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HROLLER(1) Ganeti | Version @GANETI_VERSION@
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============================================
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NAME
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----
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hroller \- Cluster rolling maintenance scheduler for Ganeti
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SYNOPSIS
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--------
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**hroller** {backend options...} [algorithm options...] [reporting options...]
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**hroller** \--version
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Backend options:
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{ **-m** *cluster* | **-L[** *path* **]** | **-t** *data-file* |
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**-I** *path* }
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Algorithm options:
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**[ -G *name* ]**
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**[ -O *name...* ]**
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Reporting options:
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**[ -v... | -q ]**
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**[ -S *file* ]**
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DESCRIPTION
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-----------
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hroller is a cluster maintenance reboot scheduler. It can calculate
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which set of nodes can be rebooted at the same time while avoiding
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having both primary and secondary nodes being rebooted at the same time.
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ALGORITHM FOR CALCULATING OFFLINE REBOOT GROUPS
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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hroller will view the nodes as vertices of an undirected graph,
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connecting by instances which have both a primary and a secondary node.
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It will then color the graph using a few different heuristics, and
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return the minimum-size color set found. Node with the same color don't
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share an edge, and as such don't have an instance with both primary and
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secondary node on them, so they are safe to be rebooted concurrently.
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OPTIONS
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-------
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Currently only standard htools options are supported. For a description of them
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check **htools**\(7) and **hbal**\(1).
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BUGS
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----
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The master node should be always the last node of the last group, or anyway
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somehow easily identifiable. Right now this is not done.
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Offline nodes should be ignored.
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If instances are online the tool should refuse to do offline rolling
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maintenances, unless explicitly requested.
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End-to-end shelltests should be provided.
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Online rolling maintenances (where instance need not be shut down, but
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are migrated from node to node) are not supported yet. Hroller by design
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should support them both with and without secondary node replacement.
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EXAMPLE
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-------
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Note that these examples may not for the latest version.
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Offline Rolling node reboot output
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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With the default options, the program shows one reboot group per line as
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a comma-separated list.
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    $ hroller
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    'Node Reboot Groups'
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    node1.example.com,node3.example.com,node5.example.com
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    node8.example.com,node6.example.com,node2.example.com
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    node7.example.com,node4.example.com
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.. vim: set textwidth=72 :
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.. Local Variables:
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.. mode: rst
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.. fill-column: 72
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.. End: