsPerVersion,
+      agents_per_os: agentsPerOS,
     };
   } catch (error) {
     if (error.statusCode === 404) {

x-pack/plugins/fleet/server/integration_tests/fleet_usage_telemetry.test.ts

@@ -130,6 +130,12 @@ describe('fleet usage telemetry', () => {
           last_checkin: '2022-11-21T12:26:24Z',
           active: true,
           policy_id: 'policy1',
+          local_metadata: {
+            os: {
+              name: 'Ubuntu',
+              version: '22.04.2 LTS (Jammy Jellyfish)',
+            },
+          },
         },
         {
           create: {
@@ -144,6 +150,12 @@ describe('fleet usage telemetry', () => {
           last_checkin: '2022-11-21T12:27:24Z',
           active: true,
           policy_id: 'policy1',
+          local_metadata: {
+            os: {
+              name: 'Ubuntu',
+              version: '20.04.5 LTS (Focal Fossa)',
+            },
+          },
         },
         {
           create: {
@@ -158,6 +170,12 @@ describe('fleet usage telemetry', () => {
           last_checkin: '2021-11-21T12:27:24Z',
           active: false,
           policy_id: 'policy1',
+          local_metadata: {
+            os: {
+              name: 'Ubuntu',
+              version: '20.04.5 LTS (Focal Fossa)',
+            },
+          },
         },
       ],
       refresh: 'wait_for',
@@ -374,6 +392,18 @@ describe('fleet usage telemetry', () => {
         ],
         agent_checkin_status: { error: 1, degraded: 1 },
         agents_per_policy: [2],
+        agents_per_os: [
+          {
+            name: 'Ubuntu',
+            version: '20.04.5 LTS (Focal Fossa)',
+            count: 1,
+          },
+          {
+            name: 'Ubuntu',
+            version: '22.04.2 LTS (Jammy Jellyfish)',
+            count: 1,
+          },
+        ],
         fleet_server_config: {
           policies: [
             {

x-pack/plugins/fleet/server/services/telemetry/fleet_usage_sender.ts

@@ -24,7 +24,7 @@ const FLEET_AGENTS_EVENT_TYPE = 'fleet_agents';
 
 export class FleetUsageSender {
   private taskManager?: TaskManagerStartContract;
-  private taskVersion = '1.1.0';
+  private taskVersion = '1.1.1';
   private taskType = 'Fleet-Usage-Sender';
   private wasStarted: boolean = false;
   private interval = '1h';

x-pack/plugins/fleet/server/services/telemetry/fleet_usages_schema.ts

@@ -261,4 +261,26 @@ export const fleetUsagesSchema: RootSchema<any> = {
       _meta: { description: 'Top messages from fleet server error logs' },
     },
   },
+  agents_per_os: {
+    properties: {
+      name: {
+        type: 'keyword',
+        _meta: {
+          description: 'Agent OS enrolled to this kibana',
+        },
+      },
+      version: {
+        type: 'keyword',
+        _meta: {
+          description: 'Agent OS version enrolled to this kibana',
+        },
+      },
+      count: {
+        type: 'long',
+        _meta: {
+          description: 'Number of agents enrolled that use this OS',
+        },
+      },
+    },
+  },
 };