Because it's Friday, I was bitten by a filled-up volume on my VPS again, because Prometheus somehow is randomly crashing my VPS, and because I like thinkering and Python, I wrote a little notification script.

Yes, it checks for available disk space on your nodes, with configuration per hostname (it's all contained in the source file).

It takes paths and the amount of GB you want available as configuration under FILESYSTEMS.

Here it is:

import http.client, urllib
import os
import socket
import sys


HOSTNAME = socket.getfqdn()

APP_TOKEN = '<your_pushover_app_token>'
USER_KEY = '<your_pushover_userkey>'

FILESYSTEMS = {
    'host001.example.com': [
        ('/', 1),
        ('/var/local', 5),
        ('/home', 5),
    ],
    'host002': [
        ('/', 5),
        ('/stuff', 100),
    ],
}

def needs_notifying(size_trigger, size_available):
    """Checks whether we need to send a notification

    Args:
    size_trigger: minimum amount of free space in GB
    size_available: currently available free space in bytes
    """
    return size_available <= (size_trigger * 1024*1024*1024)


def send_message(message):
    conn = http.client.HTTPSConnection("api.pushover.net:443")
    conn.request("POST", "/1/messages.json",
      urllib.parse.urlencode({
        "token": APP_TOKEN,
        "user": USER_KEY,
        "message": message,
      }), { "Content-type": "application/x-www-form-urlencoded" })
    conn.getresponse()


def send_lowdisk_message(messages):
    message = '[{}] Low disk space on the following volumes:\n{}'.format(HOSTNAME, '\n'.join(messages))
    send_message(message)


try:
    filesystems = FILESYSTEMS[HOSTNAME]
except KeyError:
    send_message('[spacealarm] No filesystem configuration found for {}'.format(HOSTNAME))
    sys.exit(1)

messages = []

for filesystem in filesystems:
    statvfs = os.statvfs(filesystem[0])

    #statvfs.f_frsize * statvfs.f_blocks     # Size of filesystem in bytes
    #statvfs.f_frsize * statvfs.f_bfree      # Actual number of free bytes
    #statvfs.f_frsize * statvfs.f_bavail     # Number of free bytes that ordinary users
                                             # are allowed to use (excl. reserved space)

    if needs_notifying(filesystem[1], statvfs.f_frsize * statvfs.f_bavail):
        messages.append('{}: {:.1f}MB free'.format(filesystem[0], statvfs.f_frsize * statvfs.f_bavail / 1024/1024))

if messages:
    send_lowdisk_message(messages)