Keep max CPU and Memory using container stats

max_stats_watcher.py

#!/usr/bin/env python3
#
# Simple utility to watch the stats for a single docker container.
# It writes stats to two files 'max-cpu.txt' and 'max-mem.txt'
# for the maximum observed CPU and memory.
# The utility runs the stats every 60 seconds.
#
# Stats look like this...
#
# CONTAINER ID   NAME              CPU %     MEM USAGE / LIMIT     MEM %     NET I/O        BLOCK I/O        PIDS
# 438738fa238c   fragmentor_db_1   574.60%   127.2GiB / 243.9GiB   52.16%    47kB / 118kB   177GB / 8.88GB   38
#
# Run with: nohup ./max_stats_watcher.py &

import subprocess
import re
import time

_STATS_RE = re.compile(r'([0-9a-f]+)\s*(\S+)\s*(?P<cpu_pcent>\S+)%\s*(?P<mem>[\d.]+)(?P<mem_unit>\S+)\s+/\s+(\S+)\s+(\S+)%.*', re.MULTILINE)
_MAX_CPU = 2546.01
_MAX_MEM = 163.2

if __name__ == '__main__':

    while True:
    
        process = subprocess.run(['docker', 'stats', '--no-stream'], stdout=subprocess.PIPE)
        stats = process.stdout.decode('utf-8').replace('\n', '\n')
        match = _STATS_RE.search(stats)
        cpu = float(match.group('cpu_pcent'))
        mem = float(match.group('mem'))
        mem_unit = match.group('mem_unit')
        if cpu >= _MAX_CPU:
            print(f'New max cpu ({cpu}%)')
            _MAX_CPU = cpu
            with open('max-cpu.txt', 'w') as cpu_file:
                cpu_file.write(stats)
        if mem_unit == 'GiB' and mem >= _MAX_MEM:
            print(f'New max mem ({mem}GiB)')
            _MAX_MEM = mem
            with open('max-mem.txt', 'w') as mem_file:
                mem_file.write(stats)
            
        time.sleep(60)