Shrink API is used to shrink an existing index into a new index with a fewer number of shards. If the data in the index is no longer changing, the index can be optimized for search and aggregation by reducing the number of shards. The number of shards in the destination index must be a factor of the original index. For example, an index with 6 primary shards can be shrunk into 3, 2, or 1 shards. When working with time-sensitive data, such as logs, data is only indexed into the current indexes and older indexes are mostly read only. Shrink API doesn't re-index the document; it simply relinks the index segments to the new index.
To shrink an index, the index should be marked as read-only, and either a primary or a replica of all the shards of the index should be moved to one node. We can force the allocation of the shards to one node and mark it as read only as shown...
