Mini Shell

# coding: utf-8

# Copyright © Cloud Linux GmbH & Cloud Linux Software, Inc 2010-2019 All Rights Reserved
#
# Licensed under CLOUD LINUX LICENSE AGREEMENT
# http://cloudlinux.com/docs/LICENSE.TXT
from __future__ import print_function
from __future__ import division
from __future__ import absolute_import
import fcntl
import os

import contextlib
import psutil
import subprocess
import simplejson as json   # because of unicode handling
from abc import ABCMeta, abstractmethod
from time import time

from . import (
    INSTALLING_STATUS,
    REMOVING_STATUS,
    AcquireInterpreterLockError,
)
from future.utils import with_metaclass

from clcommon.utils import is_testing_enabled_repo
from clcommon.group_info_reader import GroupInfoReader


MAX_CACHE_AGE_SEC = 24 * 3600


class PkgManagerError(Exception):
    pass


class BasePkgManager(with_metaclass(ABCMeta, object)):
    """
    Class responsible for all interactions with Yum, interpreter versions
    installation/removal and gathering info about already installed versions
    """

    _testing_repo_enabled_cache = None
    _config_dir = None

    _versions_info = None
    _yum_cmd = None
    _alt_names = None
    _redirect_log = None
    _install_cmd = None
    _remove_cmd = None

    @classmethod
    def run_background(cls, command):
        fnull = open(os.devnull, 'w')
        return subprocess.Popen(
            command,
            stdin=fnull,
            stdout=fnull,
            stderr=fnull,
            shell=True,
            executable='/bin/bash'
        )

    @property
    def _testing_enabled(self):
        if self._testing_repo_enabled_cache is not None:
            return self._testing_repo_enabled_cache

        res = is_testing_enabled_repo()
        self._testing_repo_enabled_cache = res
        return res

    @property
    def _yum_cache_file(self):
        if self._testing_enabled:
            return os.path.join(self._config_dir, 'yum_cache.dat.testing_enabled')
        return os.path.join(self._config_dir, 'yum_cache.dat')

    def update_yum_cache(self):
        groups = GroupInfoReader.get_group_info(self._alt_names)
        groups = list(groups.keys())
        with open(self._yum_cache_file, 'w') as f:
            for group in groups:
                f.write(f'{group}\n')

    def _read_yum_cache(self):
        """Return data from file or None if file is absent or outdated"""
        try:
            stat = os.stat(self._yum_cache_file)
        except OSError:
            return None

        if (time() - stat.st_mtime) > MAX_CACHE_AGE_SEC:
            return None

        return open(self._yum_cache_file).read()

    @staticmethod
    def _remove_silent(f):
        """ Silently remove file ignoring all errors """
        try:
            os.remove(f)
        except (OSError, IOError):
            pass

    @property
    def installed_versions(self):
        """
        Returns list of installed interpreter versions by scanning alt_node_dir
        and cache result. Cache also can be pre-filled at init time for
        testing/debugging purposes
        """
        if self._versions_info is None:
            self._versions_info = self._scan_interpreter_versions()
        return list(self._versions_info.keys())

    def get_full_version(self, maj):
        """
        Should return full interpreter version for a particular major version or
        just fallback to given version if info is not available for any reason.
        This information is taken from the hash map populated during
        installed_packages scan.

        :param maj: Major interpreter version
        :return: Full interpreter version or Major if info is not available
        """
        if self._versions_info is None:
            self._versions_info = self._scan_interpreter_versions()
        try:
            return self._versions_info[maj]['full_version']
        except KeyError:
            return maj

    @property
    def _pid_lock_file(self):
        return os.path.join(self._config_dir, 'yum.pid.lock')

    @property
    def _cache_lock_file(self):
        return os.path.join(self._config_dir, 'yum_cache.pid.lock')

    def _write_yum_status(self, pid, version=None, status=None):
        """
        :param pid: pid of Yum process
        :param version: interpreter version or None for "cache update" case
        :param status: what yum is currently doing(few predefined statuses)
        :return: None
        """
        if not os.path.exists(self._config_dir):
            self._create_config_dirs()
        json.dump({
            'pid': pid,
            'version': str(version),
            'status': status,
            'time': float(time()),
        }, open(self._pid_lock_file, 'w'))

    def _check_yum_in_progress(self):
        ongoing_yum = self._read_yum_status()
        if ongoing_yum is not None:
            return "{} of version '{}' is in progress. " \
                   "Please, wait till it's done"\
                .format(ongoing_yum['status'], ongoing_yum['version'])

    def _read_yum_status(self):
        """
        Result "None" - means installing/removing of our packages is not
        currently in progress. However, it doesn't mean that any other yum
        instance is not running at the same time, but we ok with this
        because our yum process will start processing automatically once
        standard /var/run/yum.pid lock is removed by other process
        :return: None or dict
        """

        if self._pid_lock_file is None:
            raise NotImplementedError()
        try:
            data = json.load(open(self._pid_lock_file))
        except Exception:
            # No file or it's broken:
            self._remove_silent(self._pid_lock_file)
            return None

        if not psutil.pid_exists(data.get('pid')):              #pylint: disable=E1101
            self._remove_silent(self._pid_lock_file)
            return None

        # TODO check timeout and stop it or just run with bash "timeout ..."
        try:
            pid, _ = os.waitpid(data['pid'], os.WNOHANG)
        except OSError:
            # Case when we exit before completion and yum process is no
            # longer our child process
            return data  # still working, wait...

        if pid == 0:  # still working, wait...
            return data

        self._remove_silent(self._pid_lock_file)
        return None  # It was zombie and has already finished

    def format_cmd_string_for_installing(self, version):
        """
        Formatting cmd string for installing package
        :return: formatted cmd string
        :param version: version of interpreter for installing
        :rtype: str
        """

        return self._install_cmd.format(version)

    def format_cmd_string_for_removing(self, version):
        """
        Formatting cmd string for removing package
        :return: formatted cmd string
        :param version: version of interpreter for removing
        :rtype: str
        """

        return self._remove_cmd.format(version)

    def install_version(self, version):
        """Return None or Error string"""
        err = self._verify_action(version)
        if err:
            return err

        if version in self.installed_versions:
            return 'Version "{}" is already installed'.format(version)

        available = self.checkout_available()
        if available is None:
            return ('Updating available versions cache is currently '
                    'in progress. Please, try again in a few minutes')

        if version not in available:
            return ('Version "{}" is not available. '
                    'Please, make sure you typed it correctly'.format(version))

        cmd_string = self.format_cmd_string_for_installing(version)
        p = self.run_background(cmd_string)
        self._write_yum_status(p.pid, version, INSTALLING_STATUS)

    def remove_version(self, version):
        """Return None or Error string"""
        err = self._verify_action(version)
        if err:
            return err

        if version not in self.installed_versions:
            return 'Version "{}" is not installed'.format(version)

        if self.is_interpreter_locked(version):
            return "This version is currently in use by another operation. " \
                   "Please, wait until it's complete and try again"

        if self._is_version_in_use(version):
            return "It's not possible to uninstall version which is " \
                   "currently in use by applications"

        cmd_string = self.format_cmd_string_for_removing(version)
        p = self.run_background(cmd_string)
        self._write_yum_status(p.pid, version, REMOVING_STATUS)

    def in_progress(self):
        """
        Should return version and it's status for versions that is
        currently installing|removing
        """
        ongoing_yum = self._read_yum_status()
        if ongoing_yum is not None and \
                ongoing_yum['status'] in (INSTALLING_STATUS, REMOVING_STATUS,):
            return {
                ongoing_yum['version']: {
                    'status': ongoing_yum['status'],
                    'base_dir': '',
                }
            }
        return None

    @contextlib.contextmanager
    def acquire_interpreter_lock(self, interpreter_version):
        lock_name = self._get_lock_file_path(interpreter_version)

        try:
            lf = open(lock_name, 'w')
        except IOError:
            raise AcquireInterpreterLockError(interpreter_version)

        try:
            fcntl.flock(lf, fcntl.LOCK_EX | fcntl.LOCK_NB)
        except IOError:
            # TODO: try to use LOCK_SH here
            # It's ok if it's already locked because we allow multiple
            # operations for different applications at the same time
            # with the same "--new-version"
            pass

        try:
            yield
        finally:  # Protection from exception in "context code"
            lf.close()

    @abstractmethod
    def checkout_available(self):
        raise NotImplementedError()

    @abstractmethod
    def _scan_interpreter_versions(self):
        raise NotImplementedError()

    @abstractmethod
    def _create_config_dirs(self):
        raise NotImplementedError()

    def is_interpreter_locked(self, interpreter_version):
        lock_name = self._get_lock_file_path(interpreter_version)
        if not os.path.isfile(lock_name):
            return False
        lf = open(lock_name, 'w')
        try:
            fcntl.flock(lf, fcntl.LOCK_EX | fcntl.LOCK_NB)
        except IOError:
            return True
        finally:
            lf.close()
        return False

    @abstractmethod
    def _verify_action(self, version):
        raise NotImplementedError()

    def _get_lock_file_path(self, version):
        raise NotImplementedError()

    @abstractmethod
    def _is_version_in_use(self, version):
        raise NotImplementedError()