A simple filesystem logger to record a long-running job and serve its status via a Web API.

It exports two classes: JobLogger which saves information to a file, and JobStatusCheck which serves log contents via a Web API.

Prerequisites

• Create a logs/jobs/ folder in the app service's wwwroot folder.
• Node 8.9 or above.

Usage

Log information

The log() function is asynchronous. You don't have to await it (to save time), but then the order of log messages is not guaranteed.

Each log must end with the magic string -- All done! -- (stored in the JOB_DONE_MAGIC_STRING), otherwise the .done variable in the response will be false and the frontend wouldn't know when to stop polling the endpoint.

const guid = require('node-uuid');
const { JobLogger, JOB_DONE_MAGIC_STRING } = require('imago-job-logger');

let jobId = guid();

let logger = new JobLogger(this.jobId);

await logger.log('Old app did not exist, so nothing to delete.');
await logger.log(JOB_DONE_MAGIC_STRING); // -- All done! --

Serve log contents to frontend

We assume that the frontend will call this endpoint regularly (for example, each second) and will stop calling the endpoint when response.done is true.

Code inside a route:

const express = require('express');
const { JobStatusCheck } = require('imago-job-logger');

const router = express.Router();

// For the frontend to read the job log of the import job while it is being
// executed:
router.get('/job-status', async (request, response) => {
  new JobStatusCheck().process(request, response);
});

Sample response

There are three variables in the response. success means that the log was found successfully, done means that the job that is being logged has completed, and log contains the log itself.

{
	"success": true,
	"done": true,
	"log": "Old app did not exist, so nothing to delete.
	-- All done! --"
}