SERVER-27155 Change replSetRequestVotes to not store dryRun votes as if they were real

(cherry picked from commit 7c2a4522ff4586d6a999a143988b7f7fa9097af5)

2 files changed, 85 insertions, 1 deletions

diff --git a/src/mongo/db/repl/replication_coordinator_impl.cpp b/src/mongo/db/repl/replication_coordinator_impl.cpp
index 698f810fe6e..ad00b7e86a8 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl.cpp
@@ -3204,7 +3204,7 @@ Status ReplicationCoordinatorImpl::processReplSetRequestVotes(
         return cbh.getStatus();
     }
     _replExecutor.wait(cbh.getValue());
-    if (response->getVoteGranted()) {
+    if (!args.isADryRun() && response->getVoteGranted()) {
         LastVote lastVote;
         lastVote.setTerm(args.getTerm());
         lastVote.setCandidateIndex(args.getCandidateIndex());
diff --git a/src/mongo/db/repl/replication_coordinator_impl_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
index 91fde3615b0..9dfd6f11045 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
@@ -46,6 +46,7 @@
 #include "mongo/db/repl/read_concern_response.h"
 #include "mongo/db/repl/repl_set_heartbeat_args.h"
 #include "mongo/db/repl/repl_set_heartbeat_args_v1.h"
+#include "mongo/db/repl/repl_set_request_votes_args.h"
 #include "mongo/db/repl/repl_settings.h"
 #include "mongo/db/repl/replica_set_config.h"
 #include "mongo/db/repl/replication_coordinator.h"  // ReplSetReconfigArgs
@@ -4579,6 +4580,89 @@ TEST_F(ReplCoordTest, PopulateUnsetWriteConcernOptionsSyncModeReturnsInputIfWMod
            getReplCoord()->populateUnsetWriteConcernOptionsSyncMode(wc).syncMode);
 }
 
+TEST_F(ReplCoordTest, NodeStoresElectionVotes) {
+    assertStartSuccess(BSON("_id"
+                            << "mySet"
+                            << "version" << 2 << "members"
+                            << BSON_ARRAY(BSON("host"
+                                               << "node1:12345"
+                                               << "_id" << 0)
+                                          << BSON("host"
+                                                  << "node2:12345"
+                                                  << "_id" << 1) << BSON("host"
+                                                                         << "node3:12345"
+                                                                         << "_id" << 2))),
+                       HostAndPort("node1", 12345));
+    auto time = OpTime(Timestamp(100, 0), 1);
+    ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
+    getReplCoord()->setMyLastAppliedOpTime(time);
+    getReplCoord()->setMyLastDurableOpTime(time);
+    simulateSuccessfulV1Election();
+
+    OperationContextReplMock txn;
+
+    ReplSetRequestVotesArgs args;
+    ASSERT_OK(args.initialize(BSON(
+        "replSetRequestVotes" << 1 << "setName"
+                              << "mySet"
+                              << "term" << 7LL << "candidateIndex" << 2LL << "configVersion" << 2LL
+                              << "dryRun" << false << "lastCommittedOp" << time.toBSON())));
+    ReplSetRequestVotesResponse response;
+
+    ASSERT_OK(getReplCoord()->processReplSetRequestVotes(&txn, args, &response));
+    ASSERT_EQUALS("", response.getReason());
+    ASSERT_TRUE(response.getVoteGranted());
+
+    auto lastVote = getExternalState()->loadLocalLastVoteDocument(&txn);
+    ASSERT_OK(lastVote.getStatus());
+
+    // This is not a dry-run election so the last vote should include the new term and candidate.
+    ASSERT_EQUALS(lastVote.getValue().getTerm(), 7);
+    ASSERT_EQUALS(lastVote.getValue().getCandidateIndex(), 2);
+}
+
+TEST_F(ReplCoordTest, NodeDoesNotStoreDryRunVotes) {
+    assertStartSuccess(BSON("_id"
+                            << "mySet"
+                            << "version" << 2 << "members"
+                            << BSON_ARRAY(BSON("host"
+                                               << "node1:12345"
+                                               << "_id" << 0)
+                                          << BSON("host"
+                                                  << "node2:12345"
+                                                  << "_id" << 1) << BSON("host"
+                                                                         << "node3:12345"
+                                                                         << "_id" << 2))),
+                       HostAndPort("node1", 12345));
+    auto time = OpTime(Timestamp(100, 0), 1);
+    ASSERT(getReplCoord()->setFollowerMode(MemberState::RS_SECONDARY));
+    getReplCoord()->setMyLastAppliedOpTime(time);
+    getReplCoord()->setMyLastDurableOpTime(time);
+    simulateSuccessfulV1Election();
+
+    OperationContextReplMock txn;
+
+    ReplSetRequestVotesArgs args;
+    ASSERT_OK(args.initialize(BSON(
+        "replSetRequestVotes" << 1 << "setName"
+                              << "mySet"
+                              << "term" << 7LL << "candidateIndex" << 2LL << "configVersion" << 2LL
+                              << "dryRun" << true << "lastCommittedOp" << time.toBSON())));
+    ReplSetRequestVotesResponse response;
+
+    ASSERT_OK(getReplCoord()->processReplSetRequestVotes(&txn, args, &response));
+    ASSERT_EQUALS("", response.getReason());
+    ASSERT_TRUE(response.getVoteGranted());
+
+    auto lastVote = getExternalState()->loadLocalLastVoteDocument(&txn);
+    ASSERT_OK(lastVote.getStatus());
+
+    // This is a dry-run election so the last vote should not be updated with the new term and
+    // candidate.
+    ASSERT_EQUALS(lastVote.getValue().getTerm(), 1);
+    ASSERT_EQUALS(lastVote.getValue().getCandidateIndex(), 0);
+}
+
 // TODO(schwerin): Unit test election id updating
 }  // namespace
 }  // namespace repl