Скачать или смотреть Fixing Multiple Executions of Scheduled Tasks in ASP.NET Core 3.1 Hosted Services

Learn how to troubleshoot and resolve issues related to multiple executions of scheduled tasks in ASP.NET Core 3.1 hosted services, especially in production environments.
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Resolving Multiple Executions of Scheduled Tasks in ASP.NET Core 3.1 Hosted Services

When working with hosted services in ASP.NET Core 3.1, many developers run into a perplexing issue: their scheduled tasks execute multiple times in a production environment, despite being configured to run only once daily. This problem can lead to unexpected behaviors, such as sending multiple emails when only one was intended. If you're experiencing this issue, you're not alone, and understanding the root cause can save you from headaches down the line.

The Problem

A user faced an issue where their background tasks, implemented using an inherited abstract class, executed multiple times. For example:

In development, a job scheduled to send an email once at 2:00 AM functions perfectly, firing just once.

Upon deployment to AWS EC2, the same job triggered between 5-13 emails on some days, raising the question of scalability and configuration inconsistency.

This unexpected behavior can be particularly frustrating to troubleshoot, especially when everything seems to work correctly in a local environment with a similar setup.

An Overview of the Implementation

The hosted service is based on an abstract class called ScheduledBackgroundWorker<T>. The key components of its design include:

Crontab Schedule: Defines when the task should run (in cron syntax).

Execution Logic: Contains methods to execute on start and stop, along with caching mechanisms to prevent re-running tasks within certain time frames.

The ExecuteStartAsync method checks if the task has already run using a distributed cache to keep track.

Key Code Snippet

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Despite having this logic, the issue persisted in the production environment.

What May Be Causing the Issue?

After examining the code and deployment settings, the problem was traced back to a configuration in IIS. Specifically, the Max Worker Processes setting was greater than 1. This means that multiple instances were processing the job independently, leading to duplicate executions of the same task across processes.

Steps to Resolve the Issue

Here’s how you can troubleshoot and potentially resolve similar issues in your hosted service:

Check IIS Application Pool Settings:

Navigate to the IIS Manager.

Locate the application pool your application is using.

Set the Maximum Worker Processes to 1. This ensures that only one instance of your application can handle requests and scheduled tasks.

Review Caching Logic:

Ensure your caching mechanism is reliably preventing multiple task executions.

Consider implementing additional logging to monitor whether the cache state behaves as expected.

Test in Different Environments:

Consider using staging environments that mimic production settings closely.

Test variations of your configuration before deployment to catch potential problems early.

Monitor Task Executions:

Implement logging within your task execution logic to track precisely how often and when your tasks are firing. This detailed information can help pinpoint any unexpected behaviors down the line.

Use Health Checks:

Consider integrating health checks to assess the status of your scheduled tasks regularly. This can provide early warning signs if something goes wrong again.

Conclusion

By taking these steps and understanding the implications of IIS configurations, you can resolve issues related to multiple task executions in ASP.NET Core 3.1 hosted services. Always remember that while development may behave differently than production, careful management of your deployment settings can lead to reliable and predictable application beh