Скачать или смотреть How to Use ServiceMonitor to Check Services via External Hostname in Kubernetes

Discover how to configure `ServiceMonitor` in Kubernetes for effective monitoring of services using external hostnames and manage them seamlessly.
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This video is based on the question https://stackoverflow.com/q/70278726/ asked by the user 'Patrick Cornelissen' ( https://stackoverflow.com/u/33624/ ) and on the answer https://stackoverflow.com/a/70281521/ provided by the user 'avinashpancham' ( https://stackoverflow.com/u/14089081/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Use ServiceMonitor to Check Services via External Hostname in Kubernetes

In a Kubernetes environment, efficiently monitoring services is crucial for maintaining infrastructure performance and reliability. If you're utilizing external-DNS to manage your DNS records, you may run into issues when trying to automatically link these external hostnames to your monitoring setup, particularly with ServiceMonitor. In this guide, we’ll tackle the common problem of using ServiceMonitor with external hostnames and provide you with a clear solution to make it work seamlessly.

The Problem at Hand

You have set up an external DNS service that automatically creates and binds DNS entries based on service annotations in Kubernetes. For instance, let's say you have a service defined for your alertmanager like this:

[[See Video to Reveal this Text or Code Snippet]]

You want to leverage the Prometheus blackbox exporter to monitor this service automatically using the annotations provided by your services without having to manually configure each instance. However, your ServiceMonitor doesn’t seem to match the services, causing your monitoring to fail.

The Solution

Let’s break down the solution to get your ServiceMonitor working with your external-hostname based services step by step.

1. Adjusting the ServiceMonitor Selector

The main issue we're encountering is with the labels on your ServiceMonitor not matching the labels on your service. Your service has this label:

[[See Video to Reveal this Text or Code Snippet]]

In your ServiceMonitor, however, you currently have it set to match any value for that label:

[[See Video to Reveal this Text or Code Snippet]]

To resolve the issue, update the ServiceMonitor to have a matchLabels selector that specifically matches the true value of the label. It should look like this:

[[See Video to Reveal this Text or Code Snippet]]

2. Configuring the Namespace Selector

Another crucial aspect is the namespaceSelector in your ServiceMonitor. You defined it as:

[[See Video to Reveal this Text or Code Snippet]]

This configuration may not behave as expected in this context. The namespaceSelector is designed to allow you to specify the labels of the namespace from which you want to select resources. By setting it to any: true, you're instructing Kubernetes to only look for namespaces that have this label.

If your goal is to include all namespaces in your monitoring setup, it is better to remove the namespaceSelector line entirely from the ServiceMonitor.

3. Complete Example of the ServiceMonitor

With the above adjustments, your ServiceMonitor configuration should look more like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By making these simple adjustments to your ServiceMonitor, you can automate the monitoring of your services using external hostnames without having to configure each service manually. Always remember that matching labels are critical in ensuring that Prometheus can scrape the metrics as expected. If you follow the steps outlined above, you should be well on your way to effective service monitoring in your Kubernetes environment.

With this knowledge, you can streamline your monitoring processes and leverage the full capabilities of Kubernetes and Prometheus together!