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

These are some simple cluster tools for fixing common problems. Right
now N+1 and rebalancing are included.


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).

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).

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

The 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.

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 \
      --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

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

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