Logger

It includes many features:

  • Provides debug, info, warn, and error levels.

  • Supports multiple backends which are automatically supervised when plugged into Logger.

  • Formats, truncates, and alternates between async/sync when under stress to avoid clogging Logger backends.

  • Integrates with Erlang's :logger to convert terms to Elixir syntax.

  • Automatically includes metadata like :application, :mfa(module function and arity), :file, :line, :pid, :crash_reason etc

  • Advanced: Format and include more information in prod

Usage

Note the arguments given to info/2 will only be evaluated if a message is logged(its a high enough log level)

  require Logger
  
  # Every log call in this process will have this metadata
  Logger.metadata(request_id: request_id)
  # 2nd arg is metadata
  Logger.info("Successfully processed payment", confirmation_code: c)
  #......
	Logger.info("Deleting user from the system: #{inspect(user)}")

Levels, setting logger to any level will show all above too

  • :emergency - when system is unusable, panics

  • :alert - for alerts, actions that must be taken immediately, ex. corrupted database

  • :critical - for critical conditions

  • :error - for errors

  • :warning - for warnings

  • :notice - for normal, but signifant, messages

  • :info - for information of any kind

  • :debug - for debug-related messages

Config

# Our Logger general configuration
config :logger,
  backends: [:console],
  compile_time_purge_level: :debug

# Our Console Backend-specific configuration
config :logger, :console,
  format: "\n##### $time $metadata[$level] $levelpad$message\n",
  metadata: :all
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