Terraform Enterprise >= v202406-1 (776) fails with "ERR DB index is out of range"

Problem

Terraform Enterprise (TFE) version v202406-1 or newer fails to start and displays the following Redis error.

Health check Failure (redis) : ERR DB index is out of range

Cause

This issue occurs because of a change in TFE v202406-1 that updated its Sidekiq dependency. This update requires an additional Redis database index that is not available in certain Redis server implementations, such as some non-OSS versions of Redis.

As a result, TFE installations that rely on a Redis server without support for multiple database indexes will fail to start.

Solutions

There are three potential solutions depending on your Redis implementation and ability to upgrade Terraform Enterprise.

Solution 1: Migrate to a Multi-Database Redis Implementation

Migrate your Redis data store to an open-source software (OSS) or multi-database compatible implementation. An example of a compatible service is ElastiCache for Redis on AWS.

Solution 2: Upgrade TFE for Redis Enterprise Support

If you are using Redis Enterprise, upgrade to Terraform Enterprise version v202411-1 or later. This version and subsequent releases include updated application settings to support Redis Enterprise.

Solution 3: Upgrade TFE for Redis Sentinel Support

If you are using Redis Sentinel, upgrade to Terraform Enterprise version v202503-1 or later. This version and subsequent releases include updated application settings to support Redis Sentinel.

Additional Information

• Configure Redis data store connection
• v202411-1 Release Notes
• v202503-1 Release Notes