flaschenpost

flaschenpost is a logger for cloud-based applications.

A /ˈflaʃənˌpɔst/ is a „message written on a scrap of paper, rolled-up and put in an empty bottle and set adrift on the ocean; traditionally, a method used by castaways to advertise their distress to the outside world”. (from Wiktionary)

Installation

As Node.js module

$ npm install flaschenpost

As CLI

$ npm install -g flaschenpost

Quick start

First you need to integrate flaschenpost into your application.

var flaschenpost = require('flaschenpost');

Using a logger

Next, call the getLogger function to acquire a logger. If you don't provide a parameter flaschenpost identifies the caller automatically.

var logger = flaschenpost.getLogger();

In rare cases you need to specify the caller manually, e.g. if you wrap flaschenpost in your own logging module. In these cases, provide __filename as parameter.

var logger = flaschenpost.getLogger(__filename);

Then you can use the functions fatal, error, warn, info and debug to write log messages. Simply provide the message you want to log as a parameter.

logger.info('App started.');

Handling meta data

If you want to provide additional meta data, use an object as second parameter.

logger.info('App started.', {
  name: 'foo',
  bar: {
    baz: 23
  }
});

Formatting log messages

If you want to use placeholders in the log message, embrace them in double curly braces. This way you can access any property of the meta data object.

logger.info('App {{name}} started.', {
  name: 'foo'
});

Please note that you can use as many placeholders as you like.

Defining the log target

Unlike other loggers, flaschenpost only supports logging to the console. This is because a modern cloud-based application never concerns itself with routing or storage of its output stream.

When you are running an application using a TTY, the log messages will be written in a human-readable format. As soon as you redirect the output to a file or over the network, log messages are automatically written as JSON objects that can easily be processed by other tools.

Enabling and disabling log levels

By default, only the log levels fatal, error, warn and info are printed to the console. If you want to change this, set the environment variable LOG_LEVELS to the comma-separated list of desired log levels.

$ export LOG_LEVELS=debug,info

If you want to enable all log levels at once, you can provide a * character as value for the LOG_LEVELS environment variable.

$ export LOG_LEVELS=*

Setting custom log levels

If you want to change the default log levels, i.e. define other log levels, change colors or define which log levels are enabled by default, call the use function of flaschenpost.

flaschenpost.use('levels', {
  fatal: {
    color: 'blue',
    enabled: true
  },
  error: {
    color: 'red',
    enabled: true
  },
  warn: {
    color: 'yellow',
    enabled: true
  },
  info: {
    color: 'green',
    enabled: true
  },
  debug: {
    color: 'white',
    enabled: false
  }
});

Using the Express middleware

If you are writing an Express-based application and you use morgan as logger, you can easily integrate flaschenpost into it.

For that, provide the stream property when setting up morgan and call the Middleware constructor function with the desired log level.

app.use(morgan('combined', {
  stream: new flaschenpost.Middleware('info')
}));

Again, in rare cases it may be necessary to provide the file name of the caller on your own.

app.use(morgan('combined', {
  stream: new flaschenpost.Middleware('info', __filename)
}));

Uncorking a flaschenpost

From time to time you may want to inspect log files that contain messages created by flaschenpost. For that, run the CLI tool and provide the log file via stdin.

$ flaschenpost < foo.log

Running the build

This module can be built using Grunt. Besides running the tests, this also analyses the code. To run Grunt, go to the folder where you have installed flaschenpost and run grunt. You need to have grunt-cli installed.

$ grunt

License

The MIT License (MIT) Copyright (c) 2013-2015 the native web.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.