How to Build a Custom Task Scheduler in FlutterFlow

Create a `scheduled_tasks` collection with fields: name (String), description (String), schedule (String — cron expression like '0 8 * * *'), actionName (String — the Cloud Function to call), parameters (Map — JSON parameters to pass to the function), isActive (bool), lastRunAt (Timestamp), nextRunAt (Timestamp), createdBy (String), and createdAt (Timestamp). Add a subcollection `scheduled_tasks/{taskId}/execution_log` with fields: executedAt (Timestamp), status (String — success or failed), durationMs (int), error (String — null on success), and result (String — summary of what happened).

Create a scheduled Cloud Function named taskDispatcher that runs every minute via Cloud Scheduler. The function queries scheduled_tasks where isActive is true and nextRunAt is less than or equal to the current time. For each due task, call the corresponding Cloud Function by name (using a switch statement or dynamic function lookup), pass the task's parameters, record the start time, and wrap the call in a try-catch. On success, log status 'success' to the execution_log subcollection and update lastRunAt. On failure, log the error message. After execution, calculate the next run time from the cron expression and update nextRunAt on the task document.

1// Cloud Function: taskDispatcher
2const functions = require('firebase-functions');
3const admin = require('firebase-admin');
4admin.initializeApp();
5const db = admin.firestore();
6
7// Import your task action functions
8const actions = require('./taskActions');
9
10exports.taskDispatcher = functions.pubsub
11  .schedule('every 1 minutes')
12  .onRun(async () => {
13    const now = admin.firestore.Timestamp.now();
14    const dueTasks = await db
15      .collection('scheduled_tasks')
16      .where('isActive', '==', true)
17      .where('nextRunAt', '<=', now)
18      .get();
19
20    for (const doc of dueTasks.docs) {
21      const task = doc.data();
22      const start = Date.now();
23
24      try {
25        const actionFn = actions[task.actionName];
26        if (!actionFn) throw new Error(
27          `Unknown action: ${task.actionName}`);
28
29        const result = await actionFn(task.parameters);
30
31        await doc.ref.collection('execution_log').add({
32          executedAt: admin.firestore.FieldValue
33            .serverTimestamp(),
34          status: 'success',
35          durationMs: Date.now() - start,
36          result: result || 'Completed',
37        });
38      } catch (err) {
39        await doc.ref.collection('execution_log').add({
40          executedAt: admin.firestore.FieldValue
41            .serverTimestamp(),
42          status: 'failed',
43          durationMs: Date.now() - start,
44          error: err.message,
45        });
46      }
47
48      // Update lastRunAt and calculate nextRunAt
49      const nextRun = getNextCronTime(task.schedule);
50      await doc.ref.update({
51        lastRunAt: admin.firestore.FieldValue
52          .serverTimestamp(),
53        nextRunAt: admin.firestore.Timestamp
54          .fromDate(nextRun),
55      });
56    }
57  });

Add the cron-parser npm package to your Cloud Functions. Create a helper function getNextCronTime that takes a cron expression string and returns the next Date when the task should run. Use the cron-parser library's parseExpression method with the currentDate set to now. Call interval.next().toDate() to get the next occurrence. Handle invalid cron expressions with a try-catch that defaults to 24 hours from now and logs a warning. This function is called by the dispatcher after each execution to set the nextRunAt field.

1// Helper: getNextCronTime
2const cronParser = require('cron-parser');
3
4function getNextCronTime(cronExpression) {
5  try {
6    const interval = cronParser.parseExpression(
7      cronExpression,
8      { currentDate: new Date() }
9    );
10    return interval.next().toDate();
11  } catch (err) {
12    console.warn(
13      `Invalid cron: ${cronExpression}`, err
14    );
15    // Default: 24 hours from now
16    const fallback = new Date();
17    fallback.setHours(fallback.getHours() + 24);
18    return fallback;
19  }
20}

Create a TaskScheduler admin page gated by role check. At the top, add a 'Create Task' Button that opens a BottomSheet with a form: name TextField, description TextField, schedule input (use a Row of DropDowns for frequency: every X minutes/hours/days or specific time, which generates the cron expression), actionName DropDown (populated from a config document listing available action functions), and a parameters TextField (JSON format). On submit, create the scheduled_tasks document with isActive true and nextRunAt calculated from the cron expression using a Custom Function. Below the form, display a ListView of all tasks from a Backend Query ordered by name. Each task shows name, schedule description, last run status, next run time, and an isActive Switch toggle.

When an admin taps a task in the list, navigate to a TaskDetail page passing the taskId. Display the task configuration at the top, then a ListView of the execution_log subcollection ordered by executedAt descending. Each log entry shows the execution timestamp, status badge (green for success, red for failed), duration in milliseconds, and the result or error message. Add summary statistics at the top: total executions, success rate percentage, average duration, and last failure timestamp. Add a 'Run Now' Button that updates the task's nextRunAt to now, causing the dispatcher to pick it up on its next run. Add a 'Delete Task' Button with a confirmation dialog.