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A logger that outputs JSON that adheres to Heka's expected schema.

npm install --save mozlog


You must create a mozlog instance before using it's loggers. This is essentially setting the app name, the level, and the fmt.

For the brave (or those who know intel's configuration options), you can pass a config property to have fine-grained control.

// create your mozlog instance
const mozlog = require('mozlog')({
  app: 'fxa-oauth-server',
  level: 'verbose', //default is INFO
  fmt: 'pretty', //default is 'heka'
  uncaught: 'exit', // default is 'log', also available as 'ignore'
  debug: true, //default is false
  stream: process.stderr //default is process.stdout

You may want the level set down to verbose or debug when developing. Likewise, you may want the line to be readable by humans when developing, so the pretty formatter will help.

In production, the defaults will serve you well: info and heka.

var log = mozlog('routes.client.register');, { some: details });
// such as
log.debug('newClient', { id:, name: });

First parameter is a string "op". It should be unique within the file. Second parameter is some optional object, with keys and values that would make sense when looking at the logs again.

The debug option (not level) in the config will add in some asserts that your usage adheres to the above: that there's only ever at most 2 arguments to a log function, the first is a string without spaces.