Record Docker memory usage in CSV format

stream_docker_stats.py

import subprocess
import time
from sys import argv

run_args = "docker stats --format {{.MemUsage}}".split()
if len(argv) > 1:
    run_args.append(argv[1])
background = subprocess.Popen(run_args, stdout=subprocess.PIPE)
units = {'Ki': 1e3, 'Mi': 1e6, 'Gi': 1e9, 'Ti': 1e12}
print("timestamp_seconds", "memory_bytes", flush=True)
start, now = None, 0
while True:
    output = background.stdout.readline()
    if output == "" and start is not None:
        # exit when the container is done
        break
    if output:
        output = output.decode("utf-8").split(" /")[0].strip()
        if len(output) > 50:
            # there is some garbage in the first output
            continue
        number = float(output[7:-3]) * units.get(output[-3:-1], 1)
        if start is None:
            start = time.time()
        else:
            now = time.time() - start
        print(round(now), round(number), flush=True, sep=";")
    time.sleep(1)