pool.clj

(def db-config
  {:classname "org.h2.Driver"
   :subprotocol "h2"
   :subname "mem:todo"
   :user ""
   :password ""})

(defn pool
  [config]
  (let [cpds
        (doto
          (ComboPooledDataSource.)
          (.setDriverClass (:classname config))
          (.setJdbcUrl (str "jdbc:" (:subprotocol config) ":" (:subname config)))
          (.setUser (:user config))
          (.setPassword (:password config))
          (.setMaxPoolSize 6)
          (.setMinPoolSize 1)
          (.setInitialPoolSize 1))]
    {:datasource cpds}))

(def pooled-db (delay (pool db-config)))

(defn db-connection [] @pooled-db)