Implemented a simple SQL based TTL cache

README.md

@@ -286,11 +286,13 @@ Configuration can be set using environment variables
 | `DWN_REGISTRATION_PROOF_OF_WORK_SEED`             | Seed to generate the challenge nonce from, this allows all DWN instances in a cluster to generate the same challenge.   | unset                  |
 | `DWN_REGISTRATION_PROOF_OF_WORK_ENABLED`          | Require new users to complete a proof-of-work challenge                                                                 | `false`                |
 | `DWN_REGISTRATION_PROOF_OF_WORK_INITIAL_MAX_HASH` | Initial maximum allowed hash in 64 char HEX string. The more leading zeros (smaller number) the higher the difficulty.  | `false`                |
-| `DWN_TERMS_OF_SERVICE_FILE_PATH`                  | Required terms of service agreement if set. Value is path to the terms of service file.                                 | unset                  |
 | `DWN_STORAGE`                                     | URL to use for storage by default. See [Storage Options](#storage-options) for details                                  | `level://data`         |
 | `DWN_STORAGE_MESSAGES`                            | URL to use for storage of messages.                                                                                     | value of `DWN_STORAGE` |
 | `DWN_STORAGE_DATA`                                | URL to use for data storage                                                                                             | value of `DWN_STORAGE` |
 | `DWN_STORAGE_EVENTS`                              | URL to use for event storage                                                                                            | value of `DWN_STORAGE` |
+| `DWN_TERMS_OF_SERVICE_FILE_PATH`                  | Required terms of service agreement if set. Value is path to the terms of service file.                                 | unset                  |
+| `DWN_TTL_CACHE_URL`                               | URL of the TTL cache used by the DWN. Currently only supports SQL databases.                                            | `sqlite://`            |
+
 
 ### Storage Options
 

src/config.ts

@@ -17,6 +17,17 @@ export const config = {
    */
   baseUrl: process.env.DWN_BASE_URL || 'http://localhost',
 
+  /**
+   * Port that server listens on.
+   */
+  port: parseInt(process.env.DS_PORT || '3000'),
+
+  /**
+   * The URL of the TTL cache used by the DWN. Currently only supports SQL databases.
+   * NOTE: Used for session/state keeping, thus requires the cache to be commonly addressable by nodes in a cloud cluster environment.
+   */
+  ttlCacheUrl: process.env.DWN_TTL_CACHE_URL || 'sqlite://',
+
   /**
    * Used to populate the `version` and `sdkVersion` properties returned by the `/info` endpoint.
    *
@@ -28,8 +39,7 @@ export const config = {
   packageJsonPath:  process.env.npm_package_json ||  process.env.DWN_SERVER_PACKAGE_JSON || '/dwn-server/package.json',
   // max size of data that can be provided with a RecordsWrite
   maxRecordDataSize: bytes(process.env.MAX_RECORD_DATA_SIZE || '1gb'),
-  // port that server listens on
-  port: parseInt(process.env.DS_PORT || '3000'),
+
   // whether to enable 'ws:'
   webSocketSupport: { on: true, off: false }[process.env.DS_WEBSOCKET_SERVER] ?? true,
   // where to store persistent data

src/dwn-server.ts

@@ -74,7 +74,7 @@ export class DwnServer {
       }));
     }
 
-    this.#httpApi = new HttpApi(this.config, this.dwn, registrationManager);
+    this.#httpApi = await HttpApi.create(this.config, this.dwn, registrationManager);
 
     await this.#httpApi.start(this.config.port, () => {
       log.info(`HttpServer listening on port ${this.config.port}`);

src/http-api.ts

@@ -32,38 +32,45 @@ export class HttpApi {
   registrationManager: RegistrationManager;
   dwn: Dwn;
 
-  constructor(config: DwnServerConfig, dwn: Dwn, registrationManager?: RegistrationManager) {
+  private constructor() { }
+
+  public static async create(config: DwnServerConfig, dwn: Dwn, registrationManager?: RegistrationManager): Promise<HttpApi> {
+    const httpApi = new HttpApi();
+
     log.info(config);
 
-    this.#packageInfo = {
+    httpApi.#packageInfo = {
       server: config.serverName,
     };
 
     try {
       // We populate the `version` and `sdkVersion` properties from the `package.json` file.
       const packageJson = JSON.parse(readFileSync(config.packageJsonPath).toString());
-      this.#packageInfo.version = packageJson.version;
-      this.#packageInfo.sdkVersion = packageJson.dependencies ? packageJson.dependencies['@tbd54566975/dwn-sdk-js'] : undefined;
+      httpApi.#packageInfo.version = packageJson.version;
+      httpApi.#packageInfo.sdkVersion = packageJson.dependencies ? packageJson.dependencies['@tbd54566975/dwn-sdk-js'] : undefined;
     } catch (error: any) {
       log.error('could not read `package.json` for version info', error);
     }
 
-    this.#config = config;
-    this.#api = express();
-    this.#server = http.createServer(this.#api);
-    this.dwn = dwn;
+    httpApi.#config = config;
+    httpApi.#api = express();
+    httpApi.#server = http.createServer(httpApi.#api);
+    httpApi.dwn = dwn;
 
     if (registrationManager !== undefined) {
-      this.registrationManager = registrationManager;
+      httpApi.registrationManager = registrationManager;
     }
 
     // create the Web5 Connect Server
-    this.web5ConnectServer = new Web5ConnectServer({
+    httpApi.web5ConnectServer = await Web5ConnectServer.create({
       baseUrl: `${config.baseUrl}:${config.port}`,
+      sqlTtlCacheUrl: config.ttlCacheUrl,
     });
 
-    this.#setupMiddleware();
-    this.#setupRoutes();
+    httpApi.#setupMiddleware();
+    httpApi.#setupRoutes();
+
+    return httpApi;
   }
 
   get server(): http.Server {

src/web5-connect/sql-ttl-cache.ts

@@ -0,0 +1,133 @@
+import type { Dialect } from '@tbd54566975/dwn-sql-store';
+import { Kysely } from 'kysely';
+
+/**
+ * The SqlTtlCache is responsible for storing and retrieving cache data with TTL (Time-to-Live).
+ */
+export class SqlTtlCache {
+  private static readonly cacheTableName = 'cacheEntries';
+  private static readonly cleanupIntervalInSeconds = 60;
+
+  private db: Kysely<CacheDatabase>;
+  private cleanupTimer: NodeJS.Timeout;
+
+  private constructor(sqlDialect: Dialect) {
+    this.db = new Kysely<CacheDatabase>({ dialect: sqlDialect });
+  }
+
+  /**
+   * Creates a new SqlTtlCache instance.
+   */
+  public static async create(sqlDialect: Dialect): Promise<SqlTtlCache> {
+    const cacheManager = new SqlTtlCache(sqlDialect);
+
+    await cacheManager.initialize();
+
+    return cacheManager;
+  }
+
+  private async initialize(): Promise<void> {
+    await this.db.schema
+      .createTable(SqlTtlCache.cacheTableName)
+      .ifNotExists()
+      .addColumn('key', 'text', (column) => column.primaryKey())
+      .addColumn('value', 'text')
+      .addColumn('expiry', 'integer')
+      .execute();
+
+    // Add an index to the expiry column
+    await this.db.schema
+      .createIndex('index_expiry')
+      .ifNotExists()
+      .on(SqlTtlCache.cacheTableName)
+      .column('expiry')
+      .execute();
+
+    // Start the cleanup timer
+    this.startCleanupTimer();
+  }
+
+  /**
+   * Starts a timer to periodically clean up expired cache entries.
+   */
+  private startCleanupTimer(): void {
+    this.cleanupTimer = setInterval(async () => {
+      await this.cleanUpExpiredEntries();
+    }, SqlTtlCache.cleanupIntervalInSeconds * 1000);
+  }
+
+  /**
+   * Inserts a cache entry.
+   * @param ttl The time-to-live in seconds.
+   */
+  public async insert(key: string, value: object, ttl: number): Promise<void> {
+    const expiry = Date.now() + (ttl * 1000);
+
+    const objectString = JSON.stringify(value);
+
+    await this.db
+      .insertInto(SqlTtlCache.cacheTableName)
+      .values({ key, value: objectString, expiry })
+      .execute();
+  }
+
+  /**
+   * Retrieves a cache entry if it is not expired and cleans up expired entries.
+   */
+  public async get(key: string): Promise<object | undefined> {
+    // clean up expired entries but no need to await for it to finish
+    this.cleanUpExpiredEntries();
+
+    const result = await this.db
+      .selectFrom(SqlTtlCache.cacheTableName)
+      .select('key')
+      .select('value')
+      .select('expiry')
+      .where('key', '=', key)
+      .execute();
+
+    if (result.length === 0) {
+      return undefined;
+    }
+
+    const entry = result[0];
+
+    // if the entry is expired, don't return it and delete it
+    if (Date.now() >= entry.expiry) {
+      this.delete(key); // no need to await
+      return undefined;
+    }
+
+    return JSON.parse(entry.value);
+  }
+
+  /**
+   * Deletes a cache entry.
+   */
+  public async delete(key: string): Promise<void> {
+    await this.db
+      .deleteFrom(SqlTtlCache.cacheTableName)
+      .where('key', '=', key)
+      .execute();
+  }
+
+  /**
+   * Periodically clean up expired cache entries.
+   */
+  public async cleanUpExpiredEntries(): Promise<void> {
+    await this.db
+      .deleteFrom(SqlTtlCache.cacheTableName)
+      .where('expiry', '<', Date.now())
+      .execute();
+  }
+}
+
+interface CacheEntry {
+  key: string;
+  value: string;
+  expiry: number;
+}
+
+interface CacheDatabase {
+  cacheEntries: CacheEntry;
+}

src/web5-connect/web5-connect-server.ts

@@ -1,4 +1,6 @@
+import { getDialectFromURI } from "../storage.js";
 import { randomUuid } from '@web5/crypto/utils';
+import { SqlTtlCache } from "./sql-ttl-cache.js";
 
 /**
  * The Web5 Connect Request object.
@@ -29,16 +31,30 @@ export type SetWeb5ConnectRequestResult = {
  * The Web5 Connect Server is responsible for handling the Web5 Connect flow.
  */
 export class Web5ConnectServer {
+  public static readonly ttlInSeconds = 600;
 
   private baseUrl: string;
-  private dataStore = new Map(); // TODO: turn this into a TTL cache (https://github.com/TBD54566975/dwn-server/issues/138)
+  private cache: SqlTtlCache;
 
   /**
    * Creates a new instance of the Web5 Connect Server.
    * @param params.baseUrl The the base URL of the connect server including the port.
    *                       This is given to the Identity Provider (wallet) to fetch the Web5 Connect Request object.
    */
-  public constructor({ baseUrl }: {
+  public static async create({ baseUrl, sqlTtlCacheUrl }: {
+    baseUrl: string;
+    sqlTtlCacheUrl: string;
+  }): Promise<Web5ConnectServer> {
+    const web5ConnectServer = new Web5ConnectServer({ baseUrl });
+
+    // Initialize TTL cache.
+    const sqlDialect = getDialectFromURI(new URL(sqlTtlCacheUrl));
+    web5ConnectServer.cache = await SqlTtlCache.create(sqlDialect);
+
+    return web5ConnectServer;
+  }
+
+  private constructor({ baseUrl }: {
     baseUrl: string;
   }) {
     this.baseUrl = baseUrl;
@@ -54,22 +70,22 @@ export class Web5ConnectServer {
     const request_uri = `${this.baseUrl}/connect/${requestId}.jwt`;
 
     // Store the Request Object.
-    this.dataStore.set(`request:${requestId}`, request);
+    this.cache.insert(`request:${requestId}`, request, Web5ConnectServer.ttlInSeconds);
 
     return {
       request_uri,
-      expires_in  : 600,
+      expires_in  : Web5ConnectServer.ttlInSeconds,
     };
   }
 
   /**
    * Returns the Web5 Connect Request object. The request ID can only be used once.
    */
   public async getWeb5ConnectRequest(requestId: string): Promise<Web5ConnectRequest | undefined> {
-    const request = this.dataStore.get(`request:${requestId}`);
+    const request = this.cache.get(`request:${requestId}`);
 
     // Delete the Request Object from the data store now that it has been retrieved.
-    this.dataStore.delete(`request:${requestId}`);
+    this.cache.delete(`request:${requestId}`);
 
     return request;
   }
@@ -78,17 +94,17 @@ export class Web5ConnectServer {
    * Sets the Web5 Connect Response object, which is also an OIDC ID token.
    */
   public async setWeb5ConnectResponse(state: string, response: Web5ConnectResponse): Promise<any> {
-    this.dataStore.set(`response:${state}`, response);
+    this.cache.insert(`response:${state}`, response, Web5ConnectServer.ttlInSeconds);
   }
 
   /**
    * Gets the Web5 Connect Response object. The `state` string can only be used once.
    */
   public async getWeb5ConnectResponse(state: string): Promise<Web5ConnectResponse | undefined> {
-    const response = this. dataStore.get(`response:${state}`);
+    const response = this. cache.get(`response:${state}`);
 
     // Delete the Response object from the data store now that it has been retrieved.
-    this.dataStore.delete(`response:${state}`);
+    this.cache.delete(`response:${state}`);
 
     return response;
   }

tests/connection/connection-manager.spec.ts

@@ -23,7 +23,7 @@ describe('InMemoryConnectionManager', () => {
   beforeEach(async () => {
     dwn = await getTestDwn({ withEvents: true });
     connectionManager = new InMemoryConnectionManager(dwn);
-    const httpApi = new HttpApi(config, dwn);
+    const httpApi = await HttpApi.create(config, dwn);
     server = await httpApi.start(9002);
     wsApi = new WsApi(server, dwn, connectionManager);
     wsApi.start();

tests/http-api.spec.ts

@@ -69,7 +69,7 @@ describe('http api', function () {
 
     dwn = await getTestDwn({ tenantGate: registrationManager });
 
-    httpApi = new HttpApi(config, dwn, registrationManager);
+    httpApi = await HttpApi.create(config, dwn, registrationManager);
 
   });
 
@@ -1064,7 +1064,7 @@ describe('http api', function () {
       server.closeAllConnections();
 
       config.webSocketSupport = false;
-      httpApi = new HttpApi(config, dwn, registrationManager);
+      httpApi = await HttpApi.create(config, dwn, registrationManager);
       server = await httpApi.start(3000);
 
       resp = await fetch(`http://localhost:3000/info`);
@@ -1088,7 +1088,7 @@ describe('http api', function () {
       // set the config to an invalid file path
       const packageJsonConfig = config.packageJsonPath;
       config.packageJsonPath = '/some/invalid/file.json';
-      httpApi = new HttpApi(config, dwn, registrationManager);
+      httpApi = await HttpApi.create(config, dwn, registrationManager);
       server = await httpApi.start(3000);
 
       const resp = await fetch(`http://localhost:3000/info`);
@@ -1117,7 +1117,7 @@ describe('http api', function () {
       // set a custom name for the `serverName`
       const serverName = config.serverName;
       config.serverName = '@web5/dwn-server-2'
-      httpApi = new HttpApi(config, dwn, registrationManager);
+      httpApi = await HttpApi.create(config, dwn, registrationManager);
       server = await httpApi.start(3000);
 
       const resp = await fetch(`http://localhost:3000/info`);