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.
Minimum supported Erlang/OTP version is 20.
We deploy our applications as dockerized containers in Google Container Engine (Kubernetes cluster), in this case all your logs will go to stdout
and log solution on top of Kubernetes should collect and persist it elsewhere.
In GKE it is persisted in Google Cloud Logger, but traditional single Logger output may contain newlines for a single log line, and GCL counts each new line as separate log entry, this making it hard to search over it.
This backend makes sure that there is only one line per log record and adds additional integration niceness, like LogEntry format support.
After adding this back-end you may also be interested in redirecting otp and sasl reports to Logger (see "Error Logger configuration" section).
LoggerJSON provides two JSON formatters out of the box (see below for implementing your own custom formatter).
The LoggerJSON.Formatters.BasicLogger
formatter provides a generic JSON formatted message with no vendor specific entries in the payload. A sample log entry from LoggerJSON.Formatters.BasicLogger
looks like the following:
{
"time": "2020-04-02T11:59:06.710Z",
"severity": "debug",
"message": "hello",
"metadata": {
"user_id": 13
}
}
The other formatter that comes with LoggerJSON is LoggerJSON.Formatters.GoogleCloudLogger
and generates JSON that is compatible with the
Google Cloud Logger LogEntry format:
{
"message":"hello",
"logging.googleapis.com/sourceLocation":{
"file":"/os/logger_json/test/unit/logger_json_test.exs",
"function":"Elixir.LoggerJSONGoogleTest.test metadata can be configured/1",
"line":71
},
"severity":"DEBUG",
"time":"2018-10-19T01:10:49.582Z",
"user_id":13
}
Log entry in Google Cloud Logger would looks something like this:
{
"httpRequest":{
"latency":"0.350s",
"remoteIp":"::ffff:10.142.0.2",
"requestMethod":"GET",
"requestPath":"/",
"requestUrl":"http://10.16.0.70/",
"status":200,
"userAgent":"kube-probe/1.10+"
},
"insertId":"1g64u74fgmqqft",
"jsonPayload":{
"message":"",
"phoenix":{
"action":"index",
"controller":"Elixir.MyApp.Web.PageController",
},
"request_id":"2lfbl1r3m81c40e5v40004c2",
"vm":{
"hostname":"myapp-web-66979fc-vbk4q",
"pid":1,
}
},
"logName":"projects/hammer-staging/logs/stdout",
"metadata":{
"systemLabels":{},
"userLabels":{}
},
"operation":{
"id":"2lfbl1r3m81c40e5v40004c2"
},
"receiveTimestamp":"2018-10-18T14:33:35.515253723Z",
"resource":{},
"severity":"INFO",
"sourceLocation":{
"file":"iex",
"function":"Elixir.LoggerJSON.Plug.call/2",
"line":"36"
},
"timestamp":"2018-10-18T14:33:33.263Z"
}
You can change this structure by implementing LoggerJSON.Formatter
behaviour and passing module
name to :formatter
config option. Example module can be found in LoggerJSON.Formatters.GoogleCloudLogger
.
config :logger_json, :backend,
formatter: MyFormatterImplementation
It's available on Hex, the package can be installed as:
- Add
:logger_json
to your list of dependencies inmix.exs
:
def deps do
[{:logger_json, "~> 4.2"}]
end
- Set configuration in your
config/config.exs
:
config :logger_json, :backend,
metadata: :all
Some integrations (for eg. Plug) uses metadata
to log request
and response parameters. You can reduce log size by replacing :all
(which means log all) with a list of the ones that you actually need.
- Replace default Logger
:console
back-end withLoggerJSON
:
config :logger,
backends: [LoggerJSON]
- Optionally. Log requests and responses by replacing a
Plug.Logger
in your endpoint with a:
plug LoggerJSON.Plug
- Optionally. Use Ecto telemetry for additional metadata:
Attach telemetry handler for Ecto events in start/2
function in application.ex
:ok =
:telemetry.attach(
"logger-json-ecto",
[:my_app, :repo, :query],
&LoggerJSON.Ecto.telemetry_logging_handler/4,
:debug
)
Prevent duplicate logging of events, by setting log
configuration option to false
config :my_app, MyApp.Repo,
adapter: Ecto.Adapters.Postgres,
log: false
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, []}
You can replace default Jason encoder with other module that supports encode_to_iodata!/1
function and
enconding fragments.
The docs can be found at https://hexdocs.pm/logger_json
Many source code has been taken from original Elixir Logger :console
back-end source code, so I want to thank all it's authors and contributors.
Part of LoggerJSON.Plug
module have origins from plug_logger_json
by @bleacherreport,
originally licensed under Apache License 2.0. Part of LoggerJSON.PlugTest
are from Elixir's Plug licensed under Apache 2.
Copyright (c) 2016 Nebo #15
Released under the MIT License, which can be found in LICENSE.md.