You can create a C3P0 connection pool with any clojure.java.jdbc connection spec map. (Currently, only maps with :subname and :subprotocol are supported.) connection-pool-spec will return a clojure.java.jdbc connection spec you can use directly with JDBC:

(require '[clojure.java.jdbc :as jdbc]
         '[metabase.connection-pool :as connection-pool])

;;; Create a C3P0 connection pool

(let [pool-spec (connection-pool/connection-pool-spec my-jdbc-spec)]
  (jdbc/query pool-spec ["SELECT *"]))

(You will almost certainly want to store your pool somewhere, such as in an atom).

You can set connection pool options such as size in a c3p0.properties file, or by passing them as a map to connection-pool-spec:

(def ^:private connection-pool-properties
  {"maxIdleTime"     (* 3 60 60)
   "minPoolSize"     1
   "initialPoolSize" 1
   "maxPoolSize"     15})
   
(def my-pool-spec 
  (connection-pool/connection-pool-spec my-jdbc-spec connection-pool-properties))

See https://www.mchange.com/projects/c3p0/#configuration_properties for a list of all options.

destroy-connection-pool! will destroy the connection pool you created:

(connection-pool/destroy-connection-pool! (:datasource pool-spec))

Note that due to me making bad decisions that I haven't fixed yet you currently have to pull the DataSource out of the pool spec yourself. (I plan to fix this in the future)

Copyright © 2019 Metabase, Inc. This project is licensed under the Eclipse Public License, same as Clojure.