10.158.36.211 and 10.158.36.212 are data nodes?
Yes
Do you bulk index your documents into the same index? If so, are this index shards assigned to all data nodes?
yes, this index has 20 shards, and 3 replicas, which is distributed across 4 nodes.
Is that something like, bulk index will happen only on primary shard and then replicated to other nodes?
Also, as I have 20 shards, the data might me going to only 5 shards, where as those 5 are available on single node? is this possible?