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A collection of formatters and utilities for JSON-based logging for various cloud tools and platforms.

Supported formatters

Installation

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

def deps do
  [
    # ...
    {:logger_json, "~> 6.0"}
    # ...
  ]
end

and install it running mix deps.get.

Then, enable the formatter in your config.exs:

config :logger, :default_handler,
  formatter: {LoggerJSON.Formatters.Basic, []}

or during runtime (eg. in your application.ex):

:logger.update_handler_config(:default, :formatter, {Basic, []})

You might also want to format the log messages when migrations are running:

config :domain, MyApp.Repo,
  # ...
  start_apps_before_migration: [:logger_json]

Additionally, you may also be try redirecting otp reports to Logger (see "Configuration" section).

Configuration

Configuration can be set using 2nd element of the tuple of the :formatter option in Logger configuration. For example in config.exs:

config :logger, :default_handler,
  formatter: {LoggerJSON.Formatters.GoogleCloud, metadata: :all, project_id: "logger-101"}

or during runtime:

:logger.update_handler_config(:default, :formatter, {Basic, metadata: {:all_except, [:conn]}})

Docs

The docs can be found at https://hexdocs.pm/logger_json.

Examples

Basic

{
  "message": "Hello",
  "metadata": {
    "domain": ["elixir"]
  },
  "severity": "notice",
  "time": "2024-04-11T21:31:01.403Z"
}

Google Cloud Logger

Follows the Google Cloud Logger LogEntry format, for more details see special fields in structured payloads.

{
  "logging.googleapis.com/trace": "projects/my-projectid/traces/0679686673a",
  "logging.googleapis.com/spanId": "000000000000004a",
  "logging.googleapis.com/operation": {
    "pid": "#PID<0.29081.0>"
  },
  "logging.googleapis.com/sourceLocation": {
    "file": "/Users/andrew/Projects/os/logger_json/test/formatters/google_cloud_test.exs",
    "function": "Elixir.LoggerJSON.Formatters.GoogleCloudTest.test logs an LogEntry of a given level/1",
    "line": 44
  },
  "message": {
    "domain": ["elixir"],
    "message": "Hello"
  },
  "severity": "NOTICE",
  "time": "2024-04-12T15:07:55.020Z"
}

and this is how it looks in Google Cloud Logger:

{
  "insertId": "1d4hmnafsj7vy1",
  "jsonPayload": {
    "message": "Hello",
    "logging.googleapis.com/spanId": "000000000000004a",
    "domain": ["elixir"],
    "time": "2024-04-12T15:07:55.020Z"
  },
  "resource": {
    "type": "gce_instance",
    "labels": {
      "zone": "us-east1-d",
      "project_id": "firezone-staging",
      "instance_id": "3168853301020468373"
    }
  },
  "timestamp": "2024-04-12T15:07:55.023307594Z",
  "severity": "NOTICE",
  "logName": "projects/firezone-staging/logs/cos_containers",
  "operation": {
    "id": "F8WQ1FsdFAm5ZY0AC1PB",
    "producer": "#PID<0.29081.0>"
  },
  "trace": "projects/firezone-staging/traces/bc007e40a2e9edffa23785d8badc43b8",
  "sourceLocation": {
    "file": "lib/phoenix/logger.ex",
    "line": "231",
    "function": "Elixir.Phoenix.Logger.phoenix_endpoint_stop/4"
  },
  "receiveTimestamp": "2024-04-12T15:07:55.678986520Z"
}

Exception that can be sent to Google Cloud Error Reporter:

{
  "httpRequest": {
    "protocol": "HTTP/1.1",
    "referer": "http://www.example.com/",
    "remoteIp": "",
    "requestMethod": "PATCH",
    "requestUrl": "http://www.example.com/",
    "status": 503,
    "userAgent": "Mozilla/5.0"
  },
  "logging.googleapis.com/operation": {
    "pid": "#PID<0.250.0>"
  },
  "logging.googleapis.com/sourceLocation": {
    "file": "/Users/andrew/Projects/os/logger_json/test/formatters/google_cloud_test.exs",
    "function": "Elixir.LoggerJSON.Formatters.GoogleCloudTest.test logs exception http context/1",
    "line": 301
  },
  "@type": "type.googleapis.com/google.devtools.clouderrorreporting.v1beta1.ReportedErrorEvent",
  "context": {
    "httpRequest": {
      "protocol": "HTTP/1.1",
      "referer": "http://www.example.com/",
      "remoteIp": "",
      "requestMethod": "PATCH",
      "requestUrl": "http://www.example.com/",
      "status": 503,
      "userAgent": "Mozilla/5.0"
    },
    "reportLocation": {
      "filePath": "/Users/andrew/Projects/os/logger_json/test/formatters/google_cloud_test.exs",
      "functionName": "Elixir.LoggerJSON.Formatters.GoogleCloudTest.test logs exception http context/1",
      "lineNumber": 301
    }
  },
  "domain": ["elixir"],
  "message": "Hello",
  "serviceContext": {
    "service": "nonode@nohost"
  },
  "stack_trace": "** (EXIT from #PID<0.250.0>) :foo",
  "severity": "DEBUG",
  "time": "2024-04-11T21:34:53.503Z"
}

Datadog

Adheres to the default standard attribute list as much as possible.

{
  "domain": ["elixir"],
  "http": {
    "method": "GET",
    "referer": "http://www.example2.com/",
    "request_id": null,
    "status_code": 200,
    "url": "http://www.example.com/",
    "url_details": {
      "host": "www.example.com",
      "path": "/",
      "port": 80,
      "queryString": "",
      "scheme": "http"
    },
    "useragent": "Mozilla/5.0"
  },
  "logger": {
    "file_name": "/Users/andrew/Projects/os/logger_json/test/formatters/datadog_test.exs",
    "line": 239,
    "method_name": "Elixir.LoggerJSON.Formatters.DatadogTest.test logs http context/1",
    "thread_name": "#PID<0.225.0>"
  },
  "message": "Hello",
  "network": {
    "client": {
      "ip": "127.0.0.1"
    }
  },
  "syslog": {
    "hostname": "MacBook-Pro",
    "severity": "debug",
    "timestamp": "2024-04-11T23:10:47.967Z"
  }
}

Elastic

Follows the Elastic Common Schema (ECS) format.

{
  "@timestamp": "2024-05-21T15:17:35.374Z",
  "ecs.version": "8.11.0",
  "log.level": "info",
  "log.logger": "Elixir.LoggerJSON.Formatters.ElasticTest",
  "log.origin": {
    "file.line": 18,
    "file.name": "/app/logger_json/test/logger_json/formatters/elastic_test.exs",
    "function": "test logs message of every level/1"
  },
  "message": "Hello"
}

When an error is thrown, the message field is populated with the error message and the error. fields will be set:

Note: when throwing a custom exception type that defines the fields id and/or code, then the error.id and/or error.code fields will be set respectively.

{
  "@timestamp": "2024-05-21T15:20:11.623Z",
  "ecs.version": "8.11.0",
  "error.message": "runtime error",
  "error.stack_trace": "** (RuntimeError) runtime error\n    test/logger_json/formatters/elastic_test.exs:191: anonymous fn/0 in LoggerJSON.Formatters.ElasticTest.\"test logs exceptions\"/1\n",
  "error.type": "Elixir.RuntimeError",
  "log.level": "error",
  "message": "runtime error"
}

Any custom metadata fields will be added to the root of the message, so that your application can fill any other ECS fields that you require:

Note that this also allows you to produce messages that do not strictly adhere to the ECS specification.

// with Logger.metadata(:"device.model.name": "My Awesome Device")
{
  "@timestamp": "2024-05-21T15:17:35.374Z",
  "ecs.version": "8.11.0",
  "log.level": "info",
  "log.logger": "Elixir.LoggerJSON.Formatters.ElasticTest",
  "log.origin": {
    "file.line": 18,
    "file.name": "/app/logger_json/test/logger_json/formatters/elastic_test.exs",
    "function": "test logs message of every level/1"
  },
  "message": "Hello",
  "device.model.name": "My Awesome Device"
}

Copyright (c) 2016 Andrew Dryga

Released under the MIT License, which can be found in LICENSE.md.