SERVER-57010 Check default write concern during replica set reconfig When the feature flag is enabled

11 files changed, 170 insertions, 11 deletions

diff --git a/jstests/replsets/libs/rename_across_dbs.js b/jstests/replsets/libs/rename_across_dbs.js
index a602b51326f..59b0fba4e14 100644
--- a/jstests/replsets/libs/rename_across_dbs.js
+++ b/jstests/replsets/libs/rename_across_dbs.js
@@ -48,6 +48,15 @@ var RenameAcrossDatabasesTest = function(options) {
         replTest.startSet();
         replTest.initiate();
 
+        // This test performs a reconfig that will change the implicit default write concern
+        // from {w: "majority"} to {w: 1}. In order for this reconfig to succeed, we must first
+        // set the cluster-wide write concern.
+        assert.commandWorked(replTest.getPrimary().adminCommand({
+            setDefaultRWConcern: 1,
+            defaultWriteConcern: {w: "majority"},
+            writeConcern: {w: "majority"}
+        }));
+
         // If provided in 'options', we set the featureCompatibilityVersion. We do this prior to
         // adding any other members to the replica set.
         if (options.setFeatureCompatibilityVersion) {
diff --git a/jstests/replsets/reconfig_add_remove_arbiter.js b/jstests/replsets/reconfig_add_remove_arbiter.js
index 0ae14b64b0d..7cbb733c306 100644
--- a/jstests/replsets/reconfig_add_remove_arbiter.js
+++ b/jstests/replsets/reconfig_add_remove_arbiter.js
@@ -14,9 +14,16 @@ const replTest = new ReplSetTest({nodes: 2});
 replTest.startSet();
 replTest.initiate();
 
+const primary = replTest.getPrimary();
+// This test performs a reconfig that will change the implicit default write concern
+// from {w: "majority"} to {w: 1}. In order for this reconfig to succeed, we must first
+// set the cluster-wide write concern.
+assert.commandWorked(primary.adminCommand(
+    {setDefaultRWConcern: 1, defaultWriteConcern: {w: "majority"}, writeConcern: {w: "majority"}}));
+
 jsTestLog('Start arbiter');
 const arbiterConn = replTest.add();
-const admin = replTest.getPrimary().getDB('admin');
+const admin = primary.getDB('admin');
 const conf = replTest.getReplSetConfigFromNode();
 conf.members.push({_id: 2, host: arbiterConn.host, arbiterOnly: true});
 conf.version++;
diff --git a/jstests/replsets/reconfig_fails_no_cwwc_set.js b/jstests/replsets/reconfig_fails_no_cwwc_set.js
new file mode 100644
index 00000000000..326f193ffd7
--- /dev/null
+++ b/jstests/replsets/reconfig_fails_no_cwwc_set.js
@@ -0,0 +1,62 @@
+/*
+ * Test that a reconfig that would change the implicit default write concern fails.
+ * In order to perform such a reconfig, users must set a cluster-wide write concern.
+ *
+ * @tags: [requires_fcv_50]
+ */
+
+(function() {
+'use strict';
+
+load("jstests/libs/write_concern_util.js");  // For 'isDefaultWriteConcernMajorityFlagEnabled()'.
+
+const rst = new ReplSetTest({nodes: 2});
+rst.startSet();
+rst.initiate();
+
+const primary = rst.getPrimary();
+
+const featureFlagEnabled = isDefaultWriteConcernMajorityFlagEnabled(primary);
+let cwwc = primary.adminCommand({getDefaultRWConcern: 1});
+if (featureFlagEnabled) {
+    assert(cwwc.hasOwnProperty("defaultWriteConcern"));
+    assert.eq({w: "majority", wtimeout: 0}, cwwc.defaultWriteConcern, tojson(cwwc));
+} else {
+    assert(!cwwc.hasOwnProperty("defaultWriteConcern"));
+}
+
+jsTestLog("Starting arbiter");
+const arbiter = rst.add();
+const config = rst.getReplSetConfigFromNode();
+config.members.push({_id: 2, host: arbiter.host, arbiterOnly: true});
+config.version++;
+const reconfigErrorMsg =
+    "Reconfig attempted to install a config that would change the implicit default write concern";
+
+if (featureFlagEnabled) {
+    // Adding the arbiter would change the implicit default write concern from {w: majority} to
+    // {w:1}, so we fail the reconfig.
+    let res = assert.commandFailed(primary.adminCommand({replSetReconfig: config}));
+    assert.eq(res.code, ErrorCodes.NewReplicaSetConfigurationIncompatible);
+    assert(res.errmsg.includes(reconfigErrorMsg));
+
+    // A force reconfig should also fail.
+    res = assert.commandFailed(primary.adminCommand({replSetReconfig: config, force: true}));
+    assert.eq(res.code, ErrorCodes.NewReplicaSetConfigurationIncompatible);
+    assert(res.errmsg.includes(reconfigErrorMsg));
+
+    assert.commandWorked(primary.adminCommand(
+        {setDefaultRWConcern: 1, defaultWriteConcern: {w: 1}, writeConcern: {w: "majority"}}));
+
+    // After setting the cluster-wide write concern, the same reconfig command should succeed.
+    assert.commandWorked(primary.adminCommand({replSetReconfig: config}));
+
+    cwwc = primary.adminCommand({getDefaultRWConcern: 1});
+    assert(cwwc.hasOwnProperty("defaultWriteConcern"));
+    assert.eq({w: 1, wtimeout: 0}, cwwc.defaultWriteConcern, tojson(cwwc));
+} else {
+    assert.commandWorked(primary.adminCommand({replSetReconfig: config}));
+}
+
+rst.stopSet();
+})();
diff --git a/src/mongo/db/read_write_concern_defaults.cpp b/src/mongo/db/read_write_concern_defaults.cpp
index 183805cf64d..c982ef78bda 100644
--- a/src/mongo/db/read_write_concern_defaults.cpp
+++ b/src/mongo/db/read_write_concern_defaults.cpp
@@ -161,6 +161,23 @@ RWConcernDefault ReadWriteConcernDefaults::generateNewCWRWCToBeSavedOnDisk(
     return rwc;
 }
 
+bool ReadWriteConcernDefaults::isCWWCSet(OperationContext* opCtx) {
+    // TODO (SERVER-57042): Call getDefault() instead and return writeConcernSource == KGlobal.
+    auto cached = _getDefaultCWRWCFromDisk(opCtx);
+    if (!cached) {
+        return false;
+    }
+
+    auto wc = cached.get().getDefaultWriteConcern();
+    if (!wc) {
+        return false;
+    }
+
+    // CWWC should have "usedDefault" flag set to false, as this flag only set to true if the
+    // default constructed WC is used.
+    return !wc.get().usedDefault;
+}
+
 void ReadWriteConcernDefaults::observeDirectWriteToConfigSettings(OperationContext* opCtx,
                                                                   BSONElement idElem,
                                                                   boost::optional<BSONObj> newDoc) {
diff --git a/src/mongo/db/read_write_concern_defaults.h b/src/mongo/db/read_write_concern_defaults.h
index 2108cb8c189..1ce216c2b80 100644
--- a/src/mongo/db/read_write_concern_defaults.h
+++ b/src/mongo/db/read_write_concern_defaults.h
@@ -130,6 +130,11 @@ public:
                                                      const boost::optional<WriteConcern>& wc);
 
     /**
+     * Returns true if cluster-wide write concern is set and false otherwise.
+     */
+    bool isCWWCSet(OperationContext* opCtx);
+
+    /**
      * Invalidates the cached RWC defaults, causing them to be refreshed.
      *
      * After this call returns, the read methods below (getDefault, getDefaultReadConcern,
diff --git a/src/mongo/db/read_write_concern_defaults_test.cpp b/src/mongo/db/read_write_concern_defaults_test.cpp
index 1d558ff2ed4..73009587628 100644
--- a/src/mongo/db/read_write_concern_defaults_test.cpp
+++ b/src/mongo/db/read_write_concern_defaults_test.cpp
@@ -54,6 +54,10 @@ protected:
         return ReadWriteConcernDefaults::get(getServiceContext()).getDefault(_opCtx);
     }
 
+    bool isCWWCSet() {
+        return ReadWriteConcernDefaults::get(getServiceContext()).isCWWCSet(_opCtx);
+    }
+
     ReadWriteConcernDefaultsLookupMock _lookupMock;
 
     bool _isDefaultWCMajorityEnabled{
@@ -72,6 +76,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithAbsentCWRWCWithImplicitWC
     auto defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
     ASSERT(!defaults.getDefaultWriteConcern());
+    ASSERT(!isCWWCSet());
     ASSERT(!defaults.getUpdateOpTime());
     ASSERT(!defaults.getUpdateWallClockTime());
     ASSERT_EQ(Date_t(), defaults.localUpdateWallClockTime());
@@ -89,6 +94,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithAbsentCWRWCWithImplicitWC
 
     // By not calling _lookupMock.setLookupCallReturnValue(), tests _defaults.lookup() returning
     // boost::none.
+    ASSERT(!isCWWCSet());
     auto defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
     ASSERT(defaults.getDefaultWriteConcern());
@@ -105,6 +111,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithCWRWCNeverSetWithImplicit
     // _defaults.lookup() returning default constructed RWConcern not boost::none.
     _lookupMock.setLookupCallReturnValue({});
 
+    ASSERT(!isCWWCSet());
     auto defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
     ASSERT(!defaults.getDefaultWriteConcern());
@@ -124,6 +131,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithCWRWCNeverSetWithImplicit
     createDefaults(true /* isImplicitWCMajority */);
 
     // _defaults.lookup() returning default constructed RWConcern not boost::none.
+    ASSERT(!isCWWCSet());
     _lookupMock.setLookupCallReturnValue({});
     auto defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
@@ -143,6 +151,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithUnsetCWRWCWithImplicitWCW
     newDefaults.setUpdateWallClockTime(Date_t::fromMillisSinceEpoch(1234));
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults));
 
+    ASSERT(!isCWWCSet());
     auto defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
     ASSERT(!defaults.getDefaultWriteConcern());
@@ -166,6 +175,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithUnsetCWRWCWithImplicitWCM
     newDefaults.setUpdateWallClockTime(Date_t::fromMillisSinceEpoch(1234));
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults));
 
+    ASSERT(!isCWWCSet());
     auto defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
     ASSERT(defaults.getDefaultWriteConcern());
@@ -184,6 +194,8 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithSetCWRWCWithImplicitWCW1)
         repl::ReadConcernArgs(repl::ReadConcernLevel::kLocalReadConcern));
     WriteConcernOptions wc;
     wc.wNumNodes = 4;
+    wc.usedDefault = false;
+    wc.usedDefaultW = false;
     newDefaults.setDefaultWriteConcern(wc);
     newDefaults.setUpdateOpTime(Timestamp(1, 2));
     newDefaults.setUpdateWallClockTime(Date_t::fromMillisSinceEpoch(1234));
@@ -192,6 +204,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithSetCWRWCWithImplicitWCW1)
     }
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults));
 
+    ASSERT(isCWWCSet());
     auto defaults = getDefault();
     ASSERT(defaults.getDefaultReadConcern()->getLevel() ==
            repl::ReadConcernLevel::kLocalReadConcern);
@@ -226,6 +239,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithSetCWRWCWithImplicitWCMaj
     }
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults));
 
+    ASSERT(isCWWCSet());
     auto defaults = getDefault();
     ASSERT(defaults.getDefaultReadConcern()->getLevel() ==
            repl::ReadConcernLevel::kLocalReadConcern);
@@ -246,17 +260,14 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWriteConcernSourceImplicitWit
     createDefaults(true /* isImplicitWCMajority */);
 
     RWConcernDefault newDefaults;
-    WriteConcernOptions wc;
-    wc.wNumNodes = 4;
-    wc.usedDefault = true;
-    wc.usedDefaultW = false;
-    newDefaults.setDefaultWriteConcern(wc);
+    newDefaults.setDefaultWriteConcern(WriteConcernOptions());
     newDefaults.setUpdateOpTime(Timestamp(1, 2));
     newDefaults.setUpdateWallClockTime(Date_t::fromMillisSinceEpoch(1234));
     newDefaults.setDefaultWriteConcernSource(DefaultWriteConcernSourceEnum::kGlobal);
 
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults));
 
+    ASSERT(!isCWWCSet());
     // The default write concern source should be set to implicit if wc.usedDefault is true
     auto defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
@@ -279,6 +290,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithSetAndUnSetCWRCWithImplic
     newDefaults.setUpdateWallClockTime(Date_t::fromMillisSinceEpoch(1234));
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults));
 
+    ASSERT(!isCWWCSet());
     auto defaults = getDefault();
     ASSERT(defaults.getDefaultReadConcern()->getLevel() ==
            repl::ReadConcernLevel::kLocalReadConcern);
@@ -298,6 +310,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithSetAndUnSetCWRCWithImplic
 
     ReadWriteConcernDefaults::get(getServiceContext()).refreshIfNecessary(_opCtx);
 
+    ASSERT(!isCWWCSet());
     defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
     ASSERT(!defaults.getDefaultWriteConcern());
@@ -324,7 +337,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithSetAndUnSetCWRCWithImplic
     newDefaults.setUpdateWallClockTime(Date_t::fromMillisSinceEpoch(1234));
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults));
 
-
+    ASSERT(!isCWWCSet());
     auto defaults = getDefault();
     ASSERT(defaults.getDefaultReadConcern()->getLevel() ==
            repl::ReadConcernLevel::kLocalReadConcern);
@@ -343,6 +356,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithSetAndUnSetCWRCWithImplic
 
     ReadWriteConcernDefaults::get(getServiceContext()).refreshIfNecessary(_opCtx);
 
+    ASSERT(!isCWWCSet());
     defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
     ASSERT(defaults.getDefaultWriteConcern());
@@ -358,6 +372,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultLookupFailure) {
     createDefaults(true /* isImplicitWCMajority */);
     _lookupMock.setLookupCallFailure(Status{ErrorCodes::Error(1234), "foobar"});
     ASSERT_THROWS_CODE_AND_WHAT(getDefault(), AssertionException, 1234, "foobar");
+    ASSERT_THROWS_CODE_AND_WHAT(isCWWCSet(), AssertionException, 1234, "foobar");
 }
 
 TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithoutInvalidateDoesNotCallLookup) {
@@ -368,6 +383,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithoutInvalidateDoesNotCallL
     newDefaults.setUpdateWallClockTime(Date_t::fromMillisSinceEpoch(1234));
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults));
 
+    ASSERT(!isCWWCSet());
     auto defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
     ASSERT(!defaults.getDefaultWriteConcern());
@@ -383,6 +399,8 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithoutInvalidateDoesNotCallL
         repl::ReadConcernArgs(repl::ReadConcernLevel::kLocalReadConcern));
     WriteConcernOptions wc;
     wc.wNumNodes = 4;
+    wc.usedDefault = false;
+    wc.usedDefaultW = false;
     newDefaults2.setDefaultWriteConcern(wc);
     newDefaults2.setUpdateOpTime(Timestamp(3, 4));
     newDefaults2.setUpdateWallClockTime(Date_t::fromMillisSinceEpoch(5678));
@@ -391,6 +409,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestGetDefaultWithoutInvalidateDoesNotCallL
     }
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults2));
 
+    ASSERT(!isCWWCSet());
     auto defaults2 = getDefault();
     ASSERT(!defaults2.getDefaultReadConcern());
     ASSERT(!defaults2.getDefaultWriteConcern());
@@ -411,6 +430,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestInvalidate) {
     newDefaults.setUpdateWallClockTime(Date_t::fromMillisSinceEpoch(1234));
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults));
 
+    ASSERT(!isCWWCSet());
     auto defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
     ASSERT(!defaults.getDefaultWriteConcern());
@@ -426,6 +446,8 @@ TEST_F(ReadWriteConcernDefaultsTest, TestInvalidate) {
         repl::ReadConcernArgs(repl::ReadConcernLevel::kLocalReadConcern));
     WriteConcernOptions wc;
     wc.wNumNodes = 4;
+    wc.usedDefault = false;
+    wc.usedDefaultW = false;
     newDefaults2.setDefaultWriteConcern(wc);
     newDefaults2.setUpdateOpTime(Timestamp(3, 4));
     newDefaults2.setUpdateWallClockTime(Date_t::fromMillisSinceEpoch(5678));
@@ -435,6 +457,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestInvalidate) {
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults2));
 
     ReadWriteConcernDefaults::get(getServiceContext()).invalidate();
+    ASSERT(isCWWCSet());
     auto defaults2 = getDefault();
     ASSERT(defaults2.getDefaultReadConcern()->getLevel() ==
            repl::ReadConcernLevel::kLocalReadConcern);
@@ -451,6 +474,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestRefreshDefaultsWithEmptyCacheAndAbsentD
     createDefaults(false /* isImplicitWCMajority */);
     ReadWriteConcernDefaults::get(getServiceContext()).refreshIfNecessary(_opCtx);
 
+    ASSERT(!isCWWCSet());
     auto defaults = getDefault();
     ASSERT(!defaults.getDefaultReadConcern());
     ASSERT(!defaults.getDefaultWriteConcern());
@@ -472,6 +496,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestRefreshDefaultsWithEmptyCacheAndSetDefa
 
     ReadWriteConcernDefaults::get(getServiceContext()).refreshIfNecessary(_opCtx);
 
+    ASSERT(!isCWWCSet());
     auto defaults = getDefault();
     ASSERT_EQ(Timestamp(1, 2), *defaults.getUpdateOpTime());
     ASSERT_EQ(1234, defaults.getUpdateWallClockTime()->toMillisSinceEpoch());
@@ -489,6 +514,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestRefreshDefaultsWithHigherEpoch) {
     newDefaults.setUpdateWallClockTime(Date_t::fromMillisSinceEpoch(1234));
     _lookupMock.setLookupCallReturnValue(std::move(newDefaults));
 
+    ASSERT(!isCWWCSet());
     auto defaults = getDefault();
     ASSERT_EQ(Timestamp(1, 2), *defaults.getUpdateOpTime());
     ASSERT_EQ(1234, defaults.getUpdateWallClockTime()->toMillisSinceEpoch());
@@ -503,6 +529,7 @@ TEST_F(ReadWriteConcernDefaultsTest, TestRefreshDefaultsWithHigherEpoch) {
 
     ReadWriteConcernDefaults::get(getServiceContext()).refreshIfNecessary(_opCtx);
 
+    ASSERT(!isCWWCSet());
     auto defaults2 = getDefault();
     ASSERT_EQ(Timestamp(3, 4), *defaults2.getUpdateOpTime());
     ASSERT_EQ(5678, defaults2.getUpdateWallClockTime()->toMillisSinceEpoch());
diff --git a/src/mongo/db/repl/SConscript b/src/mongo/db/repl/SConscript
index 67b2c9f9580..eb8ce074e9e 100644
--- a/src/mongo/db/repl/SConscript
+++ b/src/mongo/db/repl/SConscript
@@ -1686,6 +1686,7 @@ env.CppUnitTest(
         'topology_coordinator_v1_test.cpp',
     ],
     LIBDEPS=[
+        '$BUILD_DIR/mongo/db/read_write_concern_defaults_mock',
         'isself',
         'repl_coordinator_impl',
         'repl_coordinator_test_fixture',
diff --git a/src/mongo/db/repl/replication_coordinator_impl.cpp b/src/mongo/db/repl/replication_coordinator_impl.cpp
index 0fb1400aafe..80b7a39f614 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl.cpp
@@ -3451,6 +3451,29 @@ Status ReplicationCoordinatorImpl::_doReplSetReconfig(OperationContext* opCtx,
         return status;
     ReplSetConfig newConfig = newConfigStatus.getValue();
 
+    // If the new config changes the replica set's implicit default write concern, we fail the
+    // reconfig command. This includes force reconfigs, but excludes reconfigs that bump the config
+    // term during step-up. The user should set a cluster-wide write concern and attempt the
+    // reconfig command again. We also need to exclude shard servers from this validation, as shard
+    // servers don't store the cluster-wide write concern.
+    if (!skipSafetyChecks /* skipping step-up reconfig */ &&
+        repl::feature_flags::gDefaultWCMajority.isEnabled(
+            serverGlobalParams.featureCompatibility) &&
+        serverGlobalParams.clusterRole != ClusterRole::ShardServer &&
+        !repl::enableDefaultWriteConcernUpdatesForInitiate.load()) {
+        bool currIDWC = oldConfig.isImplicitDefaultWriteConcernMajority();
+        bool newIDWC = newConfig.isImplicitDefaultWriteConcernMajority();
+        bool isCWWCSet = ReadWriteConcernDefaults::get(opCtx).isCWWCSet(opCtx);
+        if (!isCWWCSet && currIDWC != newIDWC) {
+            return Status(
+                ErrorCodes::NewReplicaSetConfigurationIncompatible,
+                str::stream()
+                    << "Reconfig attempted to install a config that would change the "
+                       "implicit default write concern. Use the setDefaultRWConcern command to "
+                       "set a cluster-wide write concern and try the reconfig again.");
+        }
+    }
+
     BSONObj oldConfigObj = oldConfig.toBSON();
     BSONObj newConfigObj = newConfig.toBSON();
     audit::logReplSetReconfig(opCtx->getClient(), &oldConfigObj, &newConfigObj);
diff --git a/src/mongo/db/repl/replication_coordinator_impl_reconfig_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_reconfig_test.cpp
index b3fb19795f7..4fdb2403540 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_reconfig_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_reconfig_test.cpp
@@ -32,6 +32,7 @@
 #include "mongo/platform/basic.h"
 
 #include "mongo/db/jsobj.h"
+#include "mongo/db/read_write_concern_defaults_cache_lookup_mock.h"
 #include "mongo/db/repl/repl_server_parameters_gen.h"
 #include "mongo/db/repl/repl_set_config.h"
 #include "mongo/db/repl/repl_set_heartbeat_args_v1.h"
@@ -1953,6 +1954,14 @@ TEST_F(ReplCoordReconfigTest, NodesWithNewlyAddedFieldSetHavePriorityZero) {
 }
 
 TEST_F(ReplCoordReconfigTest, ArbiterNodesShouldNeverHaveNewlyAddedField) {
+    RWConcernDefault newDefaults;
+    WriteConcernOptions wc;
+    wc.wMode = "majority";
+    wc.usedDefault = false;
+    wc.usedDefaultW = false;
+    newDefaults.setDefaultWriteConcern(wc);
+    lookupMock.setLookupCallReturnValue(std::move(newDefaults));
+
     setUpNewlyAddedFieldTest();
 
     auto opCtx = makeOperationContext();
diff --git a/src/mongo/db/repl/replication_coordinator_test_fixture.cpp b/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
index 802b4e921fb..2c6a45f4d0a 100644
--- a/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
+++ b/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
@@ -144,8 +144,7 @@ void ReplCoordTest::init() {
 
     // The ReadWriteConcernDefaults decoration on the service context won't always be created,
     // so we should manually instantiate it to ensure it exists in our tests.
-    ReadWriteConcernDefaults::create(service, _lookupMock.getFetchDefaultsFn());
-    enableDefaultWriteConcernUpdatesForInitiate.store(true);
+    ReadWriteConcernDefaults::create(service, lookupMock.getFetchDefaultsFn());
 
     TopologyCoordinator::Options settings;
     auto topo = std::make_unique<TopologyCoordinator>(settings);
diff --git a/src/mongo/db/repl/replication_coordinator_test_fixture.h b/src/mongo/db/repl/replication_coordinator_test_fixture.h
index 46a81edaff0..4589c82aca5 100644
--- a/src/mongo/db/repl/replication_coordinator_test_fixture.h
+++ b/src/mongo/db/repl/replication_coordinator_test_fixture.h
@@ -320,6 +320,8 @@ protected:
      */
     void simulateCatchUpAbort();
 
+    ReadWriteConcernDefaultsLookupMock lookupMock;
+
 private:
     std::unique_ptr<ReplicationCoordinatorImpl> _repl;
     // Owned by ReplicationCoordinatorImpl
@@ -335,8 +337,6 @@ private:
 
     ReplSettings _settings;
     bool _callShutdown = false;
-
-    ReadWriteConcernDefaultsLookupMock _lookupMock;
 };
 
 }  // namespace repl