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:

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

def deps do [{:plug_logger_json, "~> 0.5.0"}] end
Ensure plug_logger_json is started before your application:

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

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 if you want to filter params or headers or suppress any logged keys:
```
  config :plug_logger_json,
    filtered_keys: ["password", "authorization"],
    suppressed_keys: ["api_version", "log_type"]
```

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.

trumant/plug_logger_json