Call nodejs kafka script inside Angular 8 application - node.js

Question

How to call nodejs kafka consumer script from Angular component.
I am able to run the same script in terminal using "npm filename.js" but it is throwing an error while calling same from Angular component.

Answer 1

An angular component runs on the client, the kafka script runs on the server. You'll have to create a proxy endpoint to call the script. Depending on which server side Web API Framework you're using this would be done different ways.
To help you understand this further, if you were using express.js, you'd need to have an endpoint to trigger the call (it should be a POST endpoint):
// POST method route
app.post('/triggerKafka', function (req, res) {
const exec = require('child_process').exec, child;
const testscript = exec('bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic yourTopic --from-beginning');
testscript.stdout.on('data', function(data){
console.log(data);
// sendBackInfo();
});
testscript.stderr.on('data', function(data){
console.log(data);
// triggerErrorStuff();
});
})
Now, I should say that this is probably not the way you want to do this. For one thing, you don't want to give people outside your control the ability to start and stop Kafka listening.
You should try to set up your Kafka consumer on the startup of your web application (server side); and provide a mechanism for connecting to it in a similar fashion as above -- proxying the calls through an API endpoint that you set up.
To start Kafka when your web application starts; you need to put the correct information in your node.js web application server startup. In your package.json if you have a "scripts" section you can add the following:
"scripts" : {
"start" : "<whateveryouhavenow>.sh && npm filename.js"
}
The important part here is the && npmfile.js; that says to run your command as well as the command that preceded it. There are more options here, but I provided just one.
Depending on what server side framework you're running and what task-running tool you're using, it would be different (whether it's npm, gulp, grunt, or something else).