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+/**
+ *    Copyright (C) 2023-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 <functional>
+#include <string>
+
+#include "mongo/base/string_data.h"
+#include "mongo/executor/connection_pool.h"
+#include "mongo/executor/connection_pool_stats.h"
+#include "mongo/platform/mutex.h"
+#include "mongo/stdx/unordered_map.h"
+#include "mongo/util/duration.h"
+#include "mongo/util/net/hostandport.h"
+
+namespace mongo::executor {
+/**
+ * This file is intended for simple implementations of ConnectionPool::ControllerInterface that
+ * might be shared between different libraries. Currently, it contains only one such implementation,
+ * the DyamicLimitController below.
+ */
+
+/**
+ * A simple controller that allows for the maximum and minimum pool size to have dynamic values.
+ * At construction, provide callables that return the current maximum and minimum sizes to be used
+ * by the pool.
+ *
+ * Currently, the callables that provide the max and min are stateless and don't inspect any data
+ * about the pool. The other pool parameters (maxConnecting, host/pending/refresh timeouts) are
+ * simply taken from the Optoins the relevant ConnectionPool was started with. However, this
+ * type is intended to be easily extensible to add these features in the future if needed.
+ */
+class DynamicLimitController final : public ConnectionPool::ControllerInterface {
+public:
+    DynamicLimitController(std::function<size_t()> minLoader,
+                           std::function<size_t()> maxLoader,
+                           StringData name)
+        : _minLoader(std::move(minLoader)),
+          _maxLoader(std::move(maxLoader)),
+          _name(std::move(name)) {}
+
+    void init(ConnectionPool* parent) override;
+
+    void addHost(PoolId id, const HostAndPort& host) override;
+    HostGroupState updateHost(PoolId id, const HostState& stats) override;
+    void removeHost(PoolId id) override;
+
+    ConnectionControls getControls(PoolId id) override;
+
+    Milliseconds hostTimeout() const override {
+        return getPoolOptions().hostTimeout;
+    }
+
+    Milliseconds pendingTimeout() const override {
+        return getPoolOptions().refreshTimeout;
+    }
+
+    Milliseconds toRefreshTimeout() const override {
+        return getPoolOptions().refreshRequirement;
+    }
+
+    StringData name() const override {
+        return _name;
+    }
+
+    void updateConnectionPoolStats(ConnectionPoolStats* cps) const override {}
+
+private:
+    struct PoolData {
+        HostAndPort host;
+        size_t target = 0;
+    };
+
+    std::function<size_t()> _minLoader;
+    std::function<size_t()> _maxLoader;
+    std::string _name;
+    Mutex _mutex = MONGO_MAKE_LATCH("DynamicLimitController::_mutex");
+    stdx::unordered_map<PoolId, PoolData> _poolData;
+};
+}  // namespace mongo::executor