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Fix prompt mismatch issue for ios (#47004)

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* Fix prompt mismatch issue for ios

Fixes #40884 #44463

*  If the command prompt is matched check if data is
   still pending to be read from buffer.
*  This fix adds a new timer `buffer_read_timeout`
   which will be trigerred after command prompt
   is matched and data is attempted to be read from channel.
   If not data is present of channel the timer will expire
   and response we be returned to calling function.

* Fix unit test failure

* Update to make buffer timeout float

* Update doc and fix review comment

* Fix CI issues

* Update doc

* Fix review comments

* Fix review comments
This commit is contained in:
Ganesh Nalawade 2018-10-22 21:05:15 +05:30 committed by GitHub
parent c58c0b8547
commit 335a979f1d
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GPG key ID: 4AEE18F83AFDEB23
3 changed files with 109 additions and 9 deletions
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35
docs/docsite/rst/network/user_guide/network_debug_troubleshooting.rst
View file

@ -656,3 +656,38 @@ Example Ansible inventory file
This is done to prevent secrets from leaking out, for example in ``ps`` output.
We recommend using SSH Keys, and if needed an ssh-agent, rather than passwords, where ever possible.
Miscellaneous Issues
====================
Intermittent failure while using ``network_cli`` connection type
----------------------------------------------------------------
If the command prompt received in response is not matched correctly within
the ``network_cli`` connection plugin the task might fail intermittently with truncated
response or with the error message ``operation requires privilege escalation``.
Starting in 2.7.1 a new buffer read timer is added to ensure prompts are matched properly
and a complete response is send in output. The timer default value is 0.2 seconds and
can be adjusted on a per task basis or can be set globally in seconds.
Example Per task timer setting
.. code-block:: yaml
- name: gather ios facts
ios_facts:
gather_subset: all
register: result
vars:
ansible_buffer_read_timeout: 2
To make this a global setting, add the following to your ``ansible.cfg`` file:
.. code-block:: ini
[persistent_connection]
buffer_read_timeout = 2
This timer delay per command executed on remote host can be disabled by setting the value to zero.

74
lib/ansible/plugins/connection/network_cli.py
View file

@ -157,6 +157,21 @@ options:
- name: ANSIBLE_PERSISTENT_COMMAND_TIMEOUT
vars:
- name: ansible_command_timeout
persistent_buffer_read_timeout:
type: float
description:
- Configures, in seconds, the amount of time to wait for the data to be read
from Paramiko channel after the command prompt is matched. This timeout
value ensures that command prompt matched is correct and there is no more data
left to be received from remote host.
default: 0.1
ini:
- section: persistent_connection
key: buffer_read_timeout
env:
- name: ANSIBLE_PERSISTENT_BUFFER_READ_TIMEOUT
vars:
- name: ansible_buffer_read_timeout
"""
import getpass
@ -164,6 +179,7 @@ import json
import logging
import re
import os
import signal
import socket
import traceback
from io import BytesIO
@ -184,6 +200,10 @@ except ImportError:
display = Display()
class AnsibleCmdRespRecv(Exception):
pass
class Connection(NetworkConnectionBase):
''' CLI (shell) SSH connections on Paramiko '''
@ -200,6 +220,7 @@ class Connection(NetworkConnectionBase):
self._matched_pattern = None
self._last_response = None
self._history = list()
self._command_response = None
self._terminal = None
self.cliconf = None
@ -342,15 +363,39 @@ class Connection(NetworkConnectionBase):
'''
Handles receiving of output from command
'''
recv = BytesIO()
handled = False
self._matched_prompt = None
self._matched_cmd_prompt = None
recv = BytesIO()
handled = False
command_prompt_matched = False
matched_prompt_window = window_count = 0
command_timeout = self.get_option('persistent_command_timeout')
self._validate_timeout_value(command_timeout, "persistent_command_timeout")
buffer_read_timeout = self.get_option('persistent_buffer_read_timeout')
self._validate_timeout_value(buffer_read_timeout, "persistent_buffer_read_timeout")
while True:
data = self._ssh_shell.recv(256)
if command_prompt_matched:
try:
signal.signal(signal.SIGALRM, self._handle_buffer_read_timeout)
signal.setitimer(signal.ITIMER_REAL, buffer_read_timeout)
data = self._ssh_shell.recv(256)
signal.alarm(0)
# if data is still received on channel it indicates the prompt string
# is wrongly matched in between response chunks, continue to read
# remaining response.
command_prompt_matched = False
# restart command_timeout timer
signal.signal(signal.SIGALRM, self._handle_command_timeout)
signal.alarm(command_timeout)
except AnsibleCmdRespRecv:
return self._command_response
else:
data = self._ssh_shell.recv(256)
# when a channel stream is closed, received data will be empty
if not data:
@ -376,7 +421,11 @@ class Connection(NetworkConnectionBase):
if self._find_prompt(window):
self._last_response = recv.getvalue()
resp = self._strip(self._last_response)
return self._sanitize(resp, command)
self._command_response = self._sanitize(resp, command)
if buffer_read_timeout == 0.0:
return self._command_response
else:
command_prompt_matched = True
def send(self, command, prompt=None, answer=None, newline=True, sendonly=False, prompt_retry_check=False, check_all=False):
'''
@ -398,6 +447,17 @@ class Connection(NetworkConnectionBase):
display.vvvv(traceback.format_exc(), host=self._play_context.remote_addr)
raise AnsibleConnectionFailure("timeout trying to send command: %s" % command.strip())
def _handle_buffer_read_timeout(self, signum, frame):
display.vvvv("Response received, triggered 'persistent_buffer_read_timeout' timer of %s seconds"
% self.get_option('persistent_buffer_read_timeout'), host=self._play_context.remote_addr)
raise AnsibleCmdRespRecv()
def _handle_command_timeout(self, signum, frame):
msg = 'command timeout triggered, timeout value is %s secs.\nSee the timeout setting options in the Network Debug and Troubleshooting Guide.'\
% self.get_option('persistent_command_timeout')
display.display(msg, log_only=True)
raise AnsibleConnectionFailure(msg)
def _strip(self, data):
'''
Removes ANSI codes from device response
@ -488,3 +548,7 @@ class Connection(NetworkConnectionBase):
raise AnsibleConnectionFailure(errored_response)
return False
def _validate_timeout_value(self, timeout, timer_name):
if timeout < 0:
raise AnsibleConnectionFailure("'%s' timer value '%s' is invalid, value should be greater than or equal to zero." % (timer_name, timeout))

9
test/units/plugins/connection/test_network_cli.py
View file

@ -21,6 +21,7 @@ from __future__ import (absolute_import, division, print_function)
__metaclass__ = type
import re
import time
import json
from io import StringIO
@ -28,6 +29,7 @@ from io import StringIO
from units.compat import unittest
from units.compat.mock import patch, MagicMock
from ansible.module_utils._text import to_text
from ansible.errors import AnsibleConnectionFailure
from ansible.playbook.play_context import PlayContext
from ansible.plugins.loader import connection_loader
@ -131,15 +133,14 @@ class TestConnectionClass(unittest.TestCase):
device#
"""
mock__shell.recv.return_value = response
mock__shell.recv.side_effect = [response, None]
output = conn.send(b'command', None, None, None)
mock__shell.sendall.assert_called_with(b'command\r')
self.assertEqual(output, 'command response')
self.assertEqual(to_text(conn._command_response), 'command response')
mock__shell.reset_mock()
mock__shell.recv.return_value = b"ERROR: error message device#"
mock__shell.recv.side_effect = [b"ERROR: error message device#"]
with self.assertRaises(AnsibleConnectionFailure) as exc:
conn.send(b'command', None, None, None)