resource/aws_elasticache_replication_group: Migrate from availability_zones TypeSet attribute to preferred_cache_cluster_azs TypeList attribute

[gdavison]

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Description

When creating a Redis cluster without sharding ("Cluster Mode Disabled" in AWS terminology), it is possible to specify a list of availability zones in which to place the cluster nodes. In the AWS API, the order of the list matters: the first AZ in the list is the primary AZ for the cluster, and the remainder of the nodes are assigned in order. The number of AZs in the list must match the number of nodes, and duplicates are allowed.

As currently implemented in the AWS Provider, the parameter availability_zones is of TypeSet, where order is not guaranteed and duplicates are not permitted. This means that the practitioner has no control over the location of the primary node and there can be at most one node in a given AZ.

Additionally, the current parameter name, availability_zones, does not match the AWS API parameter name PreferredCacheClusterAZs.

A new parameter preferred_cache_cluster_azs of TypeList should be added to aws_elasticache_replication_group. Changes to aws_elasticache_replication_group should not be marked ForceNew, as the primary AZ, the order of AZs, and the number of AZs can be changed in-place.

availability_zones will be removed as part of #18439.

Specifying AZs for sharded ("Cluster Mode Enabled" in AWS terminology) clusters is described in #5118.

References

• Replaces resource/aws_elasticache_replication_group: Migrate from availability_zones TypeSet attribute to preferred_availability_zones TypeList attribute #5104

[github-actions]

This functionality has been released in v4.0.0 of the Terraform AWS Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

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