openstack/placement
Code Issues Proposed changes

Bug#898257 abstract out disk image access methods

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Rather than providing two mutually exlusive image
access methods (loop and qemu-nbd), try each in turn.
This is to prepare for a follow up patch which will
add libguestfs as a method to try.

* nova/virt/mount.py: A new Mount class to abstract the
devce allocation, partition mapping and file sys mounting,
for each access type.
* nova/virt/disk/loop.py: A specialization of the base Mount class
to provide loop back mounting support.
* nova/virt/disk/nbd.py: A specialization of the base Mount class
to provide qemu-nbd mounting support.
* nova/virt/disk/api.py: A new file containing the nova.virt.disk
module interface.
(img_handlers): A new list of access methods to try,
with the order being honored.
(_DiskImage): An internal helper class that uses the plugin classes
above, to provide the operations available on a disk image file.
When mounting, iterate over each access method until one succeeds.
If a hint is provided about a CoW format image, the list of
methods to try will be reduced accordingly.
Note expected errors are no longer raised as exceptions during mounting.
Instead, on failure to mount an image, errors are collated and raised.
Interveining errors are logged in debug mode for successful mounts.
* nova/virt/libvirt/connection.py: Adjust the function parameter
names to be more general, rather than referencing specific
implementations like 'nbd' and 'tune2fs'.
Simplify the destroy_container() by storing and passing
back a reference to the _DiskImage object, which has the
necessary state to unmount.
* nova/utils.py (trycmd): A helper function to both deal with,
commands that issue ignorable warnings to stderr,
and commands that EXIT_SUCCESS while issuing errors to stderr.
nova/virt/xenapi/vm_utils.py: Adjust for the moved virt.disk package

Change-Id: If3a4b1c8f4e2f2e7300a21071340dcc839cb36d7
This commit is contained in:
Pádraig Brady 2011-11-30 17:00:17 +00:00 committed by Pádraig Brady
parent c826f84f56
commit cb155ea378
1 changed files with 30 additions and 0 deletions

30
nova/utils.py

@ -238,6 +238,36 @@ def execute(*cmd, **kwargs):
greenthread.sleep(0)
def trycmd(*args, **kwargs):
"""
A wrapper around execute() to more easily handle warnings and errors.
Returns an (out, err) tuple of strings containing the output of
the command's stdout and stderr. If 'err' is not empty then the
command can be considered to have failed.
:discard_warnings True | False. Defaults to False. If set to True,
then for succeeding commands, stderr is cleared
"""
discard_warnings = kwargs.pop('discard_warnings', False)
try:
out, err = execute(*args, **kwargs)
failed = False
except exception.ProcessExecutionError, exn:
out, err = '', str(exn)
LOG.debug(err)
failed = True
if not failed and discard_warnings and err:
# Handle commands that output to stderr but otherwise succeed
LOG.debug(err)
err = ''
return out, err
def ssh_execute(ssh, cmd, process_input=None,
addl_env=None, check_exit_code=True):
LOG.debug(_('Running cmd (SSH): %s'), ' '.join(cmd))