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 al‐
       gorithm 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.

       If the input file name is - (a single minus sign), then the request data will be read from stdin.

       Apart from input data, hail collects data over the network from all MonDs with the --mond  option.   Cur‐
       rently it uses only data produced by the CPUload collector.

   ALGORITHM
       On  regular  node  groups, the program uses a simplified version of the hbal algorithm; for allocation on
       node groups with exclusive storage see below.

       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  (pri‐
       mary 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 al‐
       gorithm 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.

       For allocation on node groups with exclusive storage, the lost-allocations metrics is used instead to de‐
       termine  which  node  to allocate an instance on.  For a node the allocation vector is the vector of, for
       each instance policy interval in decreasing order, the number of instances minimally compliant with  that
       interval that still can be placed on that node.  The lost-allocations vector for an instance on a node is
       the  difference  of  the  allocation  vectors for that node before and after placing the instance on that
       node.  The lost-allocations metrics is the lost allocation vector followed by the remaining disk space on
       the chosen node, all compared lexicographically.

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.  The format of the file is described in the man page htools(1).

       --mond=*yes|no*
              If  given  the  program will query all MonDs to fetch data from the supported data collectors over
              the network.

       --mond-data datafile
              The name of the file holding the data provided by MonD, to override querying MonDs over  the  net‐
              work.  This is mostly used for debugging.  The file must be in JSON format and present an array of
              JSON  objects  , one for every node, with two members.  The first member named node is the name of
              the node and the second member named reports is an array of report objects.   The  report  objects
              must be in the same format as produced by the monitoring agent.

       --ignore-dynu
              If given, all dynamic utilisation information will be ignored by assuming it to be 0.  This option
              will take precedence over any data passed by the MonDs with the --mond and the --mond-data option.

       --ignore-soft-errors
              If  given, all checks for soft errors will be omitted when searching for possible allocations.  In
              this way a useful decision can be made even in overloaded clusters.

       --no-capacity-checks
              Normally, hail will only consider those allocations where all instances of a node can  immediately
              restarted  should that node fail.  With this option given, hail will check only N+1 redundancy for
              DRBD instances.

       --restrict-allocation-to
              Only consider alloctions on the specified nodes.  This overrides any restrictions given in the al‐
              location request.

       --simulate description
              Backend specification: similar to the -t option, this allows overriding the cluster  data  with  a
              simulated cluster.  For details about the description, see the man page htools(1).

       -S filename, --save-cluster=*filename*
              If  given,  the  state of the cluster before and the iallocator run is saved to a file named file‐
              name.pre-ialloc, respectively filename.post-ialloc.  This allows re-feeding the cluster  state  to
              any of the htools utilities via the -t option.

       -v     This  option increases verbosity and can be used for debugging in order to understand how the IAl‐
              locator 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  in‐
       stance 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).

BUGS

       Networks  (as  configured  by  gnt-network(8)) are not taken into account in Ganeti 2.7.  The only way to
       guarantee that they work correctly is having your networks connected to all  nodegroups.   This  will  be
       fixed in a future version.

REPORTING BUGS

       Report  bugs  to the project's issue tracker (https://github.com/ganeti/ganeti/issues) or contact the de‐
       velopers using the Ganeti mailing list.

SEE ALSO

       Ganeti overview and specifications: ganeti(7) (general overview), ganeti-os-interface(7) (guest OS defin‐
       itions), ganeti-extstorage-interface(7) (external storage providers).

       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-stor‐
       age(8) (storage commands), gnt-group(8) (node group commands), gnt-backup(8) (instance import/export com‐
       mands), 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-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), hinfo(1) (cluster information
       printer), mon-collector(7) (data collectors interface).

COPYRIGHT

       Copyright (C) 2006-2015 Google Inc.  All rights reserved.

       Redistribution and use in source and binary forms, with or without modification, are  permitted  provided
       that the following conditions are met:

       1.   Redistributions  of  source code must retain the above copyright notice, this list of conditions and
       the following disclaimer.

       2.  Redistributions in binary form must reproduce the above copyright notice, this list of conditions and
       the following disclaimer in the documentation and/or other materials provided with the distribution.

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Ganeti                                                                                                   HAIL(1)