[licensing] add license fetcher cache (reloaded) (#170207)

## Summary

#170006 was reverted because of
significant increases of run duration on some of our FTR test suites,
apparently because of the throttling that was added...

This PR reopens #170006 without
the throttling

---------

Co-authored-by: kibanamachine <[email protected]>

x-pack/plugins/licensing/server/license_fetcher.test.ts

@@ -0,0 +1,172 @@
+/*
+ * 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 type * as estypes from '@elastic/elasticsearch/lib/api/typesWithBodyKey';
+import { getLicenseFetcher } from './license_fetcher';
+import { loggerMock, type MockedLogger } from '@kbn/logging-mocks';
+import { elasticsearchServiceMock } from '@kbn/core/server/mocks';
+
+type EsLicense = estypes.XpackInfoMinimalLicenseInformation;
+
+const delay = (ms: number) => new Promise((res) => setTimeout(res, ms));
+
+function buildRawLicense(options: Partial<EsLicense> = {}): EsLicense {
+  return {
+    uid: 'uid-000000001234',
+    status: 'active',
+    type: 'basic',
+    mode: 'basic',
+    expiry_date_in_millis: 1000,
+    ...options,
+  };
+}
+
+describe('LicenseFetcher', () => {
+  let logger: MockedLogger;
+  let clusterClient: ReturnType<typeof elasticsearchServiceMock.createClusterClient>;
+
+  beforeEach(() => {
+    logger = loggerMock.create();
+    clusterClient = elasticsearchServiceMock.createClusterClient();
+  });
+
+  it('returns the license for successful calls', async () => {
+    clusterClient.asInternalUser.xpack.info.mockResponse({
+      license: buildRawLicense({
+        uid: 'license-1',
+      }),
+      features: {},
+    } as any);
+
+    const fetcher = getLicenseFetcher({
+      logger,
+      clusterClient,
+      cacheDurationMs: 50_000,
+    });
+
+    const license = await fetcher();
+    expect(license.uid).toEqual('license-1');
+  });
+
+  it('returns the latest license for successful calls', async () => {
+    clusterClient.asInternalUser.xpack.info
+      .mockResponseOnce({
+        license: buildRawLicense({
+          uid: 'license-1',
+        }),
+        features: {},
+      } as any)
+      .mockResponseOnce({
+        license: buildRawLicense({
+          uid: 'license-2',
+        }),
+        features: {},
+      } as any);
+
+    const fetcher = getLicenseFetcher({
+      logger,
+      clusterClient,
+      cacheDurationMs: 50_000,
+    });
+
+    let license = await fetcher();
+    expect(license.uid).toEqual('license-1');
+
+    license = await fetcher();
+    expect(license.uid).toEqual('license-2');
+  });
+
+  it('returns an error license in case of error', async () => {
+    clusterClient.asInternalUser.xpack.info.mockResponseImplementation(() => {
+      throw new Error('woups');
+    });
+
+    const fetcher = getLicenseFetcher({
+      logger,
+      clusterClient,
+      cacheDurationMs: 50_000,
+    });
+
+    const license = await fetcher();
+    expect(license.error).toEqual('woups');
+  });
+
+  it('returns a license successfully fetched after an error', async () => {
+    clusterClient.asInternalUser.xpack.info
+      .mockResponseImplementationOnce(() => {
+        throw new Error('woups');
+      })
+      .mockResponseOnce({
+        license: buildRawLicense({
+          uid: 'license-1',
+        }),
+        features: {},
+      } as any);
+
+    const fetcher = getLicenseFetcher({
+      logger,
+      clusterClient,
+      cacheDurationMs: 50_000,
+    });
+
+    let license = await fetcher();
+    expect(license.error).toEqual('woups');
+    license = await fetcher();
+    expect(license.uid).toEqual('license-1');
+  });
+
+  it('returns the latest fetched license after an error within the cache duration period', async () => {
+    clusterClient.asInternalUser.xpack.info
+      .mockResponseOnce({
+        license: buildRawLicense({
+          uid: 'license-1',
+        }),
+        features: {},
+      } as any)
+      .mockResponseImplementationOnce(() => {
+        throw new Error('woups');
+      });
+
+    const fetcher = getLicenseFetcher({
+      logger,
+      clusterClient,
+      cacheDurationMs: 50_000,
+    });
+
+    let license = await fetcher();
+    expect(license.uid).toEqual('license-1');
+    license = await fetcher();
+    expect(license.uid).toEqual('license-1');
+  });
+
+  it('returns an error license after an error exceeding the cache duration period', async () => {
+    clusterClient.asInternalUser.xpack.info
+      .mockResponseOnce({
+        license: buildRawLicense({
+          uid: 'license-1',
+        }),
+        features: {},
+      } as any)
+      .mockResponseImplementationOnce(() => {
+        throw new Error('woups');
+      });
+
+    const fetcher = getLicenseFetcher({
+      logger,
+      clusterClient,
+      cacheDurationMs: 1,
+    });
+
+    let license = await fetcher();
+    expect(license.uid).toEqual('license-1');
+
+    await delay(50);
+
+    license = await fetcher();
+    expect(license.error).toEqual('woups');
+  });
+});

x-pack/plugins/licensing/server/license_fetcher.ts

@@ -0,0 +1,133 @@
+/*
+ * 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 type * as estypes from '@elastic/elasticsearch/lib/api/typesWithBodyKey';
+import { createHash } from 'crypto';
+import stringify from 'json-stable-stringify';
+import type { MaybePromise } from '@kbn/utility-types';
+import { isPromise } from '@kbn/std';
+import type { IClusterClient, Logger } from '@kbn/core/server';
+import type {
+  ILicense,
+  PublicLicense,
+  PublicFeatures,
+  LicenseType,
+  LicenseStatus,
+} from '../common/types';
+import { License } from '../common/license';
+import type { ElasticsearchError, LicenseFetcher } from './types';
+
+export const getLicenseFetcher = ({
+  clusterClient,
+  logger,
+  cacheDurationMs,
+}: {
+  clusterClient: MaybePromise<IClusterClient>;
+  logger: Logger;
+  cacheDurationMs: number;
+}): LicenseFetcher => {
+  let currentLicense: ILicense | undefined;
+  let lastSuccessfulFetchTime: number | undefined;
+
+  return async () => {
+    const client = isPromise(clusterClient) ? await clusterClient : clusterClient;
+    try {
+      const response = await client.asInternalUser.xpack.info();
+      const normalizedLicense =
+        response.license && response.license.type !== 'missing'
+          ? normalizeServerLicense(response.license)
+          : undefined;
+      const normalizedFeatures = response.features
+        ? normalizeFeatures(response.features)
+        : undefined;
+
+      const signature = sign({
+        license: normalizedLicense,
+        features: normalizedFeatures,
+        error: '',
+      });
+
+      currentLicense = new License({
+        license: normalizedLicense,
+        features: normalizedFeatures,
+        signature,
+      });
+      lastSuccessfulFetchTime = Date.now();
+
+      return currentLicense;
+    } catch (error) {
+      logger.warn(
+        `License information could not be obtained from Elasticsearch due to ${error} error`
+      );
+
+      if (lastSuccessfulFetchTime && lastSuccessfulFetchTime + cacheDurationMs > Date.now()) {
+        return currentLicense!;
+      } else {
+        const errorMessage = getErrorMessage(error);
+        const signature = sign({ error: errorMessage });
+
+        return new License({
+          error: getErrorMessage(error),
+          signature,
+        });
+      }
+    }
+  };
+};
+
+function normalizeServerLicense(
+  license: estypes.XpackInfoMinimalLicenseInformation
+): PublicLicense {
+  return {
+    uid: license.uid,
+    type: license.type as LicenseType,
+    mode: license.mode as LicenseType,
+    expiryDateInMillis:
+      typeof license.expiry_date_in_millis === 'string'
+        ? parseInt(license.expiry_date_in_millis, 10)
+        : license.expiry_date_in_millis,
+    status: license.status as LicenseStatus,
+  };
+}
+
+function normalizeFeatures(rawFeatures: estypes.XpackInfoFeatures) {
+  const features: PublicFeatures = {};
+  for (const [name, feature] of Object.entries(rawFeatures)) {
+    features[name] = {
+      isAvailable: feature.available,
+      isEnabled: feature.enabled,
+    };
+  }
+  return features;
+}
+
+function sign({
+  license,
+  features,
+  error,
+}: {
+  license?: PublicLicense;
+  features?: PublicFeatures;
+  error?: string;
+}) {
+  return createHash('sha256')
+    .update(
+      stringify({
+        license,
+        features,
+        error,
+      })
+    )
+    .digest('hex');
+}
+
+function getErrorMessage(error: ElasticsearchError): string {
+  if (error.status === 400) {
+    return 'X-Pack plugin is not installed on the Elasticsearch cluster.';
+  }
+  return error.message;
+}

x-pack/plugins/licensing/server/licensing_config.ts

@@ -10,12 +10,18 @@ import { PluginConfigDescriptor } from '@kbn/core/server';
 
 const configSchema = schema.object({
   api_polling_frequency: schema.duration({ defaultValue: '30s' }),
+  license_cache_duration: schema.duration({
+    defaultValue: '300s',
+    validate: (value) => {
+      if (value.asMinutes() > 15) {
+        return 'license cache duration must be shorter than 15 minutes';
+      }
+    },
+  }),
 });
 
 export type LicenseConfigType = TypeOf<typeof configSchema>;
 
 export const config: PluginConfigDescriptor<LicenseConfigType> = {
-  schema: schema.object({
-    api_polling_frequency: schema.duration({ defaultValue: '30s' }),
-  }),
+  schema: configSchema,
 };