ElasticSearch: Unassigned Shards, how to fix?

Question

I have an ES cluster with 4 nodes:

number_of_replicas: 1
search01 - master: false, data: false
search02 - master: true, data: true
search03 - master: false,          


        

Answer 1

I tried to delete unassigned shards or manually assign them to particular data node. It didn't work because unassigned shards kept appearing and health status was "red" over and over. Then I noticed that one of the data nodes stuck in "restart" state. I reduce number of data nodes, killed it. Problem is not reproducible anymore.