PlugLoggerCee

A plug for formatting your logs for kibana/graylog/etc in the CEE (or lumberjack?) format, or just json. Like:

@cee {"foo":"bar"}

Installation

The package can be installed by adding cee_log_formatter to your list of dependencies in mix.exs:

def deps do
  [
    {:cee_log_formatter, "~> 0.1"}
  ]
end

Then set the format of your logs in production:

# config/prod.exs

config :logger, :console,
  level: :info,
  format: {CeeLogFormatter, :format}

Configuration

You can change the prefix line (if you just want json):

config :cee_log_formatter,
  prefix: ""

By default CeeLogFormatter will try to use Poison to encode and decode JSON, but you can configure it to any other json library that implements encode!() and decode!() callbacks:

config :cee_log_formatter, :json_library, Jason

You can add metadata to all your requests via config options:

config :cee_log_formatter,
  metadata: [
    app_name: "my-app",
    arbitrary_mfa: {MyMod, :some_func, [:arg1, :arg2]}
  ]

The metadata config takes a keyword list. If the value is a string, it is used directly in the log output. If the value is a 3-element tuple, it is expected to be a {Module, function, argument-list}, which is called for every log line to get some current value. If the value returned from the MFA is not a string, it is ignored.

For instance, you could have the current unix timestamp added to the log with:

defmodule TimestampLog do
  def current(resolution) do
    "#{:os.system_time(resolution)}"
  end
end

# in config.exs
config :cee_log_formatter,
  metadata: [
    timestamp: {TimestampLog, :current, [:second]}
  ]

You should also use the PlugLoggerJson package, which configures plug to output logs as maps so the formatter gets more info.