Modify default number of Elasticsearch shards

Question

If I have a 15 node cluster, do I have to change the

index.number_of_shards

value on all 15 nodes, and restart them, before the new value comes into effect for new indexes?

Answer 1

That is right changing index.number_of_shards defaults in config file would involve changing the setting on all nodes and then restarting the instance ideally following the guidelines for rolling restarts.

However if that is not an option and if explicitly specifying the number_of_shards in the settings while creating the new index is not ideal then the workaround would be using index templates

Example:

One can create an index_defaults default as below

PUT /_template/index_defaults 
{
  "template": "*", 
  "settings": {
    "number_of_shards": 4
  }
}

This applies the setting specified in index_defaults template to all new indexes.