SERVER-23243 Extract time-keeping from Listener

BackgroundThreadClockSource & FastClockSourceFactory

1 files changed, 73 insertions, 0 deletions

diff --git a/src/mongo/util/background_thread_clock_source.h b/src/mongo/util/background_thread_clock_source.h
new file mode 100644
index 00000000000..eecd75c0f4c
--- /dev/null
+++ b/src/mongo/util/background_thread_clock_source.h
@@ -0,0 +1,73 @@
+/**
+ *    Copyright (C) 2016 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 <chrono>
+#include <thread>
+
+#include "mongo/base/disallow_copying.h"
+#include "mongo/platform/atomic_word.h"
+#include "mongo/util/clock_source.h"
+#include "mongo/util/time_support.h"
+#include "mongo/stdx/condition_variable.h"
+#include "mongo/stdx/memory.h"
+#include "mongo/stdx/mutex.h"
+#include "mongo/stdx/thread.h"
+
+namespace mongo {
+
+/**
+ * A clock source that uses a periodic timer to build a low-resolution, fast-to-read clock.
+ * Essentially uses a background thread that repeatedly sleeps for X amount of milliseconds
+ * and wakes up to store the current time.
+ */
+class BackgroundThreadClockSource final : public ClockSource {
+    MONGO_DISALLOW_COPYING(BackgroundThreadClockSource);
+
+public:
+    BackgroundThreadClockSource(std::unique_ptr<ClockSource> clockSource, Milliseconds granularity);
+    ~BackgroundThreadClockSource() override;
+    Date_t now() override;
+
+private:
+    void _startTimerThread();
+    void _updateCurrent();
+
+    const std::unique_ptr<ClockSource> _clockSource;
+    AtomicInt64 _current;
+
+    const Milliseconds _granularity;
+
+    stdx::mutex _mutex;
+    stdx::condition_variable _condition;
+    bool _shutdownTimer;
+    stdx::thread _timer;
+};
+
+}  // namespace mongo