NAME¶
hail - Ganeti IAllocator plugin
SYNOPSIS¶
hail [
-t file |
--simulate spec ]
[options...]
input-file
hail --version
DESCRIPTION¶
hail is a Ganeti IAllocator plugin that implements the instance placement and
movement using the same algorithm as
hbal(1).
The program takes input via a JSON-file containing current cluster state and the
request details, and output (on stdout) a JSON-formatted response. In case of
critical failures, the error message is printed on stderr and the exit code is
changed to show failure.
ALGORITHM¶
The program uses a simplified version of the hbal algorithm.
For single-node allocations (non-mirrored instances), again we select the node
which, when chosen as the primary node, gives the best score.
For dual-node allocations (mirrored instances), we chose the best pair; this is
the only choice where the algorithm is non-trivial with regard to cluster
size.
For relocations, we try to change the secondary node of the instance to all the
valid other nodes; the node which results in the best cluster score is chosen.
For node changes (
change-node mode), we currently support DRBD instances
only, and all three modes (primary changes, secondary changes and all node
changes).
For group moves (
change-group mode), again only DRBD is supported, and
we compute the correct sequence that will result in a group change; job
failure mid-way will result in a split instance. The choice of node(s) on the
target group is based on the group score, and the choice of group is based on
the same algorithm as allocations (group with lowest score after placement).
The deprecated
multi-evacuate modes is no longer supported.
In all cases, the cluster (or group) scoring is identical to the hbal algorithm.
OPTIONS¶
The options that can be passed to the program are as follows:
- -p, --print-nodes
- Prints the before and after node status, in a format
designed to allow the user to understand the node's most important
parameters. See the man page htools(1) for more details about this
option.
- -t datafile, --text-data=datafile
- The name of the file holding cluster information, to
override the data in the JSON request itself. This is mostly used for
debugging.
- --simulate description
- Similar to the -t option, this allows overriding the
cluster data with a simulated cluster. For details about the description,
see the man page hspace(1).
- -S filename,
--save-cluster=filename
- If given, the state of the cluster before and the
iallocator run is saved to a file named filename.pre-ialloc,
respectively filename.post-ialloc. This allows re-feeding the
cluster state to any of the htools utilities.
- -v
- This option increases verbosity and can be used for
debugging in order to understand how the IAllocator request is parsed; it
can be passed multiple times for successively more information.
CONFIGURATION¶
For the tag-exclusion configuration (see the manpage of hbal for more details),
the list of which instance tags to consider as exclusion tags will be read
from the cluster tags, configured as follows:
- •
- get all cluster tags starting with
htools:iextags:
- •
- use their suffix as the prefix for exclusion tags
For example, given a cluster tag like
htools:iextags:service, all
instance tags of the form
service:X will be considered as exclusion
tags, meaning that (e.g.) two instances which both have a tag
service:foo will not be placed on the same primary node.
OPTIONS¶
The options that can be passed to the program are as follows:
EXIT STATUS¶
The exist status of the command will be zero, unless for some reason the
algorithm fatally failed (e.g. wrong node or instance data).
REPORTING BUGS¶
Report bugs to project website (
http://code.google.com/p/ganeti/) or contact the
developers using the Ganeti mailing list (ganeti@googlegroups.com).
SEE ALSO¶
Ganeti overview and specifications:
ganeti(7) (general overview),
ganeti-os-interface(7) (guest OS definitions).
Ganeti commands:
gnt-cluster(8) (cluster-wide commands),
gnt-job(8) (job-related commands),
gnt-node(8) (node-related
commands),
gnt-instance(8) (instance commands),
gnt-os(8) (guest
OS commands),
gnt-group(8) (node group commands),
gnt-backup(8)
(instance import/export commands),
gnt-debug(8) (debug commands).
Ganeti daemons:
ganeti-watcher(8) (automatic instance restarter),
ganeti-cleaner(8) (job queue cleaner),
ganeti-noded(8) (node
daemon),
ganeti-masterd(8) (master daemon),
ganeti-rapi(8)
(remote API daemon).
Ganeti htools:
htools(1) (generic binary),
hbal(1) (cluster
balancer),
hspace(1) (capacity calculation),
hail(1) (IAllocator
plugin),
hscan(1) (data gatherer from remote clusters).
COPYRIGHT¶
Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Google Inc. Permission is
granted to copy, distribute and/or modify under the terms of the GNU General
Public License as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
On Debian systems, the complete text of the GNU General Public License can be
found in /usr/share/common-licenses/GPL.