Subprocess TBD

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Some partially ready examples

examples/process/slow_starting_server.py

import time
import sys
import os

if len(sys.argv) != 2:
    exit(f"Usage: {sys.argv[0]} SECONDS")

print(f"{int(time.time())} - start will take {sys.argv[1]} seconds (pid: {os.getpid()})", flush=True)
time.sleep(int(sys.argv[1]))
print(f"{int(time.time())} - started", flush=True)

while True:
    time.sleep(1)
    print(f"{int(time.time())} - running", flush=True)

examples/process/wait_do_and_stop.py

#import os
#import time
#import signal
import subprocess
import sys
import time


#def test_hello():
#    run_process([sys.executable, "examples/Hello-World.py"], )
    #pid = os.fork()
    #if pid is None:
    #    raise Exception("Could not fork")

    #if pid:
    #    print(f"parent of {pid}")
    #    time.sleep(5)
    #    os.kill(pid, signal.SIGKILL)
    #else:
    #    print("child")
    #    os.environ['PYTHONPATH'] = '.'
    #    os.exec("python examples/Hello-World.py")


def run_process(command, start_timeout):
    sleep_time = 0.5
    print(command)
    proc = subprocess.Popen(command,
        stdout = subprocess.PIPE,
        stderr = subprocess.STDOUT,
        universal_newlines=True,
        bufsize=0,
    )

    out = ""
    while True:
        print("Loop")
        exit_code = proc.poll()  # returns the exit code or None if the process is still running
        if exit_code is not None:
            raise Exception("Server died")
        print(exit_code)
        this_out = proc.stdout.readline()
        #this_err = proc.stderr.readline()
        out += this_out
        print(f"Before sleep {sleep_time} for a total of {start_timeout}")
        time.sleep(sleep_time)
        start_timeout -= sleep_time
        if start_timeout <= 0:
            proc.terminate()
            raise Exception("The service has not properly started")

        if "started" in out:
            print(out)
            print("--------")
            print("It is now running")
            print("--------")
            break

    print("Do something interesting here that takes 2 seconds")
    time.sleep(2)
    proc.terminate()

    exit_code = proc.returncode
    out, _ = proc.communicate()
    return exit_code, out

print("Before")
exit_code, out = run_process([sys.executable, 'slow_starting_server.py', '3'], 4)
print("-----")
print(f"exit_code: {exit_code}")
print("OUT")
print(out)

examples/process/run_multiple_commands.py

import subprocess
import time
import os
import psutil

def run_process(*commands):
    print(f"Before Popen {os.getpid()}")
    processes = []
    for command in commands:
        proc = subprocess.Popen(command)  # This starts runing the external process
        print(f"After Popen of {proc.pid}")
        psproc = psutil.Process(proc.pid)
        print(f"name: {psproc.name()}")
        print(f"cmdline: {psproc.cmdline()}")
        processes.append(proc)

    time.sleep(1.5)

    print("Before communicate")
    for proc in processes:
        proc.communicate()
    print("After communicate")

    exit_codes = [proc.returncode for proc in processes]
    return exit_codes

print("Before run_process", flush=True)
exit_codes = run_process(
    ['python', 'process.py', '5', '0'],
    ['python', 'process.py', '4', '1'],
    ['python', 'process.py', '3', '2'],
    )
print("After run_process", flush=True)

print(f'exit code: {exit_codes}', flush=True)