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Allow nodetool cms reconfigure to ignore specific hosts - #5085

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Allow nodetool cms reconfigure to ignore specific hosts#5085
nvharikrishna wants to merge 1 commit into
apache:cassandra-6.0from
nvharikrishna:21627-cms-reconfigure-ignore-6.0

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(Same as #5084 , but for cassandra-6.0 branch)


Add a --ignore option to nodetool cms reconfigure. Hosts given to it are excluded from the new CMS, on top of any nodes that are already down.

This helps when shrinking a cluster. Today, decommissioning a CMS member hands that role to another node which may itself be due for decommission, so the CMS has to be reconfigured again and again. Excluding the departing nodes up front keeps CMS membership stable for the whole shrink, because decommissioning a node that is not a CMS member does not trigger a reconfiguration.

The ignore list applies to that one command only. It is not stored, so cms describe still reports whether the CMS matches the nodes currently in the cluster.

patch by nvharikrishna; reviewed by for CASSANDRA-21627

CASSANDRA-21627

Add a --ignore option to nodetool cms reconfigure. Hosts given to it are
excluded from the new CMS, on top of any nodes that are already down.

This helps when shrinking a cluster. Today, decommissioning a CMS member
hands that role to another node which may itself be due for decommission,
so the CMS has to be reconfigured again and again. Excluding the departing
nodes up front keeps CMS membership stable for the whole shrink, because
decommissioning a node that is not a CMS member does not trigger a
reconfiguration.

The ignore list applies to that one command only. It is not stored, so
cms describe still reports whether the CMS matches the nodes currently in
the cluster.

patch by nvharikrishna; reviewed by  <Reviewers> for CASSANDRA-21627
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