How to send notifications to Discord channel by Google Cloud Monitoring Alerting

You can use the notification channel of webhook to send the notification to your discord.

https://cloud.google.com/monitoring/support/notification-options#webhooks

Option 2

If Stackdriver not sending the webhook directly you can simply leverage the pub/sub with a cloud function that would be an easy option and cost-efficient.

Cloud monitoring alert will push the payload to pub/sub and write a simple cloud function which will consume the pub/sub's payload and send webhook to discord.

So flow will be something like : Stackdriver monitoring > Pub/Sub > CloudFunction (webhook hit to discord) > Discord

Cloud function code

const fetch = require('node-fetch');
exports.helloPubSub = (message, context) => {
  const name = message.data
    ? Buffer.from(message.data, 'base64').toString()
    : 'World';

  console.log(`Hello, ${name}!`);
 
var URL = "Discord URL";

fetch(URL, {
    'method': 'POST',
    'body': <DARA>,
    headers: data.getHeaders()
})
.then(res=> console.log(res))
.catch(err => console.error(err));
    };

Code ref & Second Gen tutorial

I just tried.

I entered a webhook url. Then clicked test connection button. It's not working: nothing hasn't recieved.

Also checked with postman with a positive result on a discord channel.

and finally found the solution in comments here:

Stackdriver doesn't send message to Discord webhook