PUT /_cluster/settings

With specifications in the request body, this API call can update cluster settings. Updates to settings can be persistent, meaning they apply across restarts, or transient, where they don’t survive a full cluster restart.

You can reset persistent or transient settings by assigning a null value. If a transient setting is reset, the first one of these values that is defined is applied:

The order of precedence for cluster settings is:

It’s best to set all cluster-wide settings with the settings API and use the elasticsearch.yml file only for local configurations. This way you can be sure that the setting is the same on all nodes. If, on the other hand, you define different settings on different nodes by accident using the configuration file, it is very difficult to notice these discrepancies.

An example of a persistent update:

PUT /_cluster/settings
{
    "persistent" : {
        "indices.recovery.max_bytes_per_sec" : "50mb"
    }
}

An example of a transient update:

PUT /_cluster/settings?flat_settings=true
{
    "transient" : {
        "indices.recovery.max_bytes_per_sec" : "20mb"
    }
}

The response to an update returns the changed setting, as in this response to the transient example:

{
    ...
    "persistent" : { },
    "transient" : {
        "indices.recovery.max_bytes_per_sec" : "20mb"
    }
}

This example resets a setting:

PUT /_cluster/settings
{
    "transient" : {
        "indices.recovery.max_bytes_per_sec" : null
    }
}

The response does not include settings that have been reset:

{
    ...
    "persistent" : {},
    "transient" : {}
}

You can also reset settings using wildcards. For example, to reset all dynamic indices.recovery settings:

PUT /_cluster/settings
{
    "transient" : {
        "indices.recovery.*" : null
    }
}