Having an ILogger shut down when my ASP.NET Core app shuts down

[DavidThielen]

Hi all;

This is in a Blazor server app. I have an ILoggerProvider that I created. It buffers log output and writes it (to an Azure BLOB) every 2 minutes. When the server shuts down, I need to have it flush the buffered output and write it to the BLOB.

Is there a way to do this? I implemented Dispose() but it appears to not be called on a shutdown. Do I need to register my ILoggerProvider in some special way?

And if there is no way in the ILogger framework to do this, is there a way to have the App Server (I use Azure) call a method in my code on shutdown? If so, I can then directly call the logger to flush.

thanks - dave

[En3Tho]

I think as an immediate workaround you can implement a hosted service that will release resources of your provider.

[DavidThielen]

I'm sorry but that's a terrible answer. That turns a lightweight class into a service and all the overhead that goes with it. And then when I scale out my web app, I then need to scale out these service instances.

At worst all I need is an event that is called when the app server is shutting down. In that I make a simple call to the logger objects.

[En3Tho]

I don't get the scaling point tbh. Hosted service is just a class that reacts to lifetime events (and that's what you need).

But I can understand the point of logic being split between classes simply to call a dispose once. That's why I called it an immediate workaround.

[davidfowl]

It should be called on shutdown, how did you add the provider to the DI container?

[DavidThielen]

BTW - off-topic but want to say that SignalR is beautifully designed.

[davidfowl]

How do you add it to the container?

[DavidThielen]

I don't add it to the container. I just searched and couldn't find anything about adding an ILoggerProvider to a container. Can you point me to a page that tells me how to do that?

I'm guessing that explains the issue - not in a container, then no way for Blazor to know to Dispose it on shutdown.

TIA

[davidfowl]

What does the wire up of your BlobLoggerProvider look like?

[DavidThielen]

First off, thanks for continuing to help on this. I add it to the system as follows. In Program.cs, in Main() I have:

builder.Logging.AddAzureBlobLogger();

And that method is:

public static ILoggingBuilder AddAzureBlobLogger(this ILoggingBuilder builder)
{
	builder.AddConfiguration();

	builder.Services.TryAddEnumerable(ServiceDescriptor.Singleton<ILoggerProvider, BlobLoggerProvider>());
	builder.Services.TryAddEnumerable(ServiceDescriptor.Singleton<IConfigureOptions<BlobLoggerOptions>, BlobLoggerOptionsSetup>());
	builder.Services.TryAddEnumerable(ServiceDescriptor.Singleton<IOptionsChangeTokenSource<BlobLoggerOptions>, LoggerProviderOptionsChangeTokenSource<BlobLoggerOptions, BlobLoggerProvider>>());

	return builder;
}

Almost all of what I did, from the [ProviderAlias("Blob")] to this code just shown I came up with by copying from the Console ILoggerProvider. There wasn't any documentation I could find on writing one. So if I missed a required step, it's because I didn't see it for the Console provider.

thanks - dave