feat(db): support MONGO_APP_NAME for per-worker MongoDB attribution (#557)

Author: Kuchizu

.env.sample

@@ -16,6 +16,9 @@ MONGO_ACCOUNTS_DATABASE_URI=mongodb://localhost:27017/hawk
 # MongoDB URL for connecting to events database
 MONGO_EVENTS_DATABASE_URI=mongodb://localhost:27017/hawk_events
 
+# MongoDB appName for per-worker load attribution (e.g. hawk-worker-limiter)
+MONGO_APP_NAME=
+
 # JWT secret key for projects tokens
 JWT_SECRET=qwerty
 

lib/db/controller.ts

@@ -20,6 +20,11 @@ export class DatabaseController {
    */
   private readonly connectionUri: string;
 
+  /**
+   * Sent to MongoDB on handshake; overrides any `appName` query param in the URI
+   */
+  private readonly appName?: string;
+
   /**
    * GridFSBucket object
    * Used to store files in GridFS
@@ -30,12 +35,14 @@ export class DatabaseController {
    * Creates controller instance
    *
    * @param connectionUri - mongo URI for connection
+   * @param appName - MongoDB appName, defaults to `process.env.MONGO_APP_NAME`
    */
-  constructor(connectionUri: string) {
+  constructor(connectionUri: string, appName?: string) {
     if (!connectionUri) {
       throw new DatabaseConnectionError('Connection URI is not specified. Check .env');
     }
     this.connectionUri = connectionUri;
+    this.appName = appName ?? process.env.MONGO_APP_NAME;
   }
 
   /**
@@ -53,6 +60,7 @@ export class DatabaseController {
       this.connection = await connect(this.connectionUri, {
         useNewUrlParser: true,
         useUnifiedTopology: true,
+        ...(this.appName ? { appName: this.appName } : {}),
       });
       this.db = await this.connection.db();