BonnierNews/lu-logger

⛔️ DEPRECATED - Logging package for the lu-greenfield project

lu-logger

Purpose and features

File name and line number of the log caller is also added when logging in debug level.

Configuration

A configuration object must be passed to the constructor when initiating the logger.

Example

const logger = require("lu-logger")({
  log: "stdout", // Or file, required
  logLevel: "debug", // Minimum level to log
  logJson: true, // Log JSON objects or string messages, defaults to true
});

Metrics

All log events will also increment a counter <metricPrefix>_logged_total with the level as label. The metricPrefix will be automatically resolved from the calling applications name in package.json. If there is no name in package.json the metricPrefix will be undefined;

Example of metrics produced:

# HELP orderapi_logged_total Counts number of logs with loglevel as label
# TYPE orderapi_logged_total counter
orderapi_logged_total{level="info"} 28
orderapi_logged_total{level="error"} 39
orderapi_logged_total{level="debug"} 2

Log output mode

When log mode file is enabled, the log will be written to a file at <app root>/logs/<NODE_ENV>.log directory, where app root is the folder containing the package.json file. Log mode stdout will log to stdout.

Example

#JSON object in the log

The JSON below is an example of a log entry when logJson is set to true (or omitted) and logLevel is set to debug.

{
  "data": {
    "meta": "meta-data"
  },
  "greenFieldLogMeta": {
    "location": "lib/logging-producer.js:38",
    "correlationId": "sample-correlation-id"
  },
  "level": "debug",
  "message": "This is the log message",
  "timestamp": "2018-02-21T12:22:19.150Z"
}

Debug metadata

This library provides a mechanism for automatically logging debug metadata (e.g. correlation IDs). This is implemented with inspiration from this article, by using an AsyncLocalStorage variable, which is local to each async context. It then provides a middleware factory for Express which sets this from the request and then logs it out automatically. The calling library is free to define how to get the metadata from the request. As an example

const express = require("express");

const { debugMeta } = require("lu-logger");

const app = express();

app.use(debugMeta.initMiddleware((req) => req.debugMeta));

Version notes:

v2.x supports node 8,10 (but works at least to node 14) v3.x supports node 12,14,16