vapor-docs/3.0/docs/logging/overview.md

Logging Overview

The logging package provides convenience APIs for logging information while your app is running. The Logger protocol declares a common interface for logging information. A default PrintLogger is available, but you can implement custom loggers to suit your specific needs.

Log

First, you will want to use a Container to create an instance of Logger. Then you can use the convenience methods to log information.

let logger = try req.make(Logger.self)
logger.info("Logger created!")

See Logger in the API docs for a list of all available methods.

Check out Service → Services for more information on how to register a custom logger.