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diff --git a/src/mongo/transport/service_executor_reserved.h b/src/mongo/transport/service_executor_reserved.h
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+++ b/src/mongo/transport/service_executor_reserved.h
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+/**
+ *    Copyright (C) 2018 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 <deque>
+
+#include "mongo/base/status.h"
+#include "mongo/platform/atomic_word.h"
+#include "mongo/stdx/condition_variable.h"
+#include "mongo/stdx/mutex.h"
+#include "mongo/transport/service_executor.h"
+#include "mongo/transport/service_executor_task_names.h"
+
+namespace mongo {
+namespace transport {
+
+/**
+ * The reserved service executor emulates a thread per connection.
+ * Each connection has its own worker thread where jobs get scheduled.
+ *
+ * The executor will start reservedThreads on start, and create a new thread every time it
+ * starts a new thread, ensuring there are always reservedThreads available for work - this
+ * means that even when you hit the NPROC ulimit, there will still be threads ready to
+ * accept work. When threads exit, they will go back to waiting for work if there are fewer
+ * than reservedThreads available.
+ */
+class ServiceExecutorReserved final : public ServiceExecutor {
+public:
+    explicit ServiceExecutorReserved(ServiceContext* ctx, std::string name, size_t reservedThreads);
+
+    Status start() override;
+    Status shutdown(Milliseconds timeout) override;
+    Status schedule(Task task, ScheduleFlags flags, ServiceExecutorTaskName taskName) override;
+
+    Mode transportMode() const override {
+        return Mode::kSynchronous;
+    }
+
+    void appendStats(BSONObjBuilder* bob) const override;
+
+private:
+    Status _startWorker();
+
+    static thread_local std::deque<Task> _localWorkQueue;
+    static thread_local int _localRecursionDepth;
+    static thread_local int64_t _localThreadIdleCounter;
+
+    AtomicBool _stillRunning{false};
+
+    mutable stdx::mutex _mutex;
+    stdx::condition_variable _threadWakeup;
+    stdx::condition_variable _shutdownCondition;
+
+    std::deque<Task> _readyTasks;
+
+    AtomicUInt32 _numRunningWorkerThreads{0};
+    size_t _numReadyThreads{0};
+    size_t _numStartingThreads{0};
+
+    const std::string _name;
+    const size_t _reservedThreads;
+};
+
+}  // namespace transport
+}  // namespace mongo