Achieving Seamless Upgrade: Reindexing Old Indices in Elasticsearch Without Downtime

Discover how to upgrade Elasticsearch seamlessly without any downtime by reindexing old indices. This step-by-step guide outlines the process, from exporting and adjusting mappings to configuring write indices and performing reindexing. Stay ahead with the latest features while ensuring uninterrupted operations.

As businesses evolve, so must their technological infrastructure. Upgrading essential tools like Elasticsearch is critical for staying competitive and ensuring optimal performance. However, migrating existing data can be a daunting task, especially when downtime is not an option. In this guide, we'll explore how to reindex old indices in Elasticsearch seamlessly, without any disruption to your operations.

Step 1: Export the Mapping of the Old Index

Before embarking on the upgrade journey, the first step is to export the mapping of the old index. This mapping serves as a blueprint for your data structure and is crucial for ensuring compatibility with the upgraded version of Elasticsearch. Run the following command to export the mapping to a JSON file:

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curl localhost:9200/my-index/_mappings > my_index_mapping.json

Step 2: Adjust the Mapping JSON

Open the exported JSON file (my_index_mapping.json) in your preferred text editor. Remove any references to the old index name to ensure seamless compatibility with the new index. Save the modified JSON file once you've made the necessary adjustments.

Step 3: Create a New Index with the Modified Mapping

With the modified mapping in hand, it's time to create a new index that aligns with the upgraded Elasticsearch version. Execute the following command to create the new index (my-new-index) with the updated mapping:

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curl -X PUT localhost:9200/my-new-index -H "Content-type:application/json" -d @my_index_mapping.json

Step 4: Configure the New Index as the Write Index

To ensure uninterrupted write operations during the transition, set the new index (my-new-index) as the write index using an alias. This alias will seamlessly redirect all write operations to the new index. Execute the following command to configure the alias:

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curl -H "Content-Type:application/json" -XPOST localhost:9200/_aliases?pretty -d ' { "actions": [ { "add": { "index": "my-new-index", "alias": "my-index", "is_write_index": true } } ] } '

Step 5: Prepare the Old Indices for Reindexing

To prevent any disruptions or data inconsistencies during the reindexing process, it's crucial to set the old indices to read-only mode. This precautionary step ensures that no changes occur to the old indices while data is being migrated. Execute the following command for each old index (my-index):

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curl -X PUT -H "Content-Type:application/json" localhost:9200/my-index/_settings -d ' { "index.blocks.read_only_allow_delete": true }'

Step 6: Perform the Reindexing

Now that everything is set up, it's time to execute the reindexing process. This step involves migrating data from the old indices to the new index seamlessly. Execute the following command to initiate the reindexing process:

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curl -H "Content-Type:application/json" -XPOST localhost:9200/_reindex?pretty -d' { "source": { "index": "my-index" }, "dest": { "index": "my-new-index" } }'

Conclusion:

Upgrading Elasticsearch doesn't have to be a daunting task, even when dealing with existing data. By following these steps, you can seamlessly reindex old indices without experiencing any downtime. This ensures that your operations remain uninterrupted while you leverage the latest features and enhancements offered by Elasticsearch. If you encounter any challenges or need further assistance during the process, don't hesitate to get in touch, and I'll be happy to help you navigate through the upgrade process smoothly.