How to Retrieve and Analyze Prometheus Monitoring Data via API

As a skilled engineer, leveraging Prometheus monitoring data can create value beyond alerts, such as analysis and cost management.

API Format

Prometheus provides a stable V1 API at /api/v1. It supports GET and POST requests and returns 2xx on success. Common error codes include 400 (Bad Request), 422 (Unprocessable Entity), and 503 (Service Unavailable).

Successful responses follow this JSON structure:

{
  "status": "success" | "error",
  "data": <data>,
  // present only when status is "error"
  "errorType": "<string>",
  "error": "<string>",
  "warnings": ["<string>"]
}

API Calls

Instant query returns data for a single point in time.

GET /api/v1/query
POST /api/v1/query

Parameters:

query=<string> – Prometheus expression.

time=<rfc3339 | unix_timestamp> – optional evaluation timestamp.

timeout=<duration> – optional timeout.

Example using curl:

curl http://localhost:9090/api/v1/query?query=node_load5{instance="192.168.214.108:9100"}

Sample response:

{
  "status":"success",
  "data":{
    "resultType":"vector",
    "result":[
      {
        "metric":{
          "__name__":"node_load5",
          "instance":"192.168.214.108:9100",
          "job":"node"
        },
        "value":[1666865246.993,"0.04"]
      }
    ]
  }
}

Range query returns data over a time interval.

GET /api/v1/query_range
POST /api/v1/query_range

Parameters:

query=<string> – expression.

start=<rfc3339 | unix_timestamp> – start time.

end=<rfc3339 | unix_timestamp> – end time.

step=<duration | float> – resolution.

timeout=<duration> – optional timeout.

Example:

curl http://localhost:9090/api/v1/query_range?query=node_load5{instance="192.168.214.108:9100"}&start=2022-10-28T02:10:10.000Z&end=2022-10-28T02:13:00.000Z&step=60s

Sample response (matrix):

{
  "status":"success",
  "data":{
    "resultType":"matrix",
    "result":[
      {
        "metric":{
          "__name__":"node_load5",
          "instance":"192.168.214.108:9100",
          "job":"node"
        },
        "values":[
          [1666923010,"0.04"],
          [1666923070,"0.04"],
          [1666923130,"0.03"]
        ]
      }
    ]
  }
}

Fetching Data in Code

In production, use a programming language such as Python. First install the requests library: pip install requests Example script test_api.py:

# -*- coding: utf-8 -*-

import requests

url = 'http://192.168.214.108:9090'
query_api = '/api/v1/query'
params = 'query=node_load5{instance="192.168.214.108:9100"}'

res = requests.get(url + query_api, params)
metrics = res.json().get("data").get("result")

if metrics:
    value = metrics[0].get('value')[1]
    print('Server 192.168.214.108 node_load5 value is %s' % value)
else:
    print('Unable to retrieve data')

Running the script prints: Server 192.168.214.108 node_load5 value is 0.01 For more advanced usage, refer to the official Prometheus API documentation.