Tell me more about the Quartz and Redis-based service: how it worked, how it scaled.

A service based on Quartz and Redis was implemented for managing a high-load task scheduler with scalability requirements.

Quartz was used as a scheduler that allows creating, launching, and managing scheduled tasks. Redis was used as a distributed storage for synchronizing state between multiple service instances and for implementing a locking mechanism to prevent the same task from being executed simultaneously by multiple nodes.

Scaling was achieved by running multiple instances of the service, which coordinated task execution through Redis. This allowed processing a large number of tasks in parallel and provided fault tolerance — if one instance failed, tasks were automatically reassigned to others.

An example of a simplified Quartz configuration using Redis for locks:

SchedulerFactory schedulerFactory = new StdSchedulerFactory();
Scheduler scheduler = schedulerFactory.getScheduler();
scheduler.start();

// Redis is used to implement DistributedLock in task execution logic
// This prevents the same task from being executed simultaneously on multiple nodes

Thus, the combination of Quartz and Redis provided reliable and scalable task scheduling in a distributed environment.