Logger-Middleware

A logger and a Connect/Express middleware for creating logging events in a standard format on the Boomerang platform. It is based on our Java Log4j configuration.

What it does

This package contains a factory function that returns an object with two functions that create a logging event.

• logger function
• Connect/Express middleware

Produced logs are logged to the console and collected by ICP.

Logging Format

The Pattern used by both the logger and the middleware is

[%d{yyyy-MM-dd hh:mm:ss.SSS}] [%p] [%z] [%c] %X{filename} : %m%n"

• See the "Pattern" section of Log4js layout docs for an explanation of it
• filename token can be passed in to the logger when imported. See Use below. It defaults to an empty string.
• Log levels are the Log4js defaults
• The category for the logger is "app"
• The category for the middleware is "http"

Logger Function

After invoking the logger library, a logger function is exposed on the returned object and can be directly invoked. It has several functions corresponding to different log levels. Those functions accept a message. See log4js usage for more information about invoking the logger function.

[2019-02-13 16:38:02.165] [INFO] [46245] [app] /index.spec.js : info test

Logger Middleware

After the logger library is initialized with a config object, a middleware function is exposed on the returned object. It can be added to a middleware chain in an Connect/Express application. It uses the default configuration for the message using the same pattern as the logger function.

[2019-02-13 16:38:02.185] [INFO] [46245] [http] /index.spec.js : ::ffff:127.0.0.1 - - "GET / HTTP/1.1" 200 - "" "node-superagent/3.8.3"

Logging Levels

Please refer to the documentation for the different logging levels. These have not been modified from the defaults for Log4js. log4js usage shows the six defaults.

Use

The factory function takes a single, optional filename parameter of type string. An easy way to get the path to the specific file that is importing the logger is to pass in the __filename global variable to the function. The library will figure out the relative path to the calling file from the project root and use that value in the log event.

const boomerangLogger = require("@boomerang/boomerang-logging-middleware")(__filename);

const { logger, middleware } = boomerangLogger;

const app = express();

app.use(middleware)
// Logs all requests received to to this route and sub-routes
app.get("/data", (req, res) => res.json({ data: "data here" }));
});

app.get("/user", (req, res, next) => {
  logger.debug(`User endpoint called by ${req.user.email}`); // Assumes user object exists on request
  res.json(req.user);
});

Examples

Please see an implementation of the middleware at BoomerangDemoNodejs