Allow configurable number of taskworkers

Right now we are limited to one taskworker in the scaffolder backend
which means you can only scaffold one thing at a time. This is a poor
user experience for larger organizations where multiple users maybe
scaffolding at the same time.

This adds an optional configuration option to increase the number
of taskworkers via the router options if you like, but defaults to
1 if not set.

Signed-off-by: jrusso1020 <jrusso@brex.com>

.changeset/seven-badgers-marry.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-scaffolder-backend': minor
+---
+
+This adds a configuration option to the scaffolder plugin router, so we can allow for multiple taskworkers. Currently with only one taskworker you are limited to scaffolding one thing at a time. Set the `taskWorkers?: number` option in your scaffolder router to get more than 1 taskworker

.github/styles/vocab.txt

@@ -241,6 +241,10 @@ supertype
 talkdesk
 Talkdesk
 tasklist
+taskworker
+Taskworker
+taskworkers
+Taskworkers
 techdocs
 Telenor
 templated

plugins/scaffolder-backend/src/service/router.ts

@@ -58,6 +58,7 @@ export interface RouterOptions {
   database: PluginDatabaseManager;
   catalogClient: CatalogApi;
   actions?: TemplateAction<any>[];
+  taskWorkers?: number;
 }
 
 function isAlpha1Template(
@@ -91,6 +92,7 @@ export async function createRouter(
     database,
     catalogClient,
     actions,
+    taskWorkers,
   } = options;
 
   const logger = parentLogger.child({ plugin: 'scaffolder' });
@@ -103,11 +105,15 @@ export async function createRouter(
   );
   const taskBroker = new StorageTaskBroker(databaseTaskStore, logger);
   const actionRegistry = new TemplateActionRegistry();
-  const worker = new TaskWorker({
-    logger,
-    taskBroker,
-    actionRegistry,
-    workingDirectory,
+  const workers = new Array(taskWorkers || 1);
+  workers.map(_ => {
+    const worker = new TaskWorker({
+      logger,
+      taskBroker,
+      actionRegistry,
+      workingDirectory,
+    });
+    return worker;
   });
 
   const actionsToRegister = Array.isArray(actions)
@@ -127,8 +133,7 @@ export async function createRouter(
       ];
 
   actionsToRegister.forEach(action => actionRegistry.register(action));
-
-  worker.start();
+  workers.forEach(worker => worker.start());
 
   router
     .get(