Add connection retry logic to connection pool

spec/database_spec.cr

@@ -63,4 +63,28 @@ describe DB::Database do
     end
     stmt.closed?.should be_true
   end
+
+  it "should not reconnect if connection is lost and retry_attempts=0" do
+    DummyDriver::DummyConnection.clear_connections
+    DB.open "dummy://localhost:1027?initial_pool_size=1&max_pool_size=1&retry_attempts=0" do |db|
+      db.exec("stmt1")
+      DummyDriver::DummyConnection.connections.size.should eq(1)
+      DummyDriver::DummyConnection.connections.first.disconnect!
+      expect_raises DB::PoolRetryAttemptsExceeded do
+        db.exec("stmt1")
+      end
+      DummyDriver::DummyConnection.connections.size.should eq(1)
+    end
+  end
+
+  it "should reconnect if connection is lost and executing same statement" 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)
+      DummyDriver::DummyConnection.connections.first.disconnect!
+      db.exec("stmt1")
+      DummyDriver::DummyConnection.connections.size.should eq(2)
+    end
+  end
 end

spec/dummy_driver.cr

@@ -9,6 +9,7 @@ class DummyDriver < DB::Driver
   class DummyConnection < DB::Connection
     def initialize(db)
       super(db)
+      @connected = true
       @@connections ||= [] of DummyConnection
       @@connections.not_nil! << self
     end
@@ -29,6 +30,14 @@ class DummyDriver < DB::Driver
       0
     end
 
+    def check
+      raise DB::ConnectionLost.new(self) unless @connected
+    end
+
+    def disconnect!
+      @connected = false
+    end
+
     protected def do_close
       super
     end
@@ -43,11 +52,13 @@ class DummyDriver < DB::Driver
     end
 
     protected def perform_query(args : Enumerable)
+      @connection.as(DummyConnection).check
       set_params args
       DummyResultSet.new self, @query
     end
 
     protected def perform_exec(args : Enumerable)
+      @connection.as(DummyConnection).check
       set_params args
       raise "forced exception due to query" if @query == "raise"
       DB::ExecResult.new 0i64, 0_i64