-Ganeti Cluster tools (htools)
-=============================
+Ganeti Cluster tools (ganeti-htools)
+====================================
-These are some simple cluster tools for fixing common problems. Right
-now N+1 and rebalancing are included.
+These are some simple cluster tools for fixing common allocation
+problems on Ganeti 2.0 clusters.
+Note that these tools are most useful for bigger cluster sizes
+(e.g. more than five or ten machines); at lower sizes, the
+computations they do can also be done manually.
-Cluster N+1 solver
-------------------
+Most of the tools revolve around the concept of keeping the cluster
+N+1 compliant: this means that in case of failure of any node, the
+instances affected can be failed over (via ``gnt-node failover`` or
+``gnt-instance failover``) to their secondary node, and there is
+enough memory reserved for this operation without needing to shutdown
+other instances or rebalance the cluster.
-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.
+**Quick start** (see the installation section for more details):
-For algorithm details and usage, see the man page hn1(1).
+- (have the ghc compiler and the prerequisite libraries installed)
+- make
+- ./hbal -m $cluster -C -p
+- look at the original and final cluster layout, and if acceptable,
+ execute the given commands
+
+
+Available tools
+---------------
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
+The rebalancer uses a simple algorithm to try to get the nodes of the
+cluster as equal as possible in their resource usage. It tries to
+repeatedly 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
------------------------
+IAllocator plugin
+~~~~~~~~~~~~~~~~~
-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.
+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``, and after that it can be used
+via ganeti's ``--iallocator`` option (in various gnt-node/gnt-instance
+commands). See the man page hail(1) for more details.
-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::
+Cluster capacity estimator
+~~~~~~~~~~~~~~~~~~~~~~~~~~
- gnt-node list -oname,mtotal,mnode,mfree,dtotal,dfree \
+The ``hspace`` program will, given an input instance specification,
+estimate how many instances of those type can be place on the cluster
+before it will become full (as in any new allocation would fail N+1
+checks). For more details, see the man page hspace(1).
+
+
+Integration with Ganeti
+-----------------------
+
+The ``hbal`` and ``hspace`` programs can either get their input from
+text files, locally from the master daemon (when run on the master
+node of a cluster), or remote from a cluster via RAPI. The "-L"
+argument enables local collection (with an optional path to the unix
+socket). For online collection via RAPI, the "-m" argument should
+specify the cluster or master node name. Only ``hbal`` and ``hspace``
+use these arguments, ``hail`` uses the standard iallocator API and
+thus doesn't need any special setup (just needs to be installed in the
+right directory).
+
+For generating the 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,ctotal,offline \
--separator '|' --no-headers > nodes
- gnt-instance list -oname,admin_ram,sda_size,status,pnode,snodes \
+ gnt-instance list -oname,be/memory,sda_size,be/vcpus,status,pnode,snodes \
--separator '|' --no-head > instances
-These two files should be saved under the names of *nodes* and *instances*.
+These two files should be saved under the names of *nodes* and
+*instances*.
+
+The ``hail`` program gets its data automatically from Ganeti when used
+as described in its section.
Installation
------------
least) and some extra Haskell libraries which usually need to be
installed manually:
-- json
-- curl
+- json (http://hackage.haskell.org/cgi-bin/hackage-scripts/package/json)
+- curl (http://hackage.haskell.org/cgi-bin/hackage-scripts/package/curl)
-One these are available, just typing *make* in the top-level directory
-should be enough.
+Once these are installed, just typing *make* in the top-level
+directory should be enough.
+
+Only the ``hail`` program needs to be installed in a specific place,
+the other tools are not location-dependent.
+
+For running the (admittedly small) unittest suite (via *make check*),
+the QuickCheck version 1 library is needed.
Internal (implementation) documentation is available in the ``apidoc``
directory.
+
+.. Local Variables:
+.. mode: rst
+.. End:
projects / ganeti-local / blobdiff