Merge pull request #345 from metabase/can_connect_qmark

THOU SHALT BE ABLE TO CHECK WHETHER THOU MAY CONNECT TO THY DATABASES

src/metabase/driver.clj

@@ -50,11 +50,15 @@
 
 
 (defmulti connection-details
-  "Return a map of connection details (in format usable by korma) for DATABASE."
+  "Return a map of connection details (in format usable by korma or equivalent) for DATABASE."
   (db-dispatch-fn "connection"))
 
 (defmulti connection
-  "Return a korma connection to DATABASE."
+  "Return a [korma or equivalent] connection to DATABASE."
+  (db-dispatch-fn "connection"))
+
+(defmulti can-connect?
+  "Check whether we can connect to DATABASE and perform a simple query."
   (db-dispatch-fn "connection"))
 
 (defmulti sync-database

src/metabase/driver/generic_sql/connection.clj

+(ns metabase.driver.generic-sql.connection
+  (:require [clojure.tools.logging :as log]
+            [korma.core :as k]
+            [metabase.driver :as driver]))
+
+(defn can-connect?
+  "Check whether we can connect to a DATABASE and perform a very simple SQL query.
+
+    (can-connect? (sel :one Database ....)) -> true"
+  [database]
+  (try (= 1 (-> (k/exec-raw (driver/connection database) "SELECT 1" :results)
+                first
+                vals
+                first))
+       (catch Throwable e
+         (log/error "Failed to connect to database:" (.getMessage e))
+         false)))

src/metabase/driver/h2/connection.clj

 (ns metabase.driver.h2.connection
-  (:require [korma.db]
-            [metabase.driver :refer [connection connection-details]]))
+  (:require korma.db
+            [metabase.driver :refer [can-connect? connection connection-details]]
+            [metabase.driver.generic-sql.connection :as generic]))
 
 (defmethod connection-details :h2 [{:keys [details]}]
   (clojure.set/rename-keys details {:conn_str :db}))
 
 (defmethod connection :h2 [database]
   (korma.db/h2 (connection-details database)))
+
+(defmethod can-connect? :h2 [database]
+  (generic/can-connect? database))

src/metabase/driver/postgres/connection.clj

 (ns metabase.driver.postgres.connection
   (:require [clojure.set :refer [rename-keys]]
             [clojure.string :as s]
-            [korma.db]
+            korma.db
             [swiss.arrows :refer :all]
             [metabase.config :as config]
-            [metabase.driver :refer [connection connection-details]]))
+            [metabase.driver :refer [can-connect? connection connection-details]]
+            [metabase.driver.generic-sql.connection :as generic]))
 
 (defmethod connection-details :postgres [database]
   (let [details (-<>> database :details :conn_str             ; get conn str like "password=corvus user=corvus ..."
@@ -26,3 +27,6 @@
   (-> (connection-details database)
       (dissoc :db-type)
       korma.db/postgres))
+
+(defmethod can-connect? :postgres [database]
+  (generic/can-connect? database))

test/metabase/driver/generic_sql/connection_test.clj

+(ns metabase.driver.generic-sql.connection-test
+  (:require [expectations :refer :all]
+            [metabase.db :refer [sel]]
+            [metabase.driver.generic-sql.connection :refer :all]
+            [metabase.models.database :refer [Database]]
+            [metabase.test-data :refer :all]))
+
+;; ## TESTS FOR CAN-CONNECT?
+
+;; Check that we can connect to the Test DB
+(expect true
+  (can-connect? @test-db))
+
+;; Lie and say Test DB is Postgres. CAN-CONNECT? should fail
+(expect false
+  (can-connect? (assoc @test-db :engine :postgres)))
+
+;; Random made-up DBs should fail
+(expect false
+  (can-connect? {:engine :postgres
+                 :details {:conn_str "host=localhost port=5432 dbname=ABCDEFGHIJKLMNOP user=rasta"}}))
+
+;; Things that you can connect to, but are not DBs, should fail
+(expect false
+  (can-connect? {:engine :postgres
+                 :details {:conn_str "host=google.com port=80"}}))