How to track when Firebase Functions Task Queues have exhausted all retries?

I am using Firebase Functions Task Queues to call numerous API endpoints.

Each function is set to retry 5 times if it encounters an error.

Now I want to track if the function completes successfully or fails completely (i.e. all retries are exhausted and the function still throws an error).

I want to track this so that if it fails completely I can update a Firestore document or send an alert of some kind.

For example, here is a Task Queue function, how do I add the above functionality?

export const someTask = functions.tasks
  .taskQueue({
    retryConfig: {
      maxAttempts: 5,
      minBackoffSeconds: 60,
    },
    rateLimits: {
      maxConcurrentDispatches: 1,
    },
  })
  .onDispatch(
    async () => {
      try {
        // Call the API
        await apiCall();
        return;
      } catch (error) {
        // Throw error so that the Task Queue will retry
        throw new functions.https.HttpsError(
          'unknown',
          'someTask error'
        );
      }
    }
  );

This cannot be done natively with because the context argument provided by onDispatch only holds authentication details

So we have to track it outside the function.

This example updates a Firestore document for each retry, success, or complete failure. There is a Firstore collection named functionStatus and the ID of each document is equal to the name of the function you want to track. In this example the document ID would be someTask. This naming convention makes it easier to update the status.

import * as functions from 'firebase-functions';
import * as admin from 'firebase-admin';

const increment = admin.firestore.FieldValue.increment;

export const someTask = functions.tasks
  .taskQueue({
    retryConfig: {
      maxAttempts: 5,
      minBackoffSeconds: 60,
    },
    rateLimits: {
      maxConcurrentDispatches: 1,
    },
  })
  .onDispatch(async () => {
    try {
      // Call the API
      await apiCall();
    } catch (error) {
      // Get the functionStatus someTask doc
      const someTaskDoc = await admin
        .firestore()
        .collection('functionStatus')
        .doc('someTask')
        .get();

      if (someTaskDoc.data()?.retries < 5) {
        // Update the retry count because we have retries left
        await admin
          .firestore()
          .collection('functionStatus')
          .doc('someTask')
          .update({ retries: increment(1) });
      } else {
        // Update the status to failed because retries are spent
        await admin
          .firestore()
          .collection('functionStatus')
          .doc('someTask')
          .update({ status: 'failed' });
      }

      // Throw the error to start the retry (or if retries are spent kill the function completely)
      throw new functions.https.HttpsError('unknown', 'someTask error');
    }

    // Everything worked. Mark function as successful
    await admin
      .firestore()
      .collection('functionStatus')
      .doc('someTask')
      .update({ status: 'success' });
  });