无法获得多处理netmiko多个设备的输出

Question

Not getting output for multiple device connection using multiprocessing

I tried the following code:

import multiprocessing as mp
from netmiko import ConnectHandler
import netmiko
import re
from datetime import datetime

def get_ip (input):
    return(re.findall(r'(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)', input))

def make_connection (ip, username, password):
                    device_connect = ConnectHandler(device_type='cisco_nxos', ip=ip, username=username, password=password)
                    output = device_connect.send_command("sh hostname")
                    print(output)
                    device_connect.disconnect()

def get_ips_nexus (file_name):
    for line in open(file_name, 'r').readlines():
        line = get_ip(line)
        for ip in line: 
            ips_nexus.append(ip)

ips_nexus = []
get_ips_nexus("ips-Copy.txt")
print(ips_nexus)
username = 'x.x.x.x'
password = 'xxxxxxxx'
startTime = datetime.now()
processes = []

for ip in ips_nexus:
            print('***********')
            print(ip)
            print('***********')
            p = mp.Process(target=make_connection, args=(ip, username, password))
            processes.append(p)
            p.start()
            print('!!!!!!!!!!!!!!!!!!!!!!!!!')

for p in processes:
    print(p)
    p.join()
print(datetime.now() - startTime

I am getting only print ip not the netmiko connected output of sh hostname.

I want to achieve multiple device connectivity using multiprocessing only!!!

Please help.

Answer 1

You are missing the if __name__ == "__main__" clause!
Add it above your for - loop for the processes:

if __name__ == "__main__":    # add this
    for ip in ips_nexus:
            print('***********')
            print(ip)
            print('***********')
            p = mp.Process(target=make_connection, args=(ip, username, password))
            processes.append(p)
            p.start()
            print('!!!!!!!!!!!!!!!!!!!!!!!!!')

Why do I need it?

First of all: If you run a code of yours, the python interpreter imports it as a " main " file. You can try it, by adding print(__name__) . Anyway, if you start a new process with multiprocessing , than the python interpreter imports your code again and runs it as an extra-process and as a new skript!!! Well, if it reaches (in your case) this part again:

p = mp.Process(target=make_connection, args=(ip, username, password))  

it will start a new process again, imports it again and so on. In the end you are going to have an infinite loop, which starts your code every time as a new process! That's the reason why you have to add the ( important ) if __name__ == "__main__" clause! By adding this, __name__ won't be __main__ after the first call of a new process!