Replace --secondary-node option with an optional parameter for --node.

This patch adds enhanced reporting and much more checks to the disk
replacement (when not switching the secondary).

Reviewed-by: imsnah

Logical volumes can be 'degraded' in a similar way to mirrored devices,
when their underlying storage has gone away (i.e. after a physical disk
failure and 'vgreduce --removemissing'). If we can detect this, we can
prevent mistaken replaces of disks that would use this LV (or its
parent) as source data.

This patch adds support for computing the degraded attribute and
modifies gnt-instance to warn if the LV is virtual.

Reviewed-by: imsnah

Currently, some LUs use logger.Error, others just feedback_fn, etc. This
patch adds three functions to mcpu.Processor than can be used to log
messages to both the log and to the user.

These function will be used to enhance the output of replace-disks for
drbd8 (at least).

Reviewed-by: imsnah

Currently, the mirror operations (add and remove children) test against
the instance's attributes. This patch changes the check tests to work
against the actual status of the device (i.e. live data) which is more
realistic.

The changes are:
  - allow add children if the device doesn't have local storage (even if
    we believe it has)
  - early return from remove children if the device is already without
    local storage

Reviewed-by: imsnah

This patch adds the following functionality:
  - DRBD8 devices can assemble without local storage (done by allowing
    None in the list of children, and making DRBD8 to ignore all
    children if any is None)
  - DRBD8 devices can attach (i.e. identify a device) which is not
    connected to backing storage but to the correct network ports; this
    is a rare case in normal operation (it's what would happen if one
    manually detaches the local disk, and the backing LV still exists)

Reviewed-by: imsnah

This patch enables the bdev.DRBD8 class report a degraded status if the
local disk is missing. This allows `gnt-instance info` to report the
actual situation in this case.

Note that DRBD7 should also behave like this, however the diskless case
is less often met there and we also don't want to change behaviour.

The patch also fixes some docstrings for the GetSyncStatus methods.

Reviewed-by: imsnah

For some cases, we don't have to have access to the children of a device
in order to remove them (e.g. md over lvs, or drbd over lvs). In order
to ease the removal process, skip over finding the child if it provides
a static dev path.

This is needed in order to support removal of children when the
underlying storage has gone away.

Reviewed-by: imsnah

This patch adds a function returning the device path if it is computable
from the disk object (and we don't need to instantiate a bdev object on
the target node in order to compute this). Only LVs support this.

Reviewed-by: imsnah

Reviewed-by: ultrotter

This patch adds a check in the prereq of LUInitCluster for the existence
of the init script.  This allows a clean abort instead of a stack dump.

Based on a report by admin@steibei.net

Reviewed-by: ultrotter

The block device creation process is the following:
  - device create
  - device assembly (on primary or depending on dev_type, on secondary
    too)
  - set sync speed
  - return

The problem is that device assembly after creation was not checked for
errors, and as this is a very unusual case, we did not have problems
with it (or we didn't detect them). The recent DevCacheManager however
tripped on this case (because the dev_path of the device is None if the
assembly fails) and the creation aborted with an unclear error message.

The patch adds a check for the assembly success and aborts the creation
of the device in this case - the error is quite clear in the instance
add, for example. The patch also changes DevCacheManager to log the
cases when dev_path is None but not raise an error (keeping consistent
with the goal that the cache manager should be transparent to the code).

For the record, this error case was detected with a mismatch between
drbd kernel module and utilities.

Reviewed-by: imsnah

This patch fixes some minor pylint warnings (unused variables, wrong
indentation, etc.) and a real bug in the recovery for drbd8 rename
procedure.

Reviewed-by: imsnah

Reviewed-by: schreiberal

Reviewed-by: schreiberal

Reviewed-by: schreiberal

The OS cleanup patches change the wire protocol. Increment the protocol number
by one.

Reviewed-By: iustinp

In order to do this for simplicity we leave the OSFromDisk function as-is and
we convert the eventual exception to an OS object in ganeti-noded. The
unmangling gets simplified and so does the code for checking whether the OS is
valid.

Reviewed-By: iustinp

The functions in ganeti-noded and rpc.py still deal with the fact that an
InvalidOS error could be returned by DiagnoseOS. As this is not the case
anymore simplify their code for the current behavior.

Reviewed-By: iustinp

Modify backend.py so that DiagnoseOS only returns OS objects rather than
InvalidOS errors, and make sure gnt-os understands the new objects. Also delete
the deprecated helper functions from gnt-os.

Reviewed-By: iustinp

Add a new FromInvalidOS static function to objects.OS that makes it easy to
create an object representing a broken OS starting from the relevant exception.

Reviewed-By: iustinp

Till now the OS object just represents a correct OS instance.  Change it so it
can represent a broken one too, by adding a "status" field: if this field is
different from the OS_VALID_STATUS constant the object is considered to be an
invalid OS, the "status" field to be a debugging message, and its boolean
status is set to false.

Reviewed-By: iustinp

This patch adds a '-n' option to burnin that takes a comma-separated
list of nodes to perform the burnin on.

Reviewed-by: ultrotter

call_os_get is never called with a real list of nodes, so there's no point in
it being multi-node. Making it single-node till a usage for multi-node call is
found.

Reviewed-By: iustinp

Remove a wrong "i" and add a missing ")" to the DiagnoseOS function doc string.

Reviewed-By: iustinp

This patch adds a search command for locating tags on all objects of the
cluster using a regex pattern.

Reviewed-by: aat

Also check whether file contents are correct for both “gnt-cluster command” and
“gnt-cluster copyfile”.

Reviewed-by: iustinp

Currently, troubleshooting DRBD problems involves a manual process of going
backwards from the DRBD device to the instance that owns it.

This patch adds a weak (i.e. not guaranteed to be correct or up-to-date)
cache of device to instance. The cache should be, in normal operation,
having correct information as the only time when devices change paths
are when they are started/stopped, and the code in backend.py adds cache
updates to exactly these operations.

The only drawback of this implementation is that we don't fully update
the cache on renames of devices (we clean the old entries but we don't
add new ones). Since the rename changes the path only for LVs (and not
drbd and md), this is less of a problem as the target of this code is
debugging DRBD and MD issues.

The patch writes files named bdev_drbd<N> (or bdev_md<N>,
bdev_xenvg_...) in /var/run/ganeti (more exactly, LOCALSTATEDIR/ganeti).
The files start with 'bdev_' and continue with the path of the device
under /dev/ (this prefix stripped), and contain the following values,
space separated:
  - instance name
  - primary or secondary (depending on how the device is on the primary
    or secondary node)
  - instance visible name: sda or sdb or not_visible, the latter case
    when the device is not the top-level device (i.e. remote_raid1
    templates will have sd[ab] for the md, but not_visible for drbd and
    logical volumes)

The cache is designed to not raise any errors, if there is an I/O error
it will only be logged in the node daemon log file. This is in order to
reduce the possible impact of the cache on the block device activation
and shutdown code.

Reviewed-by: imsnah

Allow burnin to use the new drbd8 template (for which case one needs to
disable replacement of disks, burnin does yet support that with drbd8).

The patch also changes do-replace[12] to no-replace[12] as that is what
they actually do.

Reviewed-by: imsnah

When renaming a logical volume, we should change the dev_path (and other
internal variables) in order to be consistent.

Reviewed-by: imsnah

I forgot a pair of parentheses in that revision which break the common
case. This patch adds them.

Reviewed-by: ultrotter

If the device is unconfigured (not yet did SetDiskID for it ever), it
might have a physical_id of None. This patch fixes that case.

Reviewed-by: ultrotter

Ok, I've been battling with those for a while but it seems
in the end I forgot to get rid of them! :( Doing it explicitely now.

Reviewed-By: iustinp

This patch changes whitespace only. It fixes all the functions in script/gnt-os
by putting a white line at the end of all the function descriptions and
removing it from just before the code.

Reviewed-By: iustinp

Reviewed-By: imsnah

Get rid of the tabulated form and create a simplier indented structure.
Now a valid OS looks something like:

OS: foo [global status: partial valid]
  Node: gsdtest4.euw.corp.google.com, status: valid (path: /usr/local/lib/ganeti/os/foo)
  Node: gsdtest5.euw.corp.google.com, status: valid (path: /usr/local/lib/ganeti/os/foo)
    [hidden] path: /usr/local/lib/ganeti/os2/foo, status: 'ganeti_api_version' file not found (ENOENT)
  Node: gsdtest3.euw.corp.google.com, status: 'ganeti_api_version' file not found (ENOENT) (path: /usr/local/lib/ganeti/os/foo)

Reviewed-By: imsnah

Use both _DiagnoseOSStatus and  _DiagnoseOSPath to calculate the message
associated with the first entry found on a node for an OS. Also call the rename
the relevant variables to _msg rather than just _status to reflect that they
contain a bit more than just the bare status message.

Reviewed-By: imsnah

Make _DiagnoseOSStatus only return a status message for the OS diagnose object
and create a new _DiagnoseOSPath function to get the path out. This will let us
be more flexible in the messages we display to the user.

Reviewed-By: imsnah

Reviewed-by: ultrotter