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

1 files changed, 270 insertions, 0 deletions

diff --git a/src/mongo/db/repl/vote_requester_test.cpp b/src/mongo/db/repl/vote_requester_test.cpp
new file mode 100644
index 00000000000..5a36015f8c6
--- /dev/null
+++ b/src/mongo/db/repl/vote_requester_test.cpp
@@ -0,0 +1,270 @@
+/**
+ *    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.
+ */
+
+#include "mongo/platform/basic.h"
+
+#include <memory>
+
+#include "mongo/base/status.h"
+#include "mongo/db/jsobj.h"
+#include "mongo/db/repl/vote_requester.h"
+#include "mongo/db/repl/network_interface_mock.h"
+#include "mongo/db/repl/repl_set_request_votes_args.h"
+#include "mongo/db/repl/replication_executor.h"
+#include "mongo/stdx/functional.h"
+#include "mongo/unittest/unittest.h"
+#include "mongo/util/mongoutils/str.h"
+
+namespace mongo {
+namespace repl {
+namespace {
+    using unittest::assertGet;
+
+    using RemoteCommandRequest = ReplicationExecutor::RemoteCommandRequest;
+
+    bool stringContains(const std::string &haystack, const std::string& needle) {
+        return haystack.find(needle) != std::string::npos;
+    }
+
+
+    class VoteRequesterTest : public mongo::unittest::Test {
+    public:
+        virtual void setUp() {
+            ReplicaSetConfig config;
+            ASSERT_OK(config.initialize(
+                BSON("_id" << "rs0" <<
+                     "version" << 2 <<
+                     "members" << BSON_ARRAY(
+                         BSON("_id" << 0 << "host" << "host0") <<
+                         BSON("_id" << 1 << "host" << "host1") <<
+                         BSON("_id" << 2 << "host" << "host2") <<
+                         BSON("_id" << 3 << "host" << "host3" << "votes" << 0) <<
+                         BSON("_id" << 4 << "host" << "host4" << "votes" << 0)))));
+            ASSERT_OK(config.validate());
+            long long candidateId = 0;
+            long long term = 2;
+            OpTime lastOplogEntry = OpTime(Timestamp(999,0), 1);
+
+            _requester.reset(new VoteRequester::Algorithm(config,
+                                                          candidateId,
+                                                          term,
+                                                          lastOplogEntry));
+        }
+
+        virtual void tearDown() {
+            _requester.reset(NULL);
+        }
+
+    protected:
+        int64_t countLogLinesContaining(const std::string& needle) {
+            return std::count_if(getCapturedLogMessages().begin(),
+                                 getCapturedLogMessages().end(),
+                                 stdx::bind(stringContains,
+                                            stdx::placeholders::_1,
+                                            needle));
+        }
+
+        bool hasReceivedSufficientResponses() {
+            return _requester->hasReceivedSufficientResponses();
+        }
+
+        void processResponse(const RemoteCommandRequest& request, const ResponseStatus& response) {
+            _requester->processResponse(request, response);
+        }
+
+        Status getStatus() {
+            return _requester->getStatus();
+        }
+
+        RemoteCommandRequest requestFrom(std::string hostname) {
+            return RemoteCommandRequest(HostAndPort(hostname),
+                                        "", // fields do not matter in VoteRequester
+                                        BSONObj(),
+                                        Milliseconds(0));
+        }
+
+        ResponseStatus badResponseStatus() {
+            return ResponseStatus(ErrorCodes::NodeNotFound, "not on my watch");
+        }
+
+        ResponseStatus votedYes() {
+            ReplSetRequestVotesResponse response;
+            response.setOk(true);
+            response.setVoteGranted(true);
+            response.setTerm(1);
+            return ResponseStatus(NetworkInterfaceMock::Response(response.toBSON(),
+                                                                 Milliseconds(10)));
+        }
+
+        ResponseStatus votedNoBecauseConfigVersionDoesNotMatch() {
+            ReplSetRequestVotesResponse response;
+            response.setOk(true);
+            response.setVoteGranted(false);
+            response.setTerm(1);
+            response.setReason("candidate's config version differs from mine");
+            return ResponseStatus(NetworkInterfaceMock::Response(response.toBSON(),
+                                                                 Milliseconds(10)));
+        }
+
+        ResponseStatus votedNoBecauseSetNameDiffers() {
+            ReplSetRequestVotesResponse response;
+            response.setOk(true);
+            response.setVoteGranted(false);
+            response.setTerm(1);
+            response.setReason("candidate's set name differs from mine");
+            return ResponseStatus(NetworkInterfaceMock::Response(response.toBSON(),
+                                                                 Milliseconds(10)));
+        }
+
+        ResponseStatus votedNoBecauseLastOpTimeIsGreater() {
+            ReplSetRequestVotesResponse response;
+            response.setOk(true);
+            response.setVoteGranted(false);
+            response.setTerm(1);
+            response.setReason("candidate's data is staler than mine");
+            return ResponseStatus(NetworkInterfaceMock::Response(response.toBSON(),
+                                                                 Milliseconds(10)));
+        }
+
+        ResponseStatus votedNoBecauseTermIsGreater() {
+            ReplSetRequestVotesResponse response;
+            response.setOk(true);
+            response.setVoteGranted(false);
+            response.setTerm(3);
+            response.setReason("candidate's term is lower than mine");
+            return ResponseStatus(NetworkInterfaceMock::Response(response.toBSON(),
+                                                                 Milliseconds(10)));
+        }
+
+        ResponseStatus votedNoBecauseAlreadyVoted() {
+            ReplSetRequestVotesResponse response;
+            response.setOk(true);
+            response.setVoteGranted(false);
+            response.setTerm(2);
+            response.setReason("already voted for another candidate this term");
+            return ResponseStatus(NetworkInterfaceMock::Response(response.toBSON(),
+                                                                 Milliseconds(10)));
+        }
+
+    private:
+        std::unique_ptr<VoteRequester::Algorithm> _requester;
+    };
+
+    TEST_F(VoteRequesterTest, ImmediateGoodResponseWinElection) {
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        processResponse(requestFrom("host1"), votedYes());
+        ASSERT_TRUE(hasReceivedSufficientResponses());
+        ASSERT_OK(getStatus());
+    }
+
+    TEST_F(VoteRequesterTest, BadConfigVersionWinElection) {
+        startCapturingLogMessages();
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        processResponse(requestFrom("host1"), votedNoBecauseConfigVersionDoesNotMatch());
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        ASSERT_EQUALS(1, countLogLinesContaining("Got no vote from host1"));
+        processResponse(requestFrom("host2"), votedYes());
+        ASSERT_TRUE(hasReceivedSufficientResponses());
+        ASSERT_OK(getStatus());
+        stopCapturingLogMessages();
+    }
+
+    TEST_F(VoteRequesterTest, SetNameDiffersWinElection) {
+        startCapturingLogMessages();
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        processResponse(requestFrom("host1"), votedNoBecauseSetNameDiffers());
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        ASSERT_EQUALS(1, countLogLinesContaining("Got no vote from host1"));
+        processResponse(requestFrom("host2"), votedYes());
+        ASSERT_TRUE(hasReceivedSufficientResponses());
+        ASSERT_OK(getStatus());
+        stopCapturingLogMessages();
+    }
+
+    TEST_F(VoteRequesterTest, LastOpTimeIsGreaterWinElection) {
+        startCapturingLogMessages();
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        processResponse(requestFrom("host1"), votedNoBecauseLastOpTimeIsGreater());
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        ASSERT_EQUALS(1, countLogLinesContaining("Got no vote from host1"));
+        processResponse(requestFrom("host2"), votedYes());
+        ASSERT_TRUE(hasReceivedSufficientResponses());
+        ASSERT_OK(getStatus());
+        stopCapturingLogMessages();
+    }
+
+    TEST_F(VoteRequesterTest, FailedToContactWinElection) {
+        startCapturingLogMessages();
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        processResponse(requestFrom("host1"), badResponseStatus());
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        ASSERT_EQUALS(1, countLogLinesContaining("Got failed response from host1"));
+        processResponse(requestFrom("host2"), votedYes());
+        ASSERT_TRUE(hasReceivedSufficientResponses());
+        ASSERT_OK(getStatus());
+        stopCapturingLogMessages();
+    }
+
+    TEST_F(VoteRequesterTest, AlreadyVotedWinElection) {
+        startCapturingLogMessages();
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        processResponse(requestFrom("host1"), votedNoBecauseAlreadyVoted());
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        ASSERT_EQUALS(1, countLogLinesContaining("Got no vote from host1"));
+        processResponse(requestFrom("host2"), votedYes());
+        ASSERT_TRUE(hasReceivedSufficientResponses());
+        ASSERT_OK(getStatus());
+        stopCapturingLogMessages();
+    }
+
+    TEST_F(VoteRequesterTest, StaleTermLoseElection) {
+        startCapturingLogMessages();
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        processResponse(requestFrom("host1"), votedNoBecauseTermIsGreater());
+        ASSERT_EQUALS(1, countLogLinesContaining("Got no vote from host1"));
+        ASSERT_TRUE(hasReceivedSufficientResponses());
+        ASSERT_EQUALS(getStatus().reason(), "running for a stale term");
+        stopCapturingLogMessages();
+    }
+
+    TEST_F(VoteRequesterTest, NotEnoughVotesLoseElection) {
+        startCapturingLogMessages();
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        processResponse(requestFrom("host1"), votedNoBecauseSetNameDiffers());
+        ASSERT_FALSE(hasReceivedSufficientResponses());
+        ASSERT_EQUALS(1, countLogLinesContaining("Got no vote from host1"));
+        processResponse(requestFrom("host2"), badResponseStatus());
+        ASSERT_EQUALS(1, countLogLinesContaining("Got failed response from host2"));
+        ASSERT_TRUE(hasReceivedSufficientResponses());
+        ASSERT_EQUALS(getStatus().reason(), "received insufficient votes");
+        stopCapturingLogMessages();
+    }
+
+}  // namespace
+}  // namespace repl
+}  // namespace mongo