Document the logger (and maybe change it?)

[wraithan]

The logger is a console instance by default. This means, to be safe, the user must implement:

> Object.keys(console)
[ 'log',
  'info',
  'warn',
  'error',
  'dir',
  'time',
  'timeEnd',
  'trace',
  'assert',
  'Console' ]

A logger API could be something like function logger (level, message) {} or something like that. It would require your own calls to util.format instead of relying on the logger to do it, but you could easily abstract that in your code.

[mattpage]

@wraithan you are correct. Console was used as a placeholder. A more explicit logging interface is a good idea.

[mattpage]

@wraithan, the util.log method writes to stdout. To write to stderr, we would need to use either console.error or process.stderr.write(...);

So if we adopt your suggested interface:

function logger (level, message) {}

then how about something like:

if (level === 'error'){
  console.error.apply(this, arguments);
}
else {
  console.log.apply(this, arguments);
}

although we may want to shift off the first arg.

[gvilarino]

Just saying, but why not use visionmedia/debug? It's (one of?) the most widespread standard for logging node.js. As an example, both express and mongoose use it.

In addition, the log would be quiet unless users explicitly specify insights as part of their filter.

[gvilarino]

An example of a logger based on debug would be

'use strict'

var debug = require('debug')
var config = require('./config') // helper for retrievieng app settings, overriden by env vars

const base = 'node-insights'

const logLevels = [
  'critical',
  'error',
  'warn',
  'info',
  'debug',
]

const logLevel = logLevels.indexOf(config.DEBUG)

if (logLevel > -1) {
  const scope = logLevels.slice(0, logLevel + 1)
    .map(l => `${base}:${l},${base}:${l}:*`)
    .join(',')
  debug.enable(scope)
} else if (config.DEBUG === '*') {
  debug.enable(`${base}:*`)
} else if (config.DEBUG) {
  debug.enable(config.DEBUG)
}

module.exports = class Log {
  constructor (scope) {
    logLevels.forEach(level => {
      var baseScope = `${base}:${level}`
      if (scope) baseScope += `:${scope}`
      this[level] = debug(baseScope)
    })
  }
}