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diff --git a/src/mongo/executor/async_multicaster.h b/src/mongo/executor/async_multicaster.h
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+/**
+ * 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 <vector>
+
+#include "mongo/executor/remote_command_response.h"
+#include "mongo/executor/task_executor.h"
+#include "mongo/stdx/mutex.h"
+#include "mongo/util/net/hostandport.h"
+
+namespace mongo {
+namespace executor {
+
+/**
+ * An async harness for scatter/gathering a command across an arbitrary number of specific hosts
+ */
+class AsyncMulticaster {
+public:
+    using Reply = std::tuple<HostAndPort, executor::RemoteCommandResponse>;
+    static constexpr size_t kMaxConcurrency = 100;
+
+    struct Options {
+        // maxConcurrency controls the maximum number of inflight operations.  I.e. limiting it
+        // prevents the fan out from overwhelming the host, if the number of servers to multicast
+        // to is very high.
+        size_t maxConcurrency = kMaxConcurrency;
+    };
+
+    AsyncMulticaster(executor::TaskExecutor* executor, Options options);
+
+    /**
+     * Sends the cmd out to all passed servers (via the executor), observing the multicaster's
+     * maxConcurrency.
+     *
+     * The timeout value on multicast is per operation.  The overall timeout will be:
+     *   timeoutMillis - if max concurrency is greater than servers.size()
+     * or
+     *   timeoutMillis * (servers.size() / maxConcurrency) - if not
+     */
+    std::vector<Reply> multicast(const std::vector<HostAndPort> servers,
+                                 const std::string& theDbName,
+                                 const BSONObj& theCmdObj,
+                                 OperationContext* opCtx,
+                                 Milliseconds timeoutMillis);
+
+private:
+    Options _options;
+    executor::TaskExecutor* _executor;
+};
+
+}  // namespace executor
+}  // namespace mongo