hail

Langue: en

Version: 335730 (ubuntu - 24/10/10)

Section: 1 (Commandes utilisateur)

NAME

hail - Ganeti IAllocator plugin

SYNOPSIS

hail input-file

hail --version

DESCRIPTION

hail is a Ganeti IAllocator plugin that allows automatic instance placement and automatic instance secondary node replacement 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 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 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 algoritm is non-trivial with regard to cluster size.

For node evacuations (multi-evacuate mode), we iterate over all instances which live as secondaries on those nodes and try to relocate them using the single-instance relocation algorithm.

In all cases, the cluster scoring is identical to the hbal algorithm.

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 confidered 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.

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).

SEE ALSO

hbal(1), hspace(1), hscan(1), ganeti(7), gnt-instance(8), gnt-node(8)

Copyright (C) 2009 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.