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Prometheus Service Discovery

Prometheus can be configured to use external sources (files/dns) to identify scrape targets, rather than hard-coding targets in to /etc/prometheus/prometheus.yml.

File-Based Service Discovery

File-based service discovery can be done by defining it in the config: 

# /etc/prometheus/prometheus.yml
scrape_configs:
  - job_name: 'node'
    file_sd_configs:
      - files:
        - '/var/lib/prometheus/targets.json'
This target.json file can hold a list of targets formatted like this:

Example targets.json

[
    {
        "targets": ["localhost:9100", "192.168.1.100:9100", "192.168.1.101:9100"],
        "labels": {
            "job": "node"
        }
    }
]

You can either expand the list or add more objects in the root list.
You can also use a targets.yaml file if you want.

Adding another target with another entry in the root list: 

[
    {
        "targets": ["localhost:9100", "192.168.1.100:9100", "192.168.1.101:9100"],
        "labels": {
            "job": "node"
        }
    },
    {
        "targets": ["localhost:9200"],
        "labels": {
            "job": "node"
        }
    }
]

Adding another target by expanding the existing list: 

[
    {
        "targets": ["localhost:9100", "192.168.1.100:9100", "192.168.1.101:9100", "localhost:9200"],
        "labels": {
            "job": "node"
        }
    }
]

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