#!/usr/bin/env python # Copyright (c) 2010 Citrix Systems, Inc. # Copyright 2010 United States Government as represented by the # Administrator of the National Aeronautics and Space Administration. # All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); you may # not use this file except in compliance with the License. You may obtain # a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the # License for the specific language governing permissions and limitations # under the License. # # XenAPI plugin for managing glance images # import httplib import os import os.path import pickle import shlex import shutil import subprocess import tempfile import XenAPIPlugin #FIXME(sirp): should this use pluginlib from 5.6? from pluginlib_nova import * configure_logging('glance') CHUNK_SIZE = 8192 KERNEL_DIR = '/boot/guest' def _copy_kernel_vdi(dest, copy_args): vdi_uuid = copy_args['vdi_uuid'] vdi_size = copy_args['vdi_size'] logging.debug("copying kernel/ramdisk file from %s to /boot/guest/%s", dest, vdi_uuid) filename = KERNEL_DIR + '/' + vdi_uuid #make sure KERNEL_DIR exists, otherwise create it if not os.path.isdir(KERNEL_DIR): logging.debug("Creating directory %s", KERNEL_DIR) os.makedirs(KERNEL_DIR) #read data from /dev/ and write into a file on /boot/guest of = open(filename, 'wb') f = open(dest, 'rb') #copy only vdi_size bytes data = f.read(vdi_size) of.write(data) f.close() of.close() logging.debug("Done. Filename: %s", filename) return filename def _download_tarball(sr_path, staging_path, image_id, glance_host, glance_port): """Download the tarball image from Glance and extract it into the staging area. """ conn = httplib.HTTPConnection(glance_host, glance_port) conn.request('GET', '/images/%s' % image_id) resp = conn.getresponse() if resp.status == httplib.NOT_FOUND: raise Exception("Image '%s' not found in Glance" % image_id) elif resp.status != httplib.OK: raise Exception("Unexpected response from Glance %i" % res.status) tar_cmd = "tar -zx --directory=%(staging_path)s" % locals() tar_proc = _make_subprocess(tar_cmd, stderr=True, stdin=True) chunk = resp.read(CHUNK_SIZE) while chunk: tar_proc.stdin.write(chunk) chunk = resp.read(CHUNK_SIZE) _finish_subprocess(tar_proc, tar_cmd) conn.close() def _fixup_vhds(sr_path, staging_path, uuid_stack): """Fixup the downloaded VHDs before we move them into the SR. We cannot extract VHDs directly into the SR since they don't yet have UUIDs, aren't properly associated with each other, and would be subject to a race-condition of one-file being present and the other not being downloaded yet. To avoid these we problems, we use a staging area to fixup the VHDs before moving them into the SR. The steps involved are: 1. Extracting tarball into staging area 2. Renaming VHDs to use UUIDs ('snap.vhd' -> 'ffff-aaaa-...vhd') 3. Linking the two VHDs together 4. Pseudo-atomically moving the images into the SR. (It's not really atomic because it takes place as two os.rename operations; however, the chances of an SR.scan occuring between the two rename() invocations is so small that we can safely ignore it) """ def rename_with_uuid(orig_path): """Rename VHD using UUID so that it will be recognized by SR on a subsequent scan. Since Python2.4 doesn't have the `uuid` module, we pass a stack of pre-computed UUIDs from the compute worker. """ orig_dirname = os.path.dirname(orig_path) uuid = uuid_stack.pop() new_path = os.path.join(orig_dirname, "%s.vhd" % uuid) os.rename(orig_path, new_path) return new_path, uuid def link_vhds(child_path, parent_path): """Use vhd-util to associate the snapshot VHD with its base_copy. This needs to be done before we move both VHDs into the SR to prevent the base_copy from being DOA (deleted-on-arrival). """ modify_cmd = ("vhd-util modify -n %(child_path)s -p %(parent_path)s" % locals()) modify_proc = _make_subprocess(modify_cmd, stderr=True) _finish_subprocess(modify_proc, modify_cmd) def move_into_sr(orig_path): """Move a file into the SR""" filename = os.path.basename(orig_path) new_path = os.path.join(sr_path, filename) os.rename(orig_path, new_path) return new_path def assert_vhd_not_hidden(path): """ This is a sanity check on the image; if a snap.vhd isn't present, then the image.vhd better not be marked 'hidden' or it will be deleted when moved into the SR. """ query_cmd = "vhd-util query -n %(path)s -f" % locals() query_proc = _make_subprocess(query_cmd, stdout=True, stderr=True) out, err = _finish_subprocess(query_proc, query_cmd) for line in out.splitlines(): if line.startswith('hidden'): value = line.split(':')[1].strip() if value == "1": raise Exception( "VHD %(path)s is marked as hidden without child" % locals()) orig_base_copy_path = os.path.join(staging_path, 'image.vhd') if not os.path.exists(orig_base_copy_path): raise Exception("Invalid image: image.vhd not present") base_copy_path, base_copy_uuid = rename_with_uuid(orig_base_copy_path) vdi_uuid = base_copy_uuid orig_snap_path = os.path.join(staging_path, 'snap.vhd') if os.path.exists(orig_snap_path): snap_path, snap_uuid = rename_with_uuid(orig_snap_path) vdi_uuid = snap_uuid # NOTE(sirp): this step is necessary so that an SR scan won't # delete the base_copy out from under us (since it would be # orphaned) link_vhds(snap_path, base_copy_path) move_into_sr(snap_path) else: assert_vhd_not_hidden(base_copy_path) move_into_sr(base_copy_path) return vdi_uuid def _prepare_staging_area_for_upload(sr_path, staging_path, vdi_uuids): """Hard-link VHDs into staging area with appropriate filename ('snap' or 'image.vhd') """ for name, uuid in vdi_uuids.items(): source = os.path.join(sr_path, "%s.vhd" % uuid) link_name = os.path.join(staging_path, "%s.vhd" % name) os.link(source, link_name) def _upload_tarball(staging_path, image_id, glance_host, glance_port): """ Create a tarball of the image and then stream that into Glance using chunked-transfer-encoded HTTP. """ conn = httplib.HTTPConnection(glance_host, glance_port) # NOTE(sirp): httplib under python2.4 won't accept a file-like object # to request conn.putrequest('PUT', '/images/%s' % image_id) # TODO(sirp): make `store` configurable headers = { 'content-type': 'application/octet-stream', 'transfer-encoding': 'chunked', 'x-image-meta-is_public': 'True', 'x-image-meta-status': 'queued', 'x-image-meta-type': 'vhd'} for header, value in headers.iteritems(): conn.putheader(header, value) conn.endheaders() tar_cmd = "tar -zc --directory=%(staging_path)s ." % locals() tar_proc = _make_subprocess(tar_cmd, stdout=True, stderr=True) chunk = tar_proc.stdout.read(CHUNK_SIZE) while chunk: conn.send("%x\r\n%s\r\n" % (len(chunk), chunk)) chunk = tar_proc.stdout.read(CHUNK_SIZE) conn.send("0\r\n\r\n") _finish_subprocess(tar_proc, tar_cmd) resp = conn.getresponse() if resp.status != httplib.OK: raise Exception("Unexpected response from Glance %i" % resp.status) conn.close() def _make_staging_area(sr_path): """ The staging area is a place where we can temporarily store and manipulate VHDs. The use of the staging area is different for upload and download: Download ======== When we download the tarball, the VHDs contained within will have names like "snap.vhd" and "image.vhd". We need to assign UUIDs to them before moving them into the SR. However, since 'image.vhd' may be a base_copy, we need to link it to 'snap.vhd' (using vhd-util modify) before moving both into the SR (otherwise the SR.scan will cause 'image.vhd' to be deleted). The staging area gives us a place to perform these operations before they are moved to the SR, scanned, and then registered with XenServer. Upload ====== On upload, we want to rename the VHDs to reflect what they are, 'snap.vhd' in the case of the snapshot VHD, and 'image.vhd' in the case of the base_copy. The staging area provides a directory in which we can create hard-links to rename the VHDs without affecting what's in the SR. NOTE ==== The staging area is created as a subdirectory within the SR in order to guarantee that it resides within the same filesystem and therefore permit hard-linking and cheap file moves. """ staging_path = tempfile.mkdtemp(dir=sr_path) return staging_path def _cleanup_staging_area(staging_path): """Remove staging area directory On upload, the staging area contains hard-links to the VHDs in the SR; it's safe to remove the staging-area because the SR will keep the link count > 0 (so the VHDs in the SR will not be deleted). """ shutil.rmtree(staging_path) def _make_subprocess(cmdline, stdout=False, stderr=False, stdin=False): """Make a subprocess according to the given command-line string """ kwargs = {} kwargs['stdout'] = stdout and subprocess.PIPE or None kwargs['stderr'] = stderr and subprocess.PIPE or None kwargs['stdin'] = stdin and subprocess.PIPE or None args = shlex.split(cmdline) proc = subprocess.Popen(args, **kwargs) return proc def _finish_subprocess(proc, cmdline): """Ensure that the process returned a zero exit code indicating success """ out, err = proc.communicate() ret = proc.returncode if ret != 0: raise Exception("'%(cmdline)s' returned non-zero exit code: " "retcode=%(ret)i, stderr='%(err)s'" % locals()) return out, err def download_vhd(session, args): """Download an image from Glance, unbundle it, and then deposit the VHDs into the storage repository """ params = pickle.loads(exists(args, 'params')) image_id = params["image_id"] glance_host = params["glance_host"] glance_port = params["glance_port"] uuid_stack = params["uuid_stack"] sr_path = params["sr_path"] staging_path = _make_staging_area(sr_path) try: _download_tarball(sr_path, staging_path, image_id, glance_host, glance_port) vdi_uuid = _fixup_vhds(sr_path, staging_path, uuid_stack) return vdi_uuid finally: _cleanup_staging_area(staging_path) def upload_vhd(session, args): """Bundle the VHDs comprising an image and then stream them into Glance. """ params = pickle.loads(exists(args, 'params')) vdi_uuids = params["vdi_uuids"] image_id = params["image_id"] glance_host = params["glance_host"] glance_port = params["glance_port"] sr_path = params["sr_path"] staging_path = _make_staging_area(sr_path) try: _prepare_staging_area_for_upload(sr_path, staging_path, vdi_uuids) _upload_tarball(staging_path, image_id, glance_host, glance_port) finally: _cleanup_staging_area(staging_path) return "" # Nothing useful to return on an upload def copy_kernel_vdi(session, args): vdi = exists(args, 'vdi-ref') size = exists(args, 'image-size') #Use the uuid as a filename vdi_uuid = session.xenapi.VDI.get_uuid(vdi) copy_args = {'vdi_uuid': vdi_uuid, 'vdi_size': int(size)} filename = with_vdi_in_dom0(session, vdi, False, lambda dev: _copy_kernel_vdi('/dev/%s' % dev, copy_args)) return filename def remove_kernel_ramdisk(session, args): """Removes kernel and/or ramdisk from dom0's file system""" kernel_file = exists(args, 'kernel-file') ramdisk_file = exists(args, 'ramdisk-file') if kernel_file: os.remove(kernel_file) if ramdisk_file: os.remove(ramdisk_file) return "ok" if __name__ == '__main__': XenAPIPlugin.dispatch({'upload_vhd': upload_vhd, 'download_vhd': download_vhd, 'copy_kernel_vdi': copy_kernel_vdi, 'remove_kernel_ramdisk': remove_kernel_ramdisk})