[Fleet] Implement active agent soft limit (#161289)

config/serverless.yml

@@ -2,9 +2,11 @@ interactiveSetup.enabled: false
 newsfeed.enabled: false
 xpack.security.showNavLinks: false
 xpack.serverless.plugin.enabled: true
+# Fleet settings
 xpack.fleet.internal.fleetServerStandalone: true
 xpack.fleet.internal.disableILMPolicies: true
 xpack.fleet.internal.disableProxies: true
+xpack.fleet.internal.activeAgentsSoftLimit: 25000
 
 # Enable ZDT migration algorithm
 migrations.algorithm: zdt
@@ -13,7 +15,7 @@ migrations.algorithm: zdt
 # until the controller is able to spawn the migrator job/pod
 migrations.zdt:
   metaPickupSyncDelaySec: 5
-  runOnRoles: ["ui"]
+  runOnRoles: ['ui']
 
 # Ess plugins
 xpack.securitySolutionEss.enabled: false

test/plugin_functional/test_suites/core_plugins/rendering.ts

@@ -221,6 +221,7 @@ export default function ({ getService }: PluginFunctionalProviderContext) {
         'xpack.discoverEnhanced.actions.exploreDataInContextMenu.enabled (boolean)',
         'xpack.fleet.agents.enabled (boolean)',
         'xpack.fleet.enableExperimental (array)',
+        'xpack.fleet.internal.activeAgentsSoftLimit (number)',
         'xpack.fleet.internal.disableProxies (boolean)',
         'xpack.fleet.internal.fleetServerStandalone (boolean)',
         'xpack.fleet.developer.maxAgentPoliciesWithInactivityTimeout (number)',

x-pack/plugins/fleet/common/types/index.ts

@@ -49,6 +49,7 @@ export interface FleetConfigType {
     disableILMPolicies: boolean;
     disableProxies: boolean;
     fleetServerStandalone: boolean;
+    activeAgentsSoftLimit?: number;
   };
   createArtifactsBulkBatchSize?: number;
 }

x-pack/plugins/fleet/public/applications/fleet/sections/agents/agent_list_page/components/agent_soft_limit_callout.tsx

@@ -0,0 +1,37 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import React from 'react';
+import { EuiCallOut } from '@elastic/eui';
+import { FormattedMessage, FormattedNumber } from '@kbn/i18n-react';
+
+import { useConfig } from '../../../../hooks';
+
+export const AgentSoftLimitCallout = () => {
+  const config = useConfig();
+
+  return (
+    <EuiCallOut
+      iconType="warning"
+      color="warning"
+      title={
+        <FormattedMessage
+          id="xpack.fleet.agentSoftLimitCallout.calloutTitle"
+          defaultMessage="Max number of online agents reached"
+        />
+      }
+    >
+      <FormattedMessage
+        id="xpack.fleet.agentSoftLimitCallout.calloutDescription"
+        defaultMessage="Fleet supports a maximum of {nbAgents} active agents. You need to unenroll some agents to ensure that all active agents are able to connect and new agents can be enrolled."
+        values={{
+          nbAgents: <FormattedNumber value={config.internal?.activeAgentsSoftLimit ?? 25000} />,
+        }}
+      />
+    </EuiCallOut>
+  );
+};

x-pack/plugins/fleet/public/applications/fleet/sections/agents/agent_list_page/components/index.tsx

@@ -7,3 +7,4 @@
 
 export { AgentActivityFlyout } from './agent_activity_flyout';
 export { AgentActivityButton } from './agent_activity_button';
+export { AgentSoftLimitCallout } from './agent_soft_limit_callout';

x-pack/plugins/fleet/public/applications/fleet/sections/agents/agent_list_page/hooks/index.tsx

@@ -9,3 +9,4 @@ export { useUpdateTags } from './use_update_tags';
 export { useActionStatus } from './use_action_status';
 export { useLastSeenInactiveAgentsCount } from './use_last_seen_inactive_agents_count';
 export { useInactiveAgentsCalloutHasBeenDismissed } from './use_inactive_agents_callout_has_been_dismissed';
+export { useAgentSoftLimit } from './use_agent_soft_limit';

x-pack/plugins/fleet/public/applications/fleet/sections/agents/agent_list_page/hooks/use_agent_soft_limit.test.tsx

@@ -0,0 +1,62 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { createFleetTestRendererMock } from '../../../../../../mock';
+import { useConfig, sendGetAgents } from '../../../../hooks';
+
+import { useAgentSoftLimit } from './use_agent_soft_limit';
+
+jest.mock('../../../../hooks');
+
+const mockedSendGetAgents = jest.mocked(sendGetAgents);
+const mockedUseConfig = jest.mocked(useConfig);
+
+describe('useAgentSoftLimit', () => {
+  beforeEach(() => {
+    mockedSendGetAgents.mockReset();
+    mockedUseConfig.mockReset();
+  });
+  it('should return shouldDisplayAgentSoftLimit:false if soft limit is not enabled in config', async () => {
+    const renderer = createFleetTestRendererMock();
+    mockedUseConfig.mockReturnValue({} as any);
+    const { result } = renderer.renderHook(() => useAgentSoftLimit());
+
+    expect(result.current.shouldDisplayAgentSoftLimit).toEqual(false);
+
+    expect(mockedSendGetAgents).not.toBeCalled();
+  });
+
+  it('should return shouldDisplayAgentSoftLimit:false if soft limit is enabled in config and there is less online agents than the limit', async () => {
+    const renderer = createFleetTestRendererMock();
+    mockedUseConfig.mockReturnValue({ internal: { activeAgentsSoftLimit: 10 } } as any);
+    mockedSendGetAgents.mockResolvedValue({
+      data: {
+        total: 5,
+      },
+    } as any);
+    const { result, waitForNextUpdate } = renderer.renderHook(() => useAgentSoftLimit());
+    await waitForNextUpdate();
+
+    expect(mockedSendGetAgents).toBeCalled();
+    expect(result.current.shouldDisplayAgentSoftLimit).toEqual(false);
+  });
+
+  it('should return shouldDisplayAgentSoftLimit:true if soft limit is enabled in config and there is more online agents than the limit', async () => {
+    const renderer = createFleetTestRendererMock();
+    mockedUseConfig.mockReturnValue({ internal: { activeAgentsSoftLimit: 10 } } as any);
+    mockedSendGetAgents.mockResolvedValue({
+      data: {
+        total: 15,
+      },
+    } as any);
+    const { result, waitForNextUpdate } = renderer.renderHook(() => useAgentSoftLimit());
+    await waitForNextUpdate();
+
+    expect(mockedSendGetAgents).toBeCalled();
+    expect(result.current.shouldDisplayAgentSoftLimit).toEqual(true);
+  });
+});

x-pack/plugins/fleet/public/applications/fleet/sections/agents/agent_list_page/hooks/use_agent_soft_limit.tsx

@@ -0,0 +1,38 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { useQuery } from '@tanstack/react-query';
+
+import { useConfig, sendGetAgents } from '../../../../hooks';
+
+async function fetchTotalOnlineAgents() {
+  const response = await sendGetAgents({
+    kuery: 'status:online',
+    perPage: 0,
+    showInactive: false,
+  });
+
+  if (response.error) {
+    throw new Error(response.error.message);
+  }
+
+  return response.data?.total ?? 0;
+}
+
+export function useAgentSoftLimit() {
+  const config = useConfig();
+
+  const softLimit = config.internal?.activeAgentsSoftLimit;
+
+  const { data: totalAgents } = useQuery(['fetch-total-online-agents'], fetchTotalOnlineAgents, {
+    enabled: softLimit !== undefined,
+  });
+
+  return {
+    shouldDisplayAgentSoftLimit: softLimit && totalAgents ? totalAgents > softLimit : false,
+  };
+}

x-pack/plugins/fleet/public/applications/fleet/sections/agents/agent_list_page/index.tsx

@@ -47,10 +47,11 @@ import { AgentTableHeader } from './components/table_header';
 import type { SelectionMode } from './components/types';
 import { SearchAndFilterBar } from './components/search_and_filter_bar';
 import { TagsAddRemove } from './components/tags_add_remove';
-import { AgentActivityFlyout } from './components';
+import { AgentActivityFlyout, AgentSoftLimitCallout } from './components';
 import { TableRowActions } from './components/table_row_actions';
 import { AgentListTable } from './components/agent_list_table';
 import { getKuery } from './utils/get_kuery';
+import { useAgentSoftLimit } from './hooks';
 
 const REFRESH_INTERVAL_MS = 30000;
 
@@ -396,6 +397,8 @@ export const AgentListPage: React.FunctionComponent<{}> = () => {
   const { isFleetServerStandalone } = useFleetServerStandalone();
   const showUnhealthyCallout = isFleetServerUnhealthy && !isFleetServerStandalone;
 
+  const { shouldDisplayAgentSoftLimit } = useAgentSoftLimit();
+
   const onClickAddFleetServer = useCallback(() => {
     flyoutContext.openFleetServerFlyout();
   }, [flyoutContext]);
@@ -520,6 +523,12 @@ export const AgentListPage: React.FunctionComponent<{}> = () => {
           <EuiSpacer size="l" />
         </>
       )}
+      {shouldDisplayAgentSoftLimit && (
+        <>
+          <AgentSoftLimitCallout />
+          <EuiSpacer size="l" />
+        </>
+      )}
       {/* TODO serverless agent soft limit */}
       {showUnhealthyCallout && (
         <>

x-pack/plugins/fleet/public/mock/create_test_renderer.tsx

@@ -13,6 +13,7 @@ import { render as reactRender, act } from '@testing-library/react';
 import { renderHook } from '@testing-library/react-hooks';
 import type { RenderHookResult } from '@testing-library/react-hooks';
 import { Router } from '@kbn/shared-ux-router';
+import { QueryClient, QueryClientProvider } from '@tanstack/react-query';
 
 import { themeServiceMock } from '@kbn/core/public/mocks';
 
@@ -59,6 +60,8 @@ export interface TestRenderer {
   setHeaderActionMenu: Function;
 }
 
+const queryClient = new QueryClient();
+
 export const createFleetTestRendererMock = (): TestRenderer => {
   const basePath = '/mock';
   const extensions: UIExtensionsStorage = {};
@@ -72,7 +75,11 @@ export const createFleetTestRendererMock = (): TestRenderer => {
     return (
       <startServices.i18n.Context>
         <Router history={mountHistory}>
-          <KibanaContextProvider services={{ ...startServices }}>{children}</KibanaContextProvider>
+          <QueryClientProvider client={queryClient}>
+            <KibanaContextProvider services={{ ...startServices }}>
+              {children}
+            </KibanaContextProvider>
+          </QueryClientProvider>
         </Router>
       </startServices.i18n.Context>
     );

x-pack/plugins/fleet/server/config.ts

@@ -42,6 +42,7 @@ export const config: PluginConfigDescriptor = {
     internal: {
       fleetServerStandalone: true,
       disableProxies: true,
+      activeAgentsSoftLimit: true,
     },
   },
   deprecations: ({ renameFromRoot, unused, unusedFromRoot }) => [
@@ -176,6 +177,11 @@ export const config: PluginConfigDescriptor = {
         fleetServerStandalone: schema.boolean({
           defaultValue: false,
         }),
+        activeAgentsSoftLimit: schema.maybe(
+          schema.number({
+            min: 0,
+          })
+        ),
       })
     ),
     enabled: schema.boolean({ defaultValue: true }),