Building a Simple Task Scheduling System in Next.js with a Simulated Database

Scheduling tasks in a web application allows you to automate repetitive actions like sending notifications or updating records. In this post, we’ll walk through creating a simple task scheduling system in a Next.js application using a simulated database. This approach focuses on demonstrating core concepts with minimal code.

The Concept

Our task scheduling system consists of three main parts:

1. Task Definition: Define what tasks you want to perform.
2. Task Scheduling: Schedule these tasks to run at specific times.
3. Task Execution: Execute the tasks when they are due.

1. Task Definition

First, we define the tasks we want our system to handle. Let's consider a simple task that logs a message:

const registeredTasks = {
  'log-message': async ({ message }) => {
    console.log(message);
    return message;
  },
};

Here, registeredTasks is a collection of tasks our system knows how to run. We can add more tasks as needed.

2. Task Scheduling

Next, we simulate a database with a simple array and schedule tasks by adding them to this array:

const simulatedDatabase = [];
 
const scheduleTask = ({ task, data, runAt }) => {
  simulatedDatabase.push({
    task,
    data,
    runAt,
    state: 'scheduled',
  });
};

This function schedules a task by storing it in our simulated database with the time it should run.

3. Task Execution

Finally, we create a function that periodically checks for tasks that are ready to run:

const runScheduledTasks = () => {
  const now = new Date();
 
  simulatedDatabase.forEach(async (task) => {
    if (task.state === 'scheduled' && task.runAt <= now) {
      try {
        const result = await registeredTasks[task.task](task.data);
        task.state = 'completed';
        task.result = result;
      } catch (error) {
        task.state = 'failed';
        task.error = error;
      }
    }
  });
};

This function loops through the tasks in our simulated database, runs those that are due, and updates their status.

Conclusion

By defining tasks, scheduling them, and executing them at the right time, we've built a simple yet effective task scheduling system. Although we used a simulated database, the same principles apply when integrating with a real database in production. This approach can be easily extended to handle more complex tasks and scheduling requirements.