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 target apiserver endpoints, node metrics, cAdvisor metrics, 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 Graphs
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Prometheus provides a simplistic UI for querying and graphing metrics. 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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### Visualization
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Grafana can be used to build dashboards and rich visualizations that use Prometheus as the datasource. Favor Grafana for these use cases and use the Prometheus for debugging or quickly checking available metrics.
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