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Reapply ISM policies after snapshot restore Limited availability

Reapply Index State Management (ISM) policies to Aiven for OpenSearch® using a script.

After restoring your snapshot, ISM policies that manage index rollover, retention, and deletion must be reapplied to your indices. These policies are stored in the .opendistro-ism-config index, but the assignments between indices and policies must be reapplied using a script.

What is restored​

The .opendistro-ism-config index stores ISM policy configurations and is restored with the snapshot, but policy assignments to specific indices are stored in the cluster metadata and must be reapplied.

Prerequisites​

  • A machine with network access to Aiven for OpenSearch services
  • Python 3.11 or higher installed
  • Ensure all data indices and the .opendistro-ism-config index are restored from the snapshot
  • Take the snapshot with restore_global_state: true. By default, this setting is false, and you must enable it to restore ISM policy assignments.
warning

  • Snapshot must include global state: Ensure the snapshot is created with restore_global_state: true. If the snapshot was created without the global state, the ISM policy assignments will not be available in the cluster metadata, and the script will fail to reapply the policies.

  • Script can only be run once: After ISM policies are applied, OpenSearch clears the cluster metadata that holds ISM policy assignments. This means you can only run the script once.

Validate index sync before reapplying ISM policies​

Before reapplying ISM policies, ensure the indices are synchronized between the source and target services. Check document counts to confirm they match.

For more details, see the verify the migration section in Migrate data to Aiven for OpenSearch® using snapshots.

Reapply ISM policies​

The script retrieves the ISM policy assignments stored in the cluster state and reapplies them to the corresponding indices.

warning

Potential ISM policy restore error Restoring certain ISM policies may cause an error, such as when a rollover index (for example, x-001 to x-002) already exists from a previous snapshot reload. This error can prevent secondary ISM policies, like deleting index x-001, from being applied. Ensure indices from previous rollovers or other similar situations are handled correctly before reapplying ISM policies.

To reapply ISM policies to indices in Aiven for OpenSearch:

  1. Download the script from the Aiven examples GitHub repository.

  2. Create a JSON configuration file with the connection details for your Aiven for OpenSearch service. Use avnadmin as the user and replace host, port, and password with your service information:

    {
        "host": "target-ip-or-fqdn",
        "port": target-port-number,
        "user": "avnadmin",
        "password": "the password"
    }

  3. Once your configuration file is ready, run the script.

    python avn-re-apply-ism-policies.py --config path-to-config-file

Re-running the ISM script​

You can rerun the ISM script if needed. Use the --force option to bypass the check that prevents it from running more than once.

note

Run the ISM script only after completing all data migration.

Monitor ISM task progress​

Once ISM policies are reapplied, index lifecycle management tasks like rollovers, retention, and deletion resume automatically. To monitor ISM task progress and ensure policies are enforced correctly, run the following command and replace SERVICE_URL with your Aiven for OpenSearch service's URL:

curl -X GET --insecure "$SERVICE_URL/_plugins/_ism/explain?pretty&size=100"

Alternatively, you can verify the status of individual indices:

curl -X GET --insecure "$SERVICE_URL/_plugins/_ism/explain/<index_name>?pretty"