GODRIVER-1478 Update session's last used time when executing an operation (#291)

Author: Divjot Arora

mongo/integration/sessions_test.go

@@ -50,6 +50,21 @@ func TestSessionPool(t *testing.T) {
 		got = getSessionID(mt, secondSess)
 		assert.True(mt, sessionIDsEqual(mt, want, got), "expected session ID %v, got %v", want, got)
 	})
+	mt.Run("last use time updated", func(mt *mtest.T) {
+		sess, err := mt.Client.StartSession()
+		assert.Nil(mt, err, "StartSession error: %v", err)
+		defer sess.EndSession(mtest.Background)
+		initialLastUsedTime := getSessionLastUsedTime(mt, sess)
+
+		err = mongo.WithSession(mtest.Background, sess, func(sc mongo.SessionContext) error {
+			return mt.Client.Ping(sc, readpref.Primary())
+		})
+		assert.Nil(mt, err, "WithSession error: %v", err)
+
+		newLastUsedTime := getSessionLastUsedTime(mt, sess)
+		assert.True(mt, newLastUsedTime.After(initialLastUsedTime),
+			"last used time %s is not after the initial last used time %s", newLastUsedTime, initialLastUsedTime)
+	})
 }
 
 func TestSessions(t *testing.T) {
@@ -363,3 +378,9 @@ func extractSentSessionID(mt *mtest.T) []byte {
 	_, data := lsid.Document().Lookup("id").Binary()
 	return data
 }
+
+func getSessionLastUsedTime(mt *mtest.T, sess mongo.Session) time.Time {
+	xsess, ok := sess.(mongo.XSession)
+	assert.True(mt, ok, "expected session to implement mongo.XSession, but got %T", sess)
+	return xsess.ClientSession().LastUsed
+}

x/mongo/driver/operation.go

@@ -889,8 +889,8 @@ func (op Operation) addSession(dst []byte, desc description.SelectedServer) ([]b
 	if client == nil || !description.SessionsSupported(desc.WireVersion) || desc.SessionTimeoutMinutes == 0 {
 		return dst, nil
 	}
-	if client.Terminated {
-		return dst, session.ErrSessionEnded
+	if err := client.UpdateUseTime(); err != nil {
+		return dst, err
 	}
 	lsid, _ := client.SessionID.MarshalBSON()
 	dst = bsoncore.AppendDocumentElement(dst, "lsid", lsid)

x/mongo/driver/session/client_session.go

@@ -196,8 +196,9 @@ func (c *Client) AdvanceOperationTime(opTime *primitive.Timestamp) error {
 	return nil
 }
 
-// UpdateUseTime updates the session's last used time.
-// Must be called whenver this session is used to send a command to the server.
+// UpdateUseTime sets the session's last used time to the current time. This must be called whenever the session is
+// used to send a command to the server to ensure that the session is not prematurely marked expired in the driver's
+// session pool. If the session has already been ended, this method will return ErrSessionEnded.
 func (c *Client) UpdateUseTime() error {
 	if c.Terminated {
 		return ErrSessionEnded