This patch adds the metrics of used/allocable/unallocable resources.

In case we're not enabling limits, let's restrict this to -1, instead of
-1 times the number of pcpus.

Given two cluster states, the new function can answer the following
questions:

- how much resources currently allocated
- how much resources finally allocated (delta from above is how much we
  can actually allocate on the cluster)
- unallocable resources (whatever is left free after the previous step)

We add a new field that tracks the available virtual cpus (expressed as
node cpus times the vcpu ratio).

* master:
  Fix iallocator crash when no solutions exist
  Fix IAllocator multi-evacuate message

Commit 54365762 added an un-guarded `head' call, which crashes with
“Prelude.head: empty list” when no results exists for the per-instance
allocation/relocation calls.

This patch fixes this, and also adds another check for an unguarded
`head' call during parsing of input data.
(cherry picked from commit e41f4ba0)

Since Ganeti passes full host names (not common-suffix-stripped), we
need to remove the suffix from the evac_nodes keys too. In case one node
is not part of the cluster, it will lead to a wrong error message, but
for now it fixes the problem.

Commit 54365762 added an un-guarded `head' call, which crashes with
“Prelude.head: empty list” when no results exists for the per-instance
allocation/relocation calls.

This patch fixes this, and also adds another check for an unguarded
`head' call during parsing of input data.

For some versions of haddock, this can create problems.

This removes some manual checks from a few places in the code with a
single list defined once.

GHC 6.12 has some new warnings, which are valid in most cases except
(IMHO) printf usage.

GHC 6.12 has become more picky about unused imports, so we need to
remove/tighten some of them.

… via a GHC make variable.

This allows hscan to work also with NO_CURL (but only for the local
machine, of course).

Instead of deciding based on secondary node, use the new flag.

This updates the movable flag on instances if they have only one node
(we don't rely on OpMoveInstance) or if they are set so via the command
line options.

This doesn't yet enable the use of the new flag.

This will be used instead of checking for no secondary and for
simplifying 'do not touch' instances.

This adds a short note for the new iallocator mode.

Signed-off-by: Iustin Pop <iustin@google.com>

This patch adds the new request loading/execution (trivial), but the
actual response formatting becomes more difficult as now the response
type differs by request.

Signed-off-by: Iustin Pop <iustin@google.com>

This will be used by the node evacuate IAllocator request type.

Signed-off-by: Iustin Pop <iustin@google.com>

We'll need AllocElement in both Cluster and IAlloc in the future, so we
move it to Node.hs which is imported by both.

Signed-off-by: Iustin Pop <iustin@google.com>

In preparation for multiple responses, we change from Maybe to List
(both used in the container sense).

This allows us to keep the same workflow for all kind of requests.

Signed-off-by: Iustin Pop <iustin@google.com>

Since not all structures will have these keys in the future, we move
them into per-structure keys.

Signed-off-by: Iustin Pop <iustin@google.com>

Signed-off-by: Iustin Pop <iustin@google.com>

This mode restricts the list of instances to be moved to the instances
living on the offline (and drained) nodes.

Signed-off-by: Iustin Pop <iustin@google.com>

Signed-off-by: Iustin Pop <iustin@google.com>

This should be no code change, just reordering of the options.

Signed-off-by: Iustin Pop <iustin@google.com>

In case a secondary node is already N+1 failed, currently the node
selection will accept a node that cannot start (at all) the new instance
as valid. This is wrong, so we add a new simple check to prevent the
case of instance's memory size being higher than the node's free (not
available, which might be lower than 0 for N+1 failures) memory.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

This will make it clearer than many if…then choices.

Currently we test each instance for relocation in checkMove; however, it
is a little more clear if we pass only the relocatable instances to
checkMove. The patch also slightly rewrites (indendation/style) the
second half of the checkMove function.

Currently in the balancing function we do two thing:

- take the decision where to do a new balancing round or not
- and actually computing the balancing round

This is not nice, as the two parts are conceptually separate, so this
patch splits the decision on whether to descend or not to a new
function.