An easy to parse, one line logger for Elixir Plug.Conn and Phoenix, inspired by lograge.
With the default Plug.Logger
, the log output for a request looks like:
[info] GET /articles/some-article
[info] Sent 200 in 21ms
With Logster, we've got logging that's much easier to parse and search through, such as:
[info] method=GET path=/articles/some-article format=html controller=HelloPhoenix.ArticleController action=show params={"id":"some-article"} status=200 duration=0.402 state=set
This becomes handy specially when integrating with log management services such as Logentries or Papertrail.
First, add Logster to your mix.exs
dependencies:
def deps do
[{:logster, "~> 1.0"}]
end
Then, update your dependencies:
$ mix deps.get
To use with a Phoenix application, replace Plug.Logger
in the projects endpoint.ex
file with Logster.Plugs.Logger
:
# plug Plug.Logger
plug Logster.Plugs.Logger
To use it in as a plug, just add plug Logster.Plugs.Logger
into the relevant module.
By default, Logster filters parameters named password
, and replaces the content with [FILTERED]
.
You can update the list of parameters that are filtered by adding the following to your configuration file:
config :logster, :filter_parameters, ["password", "secret", "token"]
By default, Logster won't parse and log HTTP headers.
But you can update the list of headers that should be parsed and logged. The logged headers will be added under headers
. Both plain text and JSON formatters are supported.
config :logster, :allowed_headers, ["my-header-one", "my-header-two"]
To change the Logster log level for a specific controller and/or action, you use the Logster.Plugs.ChangeLogLevel
plug.
For example, to change the logging of all requests in a controller to debug
, add the following to that controller:
plug Logster.Plugs.ChangeLogLevel, to: :debug
And to change it only for index
and show
actions:
plug Logster.Plugs.ChangeLogLevel, to: :debug when action in [:index, :show]
This is specially useful for cases such as when you want to lower the log level for a healthcheck endpoint that gets hit every few seconds.
Logster allows you to use a different formatter to get your log lines looking just how you want. It comes with two built-in formatters: Logster.StringFormatter
and Logster.JSONFormatter
To use Logster.JSONFormatter
, supply the formatter
option when you use the Logster.Plugs.Logger
plug:
plug Logster.Plugs.Logger, formatter: Logster.JSONFormatter
That means your log messages will be formatted thusly:
{"status":200,"state":"set","path":"hello","params":{},"method":"GET","format":"json","duration":20.647,"controller":"App.HelloController","action":"show"
Caution: There is no guarantee that what reaches your console will be valid JSON. The Elixir Logger
module has its own formatting which may be appended to your message. See the Logger documentation for more information.
Custom metadata can be added to logs using Logger.metadata
and configuring your logger backend:
# add metadata for all future logs from this process
Logger.metadata(%{user_id: "123", foo: "bar"})
# example for configuring console backend to include metadata in logs.
# see https://hexdocs.pm/logger/Logger.html#module-console-backend documentation for more
# config.exs
config :logger, :console, metadata: [:user_id, :foo]
The easiest way to do this app wide is to introduce a new plug which you can include in your phoenix router pipeline.
For example:
defmodule HelloPhoenix.SetLoggerMetadata do
def init(opts), do: opts
def call(conn, _opts) do
Logger.metadata user_id: get_user_id(conn),
remote_ip: format_ip(conn)
conn
end
defp format_ip(%{remote_ip: remote_ip}) when remote_ip != nil, do: :inet_parse.ntoa(remote_ip)
defp format_ip(_), do: nil
defp get_user_id(%{assigns: %{current_user: %{id: id}}}), do: id
defp get_user_id(_), do: nil
end
And then add this plug to the relevant pipelines in the router:
pipeline :browser do
plug :fetch_session
plug :fetch_flash
plug :put_secure_browser_headers
# ...
plug HelloPhoenix.SetLoggerMetadata
# ...
end
You can rename the default keys passing a map like %{key: :new_key}
:
plug Logster.Plugs.Logger, renames: %{duration: :response_time, params: :parameters}
It will log the following:
[info] method=GET path=/articles/some-article format=html controller=HelloPhoenix.ArticleController action=show parameters={"id":"some-article"} status=200 response_time=0.402 state=set
You can exclude fields with :excludes
:
plug Logster.Plugs.Logger, excludes: [:params, :status, :state]
It will log the following:
[info] method=GET path=/articles/some-article format=html controller=HelloPhoenix.ArticleController action=show duration=0.402
To write your own formatter, all that is required is a module which defines a format/1
function, which accepts a keyword list and returns a string.
Use the following mix task before pushing commits to run the same checks that are run in CI:
mix ci
The MIT License
Copyright (c) 2016-present Navin Peiris
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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