Exercise: Processes

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Given the following "external application":

examples/process/myrandom.py

import sys
import random
import time

def add_random(result_filename, count, wait, exception=''):
    total = 0
    for _ in range(int(count)):
        total += random.random()

    time.sleep(float(wait))
    if exception:
        raise Exception(exception)

    with open(result_filename, 'w') as fh:
        fh.write(str(total))


if __name__ == '__main__':
    if len(sys.argv) != 4 and len(sys.argv) != 5:
        exit(f"Usage: {sys.argv[0]} RESULT_FILENAME COUNT WAIT [EXCEPTION]")
    add_random(*sys.argv[1:])

It could be run with a command like this to create the a.txt file:

python examples/process/myrandom.py a.txt 3 1

Or like this, to raise an exception before creating the b.txt file:

python examples/process/myrandom.py b.txt 3 1 "bad thing"

Or it could be used like this:

examples/process/use_myrandom.py

from myrandom import add_random

add_random('b.txt', 2, 3)
add_random('c.txt', 2, 3, 'some error')

Write a program that will do "some work" that can be run in parallel and collect the data. Make the code work in a single process by default and allow the user to pass a number that will be the number of child processes to be used. When the child process exits it should save the results in a file and the parent process should read them in.

The "some work" can be accessing 10-20 machines using "ssh machine uptime" and creating a report from the results.

It can be fetching 10-20 URLs and reporting the size of each page.

It can be any other network intensive task.

Measure the time in both cases