neutron-tempest-plugin/neutron_tempest_plugin/common/shell.py

# Copyright (c) 2018 Red Hat, Inc.
#
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import collections
import subprocess
import sys

from oslo_log import log
from tempest.lib import exceptions as lib_exc

from neutron_tempest_plugin.common import ssh
from neutron_tempest_plugin import config
from neutron_tempest_plugin import exceptions


LOG = log.getLogger(__name__)

CONF = config.CONF

if ssh.Client.proxy_jump_host:
    # Perform all SSH connections passing through configured SSH server
    SSH_PROXY_CLIENT = ssh.Client.create_proxy_client()
else:
    SSH_PROXY_CLIENT = None


def execute(command, ssh_client=None, timeout=None, check=True):
    """Execute command inside a remote or local shell

    :param command: command string to be executed

    :param ssh_client: SSH client instance used for remote shell execution

    :param timeout: command execution timeout in seconds

    :param check: when False it doesn't raises ShellCommandError when
    exit status is not zero. True by default

    :returns: STDOUT text when command execution terminates with zero exit
    status.

    :raises ShellTimeoutExpired: when timeout expires before command execution
    terminates. In such case it kills the process, then it eventually would
    try to read STDOUT and STDERR buffers (not fully implemented) before
    raising the exception.

    :raises ShellCommandError: when command execution terminates with non-zero
    exit status.
    """
    ssh_client = ssh_client or SSH_PROXY_CLIENT
    if timeout:
        timeout = float(timeout)

    if ssh_client:
        result = execute_remote_command(command=command, timeout=timeout,
                                        ssh_client=ssh_client)
    else:
        result = execute_local_command(command=command, timeout=timeout)

    if result.exit_status == 0:
        LOG.debug("Command %r succeeded:\n"
                  "stderr:\n%s\n"
                  "stdout:\n%s\n",
                  command, result.stderr, result.stdout)
    elif result.exit_status is None:
        LOG.debug("Command %r timeout expired (timeout=%s):\n"
                  "stderr:\n%s\n"
                  "stdout:\n%s\n",
                  command, timeout, result.stderr, result.stdout)
    else:
        LOG.debug("Command %r failed (exit_status=%s):\n"
                  "stderr:\n%s\n"
                  "stdout:\n%s\n",
                  command, result.exit_status, result.stderr, result.stdout)
    if check:
        result.check()

    return result


def execute_remote_command(command, ssh_client, timeout=None):
    """Execute command on a remote host using SSH client"""
    LOG.debug("Executing command %r on remote host %r (timeout=%r)...",
              command, ssh_client.host, timeout)

    stdout = stderr = exit_status = None

    try:
        # TODO(fressi): re-implement to capture stderr
        stdout = ssh_client.exec_command(command, timeout=timeout)
        exit_status = 0

    except lib_exc.TimeoutException:
        # TODO(fressi): re-implement to capture STDOUT and STDERR and make
        # sure process is killed
        pass

    except lib_exc.SSHExecCommandFailed as ex:
        # Please note class SSHExecCommandFailed has been re-based on
        # top of ShellCommandError
        stdout = ex.stdout
        stderr = ex.stderr
        exit_status = ex.exit_status

    return ShellExecuteResult(command=command, timeout=timeout,
                              exit_status=exit_status,
                              stdout=stdout, stderr=stderr)


def execute_local_command(command, timeout=None):
    """Execute command on local host using local shell"""

    LOG.debug("Executing command %r on local host (timeout=%r)...",
              command, timeout)

    process = subprocess.Popen(command, shell=True,
                               universal_newlines=True,
                               stdout=subprocess.PIPE,
                               stderr=subprocess.PIPE)

    if timeout and sys.version_info < (3, 3):
        # TODO(fressi): re-implement to timeout support on older Pythons
        LOG.warning("Popen.communicate method doens't support for timeout "
                    "on Python %r", sys.version)
        timeout = None

    # Wait for process execution while reading STDERR and STDOUT streams
    if timeout:
        try:
            stdout, stderr = process.communicate(timeout=timeout)
        except subprocess.TimeoutExpired:
            # At this state I expect the process to be still running
            # therefore it has to be kill later after calling poll()
            LOG.exception("Command %r timeout expired.", command)
            stdout = stderr = None
    else:
        stdout, stderr = process.communicate()

    # Check process termination status
    exit_status = process.poll()
    if exit_status is None:
        # The process is still running after calling communicate():
        # let kill it and then read buffers again
        process.kill()
        stdout, stderr = process.communicate()

    return ShellExecuteResult(command=command, timeout=timeout,
                              stdout=stdout, stderr=stderr,
                              exit_status=exit_status)


class ShellExecuteResult(collections.namedtuple(
        'ShellExecuteResult', ['command', 'timeout', 'exit_status', 'stdout',
                               'stderr'])):

    def check(self):
        if self.exit_status is None:
            raise exceptions.ShellTimeoutExpired(command=self.command,
                                                 timeout=self.timeout,
                                                 stderr=self.stderr,
                                                 stdout=self.stdout)

        elif self.exit_status != 0:
            raise exceptions.ShellCommandError(command=self.command,
                                               exit_status=self.exit_status,
                                               stderr=self.stderr,
                                               stdout=self.stdout)