Changeset.

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

.changeset/cache-me-if-you-can.md

@@ -0,0 +1,82 @@
+---
+'@backstage/create-app': patch
+---
+
+Cache management has been added to the Backstage backend.
+
+To apply this change to an existing app, make the following changes:
+
+```diff
+// packages/backend/src/types.ts
+
+import { Logger } from 'winston';
+import { Config } from '@backstage/config';
+import {
++  PluginCacheManager,
+  PluginDatabaseManager,
+  PluginEndpointDiscovery,
+  UrlReader,
+} from '@backstage/backend-common';
+
+export type PluginEnvironment = {
+  logger: Logger;
+  database: PluginDatabaseManager;
++  cache: PluginCacheManager;
+  config: Config;
+  reader: UrlReader
+  discovery: PluginEndpointDiscovery;
+};
+```
+
+```diff
+// packages/backend/src/index.ts
+
+import Router from 'express-promise-router';
+import {
+  createServiceBuilder,
+  loadBackendConfig,
+  getRootLogger,
+  useHotMemoize,
+  notFoundHandler,
++  CacheManager,
+  SingleConnectionDatabaseManager,
+  SingleHostDiscovery,
+  UrlReaders,
+} from '@backstage/backend-common';
+import { Config } from '@backstage/config';
+
+function makeCreateEnv(config: Config) {
+  const root = getRootLogger();
+  const reader = UrlReaders.default({ logger: root, config });
+  const discovery = SingleHostDiscovery.fromConfig(config);
+
+  root.info(`Created UrlReader ${reader}`);
+
+  const databaseManager = SingleConnectionDatabaseManager.fromConfig(config);
++  const cacheManager = 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 };
++    const cache = cacheManager.forPlugin(plugin);
++    return { logger, database, cache, config, reader, discovery };
+  };
+}
+```
+
+To configure a cache store, add a `backend.cache` key to your app-config.yaml.
+
+```diff
+// app-config.yaml
+
+backend:
+  baseUrl: http://localhost:7000
+  listen:
+    port: 7000
+  database:
+    client: sqlite3
+    connection: ':memory:'
++  cache:
++    store: memory
+```