feat: add queue alerts feature

[mo3tazda3na]

feat: Add Queue Alerts system

Summary

This PR adds a new feature that allows users to configure automated alerts based on queue job counts. Users can define thresholds for specific job statuses (e.g., failed, waiting, active) and receive a callback notification when those thresholds are exceeded.

Key Features

• Flexible Configuration: Supports global defaults and per-queue overrides.
• Specific Status Monitoring: Monitor any job status (active, failed, waiting, delayed, etc.).
• Smart Alerting: Includes a steps option to prevent alert fatigue. For example, if threshold is 10 and steps is 5, alerts will trigger at 15, 20, 25, etc., rather than on every single increment.
• Zero UI Overhead: This runs on the server side within the API adapter.

Configuration Example

You can configure alerts by passing the queueAlerts option to createBullBoard:

const { createBullBoard } = require('@bull-board/api');
const { BullMQAdapter } = require('@bull-board/api/bullMQAdapter');
const { ExpressAdapter } = require('@bull-board/express');

createBullBoard({
  queues: [new BullMQAdapter(myQueue)],
  serverAdapter,
  options: {
    queueAlerts: {
      checkInterval: 60 * 1000, // Optional: Check every 1 minute (default)
      
      // Callback to handle the alert (e.g. send to Slack / Email / PagerDuty)
      onAlert: (data) => {
        console.log(`Alert detected for queue ${data.queueName}:`, data);
        // data = { queueName: 'BullMQ', status: 'failed', count: 12, threshold: 10 }
      },

      config: {
        // Global defaults applied to all queues
        default: {
          failed: { 
            count: 10, // Alert if more than 10 failed jobs
            steps: 5   // Alert again at 15, 20, 25...
          },
          waiting: { 
            count: 1000, // Alert if backlog > 1000
            steps: 100 
          }
        },

        // Per-queue overrides
        'Specific-Critical-Queue': {
          failed: { 
            count: 1, // Stricter threshold for critical queue
            steps: 1 
          }
        }
      }
    }
  }
});

Checklist

• Implementation of QueueAlarms class
• Integration with createBullBoard
• Type definitions updated
• Unit tests added and passing
• Examples updated

[felixmosh]

Hi @mo3tazda3na why do you think that this feature should be part of this lib?