We are running HA Elasticsearch in k8s. Recently we found one of the indexes in the Yellow status due to Unassigned shards which leads the whole cluster state to yellow.
Shard of that index status in NODE-A is STARTED and NODE-B is UNASSIGNED.
We checked more using the following API
There's some details found:
shard has exceeded the maximum number of retries  on failed allocation attempts - manually call [/_cluster/reroute?retry_failed=true] to retry, [unassigned_info[[reason=ALLOCATION_FAILED], CircuitBreakingException[[parent] Data too large, data for [<transport_request>] would be [XXX/YYYmb], which is larger than the limit of [XXX/YYYmb], real usage: [XXX/YYYmb], new bytes reserved: [XXX/YYYmb], usages [request=0/0b, fielddata=XXX/YYYmb, in_flight_requests=XXX/YYYmb, accounting=XXX/YYYmb]]; ], allocation_status[no_attempt]], expected_shard_size[XXXXXXX],
Also, I have set up another HA ES cluster with the same configuration to reproduce this using snapshot data of the cluster. however, the new cluster is green and no shard allocation is failed.
If anyone can suggest the approach to assign the shard of that index and make the cluster state to green again. Thanks.