Migrating Elasticsearch Index Lifecycle Management Policies to OpenSearch Index State Management Policies

[sumobrian]

Is your feature request related to a problem?

When migrating from Elasticsearch to OpenSearch, users often face issues with Index Lifecycle Management policies, as ILM is not directly supported in OpenSearch. OpenSearch uses Index State Management (ISM), which operates differently from ILM in terms of phases, actions, and transitions. This creates challenges for users who need to manually adapt their ILM configurations to ISM policies during migrations. Additionally, different versions of Elasticsearch may have variations in their ILM implementations, requiring careful mapping to equivalent ISM states.

What solution would you like?

We will add a feature in the OpenSearch Migrations repository to automate the conversion of ILM policies from Elasticsearch to ISM policies in OpenSearch. The tool should:

• Identify the existing ILM policies in the source Elasticsearch cluster.
• Map ILM phases and actions (e.g., hot, warm, cold, delete) to corresponding ISM states and actions.
• Handle version-specific nuances, as ILM implementations and features may differ between Elasticsearch versions.
• Generate ISM policies in a format compatible with OpenSearch, allowing users to seamlessly transition their lifecycle management configurations.

What alternatives have you considered?

• Manual Migration: Users can manually create ISM policies by referring to their existing ILM configurations. However, this approach is prone to errors and requires deep knowledge of both ILM and ISM implementations, which may vary between different versions of Elasticsearch and OpenSearch.
• Custom Scripts: Developing custom scripts to convert ILM policies to ISM policies based on each organization's specific requirements. However, this increases the complexity and workload on users and may not account for all version-specific nuances automatically.

Do you have any additional context?

ILM and ISM differ in how they manage index lifecycles. ILM uses fixed phases (hot, warm, cold, delete), while ISM offers more flexible state-based management. This feature would aim to bridge these differences, making it easier for users migrating from Elasticsearch to OpenSearch to retain their lifecycle policies and configurations without manual intervention. Additionally, the tool should consider Elasticsearch-specific features and version-specific variations, ensuring compatibility and consistency during the migration process.