Server Rack Metadata Retrieval and Persistence on Azure Environment

In order to move Pinot to cloud, cloud VM rack metadata awareness is needed for maintenance purpose and disaster recovery. In Azure use cases, fault domain (FD) metadata is needed in the Pinot ecosystem during update or fault events.

In this issue we will focus on retrieving and persisting FD and VM instance information of Azure VM for Pinot servers so that later on we can use this mapping to fit in existing Server Pool Based Instance Assignment or Replica-Group Instance Assignment based strategy for high data availability purpose.

Start by tracing how Pinot servers currently discover and persist instance metadata, then inspect the existing Server Pool Based Instance Assignment and Replica-Group Instance Assignment paths. Define the Azure fault-domain and VM-instance mapping needed by those strategies, and verify that it remains available during update or fault events.

Written by the indexing model from the issue text.