elasticsearch - what to do with unassigned shards

Question

my cluster is with yellow status because some shards are unassigned. what to do with this?

I tried set cluster.routing.allocation.disable_allocation = false

Answer 1

With newer ES versions this should do the trick (run in Kibana DevTools):

PUT /_cluster/settings
{
  "transient" : {
    "cluster.routing.rebalance.enable" : "all"
  }
}

However, this won't fix the root cause. In my case there was lots of unassigned shards because default replica size was 1 but actually I was only using single node. So I also added to my elasticsearch.yml this line:

index.number_of_replicas: 0