logging

logging

The logging submodule is used to easily configure zerolog for a more flexible and easy use.

Why

Zerolog is already a great logging framework. However, it does lack in especially one area. Area-specific levels. It requires a lot of effort to set up a system where you can configure per-area log levels. This module solves that problem.

Usage

package logging

import (
  "context"
  "github.com/rs/zerolog"
)

func main() {
  // To inject the required flags into the `flag` module
  // Allows setting the log levels via either `GO_LOG` or the -loglevel flag.
	SetupFlags()

  // If you want the logging output to include the area the message is from
	SetIncludeArea(true)

  // Optionally configure how the content of the flag and environment variable
  // get parsed. See the function documentation for details.
  SetAreaSeparator(",")
  SetAreaToLevelSeparator("=")
  SetSubAreaSeparator("::")

  // Configure the context for use with the framework.
  // IMPORTANT: SetupFlags and the various SetXXX functions must be called before
  // ConfigureLogging, otherwise they won't have any effect.

  // Use nil as 2nd argument to write only to stderr.
  ctx := ConfigureLogging(context.Background(), nil)
  // Or, to write to stderr and, in this case, stdout
  // ctx := ConfigureLogging(context.Background(), os.Stdout)

  var log zerolog.Logger

  // Then acquire your logger for the area you want

  // For the base area ("")
  log = FromContext(ctx) // or FromContext(ctx, ""), "" is cut from the area list

  // Log will now have the logging level configured for
  // the `example` area, if set. Otherwise the base area level
  log = FromContext(ctx, "example")

  // Log will now have the logging level configured for
  // the `example::sub` area, if set. Otherwise the level of `example` or base
  log = FromContext(ctx, "example", "sub")

  // You can also attach an area to the context to prepend to the requested area

  // Attach a default area to the context.
  ctxWithSubarea := WithSubarea(ctx, "example")

  // Log will now have the logging level configured for
  // the `example` area, if set. Otherwise the base area level
  log = FromContext(ctxWithSubarea)

  // Log will now have the logging level configured for
  // the `example::sub` area, if set. Otherwise the level of `example` or base
  log = FromContext(ctxWithSubarea, "sub")

  // You can also explicitly ignore the area already attached to the context

  // Log will now have the logging level configured for
  // the `example2` area, if set. Otherwise the base area level
  log = FromContextBlank(ctxWithSubarea, "example2")
}