feat(error): close resources on resource lost (#155)

spec/database_spec.cr

@@ -172,6 +172,21 @@ describe DB::Database do
     end
   end
 
+  it "should close connection on ConnectionLost" do
+    DummyDriver::DummyConnection.clear_connections
+    DB.open "dummy://localhost:1027?initial_pool_size=1&max_pool_size=1&retry_attempts=1" do |db|
+      db.exec("stmt1")
+      DummyDriver::DummyConnection.connections.size.should eq(1)
+      connection = DummyDriver::DummyConnection.connections.first
+      connection.disconnect!
+      connection.closed?.should be_false
+      db.exec("stmt1")
+      # A new connection was used for the last statement
+      DummyDriver::DummyConnection.connections.size.should eq(2)
+      connection.closed?.should be_true
+    end
+  end
+
   describe "prepared_statements connection option" do
     it "defaults to true" do
       with_dummy "dummy://localhost:1027" do |db|

src/db/error.cr

@@ -18,6 +18,7 @@ module DB
     getter resource : T
 
     def initialize(@resource : T)
+      @resource.close
     end
   end
 

src/db/pool.cr

@@ -179,10 +179,12 @@ module DB
           sleep @retry_delay if i >= current_available
           return yield
         rescue e : PoolResourceLost(T)
-          # if the connection is lost close it to release resources
+          # if the connection is lost it will be closed by
-          # and remove it from the known pool.
+          # the exception to release resources
+          # we still need to remove it from the known pool.
+          # Closed connection will be evicted from statement cache
+          # in PoolPreparedStatement#clean_connections
           sync { delete(e.resource) }
-          e.resource.close
         rescue e : PoolResourceRefused
           # a ConnectionRefused means a new connection
           # was intended to be created