mount.py

# Copyright (C) 2015 Red Hat, All rights reserved.
# Original AUTHORS:
#                   William Temple <wtemple@redhat.com>
#                   Brent Baude    <bbaude@redhat.com>
# Augments for POC by:
#                   Alex Collins   <alcollin@redhat.com>

import os
import sys
import docker
import json
import util
from docker_client import DockerClient

""" Module for mounting and unmounting containerized applications. """


class MountError(Exception):

    """Generic error mounting a candidate container."""

    def __init__(self, val):
        self.val = val

    def __str__(self):
        return str(self.val)


class Mount:

    """
    A class which contains backend-independent methods useful for mounting and
    unmounting containers.
    """

    def __init__(self, mountpoint, live=False):
        """
        Constructs the Mount class with a mountpoint.
        Optional: mount a running container live (read/write)
        """
        self.mountpoint = mountpoint
        self.live = live

    def mount(self, identifier, options=[]):
        raise NotImplementedError('Mount subclass does not implement mount() '
                                  'method.')

    def unmount(self):
        raise NotImplementedError('Mount subclass does not implement unmount()'
                                  ' method.')

    # LVM DeviceMapper Utility Methods
    @staticmethod
    def _activate_thin_device(name, dm_id, size, pool):
        """
        Provisions an LVM device-mapper thin device reflecting,
        DM device id 'dm_id' in the docker pool.
        """
        table = '0 {0} thin /dev/mapper/{1} {2}'.format(int(size) / 512,
                                                        pool, dm_id)
        cmd = ['dmsetup', 'create', name, '--table', table]
        r = util.subp(cmd)
        if r.return_code != 0:
            raise MountError('Failed to create thin device: ' + r.stderr)

    @staticmethod
    def _remove_thin_device(name):
        """
        Destroys a thin device via subprocess call.
        """
        r = util.subp(['dmsetup', 'remove', name])
        if r.return_code != 0:
            raise MountError('Could not remove thin device:\n' + r.stderr)

    @staticmethod
    def _is_device_active(device):
        """
        Checks dmsetup to see if a device is already active
        """
        cmd = ['dmsetup', 'info', device]
        dmsetup_info = util.subp(cmd)
        for dm_line in dmsetup_info.stdout.split("\n"):
            line = dm_line.split(':')
            if ('State' in line[0].strip()) and ('ACTIVE' in line[1].strip()):
                return True
        return False

    @staticmethod
    def _get_fs(thin_pathname):
        """
        Returns the file system type (xfs, ext4) of a given device
        """
        cmd = ['lsblk', '-o', 'FSTYPE', '-n', thin_pathname]
        fs_return = util.subp(cmd)
        return fs_return.stdout.strip()

    @staticmethod
    def mount_path(source, target, optstring='', bind=False):
        """
        Subprocess call to mount dev at path.
        """
        cmd = ['mount']
        if bind:
            cmd.append('--bind')
        if optstring:
            cmd.append('-o')
            cmd.append(optstring)
        cmd.append(source)
        cmd.append(target)
        r = util.subp(cmd)
        if r.return_code != 0:
            raise MountError('Could not mount docker container:\n' +
                             ' '.join(cmd) + '\n' + r.stderr)

    @staticmethod
    def get_dev_at_mountpoint(mntpoint):
        """
        Retrieves the device mounted at mntpoint, or raises
        MountError if none.
        """
        results = util.subp(['findmnt', '-o', 'SOURCE', mntpoint])
        if results.return_code != 0:
            raise MountError('No device mounted at ' + mntpoint)

        return results.stdout.replace('SOURCE\n', '').strip().split('\n')[-1]

    @staticmethod
    def unmount_path(path):
        """
        Unmounts the directory specified by path.
        """
        r = util.subp(['umount', path])
        if r.return_code != 0:
            raise ValueError(r.stderr)


class DockerMount(Mount):

    """
    A class which can be used to mount and unmount docker containers and
    images on a filesystem location.

    mnt_mkdir = Create temporary directories based on the cid at mountpoint
                for mounting containers
    """

    def __init__(self, mountpoint, live=False, mnt_mkdir=False):
        Mount.__init__(self, mountpoint, live)
        self.client = docker.Client()
        self.docker_client = DockerClient()
        self.mnt_mkdir = mnt_mkdir

    def _create_temp_container(self, iid):
        """
        Create a temporary container from a given iid.

        Temporary containers are marked with a sentinel environment
        variable so that they can be cleaned on unmount.
        """
        try:
            return self.docker_client.create_container(iid)
        except docker.errors.APIError as ex:
            raise MountError('Error creating temporary container:\n' + str(ex))

    def _clone(self, cid):
        """
        Create a temporary image snapshot from a given cid.

        Temporary image snapshots are marked with a sentinel label
        so that they can be cleaned on unmount.
        """
        try:
            iid = self.docker_client.commit(cid)
        except docker.errors.APIError as ex:
            raise MountError(str(ex))
        return self._create_temp_container(iid)

    def _identifier_as_cid(self, identifier):
        """
        Returns a container uuid for identifier.

        If identifier is an image UUID or image tag, create a temporary
        container and return its uuid.
        """

        if self.docker_client.is_a_container(identifier):
            if self.live:
                return identifier
            else:
                return self._clone(identifier)
        elif self.docker_client.is_an_image(identifier):
            return self._create_temp_container(identifier)
        else:
            raise MountError('{} did not match any image or container.'
                             ''.format(identifier))

    @staticmethod
    def _no_gd_api_dm(cid):
        # TODO: Deprecated
        desc_file = os.path.join('/var/lib/docker/devicemapper/metadata', cid)
        desc = json.loads(open(desc_file).read())
        return desc['device_id'], desc['size']

    @staticmethod
    def _no_gd_api_overlay(cid):
        # TODO: Deprecated
        prefix = os.path.join('/var/lib/docker/overlay/', cid)
        ld_metafile = open(os.path.join(prefix, 'lower-id'))
        ld_loc = os.path.join('/var/lib/docker/overlay/', ld_metafile.read())
        return (os.path.join(ld_loc, 'root'), os.path.join(prefix, 'upper'),
                os.path.join(prefix, 'work'))

    def mount(self, identifier, options=[]):
        """
        Mounts a container or image referred to by identifier to
        the host filesystem.
        """
        driver = self.docker_client.info()['Storage Driver']
        driver_mount_fn = getattr(self, "_mount_" + driver,
                                  self._unsupported_backend)
        driver_mount_fn(identifier, options)

        # Return mount path so it can be later unmounted by path
        return self.mountpoint

    def _unsupported_backend(self, identifier='', options=[]):
        # raise MountError('Atomic mount is not supported on the {} docker '
        #                  'storage backend.'
        #                  ''.format(self.client.info()['Driver']))
        driver = self.docker_client.info()['Storage Driver']
        raise MountError('Atomic mount is not supported on the {} docker '
                         'storage backend.'
                         ''.format(driver))

    def _mount_devicemapper(self, identifier, options):
        """
        Devicemapper mount backend.
        """
        if os.geteuid() != 0:
            raise MountError('Insufficient privileges to mount device.')

        if self.live and options:
            raise MountError('Cannot set mount options for live container '
                             'mount.')

        # info = self.client.info()
        info = self.docker_client.info()

        cid = self._identifier_as_cid(identifier)

        if self.mnt_mkdir:
            # If the given mount_path is just a parent dir for where
            # to mount things by cid, then the new mountpoint is the
            # mount_path plus the first 20 chars of the cid
            self.mountpoint = os.path.join(self.mountpoint, cid[:20])
            try:
                os.mkdir(self.mountpoint)
            except Exception as e:
                raise MountError(e)

        # cinfo = self.client.inspect_container(cid)
        cinfo = self.docker_client.inspect(cid)

        if self.live and not cinfo['State']['Running']:
            self._cleanup_container(cinfo)
            raise MountError('Cannot live mount non-running container.')

        options = [] if self.live else ['ro', 'nosuid', 'nodev']

        dm_dev_name, dm_dev_id, dm_dev_size = '', '', ''
        # dm_pool = info['DriverStatus'][0][1]
        dm_pool = info['Pool Name']
        try:
            #FIXME, GraphDriver isn't in inspect container output
            dm_dev_name = cinfo['GraphDriver']['Data']['DeviceName']
            dm_dev_id = cinfo['GraphDriver']['Data']['DeviceId']
            dm_dev_size = cinfo['GraphDriver']['Data']['DeviceSize']
        except:
            # TODO: deprecated when GraphDriver patch makes it upstream
            dm_dev_id, dm_dev_size = DockerMount._no_gd_api_dm(cid)
            dm_dev_name = dm_pool.replace('pool', cid)

        dm_dev_path = os.path.join('/dev/mapper', dm_dev_name)
        # If the device isn't already there, activate it.
        if not os.path.exists(dm_dev_path):
            if self.live:
                raise MountError('Error: Attempted to live-mount unactivated '
                                 'device.')

            Mount._activate_thin_device(dm_dev_name, dm_dev_id, dm_dev_size,
                                        dm_pool)

        # XFS should get nosuid
        fstype = Mount._get_fs(dm_dev_path)
        if fstype.upper() == 'XFS' and 'suid' not in options:
            if 'nosuid' not in options:
                options.append('nosuid')
        try:
            Mount.mount_path(dm_dev_path, self.mountpoint,
                             optstring=(','.join(options)))
        except MountError as de:
            if not self.live:
                Mount._remove_thin_device(dm_dev_name)
            self._cleanup_container(cinfo)
            raise de

    def _mount_overlay(self, identifier, options):
        """
        OverlayFS mount backend.
        """
        if os.geteuid() != 0:
            raise MountError('Insufficient privileges to mount device.')

        if self.live:
            raise MountError('The OverlayFS backend does not support live '
                             'mounts.')
        elif 'rw' in options:
            raise MountError('The OverlayFS backend does not support '
                             'writeable mounts.')

        cid = self._identifier_as_cid(identifier)
        # cinfo = self.client.inspect_container(cid)
        cinfo = self.docker_client.inspect(cid)

        ld, ud, wd = '', '', ''
        try:
            #FIXME, GraphDriver isn't in inspect container output
            ld = cinfo['GraphDriver']['Data']['lowerDir']
            ud = cinfo['GraphDriver']['Data']['upperDir']
            wd = cinfo['GraphDriver']['Data']['workDir']
        except:
            ld, ud, wd = DockerMount._no_gd_api_overlay(cid)

        options += ['ro', 'lowerdir=' + ld, 'upperdir=' + ud, 'workdir=' + wd]
        optstring = ','.join(options)
        cmd = ['mount', '-t', 'overlay', '-o', optstring, 'overlay',
               self.mountpoint]
        status = util.subp(cmd)

        if status.return_code != 0:
            self._cleanup_container(cinfo)
            raise MountError('Failed to mount OverlayFS device.\n' +
                             status.stderr.decode(sys.getdefaultencoding()))

    def _cleanup_container(self, cinfo):
        """
        Remove a container and clean up its image if necessary.
        """
        # I'm not a fan of doing this again here.
        env = cinfo['Config']['Env']
        if (env and '_RHAI_TEMP_CONTAINER' not in env) or not env:
            return

        iid = cinfo['Image']

        # self.client.remove_container(cinfo['Id'])
        self.docker_client.remove_container(cinfo['Id'])

        info = self.docker_client.inspect(iid)


        ##FIXME info['Config'] will be a null value and cause an exception if not RHEL based....
        try:
            if info['Config']:
                if '_RHAI_TEMP_CONTAINER=True' in info['Config']['Env']:
                    #FIXME THIS IS BROKEN
                    self.docker_client.remove_image(iid)
        except:
            pass

        # If we are creating temporary dirs for mount points
        # based on the cid, then we should rmdir them while
        # cleaning up.
        if self.mnt_mkdir:
            try:
                os.rmdir(self.mountpoint)
            except Exception as e:
                raise MountError(e)

    def unmount(self):
        """
        Unmounts and cleans-up after a previous mount().
        """
        # driver = self.client.info()['Driver']
        driver = self.docker_client.info()['Storage Driver']
        driver_unmount_fn = getattr(self, "_unmount_" + driver,
                                    self._unsupported_backend)
        driver_unmount_fn()

    def _unmount_devicemapper(self):
        """
        Devicemapper unmount backend.
        """
        # pool = self.client.info()['DriverStatus'][0][1]
        pool = self.docker_client.info()['Pool Name']
        dev = Mount.get_dev_at_mountpoint(self.mountpoint)

        dev_name = dev.replace('/dev/mapper/', '')
        if not dev_name.startswith(pool.rsplit('-', 1)[0]):
            raise MountError('Device mounted at {} is not a docker container.'
                             ''.format(self.mountpoint))

        cid = dev_name.replace(pool.replace('pool', ''), '')
        try:
            # self.client.inspect_container(cid)
            self.docker_client.inspect(cid)
        except docker.errors.APIError:
            raise MountError('Failed to associate device {0} mounted at {1} '
                             'with any container.'.format(dev_name,
                                                          self.mountpoint))

        Mount.unmount_path(self.mountpoint)
        cinfo = self.docker_client.inspect(cid)

        # Was the container live mounted? If so, done.
        # TODO: Container.Config.Env should be {} (iterable) not None.
        #       Fix in docker-py.
        env = cinfo['Config']['Env']
        if (env and '_RHAI_TEMP_CONTAINER' not in env) or not env:
            return

        Mount._remove_thin_device(dev_name)
        self._cleanup_container(cinfo)

    def _get_overlay_mount_cid(self):
        """
        Returns the cid of the container mounted at mountpoint.
        """
        cmd = ['findmnt', '-o', 'OPTIONS', '-n', self.mountpoint]
        r = util.subp(cmd)
        if r.return_code != 0:
            raise MountError('No devices mounted at that location.')
        optstring = r.stdout.strip().split('\n')[-1]
        upperdir = [o.replace('upperdir=', '') for o in optstring.split(',')
                    if o.startswith('upperdir=')][0]
        cdir = upperdir.rsplit('/', 1)[0]
        if not cdir.startswith('/var/lib/docker/overlay/'):
            raise MountError('The device mounted at that location is not a '
                             'docker container.')
        return cdir.replace('/var/lib/docker/overlay/', '')

    def _unmount_overlay(self):
        """
        OverlayFS unmount backend.
        """
        if Mount.get_dev_at_mountpoint(self.mountpoint) != 'overlay':
            raise MountError('Device mounted at {} is not an atomic mount.')
        cid = self._get_overlay_mount_cid()
        Mount.unmount_path(self.mountpoint)
        self._cleanup_container(self.docker_client.inspect(cid))