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An entire cluster may be set to read-only with the following dynamic setting:
- Make the whole cluster read only (indices do not accept write operations), metadata is not allowed to be modified (create or delete indices).
Don’t rely on this setting to prevent changes to your cluster. Any user with access to the cluster-update-settings API can make the cluster read-write again.
The cluster state maintains index tombstones to explicitly denote indices that have been deleted. The number of tombstones maintained in the cluster state is controlled by the following property, which cannot be updated dynamically:
Index tombstones prevent nodes that are not part of the cluster when a delete
occurs from joining the cluster and reimporting the index as though the delete
was never issued. To keep the cluster state from growing huge we only keep the
cluster.indices.tombstones.sizedeletes, which defaults to 500. You can increase it if you expect nodes to be absent from the cluster and miss more than 500 deletes. We think that is rare, thus the default. Tombstones don’t take up much space, but we also think that a number like 50,000 is probably too big.