Provided by: ganeti-htools_2.9.3-1_amd64 
NAME
hroller - Cluster rolling maintenance scheduler for Ganeti
SYNOPSIS
hroller {backend options...} [algorithm options...] [reporting options...]
hroller --version
Backend options:
{ -m cluster | -L[ path ] | -t data-file | -I path }
[ --force ]
Algorithm options:
[ -G name ] [ -O name... ] [ --node-tags tag,.. ] [ --skip-non-redundant ]
[ --offline-maintenance ] [ --ignore-non-redundant ]
Reporting options:
[ -v... | -q ] [ -S file ] [ --one-step-only ] [ --print-moves ]
DESCRIPTION
hroller is a cluster maintenance reboot scheduler. It can calculate which set of nodes
can be rebooted at the same time while avoiding having both primary and secondary nodes
being rebooted at the same time.
For backends that support identifying the master node (currently RAPI and LUXI), the
master node is scheduled as the last node in the last reboot group. Apart from this
restriction, larger reboot groups are put first.
ALGORITHM FOR CALCULATING OFFLINE REBOOT GROUPS
hroller will view the nodes as vertices of an undirected graph, with two kind of edges.
Firstly, there are edges from the primary to the secondary node of every instance.
Secondly, two nodes are connected by an edge if they are the primary nodes of two
instances that have the same secondary node. It will then color the graph using a few
different heuristics, and return the minimum-size color set found. Node with the same
color can then simultaneously migrate all instance off to their respective secondary
nodes, and it is safe to reboot them simultaneously.
OPTIONS
For a description of the standard options check htools(1) and hbal(1).
--force
Do not fail, even if the master node cannot be determined.
--node-tags tag,...
Restrict to nodes having at least one of the given tags.
--full-evacuation
Also plan moving secondaries out of the nodes to be rebooted. For each instance
the move is at most a migrate (if it was primary on that node) followed by a
replace secondary.
--skip-non-redundant
Restrict to nodes not hosting any non-redundant instance.
--offline-maintenance
Pretend that all instances are shutdown before the reboots are carried out. I.e.,
only edges from the primary to the secondary node of an instance are considered.
--ignore-non-redundnant
Pretend that the non-redundant instances do not exist, and only take instances with
primary and secondary node into account.
--one-step-only
Restrict to the first reboot group. Output the group one node per line.
--print-moves
After each group list for each affected instance a node where it can be evacuated
to. The moves are computed under the assumption that after each reboot group, all
instances are moved back to their initial position.
BUGS
If instances are online the tool should refuse to do offline rolling maintenances, unless
explicitly requested.
End-to-end shelltests should be provided.
EXAMPLES
Online Rolling reboots, using tags
Selecting by tags and getting output for one step only can be used for planing the next
maintenance step.
$ hroller --node-tags needsreboot --one-step-only -L
'First Reboot Group'
node1.example.com
node3.example.com
Typically these nodes would be drained and migrated.
$ GROUP=`hroller --node-tags needsreboot --one-step-only --no-headers -L`
$ for node in $GROUP; do gnt-node modify -D yes $node; done
$ for node in $GROUP; do gnt-node migrate -f --submit $node; done
After maintenance, the tags would be removed and the nodes undrained.
Offline Rolling node reboot output
If all instances are shut down, usually larger node groups can be found.
$ hroller --offline-maintainance -L
'Node Reboot Groups'
node1.example.com,node3.example.com,node5.example.com
node8.example.com,node6.example.com,node2.example.com
node7.example.com,node4.example.com
Rolling reboots with non-redundant instances
By default, hroller plans capacity to move the non-redundant instances out of the nodes to
be rebooted. If requested, apropriate locations for the non-redundant instances can be
shown. The assumption is that instances are moved back to their original node after each
reboot; these back moves are not part of the output.
$ hroller --print-moves -L
'Node Reboot Groups'
node-01-002,node-01-003
inst-20 node-01-001
inst-21 node-01-000
inst-30 node-01-005
inst-31 node-01-004
node-01-004,node-01-005
inst-40 node-01-001
inst-41 node-01-000
inst-50 node-01-003
inst-51 node-01-002
node-01-001,node-01-000
inst-00 node-01-002
inst-01 node-01-003
inst-10 node-01-005
inst-11 node-01-004
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-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),
hinfo(1) (cluster information printer), mon-collector(7) (data collectors interface).
COPYRIGHT
Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 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.