Ganeti Cluster tools (htools)
=============================

These are some simple cluster tools for fixing common problems. Right
now N+1 and rebalancing are included. Starting with version 0.1.0,
only Ganeti 2.0 is supported.


Cluster rebalancer
------------------

Compared to the N+1 solver, the rebalancer uses a very simple algorithm:
repeatedly try to move each instance one step, so that the cluster score
becomes better. We stop when no further move can improve the score.

For algorithm details and usage, see the man page hbal(1).

Cluster N+1 solver
------------------

This program runs a very simple brute force algorithm over the instance
placement space in order to determine the shortest number of replace-disks
needed to fix the cluster. Note this means we won't get a balanced cluster,
just one that passes N+1 checks.

For algorithm details and usage, see the man page hn1(1). **Note**:
this program is deprecated, hbal should be used instead.

IAllocator plugin
-----------------

The ``hail`` iallocator plugin can be used for allocations of mirrored
and non-mirrored instances and for relocations of mirrored
instances. It needs to be installed in Ganeti's iallocator search
path—usually ``/usr/lib/ganeti/iallocators`` or
``/usr/local/lib/ganeti/iallocators``.

Integration with Ganeti
-----------------------

The ``hbal`` and ``hn1`` programs can either get their input from text
files, or online from a cluster via RAPI. For online collection via
RAPI, the "-m" argument to both hn1 and hbal should specify the
cluster or master node name. ``hail`` uses the standard iallocator API
and thus doesn't need any special setup (just needs to be installed in
the right directory).

For text files, a separate tool (hscan) is provided to automate their
gathering if RAPI is available, which is better since it can extract
more precise information. In case RAPI is not usable for whatever
reason, the following two commands should be run::

    gnt-node list -oname,mtotal,mnode,mfree,dtotal,dfree,offline \
      --separator '|' --no-headers > nodes
    gnt-instance list -oname,admin_ram,sda_size,status,pnode,snodes \
      --separator '|' --no-head > instances

These two files should be saved under the names of *nodes* and
*instances*.

Installation
------------

If installing from source, you need a working ghc compiler (6.8 at
least) and some extra Haskell libraries which usually need to be
installed manually:

- json
- curl

Once these are available, just typing *make* in the top-level
directory should be enough.

Internal (implementation) documentation is available in the ``apidoc``
directory.