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.

       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.  Currently 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 (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.

       For allocation on node groups with exclusive storage, the lost-allocations metrics is used
       instead to determine 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 quering MonDs
              over the network.  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 ommitted when searching  for  possible
              allocations.   In  this  way  a  useful  decission  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 allocation 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  filename.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 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).

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  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-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-storage(8) (storage 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-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).

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