logging_appenders

Native dart package for logging appenders usable with the logging package.

Color Output Screenshot

It currently includes appenders for:

Local Logging
- print() PrintAppender
- Rolling File Appender. RotatingFileAppender
Remote Logging
- logz.io
- loki.
- gelf/Graylog

Performance of Remote Logging Appenders

I am not sure if it is wise to use this in production, but it's great during beta testing with a handful of users so you have all logs available.

It tries to stay reasonable performant by batching log entries and sending them off only every few seconds. If network is down it will retry later. (with an ever increasing interval).

Getting Started

After installing package logging and logging_appenders:

import 'package:logging/logging.dart';
import 'package:logging_appenders/logging_appenders.dart';

final _logger = Logger('main');

void main() {
  PrintAppender.setupLogging();

  // The above code is the same as:
  // Logger.root.level = Level.ALL;
  // PrintAppender()..attachToLogger(Logger.root);

  _logger.fine('Lorem ipsum');
}

Outputs:

$ dart main.dart
2019-08-19 15:36:03.827563 FINE main - Lorem ipsum

Support for Exception chaining

To chain exception you can use the extension method on Exception: causedBy().

int test() {
  try {
    int.parse('a');
  } catch (e, stackTrace) {
    throw Exception('unable to parse').causedBy(e, stackTrace);
  }
}
int main() {
  try {
    test();
  } catch (e, stackTrace) {
    logger.severe('catched Exception', e, stackTrace);
  }
}

Color Formatter

    PrintAppender(formatter: const ColorFormatter())
        ..attachToLogger(Logger.root);

Produces:

Color Output Screenshot

Logging to stderr

When using dart:io (ie. command line apps) it is possible to define which log levels should go to stderr instead of stdout:

PrintAppender.setupLogging(stderrLevel: Level.SEVERE);

Remote Appenders

Appender for logz.io

  final _logzIoApiSender = LogzIoApiAppender(
    // you can find your API key and the required URL from 
    // the logz.io dashboard: https://app-eu.logz.io/#/dashboard/settings/general
    apiToken: 'MY API KEY',
    url: 'https://listener-eu.logz.io:8071/',
    labels: {'app': 'MyApp', 'os': Platform.operatingSystem},
  );
  _logzIoApiSender.attachToLogger(Logger.root);
  
  
  // ...
  If you know that you no longer need the appender. it's good to dispose it:
  _logzIoApiSender.dispose();