Exporters

First PublishedFeb 16, 2026ByAtif Alam

Exporters bridge the gap between systems that don’t natively expose Prometheus metrics and Prometheus itself. An exporter runs alongside (or inside) a target, collects metrics, and exposes them on a /metrics endpoint.

Node Exporter (Host Metrics)

The most commonly used exporter — provides CPU, memory, disk, network, and filesystem metrics for Linux hosts.

Install and Run

# Download
wget https://github.com/prometheus/node_exporter/releases/download/v1.7.0/node_exporter-1.7.0.linux-amd64.tar.gz
tar xzf node_exporter-*.tar.gz
./node_exporter

Or as a systemd service:

/etc/systemd/system/node_exporter.service

[Unit]
Description=Node Exporter
After=network.target

[Service]
ExecStart=/usr/local/bin/node_exporter
Restart=always

[Install]
WantedBy=multi-user.target

Key Metrics

Metric	Type	What It Measures
node_cpu_seconds_total	Counter	CPU time per mode (user, system, idle, iowait)
node_memory_MemAvailable_bytes	Gauge	Available memory
node_memory_MemTotal_bytes	Gauge	Total memory
node_filesystem_avail_bytes	Gauge	Available disk space
node_filesystem_size_bytes	Gauge	Total disk space
node_network_receive_bytes_total	Counter	Network bytes received
node_network_transmit_bytes_total	Counter	Network bytes sent
node_load1 / node_load5 / node_load15	Gauge	System load averages
node_disk_io_time_seconds_total	Counter	Disk I/O time

Useful Queries

These are PromQL queries you’d run in the Prometheus UI (http://prometheus:9090/graph) or use in Grafana dashboard panels to visualize Node exporter data:

# CPU usage percentage
100 - (avg by (instance) (rate(node_cpu_seconds_total{mode="idle"}[5m])) * 100)

# Memory usage percentage
(1 - node_memory_MemAvailable_bytes / node_memory_MemTotal_bytes) * 100

# Disk usage percentage
(1 - node_filesystem_avail_bytes{mountpoint="/"} / node_filesystem_size_bytes{mountpoint="/"}) * 100

# Network throughput (bytes/sec)
rate(node_network_receive_bytes_total{device="eth0"}[5m])

Scrape Config

To tell Prometheus to scrape your Node exporters, add this to the Prometheus server’s prometheus.yml under scrape_configs. Each target is a host:port where Node exporter is running:

# prometheus.yml — on the Prometheus server
scrape_configs:
  - job_name: "node"
    static_configs:
      - targets: ["node1:9100", "node2:9100", "node3:9100"]

Prometheus will scrape http://node1:9100/metrics, http://node2:9100/metrics, and http://node3:9100/metrics at the global scrape_interval.

Blackbox Exporter (Probing)

Probes endpoints from the outside — HTTP, TCP, DNS, ICMP. Tests what users experience:

Use Cases

• Is my website returning 200?
• Is my API responding within 500ms?
• Is my DNS resolving correctly?
• Is port 5432 (PostgreSQL) open?

Configuration

blackbox.yml

modules:
  http_2xx:
    prober: http
    timeout: 5s
    http:
      valid_status_codes: [200, 201, 202]
      method: GET
      follow_redirects: true

  http_post:
    prober: http
    http:
      method: POST
      headers:
        Content-Type: application/json
      body: '{"check": true}'

  tcp_connect:
    prober: tcp
    timeout: 5s

  dns_lookup:
    prober: dns
    dns:
      query_name: example.com
      query_type: A

  icmp_ping:
    prober: icmp
    timeout: 5s

Scrape Config (Multi-Target)

scrape_configs:
  - job_name: "blackbox-http"
    metrics_path: /probe
    params:
      module: [http_2xx]
    static_configs:
      - targets:
          - https://example.com
          - https://api.example.com/health
          - https://staging.example.com
    relabel_configs:
      - source_labels: [__address__]
        target_label: __param_target
      - source_labels: [__param_target]
        target_label: instance
      - target_label: __address__
        replacement: blackbox-exporter:9115

Key Metrics

# Is the endpoint up? (1 = success, 0 = failure)
probe_success{instance="https://example.com"}

# Response time
probe_duration_seconds{instance="https://example.com"}

# SSL certificate expiry (days until expiration)
(probe_ssl_earliest_cert_expiry - time()) / 86400

Application Instrumentation (Client Libraries)

Instead of using an exporter, instrument your own application to expose metrics directly.

Python (prometheus_client)

from prometheus_client import Counter, Histogram, start_http_server

REQUEST_COUNT = Counter(
    'http_requests_total',
    'Total HTTP requests',
    ['method', 'status']
)
REQUEST_LATENCY = Histogram(
    'http_request_duration_seconds',
    'Request latency in seconds',
    ['method']
)

@app.route('/api/data')
def get_data():
    with REQUEST_LATENCY.labels(method='GET').time():
        # ... handle request ...
        REQUEST_COUNT.labels(method='GET', status='200').inc()
        return data

# Expose /metrics on port 8000
start_http_server(8000)

Go (prometheus/client_golang)

import (
    "github.com/prometheus/client_golang/prometheus"
    "github.com/prometheus/client_golang/prometheus/promhttp"
)

var requestCount = prometheus.NewCounterVec(
    prometheus.CounterOpts{
        Name: "http_requests_total",
        Help: "Total HTTP requests",
    },
    []string{"method", "status"},
)

func init() {
    prometheus.MustRegister(requestCount)
}

func main() {
    http.Handle("/metrics", promhttp.Handler())
    http.ListenAndServe(":8080", nil)
}

Node.js (prom-client)

const client = require('prom-client');

const requestCount = new client.Counter({
  name: 'http_requests_total',
  help: 'Total HTTP requests',
  labelNames: ['method', 'status'],
});

app.get('/metrics', async (req, res) => {
  res.set('Content-Type', client.register.contentType);
  res.end(await client.register.metrics());
});

Naming Conventions

Pattern	Example	Rule
<namespace>_<name>_<unit>	http_request_duration_seconds	Always include the unit
Counter suffix	_total	Counters should end in _total
Histogram suffix	_bucket, _sum, _count	Auto-generated
Unit suffixes	_bytes, _seconds, _total	Use base units (bytes not KB, seconds not ms)

Other Common Exporters

Exporter	Metrics From
mysqld_exporter	MySQL queries, connections, buffer pool
postgres_exporter	PostgreSQL queries, connections, replication
redis_exporter	Redis memory, keys, commands/sec
mongodb_exporter	MongoDB connections, operations, replication
nginx_exporter	Nginx connections, requests
cadvisor	Container CPU, memory, network (Docker/K8s)
kube-state-metrics	Kubernetes object states (pods, deployments, nodes)

Custom Exporters

When no existing exporter fits, write your own. The pattern:

1. Collect data from your system (API, file, database).
2. Map it to Prometheus metric types (Counter, Gauge, Histogram).
3. Expose on /metrics.

from prometheus_client import Gauge, start_http_server
import requests, time

queue_depth = Gauge('queue_depth', 'Number of items in the job queue', ['queue_name'])

def collect():
    while True:
        resp = requests.get('http://internal-api/queues')
        for queue in resp.json():
            queue_depth.labels(queue_name=queue['name']).set(queue['depth'])
        time.sleep(15)

start_http_server(9200)
collect()

Key Takeaways

• Node exporter for host metrics (CPU, memory, disk, network) — install on every machine.
• Blackbox exporter for probing endpoints from the outside (HTTP, TCP, DNS, ICMP).
• Instrument your apps with client libraries to expose request counts, latency histograms, and business metrics.
• Follow naming conventions: _total for counters, _seconds/_bytes for units.
• Use existing exporters for databases, caches, and web servers before writing custom ones.