Task Scheduler

Art Admin uses a custom task scheduler supporting recurring tasks and long-running tasks, with built-in distributed lock deduplication.

Two Task Types

Type	Method	Use Case
Recurring	AddRecurringTask	Periodic execution (log cleanup, data aggregation)
LongRunning	AddLongRunningTask	Continuous running (message queue consumer, delay queue)

Recurring Tasks

taskScheduler.AddRecurringTask(
    _dailyWorker.ClearLogs,
    interval: TimeSpan.FromMinutes(21),  // Check every 21 minutes
    allowedHours: [2, 3],                // Only run at 2-3 AM
    preventDuplicateInterval: TimeSpan.FromHours(12), // No repeats within 12h
    useDistributedLock: true             // Only one Pod executes
);

Parameters

Parameter	Description
interval	Scheduling interval (how often to check)
allowedHours	Allowed execution hours (skipped outside range)
preventDuplicateInterval	Deduplication interval (Redis dedup key)
useDistributedLock	Enable distributed lock (multi-Pod mutex)

Long-Running Tasks

taskScheduler.AddLongRunningTask(
    _demoMessageQueueWorker.ProcessQueue,
    interval: TimeSpan.FromSeconds(1),             // Outer scheduling interval
    processingInterval: TimeSpan.FromMilliseconds(100), // Interval within processing window
    runDuration: TimeSpan.FromSeconds(30),          // Processing window duration
    taskName: "demo.queue.consume"
);

Two-Level Rhythm

Outer                         Processing Window
│←── interval ──→│←── runDuration ──────────────────→│
                  │                                    │
                  │ process → wait → process → wait → │release lock
                  │    ↑                          ↑    │
                  │    └── processingInterval ─────┘    │

Writing Workers

[Service(ServiceLifetime.Transient)]
public class DailyWorker
{
    // Workers use IDbContextFactory, NOT direct ArtDbContext injection
    private readonly IDbContextFactory<ArtDbContext> _contextFactory;

    public DailyWorker(IDbContextFactory<ArtDbContext> contextFactory)
    {
        _contextFactory = contextFactory;
    }

    public async Task ClearLogs(CancellationToken cancel)
    {
        using var context = _contextFactory.CreateDbContext();
        // Cleanup logic...
    }
}

Important

Workers must use IDbContextFactory to create DbContext. Workers run outside HTTP request scope — direct ArtDbContext injection will throw.

Task Configuration

All tasks are configured centrally in TaskConfiguration.cs:

public class TaskConfiguration : ITaskConfigurationProvider
{
    public void ConfigureTasks(ITaskScheduler taskScheduler)
    {
        taskScheduler.AddRecurringTask(...);
        taskScheduler.AddLongRunningTask(...);
    }
}

Core Features

Distributed Lock Deduplication

In multi-Pod deployments, each task runs on only one Pod. Redis distributed locks handle the coordination.

Staggered Initial Delay

Each task computes an initial delay (0-30s) from a hash of taskName + PodId, preventing all tasks from starting simultaneously after restart.

Graceful Shutdown

Stop signal → Cancel task loop → Wait for current execution (max 10s) → Force exit

Dual CancellationToken mechanism:

• Loop level — CancellationToken controls whether to continue the next iteration
• Business level — Uses CancellationToken.None to ensure HTTP/DB operations complete without interruption