[source, ruby]
----
response = client.rank_eval(
  index: 'my-index-000001',
  body: {
    requests: [
      {
        id: 'JFK query',
        request: {
          query: {
            match_all: {}
          }
        },
        ratings: []
      }
    ],
    metric: {
      recall: {
        k: 20,
        relevant_rating_threshold: 1
      }
    }
  }
)
puts response
----
