LoggerBackendSqlite

What is it?

LoggerBackendSqlite will allow you to save all of your logs to an sqlite3 database.

Why is it?

This is very helpful for Nerves devices which don’t always have network access, or console access.

Usage is it?

Add logger backend ecto to your deps:

def deps do
  [
    {:logger_backend_sqlite, "~> 2.0"},
  ]
end

Configure :logger:

use Mix.Config

config :logger, [
  utc_log: true,
  handle_otp_reports: true,
  handle_sasl_reports: true,
  backends: [:console, LoggerBackendSqlite]
]

config :logger, LoggerBackendSqlite,
  database: 'debug_logs.sqlite3',
  max_logs: 9000, # defaults to 1000

You can also add the backend at runtime.

iex()> {:ok, _} = Logger.add_backend(LoggerBackendSqlite)
iex()> :ok = Logger.configure_backend(LoggerBackendSqlite, database: ":memory:", max_logs: 20)

Seeing logs:

iex(1)> require Logger
Logger
iex(2)> Logger.debug "hey!!"
:ok
iex(3)>
01:33:16.341 [debug] hey!!
iex(4)> LoggerBackendSqlite.all_logs
[
  %LoggerBackendSqlite.Log{
    application: nil,
    file: "iex",
    function: nil,
    group_leader_node: "nonode@nohost",
    id: 1,
    inserted_at: "2018-09-12 01:33:16.341631",
    level: "debug",
    line: 8,
    logged_at_dt: "2018-09-12 01:33:16Z",
    logged_at_ndt: "2018-09-12 01:33:16",
    message: "hey!!",
    module: nil,
    registered_name: nil,
    updated_at: "2018-09-12 01:33:16.341661"
  }
]

Nerves is it?

Using this on Nerves is pretty straightforward, but there is a gotcha. Nerves devices use a read only filesystem, so you need to ensure you store the database on a writable filesystem. You have two options.

/tmp

/tmp is read write, but will be cleared every boot and has a pretty small size constraint. This can be useful if you only want a few logs from a specific time.

/root

/root is the default location for your application data. There is another gotcha on this one, that on first boot, this partition will not be ready yet. A simple work can be found below:

in your config.exs

  use Mix.Config
  config :logger, LoggerBackendSqlite, [
    database: "/tmp/logs.sqlite"
  ]

then in your application code somewhere:

defmodule MyApp.FileSystemCheckup do
  @database "/root/logs.sqlite"
  @check_file "/root/check"
  require Logger

  def checkup do
    case File.write(@check_file, "any ole data") do
      :ok -> Logger.configure_backend(LoggerBackendSqlite, [database: @database])
      {:error, _} ->
        Logger.warn "Application data partition not ready yet"
        Proess.sleep(2000)
        checkup()
    end
  end
end

Why 2.0 is it?

This is a hard fork of logger_backend_ecto. It is 1.0, and I didn’t want any confusion that these are not the same thing, even tho they share the same public API.