Kibana version: 7.0.1
Elasticsearch version: 7.0.1

get_nodes creates date_histogram aggregations nested under a terms aggregation that partitions by node. A user reported that this causes issues due to Elasticsearch's search.max_buckets limit that defaults to 10,000 since 7.0, see elastic/elasticsearch#42001.

The number of buckets is in the order of num_nodes * range_width / interval. Given the default interval of 10s and the default range of 1h, this means that the aggregation would fail if the monitored cluster has 28 nodes or more.

I'm happy to discuss options to address this issue.