I am using Elasticsearch 2.3.4 and I have the following issue with rolling restart.
I need to perform some changes in the configuration or install a new plugin. I stopped my indexing processes and followed the steps described in the reference (https://www.elastic.co/guide/en/elasticsearch/reference/2.3/rolling-upgrades.html): disabled shard allocation, performed the changes, started the node. After doing it on all nodes, I enabled the shard allocation.
Now in Marvel I can see that all the replicas disappeared, and the cluster is working on the replica generation. How can I avoid this step? Can't Elasticsearch detect the existing replicas on the nodes? (I have a few TBs of data in my cluster, and this step takes hours or so, and it also has effect on the performance of the system.)
I checked the data folder on the nodes, and it seems that the (old replica) data exists in the ES data folder, but the ES doesn't use it. Now I have a node, which has only 15% free space and a lot of "orphan" shard, and thanks to this ES doesn't allocate any replica on it. Can ES free up this space or can it somehow detect the existing shards?