Cluster doesn't respect routing.allocation.require.data_type

[gorek]

Hi,

we have cluster with 2 nodes. Every node has set data_type attribute.
One node has low disk watermark exceed.
We prepared ILM policy to keep indices on one node for some time and after move it to another.
Rarely I move some indices manually to another node by set index routing.allocation.require.data_type setting.

Few days ago one of node filled up disk because moving indices to another node stops working. When I manually set routing.allocation.require.data_type to value of second node data_type parameter nothing happens (I can't see any relocating shards in _cat/shards results. cluster/allocation/explain also doesn't show anything).

Few months ago I move indices this way without problems.
All (production) indices has 0 replicas so low disk watermark should not be a problem.

Have you any idea why indices doesn't move to another node?

Elastic version: 6.8.13

Thank you.

[DavidTurner]

Cluster allocation explain is the best way to explain why a particular shard is allocated as it is. What do you mean it doesn't show anything? It will always say something about the target shard.