DataDog & Mendix: how do I create monitoring and notifications when an app is down?

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I really hope I find some DataDog experts here :-) Google hasn't been too helpful.  We're using DataDog and I would love to create some kind of monitoring to poll a URL/host and have it notify me on Slack when the Mendix application is down (503 error). It has been working fine, so this issue doesn't stem from a faulty API key or installation I think. I've looked at all the monitoring options DataDog has to offer but haven't come across one that does the job. We're not using DataDog Agent (I'm actually not even sure if that's possible with Mendix) so I feel like I'm limited. So far I've tried the Status Monitor, but I only have 4 service checks available there and none seem to work.  I've tried Log Monitoring, but can't find something to pinpoint the application going down to filter on. I read something online about a HTTP check but that needs the Agent to work...  Basically all tips and tricks are welcome. I've also looked into Mendix Alerts and sending them through a Webhook to Slack, but I wanted to try DataDog first since we already use this. But yes, suggestions on other tooling are welcome too. I'd just like a Slack notification when an app is down. 
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3 answers
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Searched for 2 days, asked the question here and found the answer within the hour. Love it.

 

I went to Digital Experience in DataDog, created API tests (there's even a template available!) and just filled in the fields. Run test every 30 seconds, notify when I you don't receive a 200 OK from the endpoint. You can do this for acceptance or test environments too. I already configured the Slack integration and selected my channels, but keep in mind you have to do this to get the notifications. 

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Hi Manon Kovacs, How did you manage to connect DataDog to Mendix? For some reasons, mendix is not sending data to DataDog. Can you please share your steps?

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hi,


If you want to monitor a Mendix app’s URL and get notified in Slack when it returns a 503 or goes down, you don’t need the DataDog Agent on the Mendix Cloud server. Instead, you use DataDog Synthetic Monitoring (API/URL tests) — this is the correct and documented way to do external HTTP uptime checks.

Why Synthetic Monitoring is the right approach

DataDog Synthetic Monitoring lets you:

  • Poll any public HTTP/HTTPS URL at regular intervals
  • Validate response content and status codes (e.g., status ≠ 200)
  • Alert when the test fails (e.g., 503 errors)
  • Trigger notifications to multiple channels (Slack, email, webhook, etc.)

This works externally and does not require a local agent running on Mendix Cloud.

How to set it up (short & practical)

1) Create a Synthetic HTTP Test

  1. Go to Datadog → Synthetic Monitoring
  2. Create a New Test → API Test / URL Test
  3. Enter your Mendix app URL:

https://yourapp.mxapps.io/
  1. Add an assertion like:
    • Status code equals 200
    • OR status code is not 503

This test will verify uptime and HTTP success.

2) Configure Frequency & Thresholds

  • Set how often the test runs (e.g., 1–5 minutes)
  • Choose locations from which the URL should be monitored
  • Configure retries and alert conditions if needed

3) Connect Slack for Alerts

Install the DataDog-Slack integration in DataDog:

  • Configure Slack workspace and channels inside DataDog
  • Use @slack-<channel> in your monitor alert message
  • Invite @Datadog to the Slack channel to enable notifications

Now when the Synthetic test fails (e.g., 503), DataDog will send alerts to Slack automatically.

Why this is better than other approaches

  • Status Monitor and service checks require the DataDog Agent, which you can’t run on Mendix Cloud directly.
  • Log monitoring alone in DataDog is unreliable for detecting server unavailability because Mendix logs do not necessarily contain a distinct “service down” event.
  • Synthetic tests simulate real traffic, so a failed HTTP response means exactly what you want — your app is unreachable or returning errors.

Optional enhancements

Once you have basic uptime testing:

  • Configure multiple tests (e.g., homepage, login endpoint)
  • Use composite alerts to reduce noise
  • Track SLOs based on uptime metrics
  • Add detailed failure messages in Slack with the Synthetic Monitoring notification templates

Working Solution

  1. Use DataDog Synthetic Monitoring (API/URL tests) to poll your Mendix URL regularly.
  2. Set a failure rule (e.g., status ≠ 200 or 503).
  3. Integrate with Slack via the DataDog Slack integration for alerts.
  4. No agent required on Mendix Cloud.



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