Hangfire.Idempotent

Hangfire.Idempotent is a lightweight extension for Hangfire that prevents duplicate jobs from being enqueued based on their method and arguments.

• ✅ Works for normal jobs, delayed jobs, and recurring jobs
• ✅ No custom job IDs or special scheduling needed
• ✅ Transparent integration through an [IdempotentJob] attribute
• ✅ Automatic deduplication during job creation

---

Installation

dotnet add package Effektor.Hangfire.Idempotent

---

Usage

1. Enable the extension in your Hangfire configuration:

GlobalConfiguration.Configuration
    .UseSqlServerStorage("your_connection_string")
    .UseIdempotent();

2. Mark your job methods with [IdempotentJob]:

using Hangfire.Idempotent;

public class OrderService
{
    [IdempotentJob]
    public void ProcessOrder(int orderId)
    {
        // Your processing logic
    }
}

3. Enqueue jobs normally:

BackgroundJob.Enqueue(() => orderService.ProcessOrder(42));

Or for recurring jobs:

RecurringJob.AddOrUpdate(() => orderService.ProcessOrder(42), Cron.Hourly);

If a job with the same method and arguments already exists in the queue, scheduled jobs, or is currently being fetched for processing, the new job will not be created.

---

How It Works

• Hooks into Hangfire's job creation pipeline using a custom IClientFilter.
• At job creation time, scans the job queues (Enqueued, Scheduled, Fetched) for existing jobs matching:
  • Same method
  • Same arguments
• If a matching job exists, the new job is canceled before it’s created.
• The [IdempotentJob] attribute is used to opt-in specific methods for deduplication.

---

Notes

• Performance: By default, scans up to 500 jobs in each state. You can adjust the number depending on your load.
• Race conditions: There is a minimal risk of race conditions when a job switches state, e.g. goes from Enqueueued -> Scheduled and similar.
• Limitations: Failed jobs are not scanned; only active jobs (Enqueued, Scheduled, Fetched) are considered for deduplication.

License

MIT License