[Status service] log plugin status changes (#126320)

* log plugin status changes

* add throttling effect

* nit

src/core/server/status/log_plugins_status.test.ts

@@ -0,0 +1,332 @@
+/*
+ * 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 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+import { TestScheduler } from 'rxjs/testing';
+import { PluginName } from '../plugins';
+import { ServiceStatus, ServiceStatusLevel, ServiceStatusLevels } from './types';
+import {
+  getPluginsStatusChanges,
+  getPluginsStatusDiff,
+  getServiceLevelChangeMessage,
+} from './log_plugins_status';
+
+type ObsInputType = Record<PluginName, ServiceStatus>;
+
+const getTestScheduler = () =>
+  new TestScheduler((actual, expected) => {
+    expect(actual).toEqual(expected);
+  });
+
+const createServiceStatus = (level: ServiceStatusLevel): ServiceStatus => ({
+  level,
+  summary: 'summary',
+});
+
+const createPluginsStatuses = (
+  input: Record<PluginName, ServiceStatusLevel>
+): Record<PluginName, ServiceStatus> => {
+  return Object.entries(input).reduce((output, [name, level]) => {
+    output[name] = createServiceStatus(level);
+    return output;
+  }, {} as Record<PluginName, ServiceStatus>);
+};
+
+describe('getPluginsStatusChanges', () => {
+  it('does not emit on first plugins$ emission', () => {
+    getTestScheduler().run(({ expectObservable, hot }) => {
+      const statuses = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.available,
+        pluginB: ServiceStatusLevels.degraded,
+      });
+
+      const overall$ = hot<ObsInputType>('-a', {
+        a: statuses,
+      });
+      const stop$ = hot<void>('');
+      const expected = '--';
+
+      expectObservable(getPluginsStatusChanges(overall$, stop$, 1)).toBe(expected);
+    });
+  });
+
+  it('does not emit if statuses do not change', () => {
+    getTestScheduler().run(({ expectObservable, hot }) => {
+      const statuses = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.available,
+        pluginB: ServiceStatusLevels.degraded,
+      });
+
+      const overall$ = hot<ObsInputType>('-a-b', {
+        a: statuses,
+        b: statuses,
+      });
+      const stop$ = hot<void>('');
+      const expected = '----';
+
+      expectObservable(getPluginsStatusChanges(overall$, stop$, 1)).toBe(expected);
+    });
+  });
+
+  it('emits if any plugin status changes', () => {
+    getTestScheduler().run(({ expectObservable, hot }) => {
+      const statusesA = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.available,
+        pluginB: ServiceStatusLevels.degraded,
+      });
+      const statusesB = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.available,
+        pluginB: ServiceStatusLevels.available,
+      });
+
+      const overall$ = hot<ObsInputType>('-a-b', {
+        a: statusesA,
+        b: statusesB,
+      });
+      const stop$ = hot<void>('');
+      const expected = '---a';
+
+      expectObservable(getPluginsStatusChanges(overall$, stop$, 1)).toBe(expected, {
+        a: [
+          {
+            previousLevel: 'degraded',
+            nextLevel: 'available',
+            impactedServices: ['pluginB'],
+          },
+        ],
+      });
+    });
+  });
+
+  it('emits everytime any plugin status changes', () => {
+    getTestScheduler().run(({ expectObservable, hot }) => {
+      const availableStatus = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.available,
+      });
+      const degradedStatus = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.degraded,
+      });
+
+      const overall$ = hot<ObsInputType>('-a-b-c-d', {
+        a: availableStatus,
+        b: degradedStatus,
+        c: degradedStatus,
+        d: availableStatus,
+      });
+      const stop$ = hot<void>('');
+      const expected = '---a---b';
+
+      expectObservable(getPluginsStatusChanges(overall$, stop$, 1)).toBe(expected, {
+        a: [
+          {
+            previousLevel: 'available',
+            nextLevel: 'degraded',
+            impactedServices: ['pluginA'],
+          },
+        ],
+        b: [
+          {
+            previousLevel: 'degraded',
+            nextLevel: 'available',
+            impactedServices: ['pluginA'],
+          },
+        ],
+      });
+    });
+  });
+
+  it('throttle events', () => {
+    getTestScheduler().run(({ expectObservable, hot }) => {
+      const statusesA = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.available,
+        pluginB: ServiceStatusLevels.degraded,
+      });
+      const statusesB = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.available,
+        pluginB: ServiceStatusLevels.available,
+      });
+      const statusesC = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.degraded,
+        pluginB: ServiceStatusLevels.available,
+      });
+
+      const overall$ = hot<ObsInputType>('-a-b--c', {
+        a: statusesA,
+        b: statusesB,
+        c: statusesC,
+      });
+      const stop$ = hot<void>('');
+      const expected = '------a';
+
+      expectObservable(getPluginsStatusChanges(overall$, stop$, 5)).toBe(expected, {
+        a: [
+          {
+            previousLevel: 'available',
+            nextLevel: 'degraded',
+            impactedServices: ['pluginA'],
+          },
+          {
+            previousLevel: 'degraded',
+            nextLevel: 'available',
+            impactedServices: ['pluginB'],
+          },
+        ],
+      });
+    });
+  });
+
+  it('stops emitting once `stop$` emits', () => {
+    getTestScheduler().run(({ expectObservable, hot }) => {
+      const statusesA = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.available,
+        pluginB: ServiceStatusLevels.degraded,
+      });
+      const statusesB = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.available,
+        pluginB: ServiceStatusLevels.available,
+      });
+      const statusesC = createPluginsStatuses({
+        pluginA: ServiceStatusLevels.degraded,
+        pluginB: ServiceStatusLevels.available,
+      });
+
+      const overall$ = hot<ObsInputType>('-a-b-c', {
+        a: statusesA,
+        b: statusesB,
+        c: statusesC,
+      });
+      const stop$ = hot<void>('----(s|)');
+      const expected = '---a|';
+
+      expectObservable(getPluginsStatusChanges(overall$, stop$, 1)).toBe(expected, {
+        a: [
+          {
+            previousLevel: 'degraded',
+            nextLevel: 'available',
+            impactedServices: ['pluginB'],
+          },
+        ],
+      });
+    });
+  });
+});
+
+describe('getPluginsStatusDiff', () => {
+  it('returns an empty list if level is the same for all plugins', () => {
+    const previousStatus = createPluginsStatuses({
+      pluginA: ServiceStatusLevels.available,
+      pluginB: ServiceStatusLevels.degraded,
+      pluginC: ServiceStatusLevels.unavailable,
+    });
+
+    const nextStatus = createPluginsStatuses({
+      pluginA: ServiceStatusLevels.available,
+      pluginB: ServiceStatusLevels.degraded,
+      pluginC: ServiceStatusLevels.unavailable,
+    });
+
+    const result = getPluginsStatusDiff(previousStatus, nextStatus);
+
+    expect(result).toEqual([]);
+  });
+
+  it('returns an single entry if only one status changed', () => {
+    const previousStatus = createPluginsStatuses({
+      pluginA: ServiceStatusLevels.available,
+      pluginB: ServiceStatusLevels.degraded,
+      pluginC: ServiceStatusLevels.unavailable,
+    });
+
+    const nextStatus = createPluginsStatuses({
+      pluginA: ServiceStatusLevels.degraded,
+      pluginB: ServiceStatusLevels.degraded,
+      pluginC: ServiceStatusLevels.unavailable,
+    });
+
+    const result = getPluginsStatusDiff(previousStatus, nextStatus);
+
+    expect(result).toEqual([
+      {
+        previousLevel: 'available',
+        nextLevel: 'degraded',
+        impactedServices: ['pluginA'],
+      },
+    ]);
+  });
+
+  it('groups plugins by previous and next level tuples', () => {
+    const previousStatus = createPluginsStatuses({
+      pluginA: ServiceStatusLevels.available,
+      pluginB: ServiceStatusLevels.available,
+      pluginC: ServiceStatusLevels.unavailable,
+    });
+
+    const nextStatus = createPluginsStatuses({
+      pluginA: ServiceStatusLevels.degraded,
+      pluginB: ServiceStatusLevels.degraded,
+      pluginC: ServiceStatusLevels.unavailable,
+    });
+
+    const result = getPluginsStatusDiff(previousStatus, nextStatus);
+
+    expect(result).toEqual([
+      {
+        previousLevel: 'available',
+        nextLevel: 'degraded',
+        impactedServices: ['pluginA', 'pluginB'],
+      },
+    ]);
+  });
+
+  it('returns one entry per previous and next level tuples', () => {
+    const previousStatus = createPluginsStatuses({
+      pluginA: ServiceStatusLevels.available,
+      pluginB: ServiceStatusLevels.degraded,
+      pluginC: ServiceStatusLevels.unavailable,
+    });
+
+    const nextStatus = createPluginsStatuses({
+      pluginA: ServiceStatusLevels.degraded,
+      pluginB: ServiceStatusLevels.unavailable,
+      pluginC: ServiceStatusLevels.available,
+    });
+
+    const result = getPluginsStatusDiff(previousStatus, nextStatus);
+
+    expect(result).toEqual([
+      {
+        previousLevel: 'available',
+        nextLevel: 'degraded',
+        impactedServices: ['pluginA'],
+      },
+      {
+        previousLevel: 'degraded',
+        nextLevel: 'unavailable',
+        impactedServices: ['pluginB'],
+      },
+      {
+        previousLevel: 'unavailable',
+        nextLevel: 'available',
+        impactedServices: ['pluginC'],
+      },
+    ]);
+  });
+});
+
+describe('getServiceLevelChangeMessage', () => {
+  it('returns a human readable message about the change', () => {
+    expect(
+      getServiceLevelChangeMessage({
+        previousLevel: 'available',
+        nextLevel: 'degraded',
+        impactedServices: ['pluginA', 'pluginB'],
+      })
+    ).toMatchInlineSnapshot(
+      `"2 plugins changed status from 'available' to 'degraded': pluginA, pluginB"`
+    );
+  });
+});