SERVER-28107 Implement OperationTimeTracker

1 files changed, 63 insertions, 0 deletions

diff --git a/src/mongo/db/operation_time_tracker.h b/src/mongo/db/operation_time_tracker.h
new file mode 100644
index 00000000000..812368b4a58
--- /dev/null
+++ b/src/mongo/db/operation_time_tracker.h
@@ -0,0 +1,63 @@
+/**
+ *    Copyright (C) 2017 MongoDB Inc.
+ *
+ *    This program is free software: you can redistribute it and/or  modify
+ *    it under the terms of the GNU Affero General Public License, version 3,
+ *    as published by the Free Software Foundation.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU Affero General Public License for more details.
+ *
+ *    You should have received a copy of the GNU Affero General Public License
+ *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ *    As a special exception, the copyright holders give permission to link the
+ *    code of portions of this program with the OpenSSL library under certain
+ *    conditions as described in each individual source file and distribute
+ *    linked combinations including the program with the OpenSSL library. You
+ *    must comply with the GNU Affero General Public License in all respects for
+ *    all of the code used other than as permitted herein. If you modify file(s)
+ *    with this exception, you may extend this exception to your version of the
+ *    file(s), but you are not obligated to do so. If you do not wish to do so,
+ *    delete this exception statement from your version. If you delete this
+ *    exception statement from all source files in the program, then also delete
+ *    it in the license file.
+ */
+
+#pragma once
+
+#include "mongo/db/logical_time.h"
+#include "mongo/db/operation_context.h"
+#include "mongo/stdx/mutex.h"
+
+namespace mongo {
+
+/**
+ * OperationTimeTracker holds the latest operationTime received from a mongod for the current
+ * operation. Mongos commands are processed via ASIO, meaning a random thread will handle the
+ * response, so this class is declared as a decoration on OperationContext.
+ */
+class OperationTimeTracker {
+public:
+    // Decorate OperationContext with OperationTimeTracker instance.
+    static const OperationContext::Decoration<OperationTimeTracker> get;
+
+    /*
+     * Return the latest operationTime.
+     */
+    LogicalTime getMaxOperationTime() const;
+
+    /*
+     * Update _maxOperationTime to max(newTime, _maxOperationTime)
+     */
+    void updateOperationTime(LogicalTime newTime);
+
+private:
+    // protects _maxOperationTime
+    mutable stdx::mutex _mutex;
+    LogicalTime _maxOperationTime;
+};
+
+}  // namespace mongo