ASP.NET Core Logging

Whenever an app is running, you need to know what’s happening behind the scenes. And whenever an app crashes or otherwise has trouble, you definitely want to know what’s going on. Logging is the simple, yet critical, way to ensure your apps are doing what they’re supposed to be doing. Logging helps you detect and identify any issues.

Now that ASP.Net Core is open source, and cross-platform, building in and linking logging functions is more straightforward than ever. The logging API in ASP.Net Core supports for a whole bunch of logging providers. You can send log details to one location or several locations. You can also connect to a third-party logger. And it’s straightforward. Notice I didn’t say easy, but it’s certainly straightforward. Thankfully, as is often the case, there are several blogs ready to help out.

Logging in ASP.NET Core

Once again, Microsoft’s extensive knowledge base comes to the rescue. While the Microsoft knowledge base, tutorials, and other blog posts are rarely the only source of helpful tips, it’s almost always the best place to start. This guide to logging in ASP.NET Core begins with a brief definition:

“ASP.NET Core supports a logging API that works with a variety of logging providers. Built-in providers let you send logs to one or more destinations, and you can plug in a third-party logging framework. This article shows how to use the built-in logging API and providers in your code.

How to create logs
To create logs, get an ILogger object from the dependency injection container. This example creates logs with the TodoController class as the category. Categories are explained later in this article.

ASP.NET Core doesn't provide async logger methods because logging should be so fast that it isn't worth the cost of using async. If you're in a situation where that's not true, consider changing the way you log. If your data store is slow, write the log messages to a fast store first, then move them to a slow store later. For example, log to a message queue that's read and persisted to slow storage by another process.

How to add providers
A logging provider takes the messages that you create with an ILogger object and displays or stores them. For example, the Console provider displays messages on the console, and the Azure App Service provider can store them in Azure blob storage. To use a provider, call the provider's Add extension method in Program.cs.”

This knowledge base entry also illustrates each instructional narrative with code snippets. After showing you the basics of how to create a log and add a provider, this tutorial post goes on to cover:

  • Sample logging output
  • NuGet packages
  • Log category
  • Log level
  • Log event ID
  • Log message template
  • Logging exceptions
  • Log filtering
  • Log scopes
  • Built-in logging providers
  • Third-party logging providers
  • Azure log streaming

ASP.NET Core - Logging

This tutorial takes you through the whole process of setting up logging for all different versions of ASP.NET Core. It also provides code snippets and listings pf third party loggers you can connect with ASP.NET Core.

“ASP.NET Core framework provides built-in supports for logging. However, we can also use third party logging provider easily in ASP.NET Core application. Before we see how to implement logging in ASP.NET Core application, let's understand the important logging interfaces and classes available in ASP.NET Core framework. The following are built-in interfaces and classes available for logging under Microsoft.Extensions.Logging namespace:

  • ILoggingFactory
  • ILoggingProvider
  • ILogger
  • LoggingFactory

ASP.NET Core framework includes built-in LoggerFactory class that implements ILoggerFactory interface. We can use it to add an instance of type ILoggerProvider and to retrieve ILogger instance for the specified category. ASP.NET Core runtime creates an instance of LoggerFactory class and registers it for ILoggerFactory with the built-in IoC container when the application starts. Thus, we can use ILoggerFactory interface anywhere in your application. The IoC container will pass an instance of LoggerFactory to your application wherever it encounters ILoggerFactory type.”

You’ll find this tutorial requires some familiarity with ASP.NET and ASP.NET Core, but does a comprehensive job of walking you through the process.

Leaner, meaner ASP.NET Core 2 logging

Blogger Nicolas Blumhardt provides a clean, well-organized tutorial on incorporating Serilog with ASP.NET Core. He also supports his statements with code snippets. “You don’t need anything special to use Serilog with .NET Core: the Serilog package works the same way across the .NET Framework and .NET Core on Windows, macOS and Linux. If you are writing .NET Core web apps with ASP.NET, you’ll want to plug into the Microsoft.Extensions.Logging subsystem to receive events from the framework: unhandled errors, diagnostic info from the request processing pipeline, events from EF, and so on.

In ASP.NET Core 2.0, the default logging provider has gained some features, like its own level control and filtering. This is good thing for the out-of-the-box experience, but if you use Serilog, you won’t want two sets of configuration to keep in sync or two logging pipelines running with subtle differences between them.”

Posted by Lafe Low on 04/13/2018

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