Exploring Expression Browser

In this lesson, you'll learn how to navigate and utilize the Expression Browser—a handy web interface for your Prometheus server that allows you to query and visualize metrics data effectively.

Accessing the Expression Browser

Begin by opening your web browser and entering the IP address of your Prometheus server. For example, if your Prometheus server is running locally on the default port 9090, simply navigate to:

http://localhost:9090

Once loaded, you'll see the Expression Browser interface. The primary component is the expression input field where you can type in your Prometheus queries.

Querying for Metrics

Checking Target Status with the "up" Metric

A common query in Prometheus is the up metric. This metric indicates whether your targets are online (1) or offline (0). When you enter the query:

up

and click execute, you'll receive a list of timeseries with associated labels. For example:

up{instance="192.168.1.168:9100", job="node"}
up{instance="192.168.21.43:80", job="ec2"}
up{instance="192.168.40.248:80", job="ec2"}
up{instance="localhost:9090", job="prometheus"}

On the right side, the current metric values will appear:

up{instance="192.168.1.168:9100", job="node"} 1
up{instance="192.168.21.43:80", job="ec2"} 0
up{instance="192.168.40.248:80", job="ec2"} 0
up{instance="localhost:9090", job="prometheus"} 1

Exploring CPU Metrics

You can also query for more advanced metrics such as node_cpu_seconds_total to monitor CPU usage. Running this query returns a series of values grouped by different CPU modes:

node_cpu_seconds_total{instance="192.168.1.168:9100", job="node", mode="idle"}
node_cpu_seconds_total{instance="192.168.1.168:9100", job="node", mode="iowait"}
node_cpu_seconds_total{instance="192.168.1.168:9100", job="node", mode="irq"}
node_cpu_seconds_total{instance="192.168.1.168:9100", job="node", mode="nice"}
node_cpu_seconds_total{instance="192.168.1.168:9100", job="node", mode="softirq"}
node_cpu_seconds_total{instance="192.168.1.168:9100", job="node", mode="steal"}
node_cpu_seconds_total{instance="192.168.1.168:9100", job="node", mode="system"}
node_cpu_seconds_total{instance="192.168.1.168:9100", job="node", mode="user"}

This table details the different CPU modes tracked by Prometheus along with their current values. Additionally, the Expression Browser provides an evaluation time option that lets you view historical data by selecting a specific date and time.

Graphical Data Visualization

The Expression Browser also offers a graphing feature to help you visualize your monitoring data. By entering a metric and adjusting chart parameters—such as the desired time range (for example, switching from a one-hour view to a 30-minute view)—you can observe the plotted trends for various timeseries. Even if some metrics have very low values, they will still be displayed on the graph.

Viewing Prometheus Server Configuration

Another valuable feature of the Expression Browser is the ability to inspect your Prometheus server's configuration. By selecting the configuration option, you can view global parameters, alerting configurations, scrape configurations, and more. For example, your current configuration might resemble the following:

global:
  scrape_interval: 15s
  evaluation_interval: 15s
alerting:
  alertmanagers:
    - follow_redirects: true
      enable_http2: true
      scheme: http
      timeout: 10s
      api_version: v2
      static_configs:
        - targets: []
scrape_configs:
  - job_name: prometheus
    honor_timestamps: true
    scrape_interval: 15s
    scrape_timeout: 10s
    metrics_path: /metrics
    scheme: http
    follow_redirects: true
    enable_http2: true
    static_configs:
      - targets:
          - localhost:9090
  - job_name: node
    honor_timestamps: true
    scrape_interval: 15s
    scrape_timeout: 10s
    metrics_path: /metrics
    scheme: http
    follow_redirects: true
    enable_http2: true
    static_configs:
      - targets:
          - 192.168.1.168:9100
  - job_name: ec2
    scrape_interval: 15s
    scrape_timeout: 10s
    metrics_path: /metrics
    scheme: http
    follow_redirects: true
    enable_http2: true
    static_configs:
      - targets: []

The configuration file lists all the target endpoints along with their statuses (up or down). You also have the option to view the alert rules and navigate to the alerts page for a list of active alerts.

Summary

The Expression Browser is a powerful tool for executing Prometheus queries and accessing detailed metrics data instantly. Whether you are troubleshooting your environment or performing a quick system check, this tool plays a critical role in your monitoring setup. For more comprehensive dashboards, you can seamlessly integrate tools like Grafana.

Happy monitoring!