Generates Prometheus metrics for Docker thin pool usage

prom-docker-thinpool-usage.py

#!/usr/bin/env python
# Generates Prometheus metrics for Docker thin pool usage

import subprocess
import re
import shutil

METRIC_PREFIX = "docker_thinpool"
PROM_DIR = "/tmp"

def write_to_prom(metrics):
    data = ""
    for k, v in metrics.iteritems():
        k = METRIC_PREFIX + "_" + k
        data += "# HELP " + k + "\n"
        data += "# TYPE " + k + " gauge\n"
        data += k + " " + str(v) + "\n"
    print data
    promfile = PROM_DIR + '/' + METRIC_PREFIX
    file = open(promfile + '.tmp', 'w')
    file.write(data)
    file.close()
    shutil.move(promfile + '.tmp', promfile + '.prom')

def convert_to_bytes(n, w):
    if 'MB' in w:
        return int(float(n)*1000000)
    elif 'GB' in w:
        return int(float(n)*1000000000)
    else:
        exit(1)

def extract_value(line):
    n = re.findall(r'\d+\.?\d+', line)
    w = re.findall(r'[a-zA-Z]+$', line)
    return convert_to_bytes(n[0], w[0])

def get_docker_info():
    try:
        return(subprocess.check_output(['docker', 'info']))
    except subprocess.CalledProcessError as e:
        print "Couldn't call docker info: " + str(e)
        exit(1)

def get_metrics(docker_info):
    metrics = {}
    for l in docker_info.splitlines():
        if "Data Space Used" in l:
            metrics['data_space_used_bytes'] = extract_value(l)
        elif "Data Space Total" in l:
            metrics['data_space_total_bytes'] = extract_value(l)
        elif "Thin Pool Minimum Free Space" in l:
            metrics['minimum_free_space_bytes'] = extract_value(l)
    return metrics

if __name__ == "__main__":
    write_to_prom(get_metrics(get_docker_info()))