没有 IHostedService 运行应用程序的整个生命周期的长时间运行的任务？

Question

I have a website page that needs the option of performing an operation that could take several minutes. To avoid performance issues and time outs, I want to run this operation outside of the HTTP request.

After some research, I found IHostedService and BackgroundService , which can be registered as a singleton using AddHostedService<T>() .

But my concern is that a hosted service is always running. Doesn't that seem like a waste of resources when I just want it to run on demand?

Does anyone know a better option to run a lengthy task, or a way to use IHostedService that doesn't need to run endlessly?

Note that the operation calls and waits for an API call. And so I cannot report the progress of the operation, nor can I set a flag in a common database regarding whether the operation has completed.

Answer 1

One option to run a lengthy task on demand while avoiding performance issues and time outs is to use a message queue . You can have your Razor Pages website send a message to the queue when the operation is requested, and have a separate service, such as a background worker , consume messages from the queue and perform the operation. This allows you to decouple the task from the web request, and also allows for the possibility of adding more worker instances to handle the workload.

Another option is to use a task scheduler that runs on demand, such as Hangfire . It allows you to schedule background jobs and monitor their progress, which can be useful in your scenario where you cannot report the progress of the operation.

You can also use IHostedService , but you need to make sure that the service is only running when it is needed. You can use a flag or a semaphore to control whether the service is running or not. You can set the flag or semaphore when the operation is requested, and clear it when the operation is completed. The service can then check the flag or semaphore in its main loop, and exit if the flag is not set.

In summary:

message queue , task scheduler , and IHostedService with controlling flag/semaphore are all viable options for running a lengthy task on demand. The best option depends on your specific use case and requirements.