From 335a979f1d30d065504bf9222460f35356a2e0b6 Mon Sep 17 00:00:00 2001 From: Ganesh Nalawade Date: Mon, 22 Oct 2018 21:05:15 +0530 Subject: [PATCH] Fix prompt mismatch issue for ios (#47004) * 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 --- .../network_debug_troubleshooting.rst | 35 +++++++++ lib/ansible/plugins/connection/network_cli.py | 74 +++++++++++++++++-- .../plugins/connection/test_network_cli.py | 9 ++- 3 files changed, 109 insertions(+), 9 deletions(-) diff --git a/docs/docsite/rst/network/user_guide/network_debug_troubleshooting.rst b/docs/docsite/rst/network/user_guide/network_debug_troubleshooting.rst index a68f00e9c71..3d734cd8512 100644 --- a/docs/docsite/rst/network/user_guide/network_debug_troubleshooting.rst +++ b/docs/docsite/rst/network/user_guide/network_debug_troubleshooting.rst @@ -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. diff --git a/lib/ansible/plugins/connection/network_cli.py b/lib/ansible/plugins/connection/network_cli.py index c27c9ad73cb..18dbd251040 100644 --- a/lib/ansible/plugins/connection/network_cli.py +++ b/lib/ansible/plugins/connection/network_cli.py @@ -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)) diff --git a/test/units/plugins/connection/test_network_cli.py b/test/units/plugins/connection/test_network_cli.py index 4807795601b..cbd64addd2b 100644 --- a/test/units/plugins/connection/test_network_cli.py +++ b/test/units/plugins/connection/test_network_cli.py @@ -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)