A complete Embulk Input Plugin in 2 dozens lines of code

config.yml

in:
  type: simple
out:
  type: file
  file_ext: csv
  path_prefix: ''
  formatter: {type: csv}

simple.clj

;: Run by `embulk -clj simple.clj config.yml` (and with this embulk fork https://github.com/huylenq/embulk)

(ns simple
  (:require [embulk.spik.core :refer :all]
            [embulk.spik.restful :refer :all]
            [clojure.spec.alpha :as s]))

(s/def ::target (partial contains? #{"posts" "comments" "albums"}))

(defconfigs
  :target {:type :string
           :spec ::target}
  {:req [:target]})

(defgraph
  "https://jsonplaceholder.typicode.com/"
  (posts [:id :string
          :userId :string
          :body :string
          :title :string]
         (:id (comments)))
  (comments [:id :string
             :email :string
             :body :string])
  (albums []))

(pumper (get graph (:target *task*)) :associations true)