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       hail - Ganeti IAllocator plugin


       hail input-file

       hail --version


       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.

       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.


       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.


       The  exist  status  of the command will be zero, unless for some reason
       the algorithm fatally failed (e.g. wrong node or instance data).


       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.