Miscellaneous cluster settingsedit

Metadataedit

An entire cluster may be set to read-only with the following dynamic setting:

cluster.blocks.read_only
Make the whole cluster read only (indices do not accept write operations), metadata is not allowed to be modified (create or delete indices).
cluster.blocks.read_only_allow_delete
Identical to cluster.blocks.read_only but allows to delete indices to free up resources.
Warning

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.

Index Tombstonesedit

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:

cluster.indices.tombstones.size
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 last cluster.indices.tombstones.size deletes, 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.

Loggeredit

The settings which control logging can be updated dynamically with the logger. prefix. For instance, to increase the logging level of the indices.recovery module to DEBUG, issue this request:

PUT /_cluster/settings
{
  "transient": {
    "logger.org.elasticsearch.indices.recovery": "DEBUG"
  }
}