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Description

This policy identifies AWS OpenSearch Domains that do not adhere to high-availability best practices, specifically the requirement for a minimum of three data nodes and the use of Zone Awareness.

Rationale​

High availability in AWS OpenSearch Service is achieved through redundancy and fault isolation across Availability Zones:

  1. Zone Awareness: When enabled, OpenSearch distributes nodes and their associated shards across two or three Availability Zones (AZs). This design ensures that the failure of a single AZ does not result in data loss or a complete service outage.
  2. Instance Count: A minimum of three data nodes is recommended for production environments. This configuration supports quorum-based master elections and ensures that the cluster remains operational with adequate capacity if a node or an Availability Zone becomes unavailable.

Impact​

If Zone Awareness is disabled or the instance count is insufficient, the OpenSearch domain becomes a single point of failure. Hardware issues, node failures, or Availability Zone disruptions may cause the cluster to enter a Red state, resulting in partial or complete loss of data availability.

Audit​

This policy flags an AWS OpenSearch Domain as INCOMPLIANT when either of the following conditions is met:

  • Cluster Config: Zone Awareness Enabled is set to false, or
  • Cluster Config: Instance Count is less than 3