ExSyslogger

ExSyslogger is custom backend for Elixir Logger that logs to syslog by wrapping erlang-syslog.

This project is a fork of exsyslog.

Requirements

• Elixir ~> 1.3

Features

• Logs to syslog
• Allows adding multiple backends with different configurations (e.g. each backend logs to a different facility with different log level)
• Custom log formatter
• Built-in JSON formatter(jason dependency is set to optional and you should explicitly add it to your dependency list)

Installation

Add :ex_syslogger as a dependency in your mix.exs file

Elixir 1.5 and above

defp deps do
  [
    {:ex_syslogger, "~> 1.5"}
  ]
end

Elixir ~> 1.4

defp deps do
  [
    {:ex_syslogger, "~> 1.3"}
  ]
end

Add :ex_syslogger to your list of included_applications:

def application do
  [included_applications: [:ex_syslogger]]
end

If you going to use JsonFormatter please we sure that jason is added as dependency in your application. For older Elixir versions it might be needed to add it to the list of applications as above.

Configuration

ExSyslogger is a Logger custom backend, as such, it relies on Logger application.

On your config.exs file tell Logger that it should add ExSyslogger backend

config :logger,
  backends: [
            {ExSyslogger, :ex_syslogger_error},
            {ExSyslogger, :ex_syslogger_debug},
            {ExSyslogger, :ex_syslogger_json}
            ]

With the configuration above, Logger application will add three ExSyslogger backend with the name {ExSyslogger, :ex_syslogger_error}, {ExSyslogger, :ex_syslogger_debug} and {ExSyslogger, :ex_syslogger_json}.

You might notice that instead of just passing the Module name, we're passing a tuple with {Module name, backend configuration name}. This allow us to have multiple backends with different configuration. Let's configure the backends:

config :logger, :ex_syslogger_error,
  level: :error,
  format: "$date $time [$level] $levelpad$node $metadata $message",
  metadata: [:module, :line, :function],
  ident: "MyApplication",
  facility: :local0,
  option: [:pid, :cons]

config :logger, :ex_syslogger_debug,
  level: :debug,
  format: "$date $time [$level] $message",
  ident: "MyApplication",
  facility: :local1,
  option: [:pid, :perror]

config :logger, :ex_syslogger_json,
  level: :debug,
  format: "$message",
  formatter: ExSyslogger.JsonFormatter,
  metadata: [:module, :line, :function],
  ident: "MyApplication",
  facility: :local1,
  option: :pid

Backend configuration properties

• level (optional): the logging level. It defaults to :info
• format (optional): Same as :console backend (Logger.Formatter). It defaults to "\n$date $time [$level] $levelpad$node $metadata $message\n"
• formatter (optional): Formatter that will be used to format the log. It default to Logger.Formatter
• metadata (optional): Same as :console backend Logger.Formatter. It defaults to []
• ident (optional): A string that's prepended to every message, and is typically set to the app name. It defaults to "Elixir"
• facility (optional): syslog facility to be used. It defaults to :local0. More documentation on erlang-syslog
• option (optional): syslog option to be used. It defaults to :ndelay. More documentation on erlang-syslog

Custom Formatters

ExSyslogger by default uses Logger.Formatter. However, it comes with a JSON formatter that formats a given log entry to a JSON string. NOTE: ExSyslogger.JsonFormatter can be use as an example if one wants to build his own formatter.

To build a custom formatter the formatter needs to implement the following functions:

compile(str) Compiles a format string

compile(binary | nil) :: [Logger.Formatter.pattern | binary]
compile({atom, atom}) :: {atom, atom}

format(format, level, msg, timestamp, metadata, config_metadata) Takes a compiled format and transforms it on a string that will be pass to syslog

format({atom, atom} | [Logger.Formatter.pattern | binary], Logger.level, Logger.message, Logger.Formatter.time, Keyword.t, [atom]) :: IO.chardata

To add the custom formatter you will need to set the formatter property on the configuration as exemplified above with ExSyslogger.JsonFormatter

Try it

In another shell:

$ tail -f /var/log/syslog

(Mac users)

$ tail -f /var/log/system.log

NOTE Mac has a funny syslog. Your info logs might not show up. You'll need to configure your Mac syslog.

Clone the project, go to examples/examples1 and run the project ($ iex -S mix).

Erlang/OTP 18 [erts-7.0.2] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false]

Interactive Elixir (1.0.5) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> Example1.run
2015-09-11 15:26:18.850 [error] nonode@nohost module=Elixir.Example1 function=run/0 line=5  Hello ExSyslogger
:ok

You should see on the tail -f something similar to:

exsyslog_error backend

Sep 11 16:26:18 bt.local MyApplication[12833]: 2015-09-11 15:26:18.850 [error] nonode@nohost module=Elixir.Example1 function=run/0 line=5  Hello ExSyslogger

exsyslog_debug backend

Sep 11 16:26:18 bt.local MyApplication[12833]: 2015-09-11 15:26:18.850 [error] Hello ExSyslogger

exsyslog_json backend

Sep 11 16:26:18 bt.local MyApplication[12833]: {"node":"nonode@nohost","module":"Elixir.Example1","message":"Hello ExSyslogger","line":5,"level":"error","function":"run/0"}

The source code is released under the MIT License. Check LICENSE for more information.