private AmbryReplica fetchBootstrapReplica(String partitionName) {
    // Clear disks tried for bootstrapping this replica
    disksAttemptedForBootstrap.remove(partitionName);
    return (AmbryReplica) bootstrapReplicas.remove(partitionName);
  }
Pop out bootstrap replica (if any) on current instance. A bootstrap replica is a replica dynamically added to
current node at runtime.
@param partitionName the partition name of bootstrap replica.
@return bootstrap replica or {@code null} if not found.
ambry-clustermap/src/main/java/com/github/ambry/clustermap/HelixClusterManager.java