Peavey

Simple structured logging for Node.js.

Overview

Structured logging allows you to treat your application logs like a queryable time-ordered database. Instead of text munging using grep & regex, you can use command-line tools like jq or log aggregators like Splunk or ElasticSearch to query your logs for particular fields, without worrying that minor modifications to what you're logging will break all your metrics & reports.

For some good information on what structured logging is and why you should use it, see https://brandur.org/logfmt and https://engineering.grab.com/structured-logging.

This library follows patterns outlined by logfmt, though it outputs in JSON format instead.

Usage

const log = require('peavey');

log.level = log.LEVELS.WARN; // Don't emit DEBUG or INFO level logs
log.caller = true            // Add caller information to every log message

log.context.set('requestId', requestId);

log.info('Processing request', 'process/start', {
  requestId: requestId,
  requestPath: req.path
});

You can create additional loggers with their own context as well:

const log = require('peavey');

let logger = new log.Logger({
  caller: false,
  level: log.LEVELS.ALL
});