Framework for admin/install tools, with ipa-ldap-updater

Currently, FreeIPA's install/admin scripts are long pieces of code
that aren't very reusable, importable, or testable.
They have been extended over time with features such as logging and
error handling, but since each tool was extended individually, there
is much inconsistency and code duplication.
This patch starts a framework which the admin tools can use, and
converts ipa-ldap-updater to use the framework.

Common tasks the tools do -- option parsing, validation, logging
setup, error handling -- are represented as methods. Individual
tools can extend, override or reuse the defaults as they see fit.

The ipa-ldap-updater has two modes (normal and --upgrade) that
don't share much functionality. They are represented by separate
classes. Option parsing, and selecting which class to run, happens
before they're instantiated.

All code is moved to importable modules to aid future testing. The
only thing that remains in the ipa-ldap-updater script is a two-line
call to the library.

First part of the work for:
https://fedorahosted.org/freeipa/ticket/2652

1 files changed, 229 insertions, 0 deletions

diff --git a/ipapython/admintool.py b/ipapython/admintool.py
new file mode 100644
index 000000000..60096e083
--- /dev/null
+++ b/ipapython/admintool.py
@@ -0,0 +1,229 @@
+# 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):
+        self.msg = msg
+        self.rval = rval
+
+    def __str__(self):
+        return self.msg or ''
+
+
+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
+            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)