SERVER-37846 Disallow using arbiters to satisfy numeric write concern when writes commit

1 files changed, 96 insertions, 0 deletions

diff --git a/src/mongo/db/repl/topology_coordinator_v1_test.cpp b/src/mongo/db/repl/topology_coordinator_v1_test.cpp
index 38ce44142c6..c44f572fe3b 100644
--- a/src/mongo/db/repl/topology_coordinator_v1_test.cpp
+++ b/src/mongo/db/repl/topology_coordinator_v1_test.cpp
@@ -5005,6 +5005,102 @@ TEST_F(TopoCoordTest, TwoNodesEligibleForElectionHandoffEqualPriorityResolveByMe
     ASSERT_EQUALS(1, getTopoCoord().chooseElectionHandoffCandidate());
 }
 
+TEST_F(TopoCoordTest, ArbiterNotIncludedInW3WriteInPSSAReplSet) {
+    // In a PSSA set, a w:3 write should only be acknowledged if both secondaries can satisfy it.
+    updateConfig(BSON("_id"
+                      << "rs0"
+                      << "version"
+                      << 2
+                      << "members"
+                      << BSON_ARRAY(BSON("_id" << 0 << "host"
+                                               << "host0:27017")
+                                    << BSON("_id" << 1 << "host"
+                                                  << "host1:27017")
+                                    << BSON("_id" << 2 << "host"
+                                                  << "host2:27017"
+                                                  << "priority"
+                                                  << 0
+                                                  << "votes"
+                                                  << 0)
+                                    << BSON("_id" << 3 << "host"
+                                                  << "host3:27017"
+                                                  << "arbiterOnly"
+                                                  << true))),
+                 0);
+
+    const auto term = getTopoCoord().getTerm();
+    makeSelfPrimary();
+
+    auto caughtUpOpTime = OpTime(Timestamp(100, 0), term);
+    auto laggedOpTime = OpTime(Timestamp(50, 0), term);
+
+    setMyOpTime(caughtUpOpTime);
+
+    // One secondary is caught up.
+    heartbeatFromMember(HostAndPort("host1"), "rs0", MemberState::RS_SECONDARY, caughtUpOpTime);
+
+    // The other is not.
+    heartbeatFromMember(HostAndPort("host2"), "rs0", MemberState::RS_SECONDARY, laggedOpTime);
+
+    // The arbiter is caught up, but should not count towards the w:3.
+    heartbeatFromMember(HostAndPort("host3"), "rs0", MemberState::RS_ARBITER, caughtUpOpTime);
+
+    ASSERT_FALSE(getTopoCoord().haveNumNodesReachedOpTime(
+        caughtUpOpTime, 3 /* numNodes */, false /* durablyWritten */));
+}
+
+TEST_F(TopoCoordTest, ArbitersNotIncludedInW2WriteInPSSAAReplSet) {
+    // In a PSSAA set, a w:2 write should only be acknowledged if at least one of the secondaries
+    // can satisfy it.
+    updateConfig(BSON("_id"
+                      << "rs0"
+                      << "version"
+                      << 2
+                      << "members"
+                      << BSON_ARRAY(BSON("_id" << 0 << "host"
+                                               << "host0:27017")
+                                    << BSON("_id" << 1 << "host"
+                                                  << "host1:27017"
+                                                  << "priority"
+                                                  << 0
+                                                  << "votes"
+                                                  << 0)
+                                    << BSON("_id" << 2 << "host"
+                                                  << "host2:27017"
+                                                  << "priority"
+                                                  << 0
+                                                  << "votes"
+                                                  << 0)
+                                    << BSON("_id" << 3 << "host"
+                                                  << "host3:27017"
+                                                  << "arbiterOnly"
+                                                  << true)
+                                    << BSON("_id" << 4 << "host"
+                                                  << "host4:27017"
+                                                  << "arbiterOnly"
+                                                  << true))),
+                 0);
+
+    const auto term = getTopoCoord().getTerm();
+    makeSelfPrimary();
+
+    auto caughtUpOpTime = OpTime(Timestamp(100, 0), term);
+    auto laggedOpTime = OpTime(Timestamp(50, 0), term);
+
+    setMyOpTime(caughtUpOpTime);
+
+    // Neither secondary is caught up.
+    heartbeatFromMember(HostAndPort("host1"), "rs0", MemberState::RS_SECONDARY, laggedOpTime);
+    heartbeatFromMember(HostAndPort("host2"), "rs0", MemberState::RS_SECONDARY, laggedOpTime);
+
+    // Both arbiters arae caught up, but neither should count towards the w:2.
+    heartbeatFromMember(HostAndPort("host3"), "rs0", MemberState::RS_ARBITER, caughtUpOpTime);
+    heartbeatFromMember(HostAndPort("host4"), "rs0", MemberState::RS_ARBITER, caughtUpOpTime);
+
+    ASSERT_FALSE(getTopoCoord().haveNumNodesReachedOpTime(
+        caughtUpOpTime, 2 /* numNodes */, false /* durablyWritten */));
+}
+
 TEST_F(HeartbeatResponseTestV1,
        ScheduleACatchupTakeoverWhenElectableAndReceiveHeartbeatFromPrimaryInCatchup) {
     updateConfig(BSON("_id"