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ASP.NET Core Performant logging

One of the hidden features of ASP.NET Core is the support for LoggerMessage.

From the documentation:

LoggerMessage features create cacheable delegates that require fewer object allocations and reduced computational overhead compared to logger extension methods, such as LogInformation, LogDebug, and LogError. For high-performance logging scenarios, use the LoggerMessage pattern.

LoggerMessage provides the following performance advantages over Logger extension methods:

  • Logger extension methods require "boxing" (converting) value types, such as int, into object. The LoggerMessage pattern avoids boxing by using static Action fields and extension methods with strongly-typed parameters.
  • Logger extension methods must parse the message template (named format string) every time a log message is written. LoggerMessage only requires parsing a template once when the message is defined.

The best way to use it is through some extension methods on the ILogger interface:

  • Create a static LoggerExtensions class
  • Add a static constructor and use the Define(LogLevel, EventId, String) method to create an Action delegate for logging a message. For the Action, specify:
    • The log level.
    • A unique event identifier (EventId) with the name of the static extension method.
    • The message template (named format string).
  • Store the created Action delegate in a private static field
  • Create an extension method that invokes the delegate
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