# LoggerJson

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JSON console back-end for Elixir Logger.

It can be used as drop-in replacement for default `:console` Logger back-end in cases where you use
use Google Cloud Logger or other JSON-based log collectors.

## Log Format

Output JSON is compatible with
[Google Cloud Logger format](https://cloud.google.com/logging/docs/reference/v1beta3/rest/v1beta3/LogLine) with
additional properties in `serviceLocation` and `metadata` objects:

  ```
  {
     "time":"2017-04-09T17:52:12.497Z",
     "severity":"DEBUG",
     "sourceLocation":{
        "moduleName":"Elixir.LoggerJSONTest",
        "line":62,
        "functionName":"test metadata can be configured to :all/1",
        "file":"/Users/andrew/Projects/logger_json/test/unit/logger_json_test.exs"
     },
     "metadata":{
        "user_id":11,
        "dynamic_metadata":5
     },
     "logMessage":"hello"
  }
  ```

## Installation

It's [available on Hex](https://hex.pm/packages/logger_json), the package can be installed as:

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

    def deps do
      [{:logger_json, "~> 0.1.0"}]
    end

  2. Ensure `logger_json` is started before your application:

    def application do
      [extra_applications: [:logger_json]]
    end

  3. Set a `:json_encoder` in your `config/config.exs`:

    config :logger_json,
      backend: [json_encoder: Poison]

## Dynamic configuration

For dynamically configuring the endpoint, such as loading data
from environment variables or configuration files, LoggerJSON provides
an `:on_init` option that allows developers to set a module, function
and list of arguments that is invoked when the endpoint starts.

    config :logger_json, :backend,
      on_init: {YourApp.Logger, :load_from_system_env, []}

## Encoders support

You can replace default Poison encoder with other module that supports `encode!/1` function. This can be even used
as custom formatter callback.

Popular Poison alternatives:

 * [exjsx](https://github.com/talentdeficit/exjsx).
 * [elixir-json](https://github.com/cblage/elixir-json) - native Elixir encoder implementation.

If your application is performance-critical, take look at [jiffy](https://github.com/davisp/jiffy).

## Documentation

The docs can be found at [https://hexdocs.pm/logger_json](https://hexdocs.pm/logger_json)