GODRIVER-1162 create driver.Expirable interface

Change-Id: I1fe083c9e66d34091677cad60370e70ef4718a7c

Author: iwysiu

x/mongo/driver/driver.go

@@ -30,6 +30,12 @@ type Connection interface {
 	Address() address.Address
 }
 
+// Expirable represents an expirable object.
+type Expirable interface {
+	Expire() error
+	Alive() bool
+}
+
 // Compressor is an interface used to compress wire messages. If a Connection supports compression
 // it should implement this interface as well. The CompressWireMessage method will be called during
 // the execution of an operation if the wire message is allowed to be compressed.

x/mongo/driver/topology/connection.go

@@ -281,8 +281,8 @@ func (c initConnection) ReadWireMessage(ctx context.Context, dst []byte) ([]byte
 	return c.readWireMessage(ctx, dst)
 }
 
-// Connection implements the driver.Connection interface. It allows reading and writing wire
-// messages.
+// Connection implements the driver.Connection interface to allow reading and writing wire
+// messages and the driver.Expirable interface to allow expiring.
 type Connection struct {
 	*connection
 	s *Server
@@ -291,6 +291,7 @@ type Connection struct {
 }
 
 var _ driver.Connection = (*Connection)(nil)
+var _ driver.Expirable = (*Connection)(nil)
 
 // WriteWireMessage handles writing a wire message to the underlying connection.
 func (c *Connection) WriteWireMessage(ctx context.Context, wm []byte) error {
@@ -388,6 +389,29 @@ func (c *Connection) Close() error {
 	return nil
 }
 
+// Expire closes this connection and will close the underlying socket.
+func (c *Connection) Expire() error {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.connection == nil {
+		return nil
+	}
+	if c.s != nil {
+		c.s.sem.Release(1)
+	}
+	err := c.close()
+	if err != nil {
+		return err
+	}
+	c.connection = nil
+	return nil
+}
+
+// Alive returns if the connection is still alive.
+func (c *Connection) Alive() bool {
+	return c.connection != nil
+}
+
 // ID returns the ID of this connection.
 func (c *Connection) ID() string {
 	c.mu.RLock()

x/mongo/driver/topology/connection_test.go

@@ -310,6 +310,17 @@ func TestConnection(t *testing.T) {
 				t.Errorf("errors do not match. got %v; want %v", got, want)
 			}
 
+			got = conn.Expire()
+			if !cmp.Equal(got, want, cmp.Comparer(compareErrors)) {
+				t.Errorf("errors do not match. got %v; want %v", got, want)
+			}
+
+			want = false
+			got = conn.Alive()
+			if !cmp.Equal(got, want) {
+				t.Errorf("Alive does not match. got %v; want %v", got, want)
+			}
+
 			want = "<closed>"
 			got = conn.ID()
 			if !cmp.Equal(got, want) {