Python worker pool that doesn't waste memory.

foo.py

#!/usr/bin/env python3
import sys
import multiprocessing as mp
import subprocess as sp
import shlex as sh

from itertools import cycle

def sh(cmd):
    return sp.Popen(cmd, shell=True, stdout=sys.stdout, stderr=sys.stderr).wait()

q = mp.Queue(mp.cpu_count())

def echo(message):
    return sh('echo {} && sleep 1'.format(message))

def exec_echo(q):
    while True:
        msg = q.get()
        echo(msg)

cpu = mp.cpu_count()
queue = mp.Queue(cpu)
for c in range(cpu):
    p = mp.Process(target=exec_echo, args=(q,))
    p.daemon = True
    p.start()

while True:
    q.put('Hello')