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Investigating Prometheus Alerts

You can investigate Prometheus/AlertManager alerts using HolmesGPT by connecting it to your AlertManager instance. This allows you to run investigations on all active alerts or a specific alert.

Single Alert Investigation

Prerequisites

Investigating a Prometheus Alert Using HolmesGPT

Step 1: Forward AlertManager

First, you need to forward the AlertManager service to your local machine so HolmesGPT can connect to it. Run the following command in your terminal:

kubectl port-forward svc/<Your-Alertmanager-Service> 9093:9093

Step 2: Create a Test Alert

Now we'll deploy a crashing workload and simulate an alert from AlertManager.

kubectl apply -f https://raw.githubusercontent.com/robusta-dev/kubernetes-demos/main/crashpod/broken.yaml
Since it takes some time for the alert to be generated, we will manually send a KubePodCrashLooping alert to AlertManager for testing purposes. To do this run: 
# Send a KubePodCrashLooping alert directly to AlertManager
curl -X POST http://localhost:9093/api/v1/alerts \
  -H "Content-Type: application/json" \
  -d '[
    {
      "labels": {
        "alertname": "KubePodCrashLooping",
        "severity": "warning",
        "namespace": "default",
        "pod": "payment-processing-worker",
        "container": "worker",
        "job": "kubernetes-pods"
      },
      "annotations": {
        "description": "Pod default/payment-processing-worker is crash looping",
        "summary": "Pod is in CrashLoopBackOff state"
      },
      "generatorURL": "http://prometheus:9090/graph?g0.expr=increase%28kube_pod_container_status_restarts_total%5B1h%5D%29%20%3E%205",
      "startsAt": "'$(date -u +%Y-%m-%dT%H:%M:%SZ)'"
    }
  ]'
You should now see the KubePodCrashLooping alert in your AlertManager UI at http://localhost:9093.

Step 3: Investigate Alerts

Finally let's use the HolmesGPT investigate subcommand to investigate the alerts. Run the following command:

holmes investigate alertmanager --alertmanager-url http://localhost:9093
AlertManager Alert Investigation

By default, HolmesGPT will fetch all active alerts from AlertManager and investigate them.

For our investigation, we will use the --alertmanager-alertname flag to focus on the specific KubePodCrashLooping alert we created earlier. 

holmes investigate alertmanager --alertmanager-url http://localhost:9093 --alertmanager-alertname "KubePodCrashLooping"
Once the investigation is complete, HolmesGPT will provide the potential Root Cause, next steps, and more.

Filtering Alerts

The holmes investigate alertmanager command supports many flags. For example, to investigate only critical alerts or alerts in a specific namespace, you can use the --alertmanager-label flag:

# Critical alerts only
holmes investigate alertmanager \
  --alertmanager-url http://localhost:9093 \
  --alertmanager-label "severity=critical"

# Production namespace issues
holmes investigate alertmanager \
  --alertmanager-url http://localhost:9093 \
  --alertmanager-label "namespace=production"

What's Next?

  • Add new data sources - Connect HolmesGPT to your databases, APM tools, and custom APIs for deeper investigations.
  • Set up remote MCP - Add data sources as remote Model Context Protocol (MCP) servers.