Log errors when tasks fail

* Log errors that occur when running a task
* Use a child logger when initalising a new TaskWorker to include the task id with any logs.

Signed-off-by: Alex Crome <afscrome@users.noreply.github.com>

.changeset/wise-nails-hang.md

@@ -0,0 +1,5 @@
+---
+'@backstage/backend-tasks': patch
+---
+
+Add error logging when a background task throws an error rather than silently swallowing it.

packages/backend-tasks/src/tasks/PluginTaskSchedulerImpl.ts

@@ -57,7 +57,12 @@ export class PluginTaskSchedulerImpl implements PluginTaskScheduler {
 
     if (scope === 'global') {
       const knex = await this.databaseFactory();
-      const worker = new TaskWorker(task.id, task.fn, knex, this.logger);
+      const worker = new TaskWorker(
+        task.id,
+        task.fn,
+        knex,
+        this.logger.child({ task: task.id }),
+      );
 
       await worker.start(
         {

packages/backend-tasks/src/tasks/TaskWorker.test.ts

@@ -119,6 +119,31 @@ describe('TaskWorker', () => {
     60_000,
   );
 
+  it.each(databases.eachSupportedId())(
+    'logs error when the task throws, %p',
+    async databaseId => {
+      const knex = await databases.init(databaseId);
+      await migrateBackendTasks(knex);
+
+      jest.spyOn(logger, 'error');
+      const fn = jest.fn().mockRejectedValue(new Error('failed'));
+      const settings: TaskSettingsV2 = {
+        version: 2,
+        initialDelayDuration: undefined,
+        cadence: '* * * * * *',
+        timeoutAfterDuration: Duration.fromMillis(60000).toISO(),
+      };
+      const checkFrequency = Duration.fromObject({ milliseconds: 100 });
+      const worker = new TaskWorker('task1', fn, knex, logger, checkFrequency);
+      worker.start(settings);
+
+      await waitForExpect(() => {
+        expect(logger.error).toBeCalled();
+      });
+    },
+    60_000,
+  );
+
   it.each(databases.eachSupportedId())(
     'runs tasks more than once even when the task throws, %p',
     async databaseId => {

packages/backend-tasks/src/tasks/TaskWorker.ts

@@ -145,6 +145,7 @@ export class TaskWorker {
       await this.fn(taskAbortController.signal);
       taskAbortController.abort(); // releases resources
     } catch (e) {
+      this.logger.error(e);
       await this.tryReleaseTask(ticket, taskSettings);
       return { result: 'failed' };
     } finally {