SERVER-33135 Remove metadata accessors from command reply APIs

Now that OP_COMMAND is dead, all remaining implementations return the same
BSONObj for data and metadata.

20 files changed, 173 insertions, 199 deletions

diff --git a/src/mongo/db/commands.cpp b/src/mongo/db/commands.cpp
index 57e82e49067..63500fe2af4 100644
--- a/src/mongo/db/commands.cpp
+++ b/src/mongo/db/commands.cpp
@@ -519,7 +519,6 @@ void Command::generateHelpResponse(OperationContext* opCtx,
     helpBuilder.append("help",
                        str::stream() << "help for: " << command.getName() << " " << command.help());
     replyBuilder->setCommandReply(helpBuilder.obj());
-    replyBuilder->setMetadata(rpc::makeEmptyMetadata());
 }
 
 bool ErrmsgCommandDeprecated::run(OperationContext* opCtx,
diff --git a/src/mongo/db/repl/abstract_oplog_fetcher_test.cpp b/src/mongo/db/repl/abstract_oplog_fetcher_test.cpp
index 388e1492461..13446ed9ff5 100644
--- a/src/mongo/db/repl/abstract_oplog_fetcher_test.cpp
+++ b/src/mongo/db/repl/abstract_oplog_fetcher_test.cpp
@@ -451,8 +451,7 @@ TEST_F(AbstractOplogFetcherTest, OplogFetcherTimesOutCorrectlyOnInitialFindReque
     net->enterNetwork();
     auto when = net->now() + initialFindMaxTime + kNetworkTimeoutBufferMS + Milliseconds(10);
     auto noi = getNet()->getNextReadyRequest();
-    RemoteCommandResponse response = {
-        {makeCursorResponse(1, {ops[0], ops[1]})}, rpc::makeEmptyMetadata(), Milliseconds(0)};
+    RemoteCommandResponse response = {{makeCursorResponse(1, {ops[0], ops[1]})}, Milliseconds(0)};
     auto request = net->scheduleSuccessfulResponse(noi, when, response);
     net->runUntil(when);
     net->runReadyNetworkOperations();
@@ -492,8 +491,7 @@ TEST_F(AbstractOplogFetcherTest, OplogFetcherTimesOutCorrectlyOnRetriedFindReque
     net->enterNetwork();
     auto when = net->now() + initialFindMaxTime + kNetworkTimeoutBufferMS + Milliseconds(10);
     auto noi = getNet()->getNextReadyRequest();
-    RemoteCommandResponse response = {
-        {makeCursorResponse(1, {ops[0], ops[1]})}, rpc::makeEmptyMetadata(), Milliseconds(0)};
+    RemoteCommandResponse response = {{makeCursorResponse(1, {ops[0], ops[1]})}, Milliseconds(0)};
     auto request = net->scheduleSuccessfulResponse(noi, when, response);
     net->runUntil(when);
     net->runReadyNetworkOperations();
@@ -503,8 +501,7 @@ TEST_F(AbstractOplogFetcherTest, OplogFetcherTimesOutCorrectlyOnRetriedFindReque
     net->enterNetwork();
     when = net->now() + retriedFindMaxTime + kNetworkTimeoutBufferMS + Milliseconds(10);
     noi = getNet()->getNextReadyRequest();
-    response = {
-        {makeCursorResponse(1, {ops[0], ops[1]})}, rpc::makeEmptyMetadata(), Milliseconds(0)};
+    response = {{makeCursorResponse(1, {ops[0], ops[1]})}, Milliseconds(0)};
     request = net->scheduleSuccessfulResponse(noi, when, response);
     net->runUntil(when);
     net->runReadyNetworkOperations();
diff --git a/src/mongo/db/repl/abstract_oplog_fetcher_test_fixture.cpp b/src/mongo/db/repl/abstract_oplog_fetcher_test_fixture.cpp
index 2b0696c8531..ed0e0f9105a 100644
--- a/src/mongo/db/repl/abstract_oplog_fetcher_test_fixture.cpp
+++ b/src/mongo/db/repl/abstract_oplog_fetcher_test_fixture.cpp
@@ -139,8 +139,7 @@ executor::RemoteCommandRequest AbstractOplogFetcherTest::processNetworkResponse(
 
 executor::RemoteCommandRequest AbstractOplogFetcherTest::processNetworkResponse(
     BSONObj obj, bool expectReadyRequestsAfterProcessing) {
-    return processNetworkResponse({obj, rpc::makeEmptyMetadata(), Milliseconds(0)},
-                                  expectReadyRequestsAfterProcessing);
+    return processNetworkResponse({obj, Milliseconds(0)}, expectReadyRequestsAfterProcessing);
 }
 
 }  // namespace repl
diff --git a/src/mongo/db/repl/base_cloner_test_fixture.cpp b/src/mongo/db/repl/base_cloner_test_fixture.cpp
index 8fb69472329..88d0a84d996 100644
--- a/src/mongo/db/repl/base_cloner_test_fixture.cpp
+++ b/src/mongo/db/repl/base_cloner_test_fixture.cpp
@@ -162,7 +162,7 @@ const Status& BaseClonerTest::getStatus() const {
 void BaseClonerTest::scheduleNetworkResponse(NetworkOperationIterator noi, const BSONObj& obj) {
     auto net = getNet();
     Milliseconds millis(0);
-    RemoteCommandResponse response(obj, BSONObj(), millis);
+    RemoteCommandResponse response(obj, millis);
     log() << "Scheduling response to request:" << noi->getDiagnosticString() << " -- resp:" << obj;
     net->scheduleResponse(noi, net->now(), response);
 }
diff --git a/src/mongo/db/repl/check_quorum_for_config_change.cpp b/src/mongo/db/repl/check_quorum_for_config_change.cpp
index 67204eed65c..f5c967163d0 100644
--- a/src/mongo/db/repl/check_quorum_for_config_change.cpp
+++ b/src/mongo/db/repl/check_quorum_for_config_change.cpp
@@ -226,7 +226,7 @@ void QuorumChecker::_tabulateHeartbeatResponse(const RemoteCommandRequest& reque
 
     if (_rsConfig->hasReplicaSetId()) {
         StatusWith<rpc::ReplSetMetadata> replMetadata =
-            rpc::ReplSetMetadata::readFromMetadata(response.metadata);
+            rpc::ReplSetMetadata::readFromMetadata(response.data);
         if (replMetadata.isOK() && replMetadata.getValue().getReplicaSetId().isSet() &&
             _rsConfig->getReplicaSetId() != replMetadata.getValue().getReplicaSetId()) {
             std::string message = str::stream()
diff --git a/src/mongo/db/repl/check_quorum_for_config_change_test.cpp b/src/mongo/db/repl/check_quorum_for_config_change_test.cpp
index 2d4c0416b3e..7829fd72ec5 100644
--- a/src/mongo/db/repl/check_quorum_for_config_change_test.cpp
+++ b/src/mongo/db/repl/check_quorum_for_config_change_test.cpp
@@ -233,7 +233,7 @@ const BSONObj makeHeartbeatRequest(const ReplSetConfig& rsConfig, int myConfigIn
 executor::RemoteCommandResponse makeHeartbeatResponse(const ReplSetConfig& rsConfig,
                                                       const stdx::chrono::milliseconds millis,
                                                       const long long configVersion = 0,
-                                                      const BSONObj& metadata = {}) {
+                                                      const BSONObj& extraFields = {}) {
     ReplSetHeartbeatResponse hbResp;
     hbResp.setSetName(rsConfig.getReplSetName());
     hbResp.setConfigVersion(configVersion);
@@ -241,7 +241,9 @@ executor::RemoteCommandResponse makeHeartbeatResponse(const ReplSetConfig& rsCon
     OpTime opTime(Timestamp(), 0);
     hbResp.setAppliedOpTime(opTime);
     hbResp.setDurableOpTime(opTime);
-    return RemoteCommandResponse(hbResp.toBSON(), metadata, duration_cast<Milliseconds>(millis));
+    auto bob = BSONObjBuilder(hbResp.toBSON());
+    bob.appendElements(extraFields);
+    return RemoteCommandResponse(bob.obj(), duration_cast<Milliseconds>(millis));
 }
 
 TEST_F(CheckQuorumForInitiate, QuorumCheckSuccessForFiveNodes) {
@@ -399,13 +401,10 @@ TEST_F(CheckQuorumForInitiate, QuorumCheckFailedDueToSetNameMismatch) {
                 (RemoteCommandResponse(
                     BSON("ok" << 0 << "code" << ErrorCodes::InconsistentReplicaSetNames << "errmsg"
                               << "replica set name doesn't match."),
-                    BSONObj(),
                     Milliseconds(8))));
         } else {
             getNet()->scheduleResponse(
-                noi,
-                startDate + 10ms,
-                (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(8))));
+                noi, startDate + 10ms, RemoteCommandResponse(BSON("ok" << 1), Milliseconds(8)));
         }
     }
     getNet()->runUntil(startDate + 10ms);
@@ -473,14 +472,14 @@ TEST_F(CheckQuorumForInitiate, QuorumCheckFailedDueToSetIdMismatch) {
                                           unexpectedId,
                                           rpc::ReplSetMetadata::kNoPrimary,
                                           -1);
-            BSONObjBuilder metadataBuilder;
-            metadata.writeToMetadata(&metadataBuilder).transitional_ignore();
+            BSONObjBuilder bob;
+            uassertStatusOK(metadata.writeToMetadata(&bob));
 
             long long configVersion = 0;
             getNet()->scheduleResponse(
                 noi,
                 startDate + 10ms,
-                makeHeartbeatResponse(rsConfig, 8ms, configVersion, metadataBuilder.obj()));
+                makeHeartbeatResponse(rsConfig, 8ms, configVersion, bob.obj()));
         } else {
             getNet()->scheduleResponse(noi, startDate + 10ms, makeHeartbeatResponse(rsConfig, 8ms));
         }
@@ -713,7 +712,6 @@ TEST_F(CheckQuorumForReconfig, QuorumCheckVetoedDueToIncompatibleSetName) {
                 (RemoteCommandResponse(
                     BSON("ok" << 0 << "code" << ErrorCodes::InconsistentReplicaSetNames << "errmsg"
                               << "replica set name doesn't match."),
-                    BSONObj(),
                     Milliseconds(8))));
         } else {
             getNet()->scheduleResponse(
@@ -949,10 +947,9 @@ TEST_F(CheckQuorumForReconfig, QuorumCheckProcessesCallbackCanceledResponse) {
                 startDate + 10ms,
                 (RemoteCommandResponse(ErrorCodes::CallbackCanceled, "Testing canceled callback")));
         } else {
-            getNet()->scheduleResponse(
-                noi,
-                startDate + 10ms,
-                (RemoteCommandResponse(BSON("ok" << 0), BSONObj(), Milliseconds(8))));
+            getNet()->scheduleResponse(noi,
+                                       startDate + Milliseconds(10),
+                                       RemoteCommandResponse(BSON("ok" << 0), Milliseconds(8)));
         }
     }
     getNet()->runUntil(startDate + 10ms);
diff --git a/src/mongo/db/repl/databases_cloner_test.cpp b/src/mongo/db/repl/databases_cloner_test.cpp
index f32c83c756a..66f2138ceaa 100644
--- a/src/mongo/db/repl/databases_cloner_test.cpp
+++ b/src/mongo/db/repl/databases_cloner_test.cpp
@@ -104,7 +104,7 @@ public:
                                  const BSONObj& obj) {
         NetworkInterfaceMock* net = getNet();
         Milliseconds millis(0);
-        RemoteCommandResponse response(obj, BSONObj(), millis);
+        RemoteCommandResponse response(obj, millis);
         net->scheduleResponse(noi, net->now(), response);
     }
 
@@ -242,11 +242,10 @@ protected:
             log() << "Sending response for network request:";
             log() << "     req: " << noi->getRequest().dbname << "." << noi->getRequest().cmdObj;
             log() << "     resp:" << responses[processedRequests].second;
-            net->scheduleResponse(noi,
-                                  net->now(),
-                                  RemoteCommandResponse(responses[processedRequests].second,
-                                                        BSONObj(),
-                                                        Milliseconds(10)));
+            net->scheduleResponse(
+                noi,
+                net->now(),
+                RemoteCommandResponse(responses[processedRequests].second, Milliseconds(10)));
 
             if ((Date_t::now() - lastLog) > Seconds(1)) {
                 lastLog = Date_t();
diff --git a/src/mongo/db/repl/initial_syncer_test.cpp b/src/mongo/db/repl/initial_syncer_test.cpp
index 2948a08ff01..fe3483cb792 100644
--- a/src/mongo/db/repl/initial_syncer_test.cpp
+++ b/src/mongo/db/repl/initial_syncer_test.cpp
@@ -162,7 +162,7 @@ public:
                                  const BSONObj& obj) {
         NetworkInterfaceMock* net = getNet();
         Milliseconds millis(0);
-        RemoteCommandResponse response(obj, BSONObj(), millis);
+        RemoteCommandResponse response(obj, millis);
         log() << "Sending response for network request:";
         log() << "     req: " << noi->getRequest().dbname << "." << noi->getRequest().cmdObj;
         log() << "     resp:" << response;
@@ -501,9 +501,6 @@ RemoteCommandResponse makeCursorResponse(CursorId cursorId,
                                          int rbid = 1) {
     OpTime futureOpTime(Timestamp(1000, 1000), 1000);
     rpc::OplogQueryMetadata oqMetadata(futureOpTime, futureOpTime, rbid, 0, 0);
-    BSONObjBuilder metadataBob;
-    ASSERT_OK(oqMetadata.writeToMetadata(&metadataBob));
-    auto metadataObj = metadataBob.obj();
 
     BSONObjBuilder bob;
     {
@@ -518,8 +515,9 @@ RemoteCommandResponse makeCursorResponse(CursorId cursorId,
             }
         }
     }
+    ASSERT_OK(oqMetadata.writeToMetadata(&bob));
     bob.append("ok", 1);
-    return {bob.obj(), metadataObj, Milliseconds(0)};
+    return {bob.obj(), Milliseconds()};
 }
 
 /**
diff --git a/src/mongo/db/repl/oplog_fetcher_test.cpp b/src/mongo/db/repl/oplog_fetcher_test.cpp
index 5209ea0c4e3..8f03c6c50cb 100644
--- a/src/mongo/db/repl/oplog_fetcher_test.cpp
+++ b/src/mongo/db/repl/oplog_fetcher_test.cpp
@@ -192,8 +192,7 @@ std::unique_ptr<ShutdownState> OplogFetcherTest::processSingleBatch(RemoteComman
 
 std::unique_ptr<ShutdownState> OplogFetcherTest::processSingleBatch(BSONObj obj,
                                                                     bool requireFresherSyncSource) {
-    return processSingleBatch({obj, rpc::makeEmptyMetadata(), Milliseconds(0)},
-                              requireFresherSyncSource);
+    return processSingleBatch({obj, Milliseconds(0)}, requireFresherSyncSource);
 }
 
 void _checkDefaultCommandObjectFields(BSONObj cmdObj) {
@@ -219,6 +218,12 @@ std::unique_ptr<OplogFetcher> OplogFetcherTest::makeOplogFetcher(ReplSetConfig c
                                            defaultBatchSize);
 }
 
+BSONObj concatenate(BSONObj a, const BSONObj& b) {
+    auto bob = BSONObjBuilder(std::move(a));
+    bob.appendElements(b);
+    return bob.obj();
+}
+
 TEST_F(
     OplogFetcherTest,
     FindQueryContainsTermAndStartTimestampIfGetCurrentTermAndLastCommittedOpTimeReturnsValidTerm) {
@@ -255,19 +260,21 @@ TEST_F(OplogFetcherTest, AwaitDataTimeoutShouldEqualHalfElectionTimeoutUnderProt
 }
 
 TEST_F(OplogFetcherTest, InvalidReplSetMetadataInResponseStopsTheOplogFetcher) {
-    auto shutdownState = processSingleBatch(
-        {makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}),
-         BSON(rpc::kReplSetMetadataFieldName << BSON("invalid_repl_metadata_field" << 1)),
-         Milliseconds(0)});
+    auto shutdownState =
+        processSingleBatch({concatenate(makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}),
+                                        BSON(rpc::kReplSetMetadataFieldName
+                                             << BSON("invalid_repl_metadata_field" << 1))),
+                            Milliseconds(0)});
 
     ASSERT_EQUALS(ErrorCodes::NoSuchKey, shutdownState->getStatus());
 }
 
 TEST_F(OplogFetcherTest, InvalidOplogQueryMetadataInResponseStopsTheOplogFetcher) {
-    auto shutdownState = processSingleBatch(
-        {makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}),
-         BSON(rpc::kOplogQueryMetadataFieldName << BSON("invalid_oq_metadata_field" << 1)),
-         Milliseconds(0)});
+    auto shutdownState =
+        processSingleBatch({concatenate(makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}),
+                                        BSON(rpc::kOplogQueryMetadataFieldName
+                                             << BSON("invalid_oq_metadata_field" << 1))),
+                            Milliseconds(0)});
 
     ASSERT_EQUALS(ErrorCodes::NoSuchKey, shutdownState->getStatus());
 }
@@ -279,10 +286,11 @@ TEST_F(OplogFetcherTest,
     ASSERT_OK(metadata.writeToMetadata(&bob));
     auto metadataObj = bob.obj();
 
-    ASSERT_OK(processSingleBatch({makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}),
-                                  metadataObj,
-                                  Milliseconds(0)})
-                  ->getStatus());
+    ASSERT_OK(
+        processSingleBatch(
+            {concatenate(makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}), metadataObj),
+             Milliseconds(0)})
+            ->getStatus());
     ASSERT_TRUE(dataReplicatorExternalState->metadataWasProcessed);
     ASSERT_EQUALS(metadata.getPrimaryIndex(),
                   dataReplicatorExternalState->replMetadataProcessed.getPrimaryIndex());
@@ -296,10 +304,11 @@ TEST_F(OplogFetcherTest, ValidMetadataWithInResponseShouldBeForwardedToProcessMe
     ASSERT_OK(replMetadata.writeToMetadata(&bob));
     ASSERT_OK(oqMetadata.writeToMetadata(&bob));
     auto metadataObj = bob.obj();
-    ASSERT_OK(processSingleBatch({makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}),
-                                  metadataObj,
-                                  Milliseconds(0)})
-                  ->getStatus());
+    ASSERT_OK(
+        processSingleBatch(
+            {concatenate(makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}), metadataObj),
+             Milliseconds(0)})
+            ->getStatus());
     ASSERT_TRUE(dataReplicatorExternalState->metadataWasProcessed);
     ASSERT_EQUALS(replMetadata.getPrimaryIndex(),
                   dataReplicatorExternalState->replMetadataProcessed.getPrimaryIndex());
@@ -315,11 +324,12 @@ TEST_F(OplogFetcherTest, MetadataAndBatchAreNotProcessedWhenSyncSourceRollsBack)
     ASSERT_OK(oqMetadata.writeToMetadata(&bob));
     auto metadataObj = bob.obj();
 
-    ASSERT_EQUALS(ErrorCodes::InvalidSyncSource,
-                  processSingleBatch({makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}),
-                                      metadataObj,
-                                      Milliseconds(0)})
-                      ->getStatus());
+    ASSERT_EQUALS(
+        ErrorCodes::InvalidSyncSource,
+        processSingleBatch(
+            {concatenate(makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}), metadataObj),
+             Milliseconds(0)})
+            ->getStatus());
     ASSERT_FALSE(dataReplicatorExternalState->metadataWasProcessed);
     ASSERT(lastEnqueuedDocuments.empty());
 }
@@ -332,11 +342,12 @@ TEST_F(OplogFetcherTest, MetadataAndBatchAreNotProcessedWhenSyncSourceIsBehind)
     ASSERT_OK(oqMetadata.writeToMetadata(&bob));
     auto metadataObj = bob.obj();
 
-    ASSERT_EQUALS(ErrorCodes::InvalidSyncSource,
-                  processSingleBatch({makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}),
-                                      metadataObj,
-                                      Milliseconds(0)})
-                      ->getStatus());
+    ASSERT_EQUALS(
+        ErrorCodes::InvalidSyncSource,
+        processSingleBatch(
+            {concatenate(makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}), metadataObj),
+             Milliseconds(0)})
+            ->getStatus());
     ASSERT_FALSE(dataReplicatorExternalState->metadataWasProcessed);
     ASSERT(lastEnqueuedDocuments.empty());
 }
@@ -349,11 +360,12 @@ TEST_F(OplogFetcherTest, MetadataAndBatchAreNotProcessedWhenSyncSourceIsNotAhead
     ASSERT_OK(oqMetadata.writeToMetadata(&bob));
     auto metadataObj = bob.obj();
 
-    ASSERT_EQUALS(ErrorCodes::InvalidSyncSource,
-                  processSingleBatch({makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}),
-                                      metadataObj,
-                                      Milliseconds(0)})
-                      ->getStatus());
+    ASSERT_EQUALS(
+        ErrorCodes::InvalidSyncSource,
+        processSingleBatch(
+            {concatenate(makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}), metadataObj),
+             Milliseconds(0)})
+            ->getStatus());
     ASSERT_FALSE(dataReplicatorExternalState->metadataWasProcessed);
     ASSERT(lastEnqueuedDocuments.empty());
 }
@@ -370,7 +382,8 @@ TEST_F(OplogFetcherTest,
     auto entry = makeNoopOplogEntry({123LL, staleOpTime});
     ASSERT_EQUALS(
         ErrorCodes::InvalidSyncSource,
-        processSingleBatch({makeCursorResponse(0, {entry}), metadataObj, Milliseconds(0)}, false)
+        processSingleBatch(
+            {concatenate(makeCursorResponse(0, {entry}), metadataObj), Milliseconds(0)}, false)
             ->getStatus());
     ASSERT_FALSE(dataReplicatorExternalState->metadataWasProcessed);
     ASSERT(lastEnqueuedDocuments.empty());
@@ -388,8 +401,8 @@ TEST_F(OplogFetcherTest, MetadataAndBatchAreProcessedWhenSyncSourceIsCurrentButM
     auto metadataObj = bob.obj();
 
     auto entry = makeNoopOplogEntry(lastFetched);
-    auto shutdownState =
-        processSingleBatch({makeCursorResponse(0, {entry}), metadataObj, Milliseconds(0)}, false);
+    auto shutdownState = processSingleBatch(
+        {concatenate(makeCursorResponse(0, {entry}), metadataObj), Milliseconds(0)}, false);
     ASSERT_OK(shutdownState->getStatus());
     ASSERT(dataReplicatorExternalState->metadataWasProcessed);
 }
@@ -404,8 +417,8 @@ TEST_F(OplogFetcherTest,
     auto metadataObj = bob.obj();
 
     auto entry = makeNoopOplogEntry(lastFetched);
-    auto shutdownState =
-        processSingleBatch({makeCursorResponse(0, {entry}), metadataObj, Milliseconds(0)}, false);
+    auto shutdownState = processSingleBatch(
+        {concatenate(makeCursorResponse(0, {entry}), metadataObj), Milliseconds(0)}, false);
     ASSERT_OK(shutdownState->getStatus());
     ASSERT(dataReplicatorExternalState->metadataWasProcessed);
 }
@@ -418,8 +431,9 @@ TEST_F(OplogFetcherTest,
     auto metadataObj = bob.obj();
     ASSERT_EQUALS(ErrorCodes::OplogStartMissing,
                   processSingleBatch(
-                      {makeCursorResponse(0, {makeNoopOplogEntry(Seconds(456), lastFetched.value)}),
-                       metadataObj,
+                      {concatenate(makeCursorResponse(
+                                       0, {makeNoopOplogEntry(Seconds(456), lastFetched.value)}),
+                                   metadataObj),
                        Milliseconds(0)})
                       ->getStatus());
     ASSERT_FALSE(dataReplicatorExternalState->metadataWasProcessed);
@@ -434,17 +448,17 @@ TEST_F(OplogFetcherTest, MetadataIsNotProcessedOnBatchThatTriggersRollback) {
     auto metadataObj = bob.obj();
     ASSERT_EQUALS(ErrorCodes::OplogStartMissing,
                   processSingleBatch(
-                      {makeCursorResponse(0, {makeNoopOplogEntry(Seconds(456), lastFetched.value)}),
-                       metadataObj,
+                      {concatenate(makeCursorResponse(
+                                       0, {makeNoopOplogEntry(Seconds(456), lastFetched.value)}),
+                                   metadataObj),
                        Milliseconds(0)})
                       ->getStatus());
     ASSERT_FALSE(dataReplicatorExternalState->metadataWasProcessed);
 }
 
 TEST_F(OplogFetcherTest, EmptyMetadataIsNotProcessed) {
-    ASSERT_OK(processSingleBatch({makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}),
-                                  rpc::makeEmptyMetadata(),
-                                  Milliseconds(0)})
+    ASSERT_OK(processSingleBatch(
+                  {makeCursorResponse(0, {makeNoopOplogEntry(lastFetched)}), Milliseconds(0)})
                   ->getStatus());
     ASSERT_FALSE(dataReplicatorExternalState->metadataWasProcessed);
 }
@@ -456,10 +470,10 @@ TEST_F(OplogFetcherTest, EmptyFirstBatchStopsOplogFetcherWithOplogStartMissingEr
 
 TEST_F(OplogFetcherTest, MissingOpTimeInFirstDocumentCausesOplogFetcherToStopWithInvalidBSONError) {
     auto metadataObj = makeOplogQueryMetadataObject(remoteNewerOpTime, rbid, 2, 2);
-    ASSERT_EQUALS(
-        ErrorCodes::InvalidBSON,
-        processSingleBatch({makeCursorResponse(0, {BSONObj()}), metadataObj, Milliseconds(0)})
-            ->getStatus());
+    ASSERT_EQUALS(ErrorCodes::InvalidBSON,
+                  processSingleBatch({concatenate(makeCursorResponse(0, {BSONObj()}), metadataObj),
+                                      Milliseconds(0)})
+                      ->getStatus());
 }
 
 TEST_F(
@@ -468,8 +482,9 @@ TEST_F(
     auto metadataObj = makeOplogQueryMetadataObject(remoteNewerOpTime, rbid, 2, 2);
     ASSERT_EQUALS(ErrorCodes::OplogStartMissing,
                   processSingleBatch(
-                      {makeCursorResponse(0, {makeNoopOplogEntry(Seconds(456), lastFetched.value)}),
-                       metadataObj,
+                      {concatenate(makeCursorResponse(
+                                       0, {makeNoopOplogEntry(Seconds(456), lastFetched.value)}),
+                                   metadataObj),
                        Milliseconds(0)})
                       ->getStatus());
 }
@@ -480,8 +495,9 @@ TEST_F(OplogFetcherTest,
     ASSERT_EQUALS(
         ErrorCodes::OplogStartMissing,
         processSingleBatch(
-            {makeCursorResponse(0, {makeNoopOplogEntry(remoteNewerOpTime, lastFetched.value + 1)}),
-             metadataObj,
+            {concatenate(makeCursorResponse(
+                             0, {makeNoopOplogEntry(remoteNewerOpTime, lastFetched.value + 1)}),
+                         metadataObj),
              Milliseconds(0)})
             ->getStatus());
 }
@@ -489,28 +505,30 @@ TEST_F(OplogFetcherTest,
 TEST_F(OplogFetcherTest,
        MissingOpTimeInSecondDocumentOfFirstBatchCausesOplogFetcherToStopWithNoSuchKey) {
     auto metadataObj = makeOplogQueryMetadataObject(remoteNewerOpTime, rbid, 2, 2);
-    ASSERT_EQUALS(ErrorCodes::NoSuchKey,
-                  processSingleBatch(
-                      {makeCursorResponse(0,
-                                          {makeNoopOplogEntry(lastFetched),
-                                           BSON("o" << BSON("msg"
-                                                            << "oplog entry without optime"))}),
-                       metadataObj,
-                       Milliseconds(0)})
-                      ->getStatus());
+    ASSERT_EQUALS(
+        ErrorCodes::NoSuchKey,
+        processSingleBatch(
+            {concatenate(makeCursorResponse(0,
+                                            {makeNoopOplogEntry(lastFetched),
+                                             BSON("o" << BSON("msg"
+                                                              << "oplog entry without optime"))}),
+                         metadataObj),
+             Milliseconds(0)})
+            ->getStatus());
 }
 
 TEST_F(OplogFetcherTest, TimestampsNotAdvancingInBatchCausesOplogFetcherStopWithOplogOutOfOrder) {
     auto metadataObj = makeOplogQueryMetadataObject(remoteNewerOpTime, rbid, 2, 2);
-    ASSERT_EQUALS(ErrorCodes::OplogOutOfOrder,
-                  processSingleBatch({makeCursorResponse(0,
-                                                         {makeNoopOplogEntry(lastFetched),
-                                                          makeNoopOplogEntry(Seconds(1000), 1),
-                                                          makeNoopOplogEntry(Seconds(2000), 1),
-                                                          makeNoopOplogEntry(Seconds(1500), 1)}),
-                                      metadataObj,
-                                      Milliseconds(0)})
-                      ->getStatus());
+    ASSERT_EQUALS(
+        ErrorCodes::OplogOutOfOrder,
+        processSingleBatch({concatenate(makeCursorResponse(0,
+                                                           {makeNoopOplogEntry(lastFetched),
+                                                            makeNoopOplogEntry(Seconds(1000), 1),
+                                                            makeNoopOplogEntry(Seconds(2000), 1),
+                                                            makeNoopOplogEntry(Seconds(1500), 1)}),
+                                        metadataObj),
+                            Milliseconds(0)})
+            ->getStatus());
 }
 
 TEST_F(OplogFetcherTest, OplogFetcherShouldExcludeFirstDocumentInFirstBatchWhenEnqueuingDocuments) {
@@ -521,8 +539,8 @@ TEST_F(OplogFetcherTest, OplogFetcherShouldExcludeFirstDocumentInFirstBatchWhenE
     auto thirdEntry = makeNoopOplogEntry({{Seconds(789), 0}, lastFetched.opTime.getTerm()}, 300);
     Fetcher::Documents documents{firstEntry, secondEntry, thirdEntry};
 
-    auto shutdownState =
-        processSingleBatch({makeCursorResponse(0, documents), metadataObj, Milliseconds(0)});
+    auto shutdownState = processSingleBatch(
+        {concatenate(makeCursorResponse(0, documents), metadataObj), Milliseconds(0)});
 
     ASSERT_EQUALS(2U, lastEnqueuedDocuments.size());
     ASSERT_BSONOBJ_EQ(secondEntry, lastEnqueuedDocuments[0]);
@@ -559,8 +577,8 @@ TEST_F(OplogFetcherTest, OplogFetcherShouldReportErrorsThrownFromCallback) {
         return Status(ErrorCodes::InternalError, "my custom error");
     };
 
-    auto shutdownState =
-        processSingleBatch({makeCursorResponse(0, documents), metadataObj, Milliseconds(0)});
+    auto shutdownState = processSingleBatch(
+        {concatenate(makeCursorResponse(0, documents), metadataObj), Milliseconds(0)});
     ASSERT_EQ(shutdownState->getStatus(), Status(ErrorCodes::InternalError, "my custom error"));
 }
 
@@ -582,8 +600,8 @@ void OplogFetcherTest::testSyncSourceChecking(rpc::ReplSetMetadata* replMetadata
 
     dataReplicatorExternalState->shouldStopFetchingResult = true;
 
-    auto shutdownState =
-        processSingleBatch({makeCursorResponse(0, documents), metadataObj, Milliseconds(0)});
+    auto shutdownState = processSingleBatch(
+        {concatenate(makeCursorResponse(0, documents), metadataObj), Milliseconds(0)});
 
     // Sync source checking happens after we have successfully pushed the operations into
     // the buffer for the next replication phase (eg. applier).
@@ -697,7 +715,8 @@ RemoteCommandRequest OplogFetcherTest::testTwoBatchHandling() {
 
     auto metadataObj = makeOplogQueryMetadataObject(remoteNewerOpTime, rbid, 2, 2);
     processNetworkResponse(
-        {makeCursorResponse(cursorId, {firstEntry, secondEntry}), metadataObj, Milliseconds(0)},
+        {concatenate(makeCursorResponse(cursorId, {firstEntry, secondEntry}), metadataObj),
+         Milliseconds(0)},
         true);
 
     ASSERT_EQUALS(1U, lastEnqueuedDocuments.size());
diff --git a/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp b/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
index 479881621eb..2b06d004d0a 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
@@ -149,7 +149,7 @@ void ReplicationCoordinatorImpl::_handleHeartbeatResponse(
         resp = cbData.response.data;
         responseStatus = hbResponse.initialize(resp, _topCoord->getTerm());
         StatusWith<rpc::ReplSetMetadata> replMetadata =
-            rpc::ReplSetMetadata::readFromMetadata(cbData.response.metadata);
+            rpc::ReplSetMetadata::readFromMetadata(cbData.response.data);
 
         LOG_FOR_HEARTBEATS(2) << "Received response to heartbeat (requestId: " << cbData.request.id
                               << ") from " << target << ", " << resp;
diff --git a/src/mongo/db/repl/replication_coordinator_impl_heartbeat_v1_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_heartbeat_v1_test.cpp
index 61a63ca9225..5bb5c2a2ee2 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_heartbeat_v1_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_heartbeat_v1_test.cpp
@@ -394,10 +394,9 @@ TEST_F(ReplCoordHBV1Test, IgnoreTheContentsOfMetadataWhenItsReplicaSetIdDoesNotM
 
         rpc::ReplSetMetadata metadata(
             opTime.getTerm(), opTime, opTime, rsConfig.getConfigVersion(), unexpectedId, 1, -1);
-        BSONObjBuilder metadataBuilder;
-        metadata.writeToMetadata(&metadataBuilder).transitional_ignore();
+        uassertStatusOK(metadata.writeToMetadata(&responseBuilder));
 
-        heartbeatResponse = makeResponseStatus(responseBuilder.obj(), metadataBuilder.obj());
+        heartbeatResponse = makeResponseStatus(responseBuilder.obj());
     }
 
     // process heartbeat
diff --git a/src/mongo/db/repl/replication_coordinator_impl_test.cpp b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
index 9d64861a4ab..f703624e158 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_test.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_test.cpp
@@ -384,9 +384,8 @@ TEST_F(ReplCoordTest, InitiateSucceedsWhenQuorumCheckPasses) {
     hbResp.setConfigVersion(0);
     hbResp.setAppliedOpTime(OpTime(Timestamp(100, 1), 0));
     hbResp.setDurableOpTime(OpTime(Timestamp(100, 1), 0));
-    getNet()->scheduleResponse(noi,
-                               startDate + Milliseconds(10),
-                               RemoteCommandResponse(hbResp.toBSON(), BSONObj(), Milliseconds(8)));
+    getNet()->scheduleResponse(
+        noi, startDate + Milliseconds(10), RemoteCommandResponse(hbResp.toBSON(), Milliseconds(8)));
     getNet()->runUntil(startDate + Milliseconds(10));
     getNet()->exitNetwork();
     ASSERT_EQUALS(startDate + Milliseconds(10), getNet()->now());
@@ -4521,9 +4520,8 @@ TEST_F(ReplCoordTest,
                                   << 3
                                   << "syncSourceIndex"
                                   << 1)));
-    BSONObjBuilder metadataBuilder;
-    ASSERT_OK(metadata.getValue().writeToMetadata(&metadataBuilder));
-    auto metadataObj = metadataBuilder.obj();
+    BSONObjBuilder responseBuilder;
+    ASSERT_OK(metadata.getValue().writeToMetadata(&responseBuilder));
 
     auto net = getNet();
     net->enterNetwork();
@@ -4538,7 +4536,8 @@ TEST_F(ReplCoordTest,
     hbResp.setConfigVersion(config.getConfigVersion());
     hbResp.setSetName(config.getReplSetName());
     hbResp.setState(MemberState::RS_SECONDARY);
-    net->scheduleResponse(noi, net->now(), makeResponseStatus(hbResp.toBSON(), metadataObj));
+    responseBuilder.appendElements(hbResp.toBSON());
+    net->scheduleResponse(noi, net->now(), makeResponseStatus(responseBuilder.obj()));
     net->runReadyNetworkOperations();
     net->exitNetwork();
 
@@ -4647,9 +4646,8 @@ TEST_F(ReplCoordTest, TermAndLastCommittedOpTimeUpdatedFromHeartbeatWhenArbiter)
                                   << 3
                                   << "syncSourceIndex"
                                   << 1)));
-    BSONObjBuilder metadataBuilder;
-    ASSERT_OK(metadata.getValue().writeToMetadata(&metadataBuilder));
-    auto metadataObj = metadataBuilder.obj();
+    BSONObjBuilder responseBuilder;
+    ASSERT_OK(metadata.getValue().writeToMetadata(&responseBuilder));
 
     auto net = getNet();
     net->enterNetwork();
@@ -4664,7 +4662,8 @@ TEST_F(ReplCoordTest, TermAndLastCommittedOpTimeUpdatedFromHeartbeatWhenArbiter)
     hbResp.setConfigVersion(config.getConfigVersion());
     hbResp.setSetName(config.getReplSetName());
     hbResp.setState(MemberState::RS_SECONDARY);
-    net->scheduleResponse(noi, net->now(), makeResponseStatus(hbResp.toBSON(), metadataObj));
+    responseBuilder.appendElements(hbResp.toBSON());
+    net->scheduleResponse(noi, net->now(), makeResponseStatus(responseBuilder.obj()));
     net->runReadyNetworkOperations();
     net->exitNetwork();
 
diff --git a/src/mongo/db/repl/replication_coordinator_test_fixture.cpp b/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
index 456c9443276..10f1babe0f2 100644
--- a/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
+++ b/src/mongo/db/repl/replication_coordinator_test_fixture.cpp
@@ -212,15 +212,8 @@ void ReplCoordTest::assertStartSuccess(const BSONObj& configDoc, const HostAndPo
 
 executor::RemoteCommandResponse ReplCoordTest::makeResponseStatus(const BSONObj& doc,
                                                                   Milliseconds millis) {
-    return makeResponseStatus(doc, BSONObj(), millis);
-}
-
-executor::RemoteCommandResponse ReplCoordTest::makeResponseStatus(const BSONObj& doc,
-                                                                  const BSONObj& metadata,
-                                                                  Milliseconds millis) {
-    log() << "Responding with " << doc << " (metadata: " << metadata << "; elapsed: " << millis
-          << ")";
-    return RemoteCommandResponse(doc, metadata, millis);
+    log() << "Responding with " << doc << " (elapsed: " << millis << ")";
+    return RemoteCommandResponse(doc, millis);
 }
 
 void ReplCoordTest::simulateEnoughHeartbeatsForAllNodesUp() {
diff --git a/src/mongo/db/repl/replication_coordinator_test_fixture.h b/src/mongo/db/repl/replication_coordinator_test_fixture.h
index b5718a65a70..2e3732a4caa 100644
--- a/src/mongo/db/repl/replication_coordinator_test_fixture.h
+++ b/src/mongo/db/repl/replication_coordinator_test_fixture.h
@@ -65,13 +65,6 @@ public:
         const BSONObj& doc, Milliseconds millis = Milliseconds(0));
 
     /**
-     * Makes a command response with the given "doc" response, metadata and optional elapsed time
-     * "millis".
-     */
-    static executor::RemoteCommandResponse makeResponseStatus(
-        const BSONObj& doc, const BSONObj& metadata, Milliseconds millis = Milliseconds(0));
-
-    /**
      * Constructs a ReplSetConfig from the given BSON, or raises a test failure exception.
      */
     static ReplSetConfig assertMakeRSConfig(const BSONObj& configBSON);
diff --git a/src/mongo/db/repl/reporter_test.cpp b/src/mongo/db/repl/reporter_test.cpp
index 5fb620d5252..8c6ac958c16 100644
--- a/src/mongo/db/repl/reporter_test.cpp
+++ b/src/mongo/db/repl/reporter_test.cpp
@@ -331,7 +331,7 @@ TEST_F(ReporterTestNoTriggerAtSetUp, IsNotActiveAfterUpdatePositionTimeoutExpire
     // Schedule a response to the updatePosition command at a time that exceeds the timeout. Then
     // make sure the reporter shut down due to a remote command timeout.
     auto updatePosRequest = net->getNextReadyRequest();
-    RemoteCommandResponse response(BSON("ok" << 1), BSONObj(), Milliseconds(0));
+    RemoteCommandResponse response(BSON("ok" << 1), Milliseconds(0));
     executor::TaskExecutor::ResponseStatus responseStatus(response);
     net->scheduleResponse(
         updatePosRequest, net->now() + updatePositionTimeout + Milliseconds(1), responseStatus);
diff --git a/src/mongo/db/repl/scatter_gather_test.cpp b/src/mongo/db/repl/scatter_gather_test.cpp
index 1d5a32b4895..8d1c8f480fb 100644
--- a/src/mongo/db/repl/scatter_gather_test.cpp
+++ b/src/mongo/db/repl/scatter_gather_test.cpp
@@ -165,21 +165,18 @@ TEST_F(ScatterGatherTest, DeleteAlgorithmAfterItHasCompleted) {
     NetworkInterfaceMock* net = getNet();
     net->enterNetwork();
     NetworkInterfaceMock::NetworkOperationIterator noi = net->getNextReadyRequest();
-    net->scheduleResponse(noi,
-                          net->now() + Seconds(2),
-                          (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+    net->scheduleResponse(
+        noi, net->now() + Seconds(2), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     ASSERT_FALSE(ranCompletion);
 
     noi = net->getNextReadyRequest();
-    net->scheduleResponse(noi,
-                          net->now() + Seconds(2),
-                          (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+    net->scheduleResponse(
+        noi, net->now() + Seconds(2), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     ASSERT_FALSE(ranCompletion);
 
     noi = net->getNextReadyRequest();
-    net->scheduleResponse(noi,
-                          net->now() + Seconds(5),
-                          (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+    net->scheduleResponse(
+        noi, net->now() + Seconds(5), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     ASSERT_FALSE(ranCompletion);
 
     net->runUntil(net->now() + Seconds(2));
@@ -208,21 +205,19 @@ TEST_F(ScatterGatherTest, DeleteAlgorithmBeforeItCompletes) {
     net->enterNetwork();
     NetworkInterfaceMock::NetworkOperationIterator noi = net->getNextReadyRequest();
     net->scheduleResponse(
-        noi, net->now(), (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+        noi, net->now(), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     ASSERT_FALSE(ranCompletion);
     // Get and process the response from the first node immediately.
     net->runReadyNetworkOperations();
 
     noi = net->getNextReadyRequest();
-    net->scheduleResponse(noi,
-                          net->now() + Seconds(2),
-                          (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+    net->scheduleResponse(
+        noi, net->now() + Seconds(2), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     ASSERT_FALSE(ranCompletion);
 
     noi = net->getNextReadyRequest();
-    net->scheduleResponse(noi,
-                          net->now() + Seconds(5),
-                          (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+    net->scheduleResponse(
+        noi, net->now() + Seconds(5), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     ASSERT_FALSE(ranCompletion);
 
     sga.reset();
@@ -248,9 +243,8 @@ TEST_F(ScatterGatherTest, DeleteAlgorithmAfterCancel) {
     NetworkInterfaceMock* net = getNet();
     net->enterNetwork();
     NetworkInterfaceMock::NetworkOperationIterator noi = net->getNextReadyRequest();
-    net->scheduleResponse(noi,
-                          net->now() + Seconds(2),
-                          (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+    net->scheduleResponse(
+        noi, net->now() + Seconds(2), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     ASSERT_FALSE(ranCompletion);
 
     // Cancel the runner so following responses won't change the result. All pending requests
@@ -347,21 +341,18 @@ TEST_F(ScatterGatherTest, DoNotProcessMoreThanSufficientResponses) {
     NetworkInterfaceMock* net = getNet();
     net->enterNetwork();
     NetworkInterfaceMock::NetworkOperationIterator noi = net->getNextReadyRequest();
-    net->scheduleResponse(noi,
-                          net->now() + Seconds(2),
-                          (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+    net->scheduleResponse(
+        noi, net->now() + Seconds(2), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     ASSERT_FALSE(ranCompletion);
 
     noi = net->getNextReadyRequest();
-    net->scheduleResponse(noi,
-                          net->now() + Seconds(2),
-                          (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+    net->scheduleResponse(
+        noi, net->now() + Seconds(2), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     ASSERT_FALSE(ranCompletion);
 
     noi = net->getNextReadyRequest();
-    net->scheduleResponse(noi,
-                          net->now() + Seconds(5),
-                          (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+    net->scheduleResponse(
+        noi, net->now() + Seconds(5), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     ASSERT_FALSE(ranCompletion);
 
     net->runUntil(net->now() + Seconds(2));
@@ -390,9 +381,8 @@ TEST_F(ScatterGatherTest, AlgorithmProcessesCallbackCanceledResponse) {
     NetworkInterfaceMock* net = getNet();
     net->enterNetwork();
     NetworkInterfaceMock::NetworkOperationIterator noi = net->getNextReadyRequest();
-    net->scheduleResponse(noi,
-                          net->now() + Seconds(2),
-                          (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+    net->scheduleResponse(
+        noi, net->now() + Seconds(2), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     ASSERT_FALSE(ranCompletion);
 
     noi = net->getNextReadyRequest();
@@ -493,7 +483,7 @@ TEST_F(ScatterGatherTest, SuccessfulScatterGatherViaRun) {
     net->enterNetwork();
     NetworkInterfaceMock::NetworkOperationIterator noi = net->getNextReadyRequest();
     net->scheduleResponse(
-        noi, net->now(), (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+        noi, net->now(), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     net->runReadyNetworkOperations();
 
     noi = net->getNextReadyRequest();
@@ -502,7 +492,7 @@ TEST_F(ScatterGatherTest, SuccessfulScatterGatherViaRun) {
 
     noi = net->getNextReadyRequest();
     net->scheduleResponse(
-        noi, net->now(), (RemoteCommandResponse(BSON("ok" << 1), BSONObj(), Milliseconds(10))));
+        noi, net->now(), (RemoteCommandResponse(BSON("ok" << 1), Milliseconds(10))));
     net->runReadyNetworkOperations();
     net->exitNetwork();
 
diff --git a/src/mongo/db/repl/vote_requester_test.cpp b/src/mongo/db/repl/vote_requester_test.cpp
index 74374d3ad36..9a11270e577 100644
--- a/src/mongo/db/repl/vote_requester_test.cpp
+++ b/src/mongo/db/repl/vote_requester_test.cpp
@@ -153,7 +153,7 @@ protected:
         ReplSetRequestVotesResponse response;
         response.setVoteGranted(true);
         response.setTerm(1);
-        return RemoteCommandResponse(response.toBSON(), BSONObj(), Milliseconds(10));
+        return RemoteCommandResponse(response.toBSON(), Milliseconds(10));
     }
 
     RemoteCommandResponse votedYesStatusNotOkBecauseFailedToStoreLastVote() {
@@ -164,7 +164,7 @@ protected:
         response.addToBSON(&result);
         auto status = Status(ErrorCodes::InterruptedDueToStepDown, "operation was interrupted");
         CommandHelpers::appendCommandStatusNoThrow(result, status);
-        return RemoteCommandResponse(result.obj(), BSONObj(), Milliseconds(10));
+        return RemoteCommandResponse(result.obj(), Milliseconds(10));
     }
 
     RemoteCommandResponse votedNoBecauseConfigVersionDoesNotMatch() {
@@ -172,7 +172,7 @@ protected:
         response.setVoteGranted(false);
         response.setTerm(1);
         response.setReason("candidate's config version differs from mine");
-        return RemoteCommandResponse(response.toBSON(), BSONObj(), Milliseconds(10));
+        return RemoteCommandResponse(response.toBSON(), Milliseconds(10));
     }
 
     RemoteCommandResponse votedNoBecauseSetNameDiffers() {
@@ -180,7 +180,7 @@ protected:
         response.setVoteGranted(false);
         response.setTerm(1);
         response.setReason("candidate's set name differs from mine");
-        return RemoteCommandResponse(response.toBSON(), BSONObj(), Milliseconds(10));
+        return RemoteCommandResponse(response.toBSON(), Milliseconds(10));
     }
 
     RemoteCommandResponse votedNoBecauseLastOpTimeIsGreater() {
@@ -188,7 +188,7 @@ protected:
         response.setVoteGranted(false);
         response.setTerm(1);
         response.setReason("candidate's data is staler than mine");
-        return RemoteCommandResponse(response.toBSON(), BSONObj(), Milliseconds(10));
+        return RemoteCommandResponse(response.toBSON(), Milliseconds(10));
     }
 
     RemoteCommandResponse votedNoBecauseTermIsGreater() {
@@ -196,7 +196,7 @@ protected:
         response.setVoteGranted(false);
         response.setTerm(3);
         response.setReason("candidate's term is lower than mine");
-        return RemoteCommandResponse(response.toBSON(), BSONObj(), Milliseconds(10));
+        return RemoteCommandResponse(response.toBSON(), Milliseconds(10));
     }
 
     RemoteCommandResponse votedNoBecauseAlreadyVoted() {
@@ -204,7 +204,7 @@ protected:
         response.setVoteGranted(false);
         response.setTerm(2);
         response.setReason("already voted for another candidate this term");
-        return RemoteCommandResponse(response.toBSON(), BSONObj(), Milliseconds(10));
+        return RemoteCommandResponse(response.toBSON(), Milliseconds(10));
     }
 
     std::unique_ptr<VoteRequester::Algorithm> _requester;
diff --git a/src/mongo/db/s/config/sharding_catalog_manager_shard_operations.cpp b/src/mongo/db/s/config/sharding_catalog_manager_shard_operations.cpp
index 9992f06acb5..7ef70b27738 100644
--- a/src/mongo/db/s/config/sharding_catalog_manager_shard_operations.cpp
+++ b/src/mongo/db/s/config/sharding_catalog_manager_shard_operations.cpp
@@ -198,7 +198,6 @@ StatusWith<Shard::CommandResponse> ShardingCatalogManager::_runCommandForAddShar
 
     return Shard::CommandResponse(std::move(host),
                                   std::move(result),
-                                  response.metadata.getOwned(),
                                   std::move(commandStatus),
                                   std::move(writeConcernStatus));
 }
diff --git a/src/mongo/db/s/migration_source_manager.cpp b/src/mongo/db/s/migration_source_manager.cpp
index d49a85ad625..d6bd884ba26 100644
--- a/src/mongo/db/s/migration_source_manager.cpp
+++ b/src/mongo/db/s/migration_source_manager.cpp
@@ -545,9 +545,7 @@ Status MigrationSourceManager::commitChunkMetadataOnConfig(OperationContext* opC
             severe() << "The current config server opTime is " << Grid::get(opCtx)->configOpTime();
             severe() << "The commit response came from "
                      << redact(commitChunkMigrationResponse.getValue().hostAndPort->toString())
-                     << " and contained:";
-            severe() << "  metadata: "
-                     << redact(commitChunkMigrationResponse.getValue().metadata.toString());
+                     << " and contained";
             severe() << "  response: "
                      << redact(commitChunkMigrationResponse.getValue().response.toString());
 
diff --git a/src/mongo/db/service_entry_point_common.cpp b/src/mongo/db/service_entry_point_common.cpp
index 16a4671961f..0f0581104e9 100644
--- a/src/mongo/db/service_entry_point_common.cpp
+++ b/src/mongo/db/service_entry_point_common.cpp
@@ -213,7 +213,7 @@ void generateErrorResponse(OperationContext* opCtx,
     // so we need to reset it to a clean state just to be sure.
     replyBuilder->reset();
     replyBuilder->setCommandReply(exception.toStatus(), extraFields);
-    replyBuilder->setMetadata(replyMetadata);
+    replyBuilder->getBodyBuilder().appendElements(replyMetadata);
 }
 
 BSONObj getErrorLabels(const boost::optional<OperationSessionInfoFromClient>& sessionOptions,
@@ -571,15 +571,10 @@ bool runCommandImpl(OperationContext* opCtx,
         }
     }
 
-    BSONObjBuilder metadataBob;
-    appendReplyMetadata(opCtx, request, &metadataBob);
+    auto commandBodyBob = replyBuilder->getBodyBuilder();
+    appendReplyMetadata(opCtx, request, &commandBodyBob);
+    appendClusterAndOperationTime(opCtx, &commandBodyBob, &commandBodyBob, startOperationTime);
 
-    {
-        auto commandBodyBob = replyBuilder->getBodyBuilder();
-        appendClusterAndOperationTime(opCtx, &commandBodyBob, &metadataBob, startOperationTime);
-    }
-
-    replyBuilder->setMetadata(metadataBob.obj());
     return ok;
 }