Add buffer clean in Huawei session preparation

[k-ribot]

No description provided.

[ktbyers]

@k-ribot Why is this needed? Do you have more details?

I would have thought it was unnecessary and slows things down.

[k-ribot]

@ktbyers We use Netmiko to connect to equipment from our tool. This tool can be used at the same time by several users. When we have more than 4 connections at the same time on a Huawei. the prompt of the last connection is wrong because it uses the result of the command "screen-length 0 temporary". This is why the delay is necessary.

Error received on the command "display version" executed after the connection:

ReadTimeout

Pattern not detected: 'Info:\\ The\\ configuration\\ takes\\ effect\\ on\\ the\\ current\\ user\\ terminal\\ interface\\ only\\.' in output.

Things you might try to fix this:
1. Explicitly set your pattern using the expect_string argument.
2. Increase the read_timeout to a larger value.

You can also look at the Netmiko session_log or debug log for more information.

[ktbyers]

Can you show what the CLI looks like when you see this message?

Pattern not detected: 'Info:\\ The\\ configuration\\ takes\\ effect\\ on\\ the\\ current\\ user\\ terminal\\ interface\\ only\\.' in output.

i.e. the message The configuration takes effect on the current...

You can probably capture this via the Netmiko session_log and just include the session_log.

I am reluctant to add the buffer clearing in the session_preparation method as it slows things down meaningfully (which is why I removed it previously). Also your error/issue doesn't exactly match what I would expect...so that is why I want to dig into it a bit more.

Thanks, Kirk

[ktbyers]

@k-ribot Are you still working on this?

I still don't see why this is needed and am pretty reluctant to just add slowness without an understanding of why it is needed.

[k-ribot]

Sorry we work on many projet, I forgot to send you the log file.
netmiko_global.log

I execute this python code:

import logging

from typing import List

from netmiko import ConnectHandler
from threading import Thread

logging.basicConfig(filename='netmiko_global.log', level=logging.DEBUG)
logger = logging.getLogger("netmiko")

def test(i: int):
    netmiko_connection = ConnectHandler(
        host='...',
        port=22,
        username='...',
        password='...',
        device_type='huawei_vrp'
    )
    netmiko_connection.send_command('display version')


threads: List[Thread] = []
for i in range(0, 4):
    threads.append(Thread(target=test, args=(i,)))

for thread in threads:
    thread.start()

I create 4 connection and I try to execute one command.

Lines 466 and 670 we can read this:
DEBUG:netmiko:[find_prompt()]: prompt is Info: The configuration takes effect on the current user terminal interface only.

Without sleep before buffer clearing 2 threads find bad prompt and client raise ReadTimeout exception.