PlugLoggerJson

A comprehenisve JSON logger Plug.

Dependencies

• Plug
• Poison

Elixir & Erlang Support

• The support policy is to support the last 2 major versions of Erlang and the three last minor versions of Elixir.

Installation

If available in Hex, the package can be installed as:

1. Add plug_logger_json to your list of dependencies in mix.exs:

   def deps do [{:plug_logger_json, "~> 0.5.0"}] end

2. Ensure plug_logger_json is started before your application:

   def application do [applications: [:plug_logger_json]] end

3. Replace Plug.Logger with Plug.LoggerJSON, log: Logger.level in your plug pipeline (endpoint.ex for phoenix apps)

or for extra attributes (see extra attributes section)

1. Replace Plug.Logger with Plug.LoggerJSON, log: Logger.level, extra_attributes_fn: &MyPlug.extra_attributes/1 in your plug pipeline (endpoint.ex for phoenix apps)

Recommended Setup

• Configure this application

  • Add to your config/config.exs or config/env_name.exs ONLY if you want to filter params or headers:

      config :plug_logger_json,
        filtered_keys: ["password", "authorization"],
    

• Configure the logger (console)

  • Add to your config/config.exs or config/env_name.exs:

      config :logger, :console,
        format: "$message\n",
        level: :info, #You may want to make this an env variable to change verbosity of the logs
        metadata: [:request_id]
    

• Configure the logger (file)

  • Add {:logger_file_backend, "~> 0.0.7"} to your mix.exs

  • Run mix deps.get

  • Add to your config/config.exs or config/env_name.exs:

      config :logger, format: "$message\n", backends: [{LoggerFileBackend, :log_file}, :console]
    
      config :logger, :log_file,
        format: "$message\n",
        level: :info,
        metadata: [:request_id],
        path: "log/my_pipeline.log"
    

• Ensure you are using Plug.Parsers (Phoenix adds this to endpoint.ex by default) to parse params & req bodies

      plug Plug.Parsers,
        parsers: [:urlencoded, :multipart, :json],
        pass: ["*/*"],
        json_decoder: Poison
  

Error Logging

• In router.ex of your phoenix project or your plug pipeline

  • Add require Logger

  • Add use Plug.ErrorHandler

  • Add the following two private functions:

      defp handle_errors(%Plug.Conn{status: 500} = conn, %{kind: kind, reason: reason, stack: stacktrace}) do
        Plug.LoggerJSON.log_error(kind, reason, stacktrace)
        send_resp(conn, 500, Poison.encode!(%{errors: %{detail: "Internal server error"}}))
      end
    
      defp handle_errors(_, _), do: nil 
    

Extra Attributes

• Additional data can be logged alongside the request by specifying a function to call which returns a map:

  def extra_attributes(conn) do
    map = %{
      "user_id" => get_in(conn.assigns, [:user, :user_id]),
      "other_id" => get_in(conn.private, [:private_resource, :id]),
      "should_not_appear" => conn.private[:does_not_exist]
    }
    map
    |> Enum.filter(&(&1 !== nil))
    |> Enum.into(%{})
  end
  plug Plug.LoggerJSON, log: Logger.level,
                        extra_attributes_fn: &MyPlug.extra_attributes/1
  

• In this example, the :user_id is retrieved from conn.assigns.user.user_id and added to the log if it exists. In the example, any values that are nil are filtered from the map. It is a requirement that the value is serialiazable as JSON by the Poison library, otherwise an error will be raised when attempting to encode the value.

Log Verbosity

• Plug Logger JSON supports two levels of logging.
• Info / Error will log api_version, date_time, duration, log_type, method, path, request_id, & status.
• Warn / Debug log levels will include everything from info plus client_id, client_version, and params / request bodies.

Contributing

Before submitting your pull request, please run:

• mix credo --strict
• mix coveralls
• mix dialyzer
• Update Changelog

Please squash your pull request's commits into a single commit with a message and detailed description explaining the commit.