Notes about a NodeJS program I wrote at work - 22nd Feb, 2023.

The NodeJS program is about preparing data and sending a POST request to an API external to this app. The app receives a response from the request for further processing. An aspect of this app is making the POST request at a regular interval, for example every 6 hours. Finally, I needed to log the API calls to a file.

In this post I discuss, in brief, the various libraries used to accomplish the task.

How to make a job run every n hours?

I used a cron task scheduler library, the node-cron. The scheduler code looked like this:

const cron = require("node-cron");
const CRON = "0 0 */6 * * *";
cron.schedule(CRON, async () => {
    console.log("Making the API request.");
    // ...
});

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How to make a POST request using form data?

For this functionality, I used the form-data library. This allowed sending form data with an uploaded file and also set custom headers. For example, creating the form data:

const FormData = require("form-data");
const formData = new FormData();
formData.append("mydata", "some data");
formData.append("myfile", fs.createReadStream("abc.xyz"));
const options = { method: "POST", body: formData, headers: { myhdr: "hdr value" } };

Send the request and receive a response using node-fetch using the earlier created form data:

const fetch = require("node-fetch");
const resp = await fetch("http://www.example.com/someapi", options);
const json_data = await resp.json();
// Do something with the response data here ...

An aspect to note is that the functionality (or similar) of the fetch npm package is the implementation in NodeJS 17.x fetch.

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What logger?

The logging needed to be both in the console as well as to a file. The logged message included a timestamp too. I used the winston logging library. The logger code looked like this:

const winston = require("winston");
const logger = winston.createLogger({
    level: "info",
    format: winston.format.combine(winston.format.timestamp(), winston.format.json()),
    transports: [
        new winston.transports.File({ filename: "log_file_name.log" }),
        new winston.transports.Console(),  
    ],
});

logger.info({ message: "Logger started" });

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Conclusion:

I had used various libraries to accomplish a task. I note that the logging is the most common task and an important aspect of developing apps.

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