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HROLLER(1) Ganeti | Version @GANETI_VERSION@

============================================

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 (currenlty

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**\(7) 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.

\--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 non-redundant instance a node

  where it can be evacuated to.

BUGS

----

Offline nodes should be ignored.

If instances are online the tool should refuse to do offline rolling

maintenances, unless explicitly requested.

End-to-end shelltests should be provided.

Online rolling maintenances (where instance need not be shut down, but

are migrated from node to node) are not supported yet. Hroller by design

should support them both with and without secondary node replacement.

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

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