WIP store-agnostic cache manager.

Signed-off-by: Eric Peterson <ericpeterson@spotify.com>

packages/backend-common/config.d.ts

@@ -68,6 +68,28 @@ export interface Config {
           connection: string | object;
         };
 
+    /** Cache connection configuration, select cache type using the `store` field */
+    cache?:
+      | {
+          store: 'memory';
+        }
+      | {
+          store: 'memcache';
+          connection: {
+            /**
+             * An array of memcache hosts, optionally including a port number.
+             * e.g. 127.0.0.1:11211
+             */
+            hosts: string[];
+
+            /**
+             * Number of milliseconds to wait before assuming there is a
+             * network timeout. Defaults to 500ms.
+             */
+            netTimeout?: number;
+          };
+        };
+
     cors?: {
       origin?: string | string[];
       methods?: string | string[];

packages/backend-common/package.json

@@ -36,10 +36,13 @@
     "@backstage/integration": "^0.5.2",
     "@google-cloud/storage": "^5.8.0",
     "@octokit/rest": "^18.5.3",
+    "@types/cache-manager": "^3.4.0",
     "@types/cors": "^2.8.6",
     "@types/dockerode": "^3.2.1",
     "@types/express": "^4.17.6",
     "archiver": "^5.0.2",
+    "cache-manager": "^3.4.3",
+    "cache-manager-memcached-store": "^4.0.0",
     "compression": "^1.7.4",
     "concat-stream": "^2.0.0",
     "cors": "^2.8.5",
@@ -54,6 +57,7 @@
     "knex": "^0.95.1",
     "lodash": "^4.17.15",
     "logform": "^2.1.1",
+    "memcache-pp": "^0.3.3",
     "minimatch": "^3.0.4",
     "minimist": "^1.2.5",
     "morgan": "^1.10.0",

packages/backend-common/src/cache/CacheManager.ts

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2021 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Config } from '@backstage/config';
+import cacheManager from 'cache-manager';
+// @ts-expect-error
+import Memcache from 'memcache-pp';
+// @ts-expect-error
+import memcachedStore from 'cache-manager-memcached-store';
+
+/**
+ * A Cache Manager, which is able to retrieve a `node-cache-manager`-compliant
+ * cache client, configured according to app configuration. If no cache is
+ * configured, or an unknown store is provided, a no-op cache instance will be
+ * returned.
+ */
+export class CacheManager {
+  private readonly storeGetterMap = {
+    memcache: this.getMemcacheClient,
+    memory: this.getMemoryClient,
+    none: this.getNoneClient,
+  };
+
+  /**
+   * Creates a new CacheManager instance by reading from the `backend` config
+   * section, specifically the `.cache` key.
+   *
+   * @param config The loaded application configuration.
+   */
+  static fromConfig(config: Config): CacheManager {
+    return new CacheManager(config.getConfig('backend.cache'));
+  }
+
+  private constructor(private readonly config: Config) {}
+
+  getClientWithTtl(ttl: number): cacheManager.Cache {
+    const store = this.config.getOptionalString(
+      'store',
+    ) as keyof CacheManager['storeGetterMap'];
+
+    if (this.storeGetterMap.hasOwnProperty(store)) {
+      return this.storeGetterMap[store].call(this, ttl);
+    }
+    return this.storeGetterMap.none.call(this, ttl);
+  }
+
+  private getMemcacheClient(ttl: number): cacheManager.Cache {
+    const hosts = this.config.getStringArray('connection.hosts');
+    const netTimeout = this.config.getOptionalNumber('connection.netTimeout');
+    return cacheManager.caching({
+      store: memcachedStore,
+      driver: Memcache,
+      options: {
+        hosts,
+        ...(netTimeout && { netTimeout }),
+      },
+      ttl,
+    });
+  }
+
+  private getMemoryClient(ttl: number): cacheManager.Cache {
+    return cacheManager.caching({
+      store: 'memory',
+      ttl,
+    });
+  }
+
+  private getNoneClient(ttl: number): cacheManager.Cache {
+    return cacheManager.caching({
+      store: 'none',
+      ttl,
+    });
+  }
+}

packages/backend-common/src/cache/index.ts

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2021 Spotify AB
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export * from './CacheManager';

packages/backend-common/src/index.ts

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+export * from './cache';
 export * from './config';
 export * from './database';
 export * from './discovery';

packages/backend/src/index.ts

@@ -24,6 +24,7 @@
 
 import Router from 'express-promise-router';
 import {
+  CacheManager,
   createServiceBuilder,
   getRootLogger,
   loadBackendConfig,
@@ -59,11 +60,12 @@ function makeCreateEnv(config: Config) {
   root.info(`Created UrlReader ${reader}`);
 
   const databaseManager = SingleConnectionDatabaseManager.fromConfig(config);
+  const cache = CacheManager.fromConfig(config);
 
   return (plugin: string): PluginEnvironment => {
     const logger = root.child({ type: 'plugin', plugin });
     const database = databaseManager.forPlugin(plugin);
-    return { logger, database, config, reader, discovery };
+    return { logger, cache, database, config, reader, discovery };
   };
 }
 

packages/backend/src/types.ts

@@ -17,6 +17,7 @@
 import { Logger } from 'winston';
 import { Config } from '@backstage/config';
 import {
+  CacheManager,
   PluginDatabaseManager,
   PluginEndpointDiscovery,
   UrlReader,
@@ -24,6 +25,7 @@ import {
 
 export type PluginEnvironment = {
   logger: Logger;
+  cache: CacheManager;
   database: PluginDatabaseManager;
   config: Config;
   reader: UrlReader;