如何安全退出自托管应用程序（退出前先做点事情）

Question

I want the self-hosted ASP.NET Core Application can delay a moment before quit when receive an exit signal.

I have multiple instances of the application behind a load balancing.

By default, if I shutdown an instance, the processing requests will be broken. And in a short time there are some new requests will still send to the offline instance because load balancing have an interval for health check.

So if I can do something before quit:

1. Disable healthcheck first, it will stop new requests from Load Balancing.
2. Continue processing all the requests that already received.

Then, the application can be "safely" quit. It allows an instance to smoothly down and users will not feel it.

So I want if there is an official solution for that, or a best practice.

Answer 1

I want the self-hosted ASP.NET Core Application can delay a moment before quit when receive an exit signal.

What is this signal? KILL or TERM?

Lets say that you want to handle TERM signal.

So, if you are using .net Core 1.X, your solution would be something like this. First, you need to add dependency to your json file

"System.Runtime.Loader" : "<version>

Then you can handle SIGTERM event bi adding method to an event

AssemblyLoadContext.Default.Unloading += YourMethodThatWillHandleSignal;

For using .NET Core 2.X, there is different solution. You can use IApplicationLifetime interface ( documentation ).

when you have this, all you can do is this:

applicationLifetime.ApplicationStopping.Register(() => Console.WriteLine("Stopping"));
applicationLifetime.ApplicationStopped.Register(() => Console.WriteLine("Stopped"));

Hope this helps.