Elasticsearch Reindex

By Opster Team

Updated: Jan 28, 2024

| 1 min read


What is reindex in Elasticsearch?

Reindex is the concept of copying existing data from a source index to a destination index which can be inside the same or a different cluster. Elasticsearch has a dedicated endpoint _reindex for this purpose. A reindexing is mostly required for updating mapping or settings.


Reindex data from a source index to destination index in the same cluster:

POST /_reindex?pretty
  "source": {
    "index": "news"
  "dest": {
    "index": "news_v2"


  • Reindex API does not copy settings and mappings from the source index to the destination index. You need to create the destination index with the desired settings and mappings before you begin the reindexing process.
  • The API exposes an extensive list of configuration options to fetch data from the source index, such as query-based indexing and selecting multiple indices as the source index.
  • In some scenarios reindex API is not useful, where reindexing requires complex data processing and data modification based on application logic. In this case, you can write your custom script using Elasticsearch scroll API to fetch the data from source index and bulk API to index data into destination index.

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Related log errors to this ES concept

Failed to shutdown the remote connection
Failed to clear scroll
Giving up on search because it failed with a non-retryable exception
Failed to clear scroll scrollId
Giving up on search because we retried retryCount times without success
Removing read only block on because reindex failed
Giving up on search because we retried times without success
Failed to parse failures array At least one of reason cause must be present
Unexpected error building entity
Failed to build scroll entity
Failed to build clear scroll entity
Error extracting body from response

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