SERVER-18253 create VoteRequester Scatter-Gather Algorithm to conduct new style elections

1 files changed, 123 insertions, 0 deletions

diff --git a/src/mongo/db/repl/vote_requester.h b/src/mongo/db/repl/vote_requester.h
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+++ b/src/mongo/db/repl/vote_requester.h
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+/**
+ *    Copyright (C) 2015 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 <memory>
+#include <vector>
+
+#include "mongo/base/disallow_copying.h"
+#include "mongo/bson/timestamp.h"
+#include "mongo/db/repl/optime.h"
+#include "mongo/db/repl/replica_set_config.h"
+#include "mongo/db/repl/replication_executor.h"
+#include "mongo/db/repl/scatter_gather_algorithm.h"
+#include "mongo/stdx/functional.h"
+
+namespace mongo {
+
+    class Status;
+
+namespace repl {
+
+    class ScatterGatherRunner;
+    class ReplSetDeclareRequestVotesArgs;
+
+    class VoteRequester {
+        MONGO_DISALLOW_COPYING(VoteRequester);
+    public:
+
+        class Algorithm : public ScatterGatherAlgorithm {
+        public:
+            Algorithm(const ReplicaSetConfig& rsConfig,
+                      long long candidateId,
+                      long long term,
+                      OpTime lastOplogEntry);
+            virtual ~Algorithm();
+            virtual std::vector<ReplicationExecutor::RemoteCommandRequest> getRequests() const;
+            virtual void processResponse(
+                    const ReplicationExecutor::RemoteCommandRequest& request,
+                    const ResponseStatus& response);
+            virtual bool hasReceivedSufficientResponses() const;
+
+            /**
+             * Returns BadValue if the term for which we are running is statel, IllegalOperation if
+             * insufficient votes are received, and Status::OK if we've won the election.
+             * 
+             * It is invalid to call this before hasReceivedSufficeintResponses returns true.
+             */
+            Status getStatus() const { return _status; }
+
+        private:
+            const ReplicaSetConfig _rsConfig;
+            const long long _candidateId;
+            const long long _term;
+            const OpTime _lastOplogEntry;
+            std::vector<HostAndPort> _targets;
+            bool _failed = false;
+            long long _responsesProcessed = 0;
+            long long _votes = 1;
+            Status _status = Status::OK();
+        };
+
+        VoteRequester();
+        virtual ~VoteRequester();
+
+        /**
+         * Begins the process of sending replSetRequestVotes commands to all non-DOWN nodes
+         * in currentConfig, in attempt to receive sufficient votes to win the election.
+         *
+         * evh can be used to schedule a callback when the process is complete.
+         * This function must be run in the executor, as it must be synchronous with the command
+         * callbacks that it schedules.
+         * If this function returns Status::OK(), evh is then guaranteed to be signaled.
+         **/
+        StatusWith<ReplicationExecutor::EventHandle> start(
+            ReplicationExecutor* executor,
+            const ReplicaSetConfig& rsConfig,
+            long long candidateId,
+            long long term,
+            OpTime lastOplogEntry,
+            const stdx::function<void ()>& onCompletion = stdx::function<void ()>());
+
+        /**
+         * Informs the VoteRequester to cancel further processing.  The "executor"
+         * argument must point to the same executor passed to "start()".
+         *
+         * Like start(), this method must run in the executor context.
+         */
+        void cancel(ReplicationExecutor* executor);
+
+    private:
+        std::unique_ptr<Algorithm> _algorithm;
+        std::unique_ptr<ScatterGatherRunner> _runner;
+        bool _isCanceled = false;
+    };
+
+}  // namespace repl
+}  // namespace mongo