Admin Indices Update Settings

Change specific index level settings in real time.

The REST endpoint is /_settings (to update all indices) or {index}/_settings to update one (or more) indices settings. The body of the request includes the updated settings, for example:

{
    "index" : {
        "number_of_replicas" : 4
    }
}

The above will change the number of replicas to 4 from the current number of replicas. Here is a curl example:

curl -XPUT 'localhost:9200/my_index/_settings' -d '
{
    "index" : {
        "number_of_replicas" : 4
    }
}
'

Below is the list of settings that can be changed using the update settings API:

Setting	Description
index.number_of_replicas	The number of replicas each shard has.
index.auto_expand_replicas	Set to an actual value (like 0-all) or false to disable it.
index.refresh_interval	The async refresh interval of a shard.
index.compound_format	The format of the index files (only applies to newly created segments).
index.merge.policy.merge_factor	The merge factor of a Lucene index.
index.term_index_interval	The Lucene index term interval. Only applies to newly created docs.
index.term_index_divisor	The Lucene reader term index divisor.
index.translog.flush_threshold_ops	When to flush based on operations.
index.translog.flush_threshold_size	When to flush based on translog (bytes) size.
index.translog.flush_threshold_period	When to flush based on a period of not flushing.
index.translog.disable_flush	Disables flushing. Note, should be set for a short interval and then enabled.
index.cache.filter.max_size	The maximum size of filter cache (per segment in shard). Set to -1 to disable.
index.cache.filter.expire	The expire after access time for filter cache. Set to -1 to disable.

Bulk Indexing Usage

For example, the update settings API can be used to dynamically change the index from being more performant for bulk indexing, and then move it to more real time indexing state. Before the bulk indexing is started, use:

curl -XPUT localhost:9200/test/_settings -d '{
    "index" : {
        "refresh_interval" : "-1",
        "merge.policy.merge_factor" : 30
    }
}'

(Another optimization option is to start the index without any replicas, and only later adding them, but that really depends on the use case).

Then, once bulk indexing is done, the settings can be updated (back to the defaults for example):

curl -XPUT localhost:9200/test/_settings -d '{
    "index" : {
        "refresh_interval" : "1s",
        "merge.policy.merge_factor" : 10
    }
}'

And, an optimize should be called:

curl -XPOST 'http://localhost:9200/test/_optimize?max_num_segments=5'