add a new optional driver method for `notify-database-updated` which allows...

add a new optional driver method for `notify-database-updated` which allows drivers to be informed when their databases are updated. then implement this method on the generic-sql driver and use it to actively shutdown any open connection pool on the updated database so that we can recreate it as needed.

src/metabase/driver.clj

@@ -166,6 +166,10 @@
     "*OPTIONAL*. Return a humanized (user-facing) version of an connection error message string.
      Generic error messages are provided in the constant `connection-error-messages`; return one of these whenever possible.")
 
+  (notify-database-updated [this, ^DatabaseInstance database]
+    "*OPTIONAL*. Notify the driver that the attributes of the DATABASE have changed.  This is specifically relevant in
+     the event that the driver was doing some caching or connection pooling.")
+
   (process-native [this, {^Integer database-id :database, {^String native-query :query} :native, :as ^Map query}]
     "Process a native QUERY. This function is called by `metabase.driver/process-query`.
 
@@ -253,6 +257,7 @@
    :describe-table-fks                (constantly nil)
    :features                          (constantly nil)
    :humanize-connection-error-message (u/drop-first-arg identity)
+   :notify-database-updated           (constantly nil)
    :process-query-in-context          (u/drop-first-arg identity)
    :sync-in-context                   (fn [_ _ f] (f))
    :table-rows-seq                    (constantly nil)})

src/metabase/driver/generic_sql.clj

@@ -104,6 +104,17 @@
                                      ;; prevent overly large pools by condensing them when connections are idle for 15m+
                                      :excess-timeout              (* 15 60)))))
 
+(defn- notify-database-updated
+  "We are being informed that a DATABASE has been updated, so lets shut down the connection pool (if it exists) under
+   the assumption that the connection details have changed."
+  [_ {:keys [id]}]
+  (log/debug (u/format-color 'red "Closing connection pool for database %d ..." id))
+  (when-let [pool (get @connection-pools id)]
+    ;; remove the cached reference to the pool so we don't try to use it anymore
+    (reset! connection-pools (dissoc @connection-pools id))
+    ;; now actively shut down the pool so that any open connections are closed
+    (.close (:datasource pool))))
+
 (defn db->pooled-connection-spec
   "Return a JDBC connection spec that includes a cp30 `ComboPooledDataSource`.
    Theses connection pools are cached so we don't create multiple ones to the same DB."
@@ -328,16 +339,17 @@
   (require 'metabase.driver.generic-sql.native
            'metabase.driver.generic-sql.query-processor)
   (merge driver/IDriverDefaultsMixin
-         {:analyze-table         analyze-table
-          :can-connect?          can-connect?
-          :describe-database     describe-database
-          :describe-table        describe-table
-          :describe-table-fks    describe-table-fks
-          :features              features
-          :field-values-lazy-seq field-values-lazy-seq
-          :process-native        (resolve 'metabase.driver.generic-sql.native/process-and-run)
-          :process-structured    (resolve 'metabase.driver.generic-sql.query-processor/process-structured)
-          :table-rows-seq        table-rows-seq}))
+         {:analyze-table           analyze-table
+          :can-connect?            can-connect?
+          :describe-database       describe-database
+          :describe-table          describe-table
+          :describe-table-fks      describe-table-fks
+          :features                features
+          :field-values-lazy-seq   field-values-lazy-seq
+          :notify-database-updated notify-database-updated
+          :process-native          (resolve 'metabase.driver.generic-sql.native/process-and-run)
+          :process-structured      (resolve 'metabase.driver.generic-sql.query-processor/process-structured)
+          :table-rows-seq          table-rows-seq}))