"allocate_explanation" : "allocation temporarily throttled"

[alexus]

Hello World!

Per Cluster Allocation Explain API | Elasticsearch Guide [6.8] | Elastic - I ran and got following:

GET /_cluster/allocation/explain

---

      "node_decision" : "throttled",
      "deciders" : [
        {
          "decider" : "throttling",
          "decision" : "THROTTLE",
          "explanation" : "reached the limit of incoming shard recoveries [6], cluster setting [cluster.routing.allocation.node_concurrent_incoming_recoveries=2] (can also be set via [cluster.routing.allocation.node_concurrent_recoveries])"
        }
      ]

After changing cluster.routing.allocation.node_concurrent_recoveries setting (REF: Cluster Level Shard Allocation | Elasticsearch Guide [6.8] | Elastic), I believe that helped to recover cluster, however I still trying to understand why it got to that point at the first place...

Please advise
Thanks you in advance!