Shrink index API

POST /<index>/_shrink/<target-index>

PUT /<index>/_shrink/<target-index>

To make shard allocation easier, we recommend you also remove the index’s replica shards. You can later re-add replica shards as part of the shrink operation.

You can use the following update index settings API request to remove an index’s replica shards, and relocate the index’s remaining shards to the same node.

PUT /my_source_index/_settings
{
  "settings": {
    "index.number_of_replicas": 0,                                
    "index.routing.allocation.require._name": "shrink_node_name"  
  }
}

It can take a while to relocate the source index. Progress can be tracked with the _cat recovery API, or the cluster health API can be used to wait until all shards have relocated with the wait_for_no_relocating_shards parameter.

You can then make the index read-only with the following request using the add index block API:

PUT /my_source_index/_block/write

The shrink index API allows you to shrink an existing index into a new index with fewer primary shards. The requested number of primary shards in the target index must be a factor of the number of shards in the source index. For example an index with 8 primary shards can be shrunk into 4, 2 or 1 primary shards or an index with 15 primary shards can be shrunk into 5, 3 or 1. If the number of shards in the index is a prime number it can only be shrunk into a single primary shard. Before shrinking, a (primary or replica) copy of every shard in the index must be present on the same node.

The current write index on a data stream cannot be shrunk. In order to shrink the current write index, the data stream must first be rolled over so that a new write index is created and then the previous write index can be shrunk.

response = client.indices.shrink(
  index: 'my_source_index',
  target: 'my_target_index',
  body: {
    settings: {
      'index.routing.allocation.require._name' => nil,
      'index.blocks.write' => nil
    }
  }
)
puts response

POST /my_source_index/_shrink/my_target_index
{
  "settings": {
    "index.routing.allocation.require._name": null, 
    "index.blocks.write": null 
  }
}

response = client.indices.shrink(
  index: 'my_source_index',
  target: 'my_target_index',
  body: {
    settings: {
      'index.number_of_replicas' => 1,
      'index.number_of_shards' => 1,
      'index.codec' => 'best_compression'
    },
    aliases: {
      my_search_indices: {}
    }
  }
)
puts response

POST /my_source_index/_shrink/my_target_index
{
  "settings": {
    "index.number_of_replicas": 1,
    "index.number_of_shards": 1, 
    "index.codec": "best_compression" 
  },
  "aliases": {
    "my_search_indices": {}
  }
}