Since all the pieces that composed the proposal in PIP-45 were finally merged and are currently ready for 2.10 release, it is now possible to add other metadata backends that can be used to support a BookKeeper + Pulsar cluster.
One of the popular systems that is most commonly used in alternative of ZooKeeper is Etcd, thus it makes sense to have this as the first non-zookeeper implementation.
Provide a Etcd implementation for the MetadataStore API. This will allow users to deploy Pulsar clusters using Etcd service for the metadata and it will not require the presence of ZooKeeper.
AbstractBatchedMetadataStore class, in order to reuse the transparent batching logic that will be shared with the ZookKeeper implementation.Work in progress: https://github.com/apache/pulsar/pull/13225