SERVER-46200 implement basic VectorClock service

1 files changed, 66 insertions, 0 deletions

diff --git a/src/mongo/db/vector_clock_mutable.h b/src/mongo/db/vector_clock_mutable.h
new file mode 100644
index 00000000000..7e99aa32f2a
--- /dev/null
+++ b/src/mongo/db/vector_clock_mutable.h
@@ -0,0 +1,66 @@
+/**
+ *    Copyright (C) 2020-present MongoDB, Inc.
+ *
+ *    This program is free software: you can redistribute it and/or modify
+ *    it under the terms of the Server Side Public License, version 1,
+ *    as published by MongoDB, Inc.
+ *
+ *    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
+ *    Server Side Public License for more details.
+ *
+ *    You should have received a copy of the Server Side Public License
+ *    along with this program. If not, see
+ *    <http://www.mongodb.com/licensing/server-side-public-license>.
+ *
+ *    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 Server Side 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/vector_clock.h"
+
+namespace mongo {
+
+/**
+ * A vector clock service that additionally permits being advanced authoritatively ("ticking").
+ *
+ * Only linked in contexts where ticking is allowed, ie. mongod, embedded, mongod-based unittests.
+ */
+class VectorClockMutable : public VectorClock {
+public:
+    // Decorate ServiceContext with VectorClockMutable*, that will resolve to the mutable vector
+    // clock implementation.
+    static VectorClockMutable* get(ServiceContext* service);
+    static VectorClockMutable* get(OperationContext* ctx);
+
+    static void registerVectorClockOnServiceContext(ServiceContext* service,
+                                                    VectorClockMutable* vectorClockMutable);
+
+    // Ticking
+    virtual LogicalTime tick(Component component, uint64_t nTicks) = 0;
+    virtual void tickTo(Component component, LogicalTime newTime) = 0;
+
+protected:
+    static bool _lessThanOrEqualToMaxPossibleTime(LogicalTime time, uint64_t nTicks);
+
+    VectorClockMutable();
+    virtual ~VectorClockMutable();
+
+    // Internal Ticking API
+    LogicalTime _advanceComponentTimeByTicks(Component component, uint64_t nTicks);
+    void _advanceComponentTimeTo(Component component, LogicalTime&& newTime);
+};
+
+}  // namespace mongo