Cluster Summary section

This portion of the Storm UI shows the version of Storm deployed in the cluster, the uptime of the Nimbus nodes, number of free worker slots, number of used worker slots, and so on. While submitting a topology to the cluster, the user first needs to make sure that the value of the Free slots column should not be zero; otherwise, the topology doesn't get any worker for processing and will wait in the queue until a workers becomes free.