Timber v3.0.0-alpha.2 Timber.Formatter View Source

Provides utilities for formatting log lines as text

This formatter is designed for use with the default :console backend provided by Elixir Logger. To use this, you’ll need to configure the console backend to call the Timber.Formatter.format/4 function instead of its default formatting function. This is done with a simple configuration change. You’ll also need to let :console know that :all metadata keys should be passed to the formatter.

The result of the configuration looks like:

config :logger, backends: [:console]
config :logger, :console,
  format: {Timber.Formatter, :format},
  metadata: :all

Further configuration options available on this module are documented below.

Configuration Recommendations: Development vs. Production

In a standard Elixir project, you will probably have different configuration files for your development and production setups. These configuration files typically take the form of config/dev.exs and config/prod.exs which override defaults set in config/config.exs.

Timber’s defaults are production ready, but the production settings also assume that you’ll be viewing the logs through the Timber console, so they forego some niceties that help when developing locally. Therefore, to help with local development, we recommended this configuration for your :dev environment:

# config/dev.exs

config :timber, Timber.Formatter,
  colorize: true,
  format: :logfmt,
  print_timestamps: true
  print_log_level: true

This will configure Timber to output logs in logfmt instead of JSON, print the log level and timestamps, and colorize the logs.

Transport Configuration Options

The following options are available when configuring the formatter:

colorize

When true, the log level will be printed in a corresponding color using ANSI console control characters to help identify it.

When false, the log level will be printed out as standard text.

Defaults to true.

escape_new_lines

When true, new lines characters are escaped as \n.

When false, new lines characters are left alone.

This circumvents issues with output devices (like Heroku Logplex) that will tranform line breaks into multiple log lines.

The default depends on on the environment variable HEROKU. If the environment variable is present, this will be set to true. Otherwise, this defaults to false. Setting the value in your application configuration will always override the initialized setting.

format

Determines the output format to use. Even though the Timber service is designed to receive log metadata in JSON format, it’s not the prettiest format to look at when you’re developing locally. Therefore, we let you print the metadata in logfmt locally to make it easier on the eyes.

Valid values:

  • :json
  • :logfmt (not supported in production)

Defaults to :json.

print_log_level

When true, the log level is printed in brackets as part of your log message.

When false, the log level is not printed.

Regardless of the setting used, the log level will be recorded as part of Timber’s metadata. Setting this to false is recommended for production usage if you only use Timber for viewing logs.

Defaults to false.

print_metadata

The Timber metadata contains additional information about your log lines, but this can become unwieldy in local development scenarios.

When true, the Timber metadata is printed out at the end of the log line (starting with the indicator “@metadata”).

When false, the Timber metadata is not printed.

Note: This should always be true in production.

Defaults to true.

print_timestamps

When true, the timestamp for the log will be output at the front of the statement.

When false, the timestamp will be suppressed. This is only useful in situations where the log will be written to an evented IO service that automatically adds timestamps for incoming data, like Heroku Logplex.

Regardless of the setting used, the timestamp will be recorded as part of Timber’s metadata. Setting this to false is recommended for production usage if you only use Timber for viewing logs.

Defaults to false.

Link to this section Summary

Functions

Handles formatting a log for the Logger application

Link to this section Types

Link to this type configuration() View Source
configuration() :: %{
  colorize: boolean(),
  escape_new_lines: boolean(),
  format: :json | :logfmt,
  print_log_level: boolean(),
  print_metadata: boolean(),
  print_timestamps: boolean()
}

Link to this section Functions

Link to this function format(level, message, ts, metadata) View Source

Handles formatting a log for the Logger application

This function allows you to integrate Timber with the default :console backend distributed with the Elixir Logger application. By default, metadata will be output as a JSON document after the @metadata keyword on the line. You can also opt for the output to be in logfmt by setting the appropriate configuration key.