mitogen/ansible_mitogen/mixins.py

# Copyright 2017, David Wilson
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from __future__ import absolute_import
import commands
import os
import pwd
import shutil
import tempfile
import traceback

import ansible
import ansible.plugins
import ansible.plugins.action

try:
    from ansible.plugins.loader import module_loader
except ImportError:  # Ansible<2.4
    from ansible.plugins import module_loader

import mitogen.core
import mitogen.master
from mitogen.utils import cast

import ansible_mitogen.connection
import ansible_mitogen.helpers
from ansible.module_utils._text import to_text


def get_command_module_name(module_name):
    """
    Given the name of an Ansible command module, return its canonical module
    path within the ansible.

    :param module_name:
        "shell"
    :return:
        "ansible.modules.commands.shell"
    """
    path = module_loader.find_plugin(module_name, '')
    relpath = os.path.relpath(path, os.path.dirname(ansible.__file__))
    root, _ = os.path.splitext(relpath)
    return 'ansible.' + root.replace('/', '.')


class ActionModuleMixin(ansible.plugins.action.ActionBase):
    """
    The Mitogen-patched PluginLoader dynamically mixes this into every action
    class that Ansible attempts to load. It exists to override all the
    assumptions built into the base action class that should really belong in
    some middle layer, or at least in the connection layer.

    Functionality is defined here for:

    * Capturing the final set of task variables and giving Connection a chance
      to update its idea of the correct execution environment, before any
      attempt is made to call a Connection method. While it's not expected for
      the interpreter to change on a per-task basis, Ansible permits this, and
      so it must be supported.

    * Overriding lots of methods that try to call out to shell for mundane
      reasons, such as copying files around, changing file permissions,
      creating temporary directories and suchlike.

    * Short-circuiting any use of Ansiballz or related code for executing a
      module remotely using shell commands and SSH.

    * Short-circuiting most of the logic in dealing with the fact that Ansible
      always runs become: tasks across at least the SSH user account and the
      destination user account, and handling the security permission issues
      that crop up due to this. Mitogen always runs a task completely within
      the target user account, so it's not a problem for us.
    """
    def __init__(self, task, connection, *args, **kwargs):
        """
        Verify the received connection is really a Mitogen connection. If not,
        transmute this instance back into the original unadorned base class.

        This allows running the Mitogen strategy in mixed-target playbooks,
        where some targets use SSH while others use WinRM or some fancier UNIX
        connection plug-in. That's because when the Mitogen strategy is active,
        ActionModuleMixin is unconditionally mixed into any action module that
        is instantiated, and there is no direct way for the monkey-patch to
        know what kind of connection will be used upfront.
        """
        super(ActionModuleMixin, self).__init__(task, connection, *args, **kwargs)
        if not isinstance(connection, ansible_mitogen.connection.Connection):
            _, self.__class__ = type(self).__bases__

    def run(self, tmp=None, task_vars=None):
        """
        Override run() to notify Connection of task-specific data, so it has a
        chance to know e.g. the Python interpreter in use.
        """
        self._connection.on_action_run(task_vars)
        return super(ActionModuleMixin, self).run(tmp, task_vars)

    def call(self, func, *args, **kwargs):
        """
        Arrange for a Python function to be called in the target context, which
        should be some function from the standard library or
        ansible_mitogen.helpers module. This junction point exists mainly as a
        nice place to insert print statements during debugging.
        """
        return self._connection.call(func, *args, **kwargs)

    COMMAND_RESULT = {
        'rc': 0,
        'stdout': '',
        'stdout_lines': [],
        'stderr': ''
    }

    def fake_shell(self, func, stdout=False):
        """
        Execute a function and decorate its return value in the style of
        _low_level_execute_command(). This produces a return value that looks
        like some shell command was run, when really func() was implemented
        entirely in Python.

        If the function raises :py:class:`mitogen.core.CallError`, this will be
        translated into a failed shell command with a non-zero exit status.

        :param func:
            Function invoked as `func()`.
        :returns:
            See :py:attr:`COMMAND_RESULT`.
        """
        dct = self.COMMAND_RESULT.copy()
        try:
            rc = func()
            if stdout:
                dct['stdout'] = repr(rc)
        except mitogen.core.CallError:
            dct['rc'] = 1
            dct['stderr'] = traceback.format_exc()

        return dct

    def _remote_file_exists(self, path):
        """
        Determine if `path` exists by directly invoking os.path.exists() in the
        target user account.
        """
        return self.call(os.path.exists, path)

    def _configure_module(self, module_name, module_args, task_vars=None):
        """
        Mitogen does not use the Ansiballz framework. This call should never
        happen when ActionMixin is active, so crash if it does.
        """
        assert False, "_configure_module() should never be called."

    def _is_pipelining_enabled(self, module_style, wrap_async=False):
        """
        Mitogen does not use SSH pipelining. This call should never happen when
        ActionMixin is active, so crash if it does.
        """
        assert False, "_is_pipelining_enabled() should never be called."

    def _make_tmp_path(self, remote_user=None):
        """
        Replace the base implementation's use of shell to implement mkdtemp()
        with an actual call to mkdtemp().
        """
        path = self.call(tempfile.mkdtemp, prefix='ansible-mitogen-tmp-')
        self._cleanup_remote_tmp = True
        return path

    def _remove_tmp_path(self, tmp_path):
        """
        Replace the base implementation's invocation of rm -rf with a call to
        shutil.rmtree().
        """
        if self._should_remove_tmp_path(tmp_path):
            return self.call(shutil.rmtree, tmp_path)

    def _transfer_data(self, remote_path, data):
        """
        This is used by the base implementation of _execute_module(), it should
        never be called.
        """
        assert False, "_transfer_data() should never be called."

    def _fixup_perms2(self, remote_paths, remote_user=None, execute=True):
        """
        Mitogen always executes ActionBase helper methods in the context of the
        target user account, so it is never necessary to modify permissions
        except to ensure the execute bit is set if requested.
        """
        if execute:
            return self._remote_chmod(remote_paths, mode='u+x')
        return self.COMMAND_RESULT.copy()

    def _remote_chmod(self, paths, mode, sudoable=False):
        """
        Issue an asynchronous set_file_mode() call for every path in `paths`,
        then format the resulting return value list with fake_shell().
        """
        return self.fake_shell(lambda: mitogen.master.Select.all(
            self._connection.call_async(
                ansible_mitogen.helpers.set_file_mode, path, mode
            )
            for path in paths
        ))

    def _remote_chown(self, paths, user, sudoable=False):
        """
        Issue an asynchronous os.chown() call for every path in `paths`, then
        format the resulting return value list with fake_shell().
        """
        ent = self.call(pwd.getpwnam, user)
        return self.fake_shell(lambda: mitogen.master.Select.all(
            self._connection.call_async(
                os.chown, path, ent.pw_uid, ent.pw_gid
            )
            for path in paths
        ))

    def _remote_expand_user(self, path, sudoable=True):
        """
        Replace the base implementation's attempt to emulate
        os.path.expanduser() with an actual call to os.path.expanduser().
        """
        if path.startswith('~'):
            path = self.call(os.path.expanduser, path)
        return path

    def _execute_module(self, module_name=None, module_args=None, tmp=None,
                        task_vars=None, persist_files=False,
                        delete_remote_tmp=True, wrap_async=False):
        """
        Collect up a module's execution environment then use it to invoke
        helpers.run_module() or helpers.run_module_async() in the target
        context.
        """
        module_name = module_name or self._task.action
        module_args = module_args or self._task.args
        task_vars = task_vars or {}

        self._update_module_args(module_name, module_args, task_vars)
        if wrap_async:
            helper = ansible_mitogen.helpers.run_module_async
        else:
            helper = ansible_mitogen.helpers.run_module

        env = {}
        self._compute_environment_string(env)

        js = self.call(
            helper,
            get_command_module_name(module_name),
            args=cast(module_args),
            env=cast(env),
        )

        data = self._parse_returned_data({
            'rc': 0,
            'stdout': js,
            'stdout_lines': [js],
            'stderr': ''
        })

        # Cutpasted from the base implementation.
        if 'stdout' in data and 'stdout_lines' not in data:
            data['stdout_lines'] = (data['stdout'] or u'').splitlines()
        if 'stderr' in data and 'stderr_lines' not in data:
            data['stderr_lines'] = (data['stderr'] or u'').splitlines()

        return data

    def _low_level_execute_command(self, cmd, sudoable=True, in_data=None,
                                   executable=None,
                                   encoding_errors='surrogate_then_replace',
                                   chdir=None):
        """
        Replace the mad rat's nest of logic in the base implementation by
        simply calling helpers.exec_command() in the target context.
        """
        if executable is None:  # executable defaults to False
            executable = self._play_context.executable
        if executable:
            cmd = executable + ' -c ' + commands.mkarg(cmd)

        rc, stdout, stderr = self.call(
            ansible_mitogen.helpers.exec_command,
            cast(cmd),
            cast(in_data),
            chdir=cast(chdir),
        )
        stdout_text = to_text(stdout, errors=encoding_errors)

        return {
            'rc': rc,
            'stdout': stdout_text,
            'stdout_lines': stdout_text.splitlines(),
            'stderr': stderr,
        }