Add more information and examples to Configuration.

content/docs/operating/configuration.md

@@ -5,6 +5,67 @@ nav_icon: sliders
 
 # Configuration
 
-The canonical definition of each configuration field is contained in the
-protocol buffer schema definition at
+Prometheus is configured via command-line flags and a configuration file. While
+the command-line flags configure general system parameters (such as storage
+locations, amount of data to keep on disk and in memory, etc.), the
+configuration file defines everything related to scraping [jobs and their
+instances](/docs/concepts/jobs_instances/), as well as which [rule files to
+load](/docs/querying/rules/#configuring-rules).
+
+To view all available command-line flags, run Prometheus with the `-h` option.
+
+To specify which configuration file to load, use the `-config.file` flag.
+A configuration file is written in ASCII protocol buffer form, and every
+available option is explained in detail in the protocol buffer schema
+definition at
 https://github.com/prometheus/prometheus/blob/master/config/config.proto.
+
+Below is an example configuration which explains the most common options with
+some comments:
+
+```
+# Global settings and defaults.
+global {
+  # By default, scrape targets every 30 seconds.
+  scrape_interval: "30s"
+  # By default, evaluate alerting and recording rules every 30 seconds.
+  evaluation_interval: "30s"
+  # Add the label service="api" to all time series scraped by this Prometheus.
+  labels {
+    label {
+      name: "service"
+      value: "api"
+    }
+  }
+  # Load two files that define recording or alerting rules.
+  rule_file: "prometheus_base.rules"
+  rule_file: "api_service.rules"
+}
+
+# Monitor Prometheus itself.
+job {
+  # This job will be named "prometheus", so a job="prometheus" label will be
+  # added to all time series scraped from it.
+  name: "prometheus"
+  # Scrape this job every 15s, overriding the global default.
+  scrape_interval: "15s"
+  # Configure a group of static HTTP targets
+  target_group {
+    target: "http://localhost:9090/metrics"
+  }
+}
+
+# Monitor a set of a API servers.
+job {
+  # This job will be named "api-server", so a job="api-server" label will be
+  # added to all time series scraped from it.
+  name: "api-server"
+  # Discover targets for this job via service discovery (DNS-SD). The sd_name
+  # provided here needs to resolve to a DNS SRV record containing a set of
+  # IP:PORT pairs.
+  sd_name: "telemetry.server.prod.api.srv.my-domain.org"
+  # The SRV records don't have information about the endpoint to scrape, so it
+  # needs to be configured separately when discovering targets dynamically.
+  metrics_path: "/metrics"
+}
+```