Magento 2 event observer not working - php

Question

I'm trying to create a simple event observer for my Magento 2 page.
app/code/Ndac/Orderinfo/etc/event.xml
<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">
<event name="sales_order_place_after">
<observer name="OrderInfo" instance="Ndac\Orderinfo\Observer\OrderInfo" />
</event>
</config>
app/code/Ndac/Orderinfo/etc/module.xml
<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd">
<module name="Orderinfo" setup_version="1.0.0"></module>
</config>
app/code/Ndac/Orderinfo/registration.php
<?php \Magento\Framework\Component\ComponentRegistrar::register(\Magento\Framework\Component\ComponentRegistrar::MODULE,"Orderinfo", __DIR__);
app/code/Ndac/Orderinfo/Observer/OrderInfo.php
<?php
namespace Ndac\Orderinfo\Observer;
use Magento\Sales\Model\Order;
use Magento\Framework\Event\Observer;
use Magento\Framework\Event\ObserverInterface;
class OrderInfo implements ObserverInterface {
// Tried it with constructor
public __construct() {
$file = fopen("/mnt/data/magento/test.txt", "w") or die ("die");
fwrite($file, "test");
fclose($file);
}
public function execute(Observer $observer)
{
$file = fopen("/mnt/data/magento/test.txt", "w") or die ("die")
fwrite($file, "test");
fclose($file);
}
}
?>
I run the following command: bin/magento setup:upgrade and the module appears on the dashboard, and its enabled, but the test.txt remains empty, after I place an order.

Answer 1

There is an issue with the file naming.
app/code/Ndac/Orderinfo/etc/event.xml
this has to be as:
app/code/Ndac/Orderinfo/etc/events.xml
It has to be events.xml. And also if this event doesn't work, then try with the checkout_onepage_controller_success_action event.
Now run the upgrade command and clear the cache.