51 lines
2.2 KiB
Markdown
51 lines
2.2 KiB
Markdown
# Prometheus
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Prometheus collects metrics (e.g. `node_memory_usage_bytes`) from *targets* by scraping their HTTP metrics endpoints. Targets are organized into *jobs*, defined in the Prometheus config. Targets may expose counter, gauge, histogram, or summary metrics.
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Here's a simple config from the Prometheus [tutorial](https://prometheus.io/docs/introduction/getting_started/).
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```
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global:
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scrape_interval: 15s
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scrape_configs:
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- job_name: 'prometheus'
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scrape_interval: 5s
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static_configs:
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- targets: ['localhost:9090']
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```
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On Kubernetes clusters, Prometheus is run as a Deployment, configured with a ConfigMap, and accessed via a Service or Ingress.
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```
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kubectl apply -f addons/prometheus -R
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```
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The ConfigMap configures Prometheus to discover apiservers, kubelets, cAdvisor, services, endpoints, and exporters. By default, data is kept in an `emptyDir` so it is persisted until the pod is rescheduled.
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### Exporters
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Exporters expose metrics for 3rd-party systems that don't natively expose Prometheus metrics.
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* [node_exporter](https://github.com/prometheus/node_exporter) - DaemonSet that exposes a machine's hardware and OS metrics
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* [kube-state-metrics](https://github.com/kubernetes/kube-state-metrics) - Deployment that exposes Kubernetes object metrics
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* [blackbox_exporter](https://github.com/prometheus/blackbox_exporter) - Scrapes HTTP, HTTPS, DNS, TCP, or ICMP endpoints and exposes availability as metrics
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### Queries and Alerts
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Prometheus provides a basic UI for querying metrics and viewing alerts. Use `kubectl` to authenticate to the apiserver and create a local port-forward to the Prometheus pod.
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```
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kubectl get pods -n monitoring
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kubectl port-forward prometheus-POD-ID 9090 -n monitoring
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```
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Visit [127.0.0.1:9090](http://127.0.0.1:9090) to query [expressions](http://127.0.0.1:9090/graph), view [targets](http://127.0.0.1:9090/targets), or check [alerts](http://127.0.0.1:9090/alerts).
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<br/>
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<br/>
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Use [Grafana](/addons/grafana.md) to view or build dashboards that use Prometheus as the datasource.
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