freeipa/ipapython/admintool.py

# Authors:
#   Petr Viktorin <pviktori@redhat.com>
#
# Copyright (C) 2012  Red Hat
# see file 'COPYING' for use and warranty information
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""A common framework for command-line admin tools, e.g. install scripts

Handles common operations like option parsing and logging
"""

import sys
import os
import traceback
from optparse import OptionGroup

from ipapython import version
from ipapython import config
from ipapython import ipa_log_manager


class ScriptError(StandardError):
    """An exception that records an error message and a return value
    """
    def __init__(self, msg='', rval=1):
        if msg is None:
            msg = ''
        self.msg = msg
        self.rval = rval

    def __str__(self):
        return self.msg


class AdminTool(object):
    """Base class for command-line admin tools

    To run the tool, call the main() classmethod with a list of command-line
    arguments.
    Alternatively, call run_cli() to run with command-line arguments in
    sys.argv, and call sys.exit() with the return value.

    Some commands actually represent multiple related tools, e.g.
    ``ipa-server-install`` and ``ipa-server-install --uninstall`` would be
    represented by separate classes. Only their options are the same.

    To handle this, AdminTool provides classmethods for option parsing
    and selecting the appropriate command class.

    A class-wide option parser is made by calling add_options.
    The options are then parsed into options and arguments, and
    get_command_class is called with those to retrieve the class.
    That class is then instantiated and run.

    Running consists of a few steps:
    - validating options or the environment (validate_options)
    - setting up logging (setup_logging)
    - running the actual command (run)

    Any unhandled exceptions are handled in handle_error.
    And at the end, either log_success or log_failure is called.

    Class attributes to define in subclasses:
    command_name - shown in logs
    log_file_name - if None, logging is to stderr only
    needs_root - if true, non-root users can't run the tool
    usage - text shown in help
    """
    command_name = None
    log_file_name = None
    needs_root = False
    usage = None

    _option_parsers = dict()

    @classmethod
    def make_parser(cls):
        """Create an option parser shared across all instances of this class"""
        parser = config.IPAOptionParser(version=version.VERSION,
            usage=cls.usage, formatter=config.IPAFormatter())
        cls.option_parser = parser
        cls.add_options(parser)

    @classmethod
    def add_options(cls, parser):
        """Add command-specific options to the option parser"""
        parser.add_option("-d", "--debug", dest="debug", default=False,
            action="store_true", help="print debugging information")

    @classmethod
    def run_cli(cls):
        """Run this command with sys.argv, exit process with the return value
        """
        sys.exit(cls.main(sys.argv))

    @classmethod
    def main(cls, argv):
        """The main entry point

        Parses command-line arguments, selects the actual command class to use
        based on them, and runs that command.

        :param argv: Command-line arguments.
        :return: Command exit code
        """
        if cls not in cls._option_parsers:
            # We use cls._option_parsers, a dictionary keyed on class, to check
            # if we need to create a parser. This is because cls.option_parser
            # can refer to the parser of a superclass.
            cls.make_parser()
            cls._option_parsers[cls] = cls.option_parser

        options, args = cls.option_parser.parse_args(argv[1:])

        command_class = cls.get_command_class(options, args)
        command = command_class(options, args)

        return command.execute()

    @classmethod
    def get_command_class(cls, options, args):
        return cls

    def __init__(self, options, args):
        self.options = options
        self.args = args
        self.safe_options = self.option_parser.get_safe_opts(options)

    def execute(self):
        """Do everything needed after options are parsed

        This includes validating options, setting up logging, doing the
        actual work, and handling the result.
        """
        try:
            self.validate_options()
            self.ask_for_options()
            self.setup_logging()
            return_value = self.run()
        except BaseException, exception:
            traceback = sys.exc_info()[2]
            error_message, return_value = self.handle_error(exception)
            if return_value:
                self.log_failure(error_message, return_value, exception,
                    traceback)
                return return_value
        self.log_success()
        return return_value

    def validate_options(self):
        """Validate self.options

        It's also possible to compute and store information that will be
        useful later, but no changes to the system should be made here.
        """
        if self.needs_root and os.getegid() != 0:
            raise ScriptError('Must be root to run %s' % self.command_name, 1)

    def ask_for_options(self):
        """Ask for missing options interactively

        Similar to validate_options. This is separate method because we want
        any validation errors to abort the script before bothering the user
        with prompts.
        """
        pass

    def setup_logging(self):
        """Set up logging"""
        ipa_log_manager.standard_logging_setup(
            self.log_file_name, debug=self.options.debug)
        ipa_log_manager.log_mgr.get_logger(self, True)

    def handle_error(self, exception):
        """Given an exception, return a message (or None) and process exit code
        """
        if isinstance(exception, ScriptError):
            return exception.msg, exception.rval or 1
        elif isinstance(exception, SystemExit):
            if isinstance(exception.code, int):
                return None, exception.code
            return str(exception.code), 1

        return str(exception), 1

    def run(self):
        """Actual running of the command

        This is where the hard work is done. The base implementation logs
        the invocation of the command.

        If this method returns (i.e. doesn't raise an exception), the tool is
        assumed to have run successfully, and the return value is used as the
        SystemExit code.
        """
        self.debug('%s was invoked with arguments %s and options: %s',
                self.command_name, self.args, self.safe_options)

    def log_failure(self, error_message, return_value, exception, backtrace):
        try:
            self.log
        except AttributeError:
            # Logging was not set up yet
            if error_message:
                print >> sys.stderr, '\n', error_message
        else:
            self.info(''.join(traceback.format_tb(backtrace)))
            self.info('The %s command failed, exception: %s: %s',
                self.command_name, type(exception).__name__, exception)
            if error_message:
                self.error(error_message)

    def log_success(self):
        try:
            self.log
        except AttributeError:
            pass
        else:
            self.info('The %s command was successful', self.command_name)