@hmcts/nodejs-logging

Node.js Logging

A logging component used by Reform's Node.js applications. Some background info:

• there are 8 log levels: ALL, TRACE, DEBUG, INFO, WARN, ERROR, FATAL and OFF.
• a level can be set via an environment variable LOG_LEVEL, the default is INFO.
• there are 3 types of logging output which is set via an environment variable LOG_OUTPUT, the default is human:
  • human - single line of a human readable output
  • single - a single line of JSON output
  • multi - a multiline formatted JSON output
• by default logging is turned off when running the unit tests.

Usage

Add it as your project's dependency:

yarn add @hmcts/nodejs-logging

Require it:

const { Logger } = require('@hmcts/nodejs-logging')

Set the logging configuration. Should be done once at application startup:

Logger.config({ 
    microservice: 'your-service-name', 
    team: 'your-team',
    environment: 'some-environemnt'
})

Then you can create a logger instance and use it to log information:

const logger = Logger.getLogger('app.js') // app.js is just an example, can be anything that's meaningful to you

logger.info({
  message: 'Yay, logging!'
})

Access logging for Express applications

Optionally you can use the built-in Express access logger:

const { Express } = require('@hmcts/nodejs-logging')

app.use(Express.accessLogger())

It will log all requests made against your application. For example, a typical HTTP 404 log error when encountering an error would look like the following:

{
  responseCode: 404,
  message: 'Not Found',
  fields: [],
  level: 'ERROR',
  environment: 'some-environemnt',
  hostname: 'My-MacBook-Pro.local',
  rootRequestId: '',
  requestId: '',
  originRequestId: '',
  type: 'nodejs',
  microservice: 'your-service-name',
  team: 'your-team',
  timestamp: '2017-01-27T11:27:23+00:00'
}

Request tracing for Express applications

An Express middleware is provided which automatically populates request headers with request tracing IDs. Sample usage:

const { RequestTracing } = require('@hmcts/nodejs-logging')

app.use(RequestTracing.middleware)

Assuming your Express application servers as the system's entry point which serves user UI, this middleware will intercept user requests and set Root-Request-Id and Request-Id headers on it. If the incoming request comes from a different service which already populated those values, they will be forwarded.

Apart from populating the headers, access to request tracing information is available at any point during request processing, e.g.:

const id = RequestTracing.getCurrentRequestId()

We can also access the original request:

const request = RequestTracing.retrieveInitialRequest()

These features are enabled by continuation-local-storage module.

Units Tests

Just do

yarn test

License

This project is licensed under the MIT License - see the LICENSE file for details.