Shard stuck in INITIALIZING state

[dipathak (Dinesh)]

We are using ES 5.2 on12 nodes cluster. Somehow the cluster went into "red" state and some primary shards went into UNASSIGNED state. After long time, 4-5 hours, one shard in still stuck in INITIALIZING state. Can someone tell me what things to look at.
Thanks.

health status index       uuid                   pri rep docs.count docs.deleted store.size pri.store.size
green  open   cauditindex kBu8IEv1Tqy3-eimaO8Gdg   5   2      15905            0      8.6mb          2.8mb
green  open   objindex    ZZdSUrs8QMCeMHRphXXx3Q   5   2        134           59      8.9mb          2.9mb
red    open   cfileindex  CxQi4EfpS_mLOYPgpM08hQ  10   2  919143416    230061071    563.2gb        187.7gb


  "0" : [
    {
      "state" : "INITIALIZING",
      "primary" : true,
      "node" : "vwIn7fqDRAyszPpi0HCC1w",
      "relocating_node" : null,
      "shard" : 0,
      "index" : "cfileindex",
      "recovery_source" : {
        "type" : "EXISTING_STORE"
      },
      "allocation_id" : {
        "id" : "wQl5llnaSCSbWov34fpepA"
      },
      "unassigned_info" : {
        "reason" : "CLUSTER_RECOVERED",
        "at" : "2017-05-19T16:12:12.211Z",
        "delayed" : false,
        "allocation_status" : "fetching_shard_data"
      }
    },

[warkolm (Mark Walkom)]

Try using https://www.elastic.co/guide/en/elasticsearch/reference/5.4/cluster-allocation-explain.html to find out what is happening.