SERVER-20743 Combine target selection and command execution in ShardRegistry.

Also, properly set the metadata field on all commands dispatched through ShardRegistry.
author: Andy Schwerin <schwerin@mongodb.com> 2015-10-02 17:44:17 -0400
committer: Andy Schwerin <schwerin@mongodb.com> 2015-10-06 12:45:03 -0400
commit: 9267d348b98e3be67a85f219ba184c35f35fc309 (patch)
tree: 2f5453f78ff8b15207f9c9df0fc0fffb1f42cb4f
parent: d9f2d8fda800fdc2cbd2be30413412c19a24f97a (diff)
download: mongo-9267d348b98e3be67a85f219ba184c35f35fc309.tar.gz
28 files changed, 378 insertions, 290 deletions
diff --git a/src/mongo/client/read_preference.cpp b/src/mongo/client/read_preference.cpp
index da94f18ff9e..1ab5c5c13e1 100644
--- a/src/mongo/client/read_preference.cpp
+++ b/src/mongo/client/read_preference.cpp
@@ -114,6 +114,9 @@ TagSet TagSet::primaryOnly() {
 ReadPreferenceSetting::ReadPreferenceSetting(ReadPreference pref, TagSet tags)
     : pref(std::move(pref)), tags(std::move(tags)) {}
 
+ReadPreferenceSetting::ReadPreferenceSetting(ReadPreference pref)
+    : ReadPreferenceSetting(pref, defaultTagSetForMode(pref)) {}
+
 StatusWith<ReadPreferenceSetting> ReadPreferenceSetting::fromBSON(const BSONObj& readPrefObj) {
     std::string modeStr;
     auto modeExtractStatus = bsonExtractStringField(readPrefObj, kModeFieldName, &modeStr);
diff --git a/src/mongo/client/read_preference.h b/src/mongo/client/read_preference.h
index 161cfc0f241..57177c69345 100644
--- a/src/mongo/client/read_preference.h
+++ b/src/mongo/client/read_preference.h
@@ -121,8 +121,7 @@ struct ReadPreferenceSetting {
      */
     ReadPreferenceSetting(ReadPreference pref, TagSet tags);
 
-    // TODO: remove when StatusWith supports non-default constructible types (SERVER-18007)
-    ReadPreferenceSetting() = default;
+    explicit ReadPreferenceSetting(ReadPreference pref);
 
     inline bool equals(const ReadPreferenceSetting& other) const {
         return (pref == other.pref) && (tags == other.tags);
@@ -148,8 +147,8 @@ struct ReadPreferenceSetting {
      */
     static StatusWith<ReadPreferenceSetting> fromBSON(const BSONObj& readPrefSettingObj);
 
-    ReadPreference pref{ReadPreference::PrimaryOnly};
-    TagSet tags{TagSet::primaryOnly()};
+    ReadPreference pref;
+    TagSet tags;
 };
 
 }  // namespace mongo
diff --git a/src/mongo/client/read_preference_test.cpp b/src/mongo/client/read_preference_test.cpp
index bbd55e5bfb8..447f37d51ca 100644
--- a/src/mongo/client/read_preference_test.cpp
+++ b/src/mongo/client/read_preference_test.cpp
@@ -102,7 +102,7 @@ TEST(ReadPreferenceSetting, Roundtrip) {
                                                                 << "ca")
                                                            << BSON("foo"
                                                                    << "bar")))));
-    checkRoundtrip(ReadPreferenceSetting());
+    checkRoundtrip(ReadPreferenceSetting(ReadPreference::PrimaryOnly));
 
     checkRoundtrip(ReadPreferenceSetting(ReadPreference::PrimaryPreferred, TagSet()));
 
diff --git a/src/mongo/db/repl/data_replicator.cpp b/src/mongo/db/repl/data_replicator.cpp
index 13a39524b03..fc457104fce 100644
--- a/src/mongo/db/repl/data_replicator.cpp
+++ b/src/mongo/db/repl/data_replicator.cpp
@@ -45,6 +45,7 @@
 #include "mongo/db/repl/optime.h"
 #include "mongo/db/repl/sync_source_selector.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/stdx/functional.h"
 #include "mongo/stdx/thread.h"
 #include "mongo/util/assert_util.h"
@@ -386,7 +387,8 @@ Status DatabasesCloner::start() {
 
     log() << "starting cloning of all databases";
     // Schedule listDatabase command which will kick off the database cloner per result db.
-    Request listDBsReq(_source, "admin", BSON("listDatabases" << true), BSON("$secondaryOk" << 1));
+    Request listDBsReq(
+        _source, "admin", BSON("listDatabases" << true), BSON(rpc::kSecondaryOkFieldName << 1));
     CBHStatus s = _exec->scheduleRemoteCommand(
         listDBsReq,
         stdx::bind(&DatabasesCloner::_onListDatabaseFinish, this, stdx::placeholders::_1));
diff --git a/src/mongo/rpc/metadata/server_selection_metadata.cpp b/src/mongo/rpc/metadata/server_selection_metadata.cpp
index a4fbbde3fca..e865c676931 100644
--- a/src/mongo/rpc/metadata/server_selection_metadata.cpp
+++ b/src/mongo/rpc/metadata/server_selection_metadata.cpp
@@ -43,11 +43,11 @@
 namespace mongo {
 namespace rpc {
 
-namespace {
-
 const char kSecondaryOkFieldName[] = "$secondaryOk";
 const char kReadPreferenceFieldName[] = "$readPreference";
 
+namespace {
+
 const char kQueryOptionsFieldName[] = "$queryOptions";
 
 const char kDollarQueryWrapper[] = "$query";
diff --git a/src/mongo/rpc/metadata/server_selection_metadata.h b/src/mongo/rpc/metadata/server_selection_metadata.h
index 1f345af9a19..279d47a0803 100644
--- a/src/mongo/rpc/metadata/server_selection_metadata.h
+++ b/src/mongo/rpc/metadata/server_selection_metadata.h
@@ -44,6 +44,18 @@ class StatusWith;
 namespace rpc {
 
 /**
+ * Symbolic constant for the "$secondaryOk" metadata field. This field should be of boolean or
+ * numeric type, and is treated as a boolean.
+ */
+extern const char kSecondaryOkFieldName[];
+
+/**
+ * Symbolic constant for the "$readPreference" metadata field. The field should be of Object type
+ * when present.
+ */
+extern const char kReadPreferenceFieldName[];
+
+/**
  * This class comprises the request metadata fields that concern server selection, that is,
  * the conditions on which servers can execute this operation.
  */
diff --git a/src/mongo/s/balance.cpp b/src/mongo/s/balance.cpp
index 8bc9ba55bac..be7785b1366 100644
--- a/src/mongo/s/balance.cpp
+++ b/src/mongo/s/balance.cpp
@@ -226,11 +226,12 @@ bool Balancer::_checkOIDs(OperationContext* txn) {
             continue;
         }
 
-        const auto shardHost = uassertStatusOK(
-            s->getTargeter()->findHost({ReadPreference::PrimaryOnly, TagSet::primaryOnly()}));
-
-        BSONObj f = uassertStatusOK(
-            grid.shardRegistry()->runCommand(txn, shardHost, "admin", BSON("features" << 1)));
+        BSONObj f = uassertStatusOK(grid.shardRegistry()->runCommandOnShard(
+            txn,
+            s,
+            ReadPreferenceSetting{ReadPreference::PrimaryOnly},
+            "admin",
+            BSON("features" << 1)));
         if (f["oidMachine"].isNumber()) {
             int x = f["oidMachine"].numberInt();
             if (oids.count(x) == 0) {
@@ -239,16 +240,21 @@ bool Balancer::_checkOIDs(OperationContext* txn) {
                 log() << "error: 2 machines have " << x << " as oid machine piece: " << shardId
                       << " and " << oids[x];
 
-                uassertStatusOK(grid.shardRegistry()->runCommand(
-                    txn, shardHost, "admin", BSON("features" << 1 << "oidReset" << 1)));
+                uassertStatusOK(grid.shardRegistry()->runCommandOnShard(
+                    txn,
+                    s,
+                    ReadPreferenceSetting{ReadPreference::PrimaryOnly},
+                    "admin",
+                    BSON("features" << 1 << "oidReset" << 1)));
 
                 const auto otherShard = grid.shardRegistry()->getShard(txn, oids[x]);
                 if (otherShard) {
-                    const auto otherShardHost = uassertStatusOK(otherShard->getTargeter()->findHost(
-                        {ReadPreference::PrimaryOnly, TagSet::primaryOnly()}));
-
-                    uassertStatusOK(grid.shardRegistry()->runCommand(
-                        txn, otherShardHost, "admin", BSON("features" << 1 << "oidReset" << 1)));
+                    uassertStatusOK(grid.shardRegistry()->runCommandOnShard(
+                        txn,
+                        otherShard,
+                        ReadPreferenceSetting{ReadPreference::PrimaryOnly},
+                        "admin",
+                        BSON("features" << 1 << "oidReset" << 1)));
                 }
 
                 return false;
diff --git a/src/mongo/s/balancer_policy.cpp b/src/mongo/s/balancer_policy.cpp
index b07119bdad5..8864a0b298b 100644
--- a/src/mongo/s/balancer_policy.cpp
+++ b/src/mongo/s/balancer_policy.cpp
@@ -69,16 +69,12 @@ namespace {
 std::string retrieveShardMongoDVersion(OperationContext* txn,
                                        ShardId shardId,
                                        ShardRegistry* shardRegistry) {
-    auto shard = shardRegistry->getShard(txn, shardId);
-    if (!shard) {
-        uassertStatusOK({ErrorCodes::ShardNotFound, "Shard not found"});
-    }
-
-    auto shardHost = uassertStatusOK(
-        shard->getTargeter()->findHost({ReadPreference::PrimaryOnly, TagSet::primaryOnly()}));
-
     BSONObj serverStatus = uassertStatusOK(
-        shardRegistry->runCommand(txn, shardHost, "admin", BSON("serverStatus" << 1)));
+        shardRegistry->runCommandOnShard(txn,
+                                         shardId,
+                                         ReadPreferenceSetting{ReadPreference::PrimaryOnly},
+                                         "admin",
+                                         BSON("serverStatus" << 1)));
     BSONElement versionElement = serverStatus["version"];
     if (versionElement.type() != String) {
         uassertStatusOK({ErrorCodes::NoSuchKey, "version field not found in serverStatus"});
diff --git a/src/mongo/s/catalog/catalog_manager_common.cpp b/src/mongo/s/catalog/catalog_manager_common.cpp
index 6d9e19d69c6..92f9f6def61 100644
--- a/src/mongo/s/catalog/catalog_manager_common.cpp
+++ b/src/mongo/s/catalog/catalog_manager_common.cpp
@@ -97,22 +97,14 @@ StatusWith<ShardType> validateHostAsShard(OperationContext* txn,
         return {ErrorCodes::BadValue, "shard name cannot be empty"};
     }
 
-    auto shardConn = shardRegistry->createConnection(connectionString);
+    const std::shared_ptr<Shard> shardConn{shardRegistry->createConnection(connectionString)};
     invariant(shardConn);
 
-    auto shardHostStatus =
-        shardConn->getTargeter()->findHost({ReadPreference::PrimaryOnly, TagSet::primaryOnly()});
-    if (!shardHostStatus.isOK()) {
-        return shardHostStatus.getStatus();
-    }
-
-    const HostAndPort& shardHost = shardHostStatus.getValue();
-
-    StatusWith<BSONObj> cmdStatus{ErrorCodes::InternalError, "uninitialized value"};
+    const ReadPreferenceSetting readPref{ReadPreference::PrimaryOnly};
 
     // Is it mongos?
-    cmdStatus =
-        shardRegistry->runCommandForAddShard(txn, shardHost, "admin", BSON("isdbgrid" << 1));
+    auto cmdStatus = shardRegistry->runCommandForAddShard(
+        txn, shardConn, readPref, "admin", BSON("isdbgrid" << 1));
     if (!cmdStatus.isOK()) {
         return cmdStatus.getStatus();
     }
@@ -123,8 +115,8 @@ StatusWith<ShardType> validateHostAsShard(OperationContext* txn,
     }
 
     // Is it a replica set?
-    cmdStatus =
-        shardRegistry->runCommandForAddShard(txn, shardHost, "admin", BSON("isMaster" << 1));
+    cmdStatus = shardRegistry->runCommandForAddShard(
+        txn, shardConn, readPref, "admin", BSON("isMaster" << 1));
     if (!cmdStatus.isOK()) {
         return cmdStatus.getStatus();
     }
@@ -158,7 +150,7 @@ StatusWith<ShardType> validateHostAsShard(OperationContext* txn,
 
     // Is it a mongos config server?
     cmdStatus = shardRegistry->runCommandForAddShard(
-        txn, shardHost, "admin", BSON("replSetGetStatus" << 1));
+        txn, shardConn, readPref, "admin", BSON("replSetGetStatus" << 1));
     if (!cmdStatus.isOK()) {
         return cmdStatus.getStatus();
     }
@@ -219,8 +211,8 @@ StatusWith<ShardType> validateHostAsShard(OperationContext* txn,
             if (hostSet.find(host) == hostSet.end()) {
                 return {ErrorCodes::OperationFailed,
                         str::stream() << "in seed list " << connectionString.toString() << ", host "
-                                      << host << " does not belong to replica set "
-                                      << foundSetName};
+                                      << host << " does not belong to replica set " << foundSetName
+                                      << "; found " << resIsMaster.toString()};
             }
         }
     }
@@ -256,19 +248,16 @@ StatusWith<ShardType> validateHostAsShard(OperationContext* txn,
  */
 StatusWith<std::vector<std::string>> getDBNamesListFromShard(
     OperationContext* txn, ShardRegistry* shardRegistry, const ConnectionString& connectionString) {
-    auto shardConn = shardRegistry->createConnection(connectionString);
+    const std::shared_ptr<Shard> shardConn{
+        shardRegistry->createConnection(connectionString).release()};
     invariant(shardConn);
 
-    auto shardHostStatus =
-        shardConn->getTargeter()->findHost({ReadPreference::PrimaryOnly, TagSet::primaryOnly()});
-    if (!shardHostStatus.isOK()) {
-        return shardHostStatus.getStatus();
-    }
-
-    const HostAndPort& shardHost = shardHostStatus.getValue();
-
     auto cmdStatus =
-        shardRegistry->runCommandForAddShard(txn, shardHost, "admin", BSON("listDatabases" << 1));
+        shardRegistry->runCommandForAddShard(txn,
+                                             shardConn,
+                                             ReadPreferenceSetting{ReadPreference::PrimaryOnly},
+                                             "admin",
+                                             BSON("listDatabases" << 1));
     if (!cmdStatus.isOK()) {
         return cmdStatus.getStatus();
     }
diff --git a/src/mongo/s/catalog/dist_lock_catalog_impl.cpp b/src/mongo/s/catalog/dist_lock_catalog_impl.cpp
index a227397ce77..87c41729056 100644
--- a/src/mongo/s/catalog/dist_lock_catalog_impl.cpp
+++ b/src/mongo/s/catalog/dist_lock_catalog_impl.cpp
@@ -36,7 +36,6 @@
 #include "mongo/base/status_with.h"
 #include "mongo/bson/util/bson_extract.h"
 #include "mongo/client/read_preference.h"
-#include "mongo/client/remote_command_targeter.h"
 #include "mongo/db/lasterror.h"
 #include "mongo/db/query/find_and_modify_request.h"
 #include "mongo/db/repl/read_concern_args.h"
@@ -155,17 +154,8 @@ DistLockCatalogImpl::DistLockCatalogImpl(ShardRegistry* shardRegistry,
 DistLockCatalogImpl::~DistLockCatalogImpl() = default;
 
 StatusWith<LockpingsType> DistLockCatalogImpl::getPing(StringData processID) {
-    auto targetStatus = _client->getConfigShard()->getTargeter()->findHost(kReadPref);
-
-    if (!targetStatus.isOK()) {
-        return targetStatus.getStatus();
-    }
-
-    auto findResult = _findOnConfig(targetStatus.getValue(),
-                                    _lockPingNS,
-                                    BSON(LockpingsType::process() << processID),
-                                    BSONObj(),
-                                    1);
+    auto findResult = _findOnConfig(
+        kReadPref, _lockPingNS, BSON(LockpingsType::process() << processID), BSONObj(), 1);
 
     if (!findResult.isOK()) {
         return findResult.getStatus();
@@ -335,14 +325,7 @@ Status DistLockCatalogImpl::unlock(const OID& lockSessionID) {
 }
 
 StatusWith<DistLockCatalog::ServerInfo> DistLockCatalogImpl::getServerInfo() {
-    auto targetStatus = _client->getConfigShard()->getTargeter()->findHost(kReadPref);
-
-    if (!targetStatus.isOK()) {
-        return targetStatus.getStatus();
-    }
-
-    auto resultStatus =
-        _client->runCommandOnConfig(targetStatus.getValue(), "admin", BSON("serverStatus" << 1));
+    auto resultStatus = _client->runCommandOnConfig(kReadPref, "admin", BSON("serverStatus" << 1));
 
     if (!resultStatus.isOK()) {
         return resultStatus.getStatus();
@@ -374,14 +357,8 @@ StatusWith<DistLockCatalog::ServerInfo> DistLockCatalogImpl::getServerInfo() {
 }
 
 StatusWith<LocksType> DistLockCatalogImpl::getLockByTS(const OID& lockSessionID) {
-    auto targetStatus = _client->getConfigShard()->getTargeter()->findHost(kReadPref);
-
-    if (!targetStatus.isOK()) {
-        return targetStatus.getStatus();
-    }
-
-    auto findResult = _findOnConfig(
-        targetStatus.getValue(), _locksNS, BSON(LocksType::lockID(lockSessionID)), BSONObj(), 1);
+    auto findResult =
+        _findOnConfig(kReadPref, _locksNS, BSON(LocksType::lockID(lockSessionID)), BSONObj(), 1);
 
     if (!findResult.isOK()) {
         return findResult.getStatus();
@@ -406,14 +383,8 @@ StatusWith<LocksType> DistLockCatalogImpl::getLockByTS(const OID& lockSessionID)
 }
 
 StatusWith<LocksType> DistLockCatalogImpl::getLockByName(StringData name) {
-    auto targetStatus = _client->getConfigShard()->getTargeter()->findHost(kReadPref);
-
-    if (!targetStatus.isOK()) {
-        return targetStatus.getStatus();
-    }
-
-    auto findResult = _findOnConfig(
-        targetStatus.getValue(), _locksNS, BSON(LocksType::name() << name), BSONObj(), 1);
+    auto findResult =
+        _findOnConfig(kReadPref, _locksNS, BSON(LocksType::name() << name), BSONObj(), 1);
 
     if (!findResult.isOK()) {
         return findResult.getStatus();
@@ -455,13 +426,14 @@ Status DistLockCatalogImpl::stopPing(StringData processId) {
     return findAndModifyStatus.getStatus();
 }
 
-StatusWith<vector<BSONObj>> DistLockCatalogImpl::_findOnConfig(const HostAndPort& host,
-                                                               const NamespaceString& nss,
-                                                               const BSONObj& query,
-                                                               const BSONObj& sort,
-                                                               boost::optional<long long> limit) {
+StatusWith<vector<BSONObj>> DistLockCatalogImpl::_findOnConfig(
+    const ReadPreferenceSetting& readPref,
+    const NamespaceString& nss,
+    const BSONObj& query,
+    const BSONObj& sort,
+    boost::optional<long long> limit) {
     repl::ReadConcernArgs readConcern(boost::none, repl::ReadConcernLevel::kMajorityReadConcern);
-    auto result = _client->exhaustiveFindOnConfigNode(host, nss, query, sort, limit, readConcern);
+    auto result = _client->exhaustiveFindOnConfig(readPref, nss, query, sort, limit, readConcern);
 
     if (!result.isOK()) {
         return result.getStatus();
diff --git a/src/mongo/s/catalog/dist_lock_catalog_impl.h b/src/mongo/s/catalog/dist_lock_catalog_impl.h
index 85c9837ba73..a38aaf088f7 100644
--- a/src/mongo/s/catalog/dist_lock_catalog_impl.h
+++ b/src/mongo/s/catalog/dist_lock_catalog_impl.h
@@ -40,10 +40,10 @@
 
 namespace mongo {
 
-struct HostAndPort;
 class NamespaceString;
-class RemoteCommandTargeter;
 class ShardRegistry;
+struct HostAndPort;
+struct ReadPreferenceSetting;
 
 class DistLockCatalogImpl final : public DistLockCatalog {
 public:
@@ -81,7 +81,7 @@ public:
     virtual Status stopPing(StringData processId) override;
 
 private:
-    StatusWith<std::vector<BSONObj>> _findOnConfig(const HostAndPort& host,
+    StatusWith<std::vector<BSONObj>> _findOnConfig(const ReadPreferenceSetting& readPref,
                                                    const NamespaceString& nss,
                                                    const BSONObj& query,
                                                    const BSONObj& sort,
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set.cpp
index c9238e52cfa..e4e323316d7 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set.cpp
@@ -1126,21 +1126,14 @@ StatusWith<OpTimePair<vector<BSONObj>>> CatalogManagerReplicaSet::_exhaustiveFin
     Status lastStatus = Status::OK();
 
     for (int retry = 0; retry < kMaxReadRetry; retry++) {
-        const auto configShard = grid.shardRegistry()->getShard(txn, "config");
-        const auto readHost = configShard->getTargeter()->findHost(kConfigReadSelector);
-        if (!readHost.isOK()) {
-            return readHost.getStatus();
-        }
-
-        repl::ReadConcernArgs readConcern(grid.shardRegistry()->getConfigOpTime(),
-                                          repl::ReadConcernLevel::kMajorityReadConcern);
+        repl::ReadConcernArgs readConcern{grid.shardRegistry()->getConfigOpTime(),
+                                          repl::ReadConcernLevel::kMajorityReadConcern};
 
-        auto result = grid.shardRegistry()->exhaustiveFindOnConfigNode(
-            readHost.getValue(), nss, query, sort, limit, readConcern);
+        auto result = grid.shardRegistry()->exhaustiveFindOnConfig(
+            kConfigReadSelector, nss, query, sort, limit, readConcern);
 
         if (ErrorCodes::isNetworkError(result.getStatus().code())) {
             lastStatus = result.getStatus();
-            configShard->getTargeter()->markHostUnreachable(readHost.getValue());
             continue;
         }
 
@@ -1168,18 +1161,10 @@ bool CatalogManagerReplicaSet::_runReadCommand(OperationContext* txn,
                                                BSONObjBuilder* result) {
     Status lastStatus = Status::OK();
     for (int retry = 0; retry < kMaxReadRetry; retry++) {
-        auto targeter = grid.shardRegistry()->getShard(txn, "config")->getTargeter();
-        auto target = targeter->findHost(settings);
-        if (!target.isOK()) {
-            return Command::appendCommandStatus(*result, target.getStatus());
-        }
-
-        auto resultStatus =
-            grid.shardRegistry()->runCommandOnConfig(target.getValue(), dbname, cmdObj);
+        auto resultStatus = grid.shardRegistry()->runCommandOnConfig(settings, dbname, cmdObj);
 
         if (ErrorCodes::isNetworkError(resultStatus.getStatus().code())) {
             lastStatus = resultStatus.getStatus();
-            targeter->markHostUnreachable(target.getValue());
             continue;
         }
 
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set_add_shard_test.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set_add_shard_test.cpp
index 6408997d55c..d5cded88dca 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set_add_shard_test.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set_add_shard_test.cpp
@@ -37,6 +37,7 @@
 #include "mongo/db/commands.h"
 #include "mongo/db/query/lite_parsed_query.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set_test_fixture.h"
 #include "mongo/s/catalog/type_changelog.h"
@@ -215,7 +216,8 @@ TEST_F(AddShardTest, AddShardStandalone) {
     // in the previous call, in the config server metadata
     onFindCommand([&](const RemoteCommandRequest& request) {
         ASSERT_EQ(request.target, configHost);
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.toString(), DatabaseType::ConfigNS);
@@ -233,7 +235,8 @@ TEST_F(AddShardTest, AddShardStandalone) {
     onFindCommand([this](const RemoteCommandRequest& request) {
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.toString(), DatabaseType::ConfigNS);
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         auto query = assertGet(LiteParsedQuery::makeFromFindCommand(nss, request.cmdObj, false));
 
@@ -329,7 +332,8 @@ TEST_F(AddShardTest, AddShardStandaloneGenerateName) {
     // in the previous call, in the config server metadata
     onFindCommand([&](const RemoteCommandRequest& request) {
         ASSERT_EQ(request.target, configHost);
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.toString(), DatabaseType::ConfigNS);
@@ -345,7 +349,8 @@ TEST_F(AddShardTest, AddShardStandaloneGenerateName) {
     });
 
     onFindCommand([this](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.toString(), DatabaseType::ConfigNS);
@@ -366,7 +371,8 @@ TEST_F(AddShardTest, AddShardStandaloneGenerateName) {
 
     // New name is being generated for the new shard
     onFindCommand([this, &existingShard](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.toString(), ShardType::ConfigNS);
         auto query = assertGet(LiteParsedQuery::makeFromFindCommand(nss, request.cmdObj, false));
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set_drop_coll_test.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set_drop_coll_test.cpp
index 32d2ffddef7..9bf0a35041c 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set_drop_coll_test.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set_drop_coll_test.cpp
@@ -35,6 +35,7 @@
 #include "mongo/db/namespace_string.h"
 #include "mongo/db/query/lite_parsed_query.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/s/catalog/dist_lock_manager_mock.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set_test_fixture.h"
@@ -105,8 +106,6 @@ public:
             ASSERT_EQ(_configHost, request.target);
             ASSERT_EQ("config", request.dbname);
 
-            ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
-
             BSONObj expectedCmd(fromjson(R"({
                 delete: "chunks",
                 deletes: [{ q: { ns: "test.user" }, limit: 0 }],
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set_log_action_test.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set_log_action_test.cpp
index 25144113704..a169cac4b76 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set_log_action_test.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set_log_action_test.cpp
@@ -35,6 +35,7 @@
 #include "mongo/executor/network_interface_mock.h"
 #include "mongo/executor/task_executor.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set_test_fixture.h"
 #include "mongo/s/catalog/type_actionlog.h"
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set_remove_shard_test.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set_remove_shard_test.cpp
index 3a1857eee58..5a15c4da606 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set_remove_shard_test.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set_remove_shard_test.cpp
@@ -38,6 +38,7 @@
 #include "mongo/executor/network_interface_mock.h"
 #include "mongo/executor/task_executor.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set_test_fixture.h"
 #include "mongo/s/catalog/type_chunk.h"
@@ -172,7 +173,8 @@ TEST_F(RemoveShardTest, RemoveShardStartDraining) {
     // Respond to request to reload information about existing shards
     onFindCommand([&](const RemoteCommandRequest& request) {
         ASSERT_EQUALS(configHost, request.target);
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         auto query = assertGet(LiteParsedQuery::makeFromFindCommand(nss, request.cmdObj, false));
@@ -348,7 +350,8 @@ TEST_F(RemoveShardTest, RemoveShardCompletion) {
     // Respond to request to reload information about existing shards
     onFindCommand([&](const RemoteCommandRequest& request) {
         ASSERT_EQUALS(configHost, request.target);
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         auto query = assertGet(LiteParsedQuery::makeFromFindCommand(nss, request.cmdObj, false));
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set_shard_collection_test.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set_shard_collection_test.cpp
index df0ab0697d2..a28192ec0b1 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set_shard_collection_test.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set_shard_collection_test.cpp
@@ -40,6 +40,7 @@
 #include "mongo/executor/network_interface_mock.h"
 #include "mongo/executor/task_executor.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/s/catalog/dist_lock_manager_mock.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set_test_fixture.h"
@@ -82,7 +83,9 @@ public:
     void expectGetDatabase(const DatabaseType& expectedDb) {
         onFindCommand([&](const RemoteCommandRequest& request) {
             ASSERT_EQUALS(configHost, request.target);
-            ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+            ASSERT_EQUALS(
+                BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                request.metadata);
 
             const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
             ASSERT_EQ(DatabaseType::ConfigNS, nss.ns());
@@ -152,7 +155,9 @@ public:
     void expectReloadChunks(const std::string& ns, const vector<ChunkType>& chunks) {
         onFindCommand([&](const RemoteCommandRequest& request) {
             ASSERT_EQUALS(configHost, request.target);
-            ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+            ASSERT_EQUALS(
+                BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                request.metadata);
 
             const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
             ASSERT_EQ(nss.ns(), ChunkType::ConfigNS);
@@ -212,7 +217,9 @@ public:
     void expectReloadCollection(const CollectionType& collection) {
         onFindCommand([&](const RemoteCommandRequest& request) {
             ASSERT_EQUALS(configHost, request.target);
-            ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+            ASSERT_EQUALS(
+                BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                request.metadata);
 
             const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
             ASSERT_EQ(nss.ns(), CollectionType::ConfigNS);
@@ -238,7 +245,9 @@ public:
     void expectLoadNewestChunk(const string& ns, const ChunkType& chunk) {
         onFindCommand([&](const RemoteCommandRequest& request) {
             ASSERT_EQUALS(configHost, request.target);
-            ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+            ASSERT_EQUALS(
+                BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                request.metadata);
 
             const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
             ASSERT_EQ(nss.ns(), ChunkType::ConfigNS);
@@ -760,7 +769,7 @@ TEST_F(ShardCollectionTest, withInitialData) {
         ASSERT_EQUALS(0, request.cmdObj["maxSplitPoints"].numberLong());
         ASSERT_EQUALS(0, request.cmdObj["maxChunkObjects"].numberLong());
 
-        ASSERT_EQUALS(rpc::makeEmptyMetadata(), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1), request.metadata);
 
         return BSON("ok" << 1 << "splitKeys"
                          << BSON_ARRAY(splitPoint0 << splitPoint1 << splitPoint2 << splitPoint3));
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set_test.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set_test.cpp
index f8dd2b959bf..44c414e239c 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set_test.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set_test.cpp
@@ -39,6 +39,7 @@
 #include "mongo/executor/network_interface_mock.h"
 #include "mongo/executor/task_executor.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/s/catalog/dist_lock_manager_mock.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set_test_fixture.h"
@@ -95,7 +96,8 @@ TEST_F(CatalogManagerReplSetTest, GetCollectionExisting) {
     onFindWithMetadataCommand([this, &expectedColl, newOpTime](
         const RemoteCommandRequest& request) {
 
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), CollectionType::ConfigNS);
@@ -155,7 +157,8 @@ TEST_F(CatalogManagerReplSetTest, GetDatabaseExisting) {
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), DatabaseType::ConfigNS);
 
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         auto query = assertGet(LiteParsedQuery::makeFromFindCommand(nss, request.cmdObj, false));
 
@@ -330,7 +333,8 @@ TEST_F(CatalogManagerReplSetTest, GetAllShardsValid) {
     });
 
     onFindCommand([this, &s1, &s2, &s3](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), ShardType::ConfigNS);
@@ -429,7 +433,8 @@ TEST_F(CatalogManagerReplSetTest, GetChunksForNSWithSortAndLimit) {
 
     onFindWithMetadataCommand([this, &chunksQuery, chunkA, chunkB, newOpTime](
         const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), ChunkType::ConfigNS);
@@ -476,7 +481,8 @@ TEST_F(CatalogManagerReplSetTest, GetChunksForNSNoSortNoLimit) {
     });
 
     onFindCommand([this, &chunksQuery](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), ChunkType::ConfigNS);
@@ -554,7 +560,8 @@ TEST_F(CatalogManagerReplSetTest, RunUserManagementReadCommand) {
     });
 
     onCommand([](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         ASSERT_EQUALS("test", request.dbname);
         ASSERT_EQUALS(BSON("usersInfo" << 1), request.cmdObj);
@@ -762,7 +769,8 @@ TEST_F(CatalogManagerReplSetTest, GetGlobalSettingsBalancerDoc) {
     });
 
     onFindCommand([this, st1](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), SettingsType::ConfigNS);
@@ -795,7 +803,8 @@ TEST_F(CatalogManagerReplSetTest, GetGlobalSettingsChunkSizeDoc) {
     });
 
     onFindCommand([this, st1](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), SettingsType::ConfigNS);
@@ -825,7 +834,8 @@ TEST_F(CatalogManagerReplSetTest, GetGlobalSettingsInvalidDoc) {
     });
 
     onFindCommand([this](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), SettingsType::ConfigNS);
@@ -857,7 +867,8 @@ TEST_F(CatalogManagerReplSetTest, GetGlobalSettingsNonExistent) {
     });
 
     onFindCommand([this](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), SettingsType::ConfigNS);
@@ -919,7 +930,8 @@ TEST_F(CatalogManagerReplSetTest, GetCollectionsValidResultsNoDb) {
 
     onFindWithMetadataCommand([this, coll1, coll2, coll3, newOpTime](
         const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), CollectionType::ConfigNS);
@@ -976,7 +988,8 @@ TEST_F(CatalogManagerReplSetTest, GetCollectionsValidResultsWithDb) {
     });
 
     onFindCommand([this, coll1, coll2](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), CollectionType::ConfigNS);
@@ -1027,7 +1040,8 @@ TEST_F(CatalogManagerReplSetTest, GetCollectionsInvalidCollectionType) {
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), CollectionType::ConfigNS);
 
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         auto query = assertGet(LiteParsedQuery::makeFromFindCommand(nss, request.cmdObj, false));
 
@@ -1070,7 +1084,8 @@ TEST_F(CatalogManagerReplSetTest, GetDatabasesForShardValid) {
     });
 
     onFindCommand([this, dbt1, dbt2](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), DatabaseType::ConfigNS);
@@ -1144,7 +1159,8 @@ TEST_F(CatalogManagerReplSetTest, GetTagsForCollection) {
     });
 
     onFindCommand([this, tagA, tagB](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), TagsType::ConfigNS);
@@ -1231,7 +1247,8 @@ TEST_F(CatalogManagerReplSetTest, GetTagForChunkOneTagFound) {
     });
 
     onFindCommand([this, chunk](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), TagsType::ConfigNS);
@@ -1276,7 +1293,8 @@ TEST_F(CatalogManagerReplSetTest, GetTagForChunkNoTagFound) {
     });
 
     onFindCommand([this, chunk](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), TagsType::ConfigNS);
@@ -1318,7 +1336,8 @@ TEST_F(CatalogManagerReplSetTest, GetTagForChunkInvalidTagDoc) {
     });
 
     onFindCommand([this, chunk](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(nss.ns(), TagsType::ConfigNS);
@@ -1502,7 +1521,8 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseSuccess) {
 
     onFindCommand([&](const RemoteCommandRequest& request) {
         ASSERT_EQUALS(configHost, request.target);
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         auto query = assertGet(LiteParsedQuery::makeFromFindCommand(nss, request.cmdObj, false));
@@ -1549,7 +1569,8 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseSuccess) {
     onFindCommand([&](const RemoteCommandRequest& request) {
         ASSERT_EQUALS(configHost, request.target);
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
         ASSERT_EQ(DatabaseType::ConfigNS, nss.ns());
         checkReadConcern(request.cmdObj, Timestamp(0, 0), repl::OpTime::kUninitializedTerm);
         return vector<BSONObj>{};
@@ -1563,7 +1584,7 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseSuccess) {
         ASSERT_EQUALS("listDatabases", cmdName);
         ASSERT_FALSE(request.cmdObj.hasField(repl::ReadConcernArgs::kReadConcernFieldName));
 
-        ASSERT_EQUALS(rpc::makeEmptyMetadata(), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1), request.metadata);
 
         return BSON("ok" << 1 << "totalSize" << 10);
     });
@@ -1576,7 +1597,7 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseSuccess) {
         ASSERT_EQUALS("listDatabases", cmdName);
         ASSERT_FALSE(request.cmdObj.hasField(repl::ReadConcernArgs::kReadConcernFieldName));
 
-        ASSERT_EQUALS(rpc::makeEmptyMetadata(), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1), request.metadata);
 
         return BSON("ok" << 1 << "totalSize" << 1);
     });
@@ -1588,7 +1609,7 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseSuccess) {
         string cmdName = request.cmdObj.firstElement().fieldName();
         ASSERT_EQUALS("listDatabases", cmdName);
 
-        ASSERT_EQUALS(rpc::makeEmptyMetadata(), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1), request.metadata);
 
         return BSON("ok" << 1 << "totalSize" << 100);
     });
@@ -1664,7 +1685,8 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseDBExists) {
     });
 
     onFindCommand([this, dbname](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         auto query = assertGet(LiteParsedQuery::makeFromFindCommand(nss, request.cmdObj, false));
@@ -1703,7 +1725,8 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseDBExistsDifferentCase) {
     });
 
     onFindCommand([this, dbname, dbnameDiffCase](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         auto query = assertGet(LiteParsedQuery::makeFromFindCommand(nss, request.cmdObj, false));
@@ -1742,7 +1765,8 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseNoShards) {
 
     // Report no databases with the same name already exist
     onFindCommand([this, dbname](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(DatabaseType::ConfigNS, nss.ns());
         checkReadConcern(request.cmdObj, Timestamp(0, 0), repl::OpTime::kUninitializedTerm);
@@ -1751,7 +1775,8 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseNoShards) {
 
     // Report no shards exist
     onFindCommand([this](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         auto query = assertGet(LiteParsedQuery::makeFromFindCommand(nss, request.cmdObj, false));
 
@@ -1790,7 +1815,8 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseDuplicateKeyOnInsert) {
 
     onFindCommand([&](const RemoteCommandRequest& request) {
         ASSERT_EQUALS(configHost, request.target);
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         auto query = assertGet(LiteParsedQuery::makeFromFindCommand(nss, request.cmdObj, false));
 
@@ -1835,7 +1861,8 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseDuplicateKeyOnInsert) {
     // Report no databases with the same name already exist
     onFindCommand([&](const RemoteCommandRequest& request) {
         ASSERT_EQUALS(configHost, request.target);
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(DatabaseType::ConfigNS, nss.ns());
         checkReadConcern(request.cmdObj, Timestamp(0, 0), repl::OpTime::kUninitializedTerm);
@@ -1850,7 +1877,7 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseDuplicateKeyOnInsert) {
         ASSERT_EQUALS("listDatabases", cmdName);
         ASSERT_FALSE(request.cmdObj.hasField(repl::ReadConcernArgs::kReadConcernFieldName));
 
-        ASSERT_EQUALS(rpc::makeEmptyMetadata(), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1), request.metadata);
 
         return BSON("ok" << 1 << "totalSize" << 10);
     });
@@ -1863,7 +1890,7 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseDuplicateKeyOnInsert) {
         ASSERT_EQUALS("listDatabases", cmdName);
         ASSERT_FALSE(request.cmdObj.hasField(repl::ReadConcernArgs::kReadConcernFieldName));
 
-        ASSERT_EQUALS(rpc::makeEmptyMetadata(), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1), request.metadata);
 
         return BSON("ok" << 1 << "totalSize" << 1);
     });
@@ -1876,7 +1903,7 @@ TEST_F(CatalogManagerReplSetTest, createDatabaseDuplicateKeyOnInsert) {
         ASSERT_EQUALS("listDatabases", cmdName);
         ASSERT_FALSE(request.cmdObj.hasField(repl::ReadConcernArgs::kReadConcernFieldName));
 
-        ASSERT_EQUALS(rpc::makeEmptyMetadata(), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1), request.metadata);
 
         return BSON("ok" << 1 << "totalSize" << 100);
     });
@@ -1946,7 +1973,8 @@ TEST_F(CatalogManagerReplSetTest, EnableShardingNoDBExists) {
 
     // Query to find if db already exists in config.
     onFindCommand([this](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
         const NamespaceString nss(request.dbname, request.cmdObj.firstElement().String());
         ASSERT_EQ(DatabaseType::ConfigNS, nss.toString());
 
@@ -1972,7 +2000,7 @@ TEST_F(CatalogManagerReplSetTest, EnableShardingNoDBExists) {
         ASSERT_EQ("admin", request.dbname);
         ASSERT_EQ(BSON("listDatabases" << 1), request.cmdObj);
 
-        ASSERT_EQUALS(rpc::makeEmptyMetadata(), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1), request.metadata);
 
         return fromjson(R"({
                 databases: [],
@@ -2177,7 +2205,9 @@ TEST_F(CatalogManagerReplSetTest, BasicReadAfterOpTime) {
         onCommandWithMetadata([this, &newOpTime, &lastOpTime](const RemoteCommandRequest& request) {
             ASSERT_EQUALS("test", request.dbname);
 
-            ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+            ASSERT_EQUALS(
+                BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                request.metadata);
 
             ASSERT_EQ(string("dummy"), request.cmdObj.firstElementFieldName());
             checkReadConcern(request.cmdObj, lastOpTime.getTimestamp(), lastOpTime.getTerm());
@@ -2212,7 +2242,8 @@ TEST_F(CatalogManagerReplSetTest, ReadAfterOpTimeShouldNotGoBack) {
     onCommandWithMetadata([this, &newOpTime, &highestOpTime](const RemoteCommandRequest& request) {
         ASSERT_EQUALS("test", request.dbname);
 
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         ASSERT_EQ(string("dummy"), request.cmdObj.firstElementFieldName());
         checkReadConcern(request.cmdObj, highestOpTime.getTimestamp(), highestOpTime.getTerm());
@@ -2240,7 +2271,8 @@ TEST_F(CatalogManagerReplSetTest, ReadAfterOpTimeShouldNotGoBack) {
     onCommandWithMetadata([this, &oldOpTime, &highestOpTime](const RemoteCommandRequest& request) {
         ASSERT_EQUALS("test", request.dbname);
 
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         ASSERT_EQ(string("dummy"), request.cmdObj.firstElementFieldName());
         checkReadConcern(request.cmdObj, highestOpTime.getTimestamp(), highestOpTime.getTerm());
@@ -2264,7 +2296,8 @@ TEST_F(CatalogManagerReplSetTest, ReadAfterOpTimeShouldNotGoBack) {
     onCommandWithMetadata([this, &oldOpTime, &highestOpTime](const RemoteCommandRequest& request) {
         ASSERT_EQUALS("test", request.dbname);
 
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         ASSERT_EQ(string("dummy"), request.cmdObj.firstElementFieldName());
         checkReadConcern(request.cmdObj, highestOpTime.getTimestamp(), highestOpTime.getTerm());
@@ -2289,21 +2322,22 @@ TEST_F(CatalogManagerReplSetTest, ReadAfterOpTimeFindThenCmd) {
     OpTime highestOpTime;
     const OpTime newOpTime(Timestamp(7, 6), 5);
 
-    onFindWithMetadataCommand(
-        [this, &newOpTime, &highestOpTime](const RemoteCommandRequest& request) {
-            ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
-            checkReadConcern(request.cmdObj, highestOpTime.getTimestamp(), highestOpTime.getTerm());
+    onFindWithMetadataCommand([this, &newOpTime, &highestOpTime](
+        const RemoteCommandRequest& request) {
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
+        checkReadConcern(request.cmdObj, highestOpTime.getTimestamp(), highestOpTime.getTerm());
 
-            ReplSetMetadata metadata(10, repl::OpTime(), newOpTime, 100, 30);
-            BSONObjBuilder builder;
-            metadata.writeToMetadata(&builder);
+        ReplSetMetadata metadata(10, repl::OpTime(), newOpTime, 100, 30);
+        BSONObjBuilder builder;
+        metadata.writeToMetadata(&builder);
 
-            SettingsType settings;
-            settings.setKey("chunksize");
-            settings.setChunkSizeMB(2);
+        SettingsType settings;
+        settings.setKey("chunksize");
+        settings.setChunkSizeMB(2);
 
-            return std::make_tuple(vector<BSONObj>{settings.toBSON()}, builder.obj());
-        });
+        return std::make_tuple(vector<BSONObj>{settings.toBSON()}, builder.obj());
+    });
 
     future1.timed_get(kFutureTimeout);
 
@@ -2321,7 +2355,8 @@ TEST_F(CatalogManagerReplSetTest, ReadAfterOpTimeFindThenCmd) {
     onCommand([this, &oldOpTime, &highestOpTime](const RemoteCommandRequest& request) {
         ASSERT_EQUALS("test", request.dbname);
 
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         ASSERT_EQ(string("dummy"), request.cmdObj.firstElementFieldName());
         checkReadConcern(request.cmdObj, highestOpTime.getTimestamp(), highestOpTime.getTerm());
@@ -2348,7 +2383,8 @@ TEST_F(CatalogManagerReplSetTest, ReadAfterOpTimeCmdThenFind) {
     onCommandWithMetadata([this, &newOpTime, &highestOpTime](const RemoteCommandRequest& request) {
         ASSERT_EQUALS("test", request.dbname);
 
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         ASSERT_EQ(string("dummy"), request.cmdObj.firstElementFieldName());
         checkReadConcern(request.cmdObj, highestOpTime.getTimestamp(), highestOpTime.getTerm());
@@ -2372,7 +2408,8 @@ TEST_F(CatalogManagerReplSetTest, ReadAfterOpTimeCmdThenFind) {
     const OpTime oldOpTime(Timestamp(3, 10), 5);
 
     onFindCommand([this, &oldOpTime, &highestOpTime](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         ASSERT_EQ(string("find"), request.cmdObj.firstElementFieldName());
         checkReadConcern(request.cmdObj, highestOpTime.getTimestamp(), highestOpTime.getTerm());
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set_test_fixture.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set_test_fixture.cpp
index 7096b781f8b..6d3231d06b1 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set_test_fixture.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set_test_fixture.cpp
@@ -45,6 +45,7 @@
 #include "mongo/executor/network_interface_mock.h"
 #include "mongo/executor/thread_pool_task_executor_test_fixture.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/s/catalog/dist_lock_manager_mock.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set.h"
 #include "mongo/s/catalog/type_changelog.h"
diff --git a/src/mongo/s/catalog/replset/catalog_manager_replica_set_upgrade_test.cpp b/src/mongo/s/catalog/replset/catalog_manager_replica_set_upgrade_test.cpp
index 1eed5931b1f..7aa61c476c5 100644
--- a/src/mongo/s/catalog/replset/catalog_manager_replica_set_upgrade_test.cpp
+++ b/src/mongo/s/catalog/replset/catalog_manager_replica_set_upgrade_test.cpp
@@ -34,6 +34,7 @@
 #include "mongo/bson/json.h"
 #include "mongo/client/remote_command_targeter_mock.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/s/catalog/config_server_version.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set.h"
 #include "mongo/s/catalog/replset/catalog_manager_replica_set_test_fixture.h"
@@ -58,7 +59,8 @@ TEST_F(CatalogManagerReplSetTestFixture, UpgradeNotNeeded) {
         launchAsync([this] { ASSERT_OK(catalogManager()->initConfigVersion(operationContext())); });
 
     onFindCommand([this](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         ASSERT_EQ(HostAndPort("config:123"), request.target);
         ASSERT_EQ("config", request.dbname);
@@ -352,7 +354,8 @@ TEST_F(CatalogManagerReplSetTestFixture, InitVersionDuplicateKeyNoOpAfterRetry)
     // Retry starts here
 
     onFindCommand([this](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         ASSERT_EQ(HostAndPort("config:123"), request.target);
         ASSERT_EQ("config", request.dbname);
@@ -483,7 +486,8 @@ TEST_F(CatalogManagerReplSetTestFixture, InitVersionDuplicateKeyTooNewAfterRetry
     // Retry starts here
 
     onFindCommand([this](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         ASSERT_EQ(HostAndPort("config:123"), request.target);
         ASSERT_EQ("config", request.dbname);
@@ -568,7 +572,8 @@ TEST_F(CatalogManagerReplSetTestFixture, InitVersionUpsertNoMatchNoOpAfterRetry)
     // Retry starts here
 
     onFindCommand([this](const RemoteCommandRequest& request) {
-        ASSERT_EQUALS(BSON(rpc::kReplSetMetadataFieldName << 1), request.metadata);
+        ASSERT_EQUALS(BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1),
+                      request.metadata);
 
         ASSERT_EQ(HostAndPort("config:123"), request.target);
         ASSERT_EQ("config", request.dbname);
diff --git a/src/mongo/s/chunk.cpp b/src/mongo/s/chunk.cpp
index 8102eb1a013..e50ce3ccddd 100644
--- a/src/mongo/s/chunk.cpp
+++ b/src/mongo/s/chunk.cpp
@@ -309,11 +309,12 @@ void Chunk::pickSplitVector(OperationContext* txn,
     BSONObj cmdObj = cmd.obj();
 
     const auto primaryShard = grid.shardRegistry()->getShard(txn, getShardId());
-    auto targetStatus =
-        primaryShard->getTargeter()->findHost({ReadPreference::PrimaryPreferred, TagSet{}});
-    uassertStatusOK(targetStatus);
-
-    auto result = grid.shardRegistry()->runCommand(txn, targetStatus.getValue(), "admin", cmdObj);
+    auto result = grid.shardRegistry()->runCommandOnShard(
+        txn,
+        primaryShard,
+        ReadPreferenceSetting{ReadPreference::PrimaryPreferred},
+        "admin",
+        cmdObj);
 
     uassertStatusOK(result.getStatus());
     uassertStatusOK(Command::getStatusFromCommandResult(result.getValue()));
diff --git a/src/mongo/s/chunk_manager.cpp b/src/mongo/s/chunk_manager.cpp
index 2531b74ea7e..b6720e81451 100644
--- a/src/mongo/s/chunk_manager.cpp
+++ b/src/mongo/s/chunk_manager.cpp
@@ -356,13 +356,13 @@ void ChunkManager::calcInitSplitsAndShards(OperationContext* txn,
     if (!initPoints || !initPoints->size()) {
         // discover split points
         const auto primaryShard = grid.shardRegistry()->getShard(txn, primaryShardId);
-        auto targetStatus =
-            primaryShard->getTargeter()->findHost({ReadPreference::PrimaryPreferred, TagSet{}});
-        uassertStatusOK(targetStatus);
-
-        NamespaceString nss(getns());
-        auto result = grid.shardRegistry()->runCommand(
-            txn, targetStatus.getValue(), nss.db().toString(), BSON("count" << nss.coll()));
+        const NamespaceString nss{getns()};
+        auto result = grid.shardRegistry()->runCommandOnShard(
+            txn,
+            primaryShard,
+            ReadPreferenceSetting{ReadPreference::PrimaryPreferred},
+            nss.db().toString(),
+            BSON("count" << nss.coll()));
 
         long long numObjects = 0;
         uassertStatusOK(result.getStatus());
diff --git a/src/mongo/s/client/shard_registry.cpp b/src/mongo/s/client/shard_registry.cpp
index e9ace5db1a4..83bf79d470e 100644
--- a/src/mongo/s/client/shard_registry.cpp
+++ b/src/mongo/s/client/shard_registry.cpp
@@ -44,6 +44,7 @@
 #include "mongo/rpc/get_status_from_command_result.h"
 #include "mongo/rpc/metadata/config_server_metadata.h"
 #include "mongo/rpc/metadata/repl_set_metadata.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/s/catalog/catalog_manager.h"
 #include "mongo/s/catalog/type_shard.h"
 #include "mongo/s/client/shard.h"
@@ -71,6 +72,20 @@ const Seconds kConfigCommandTimeout{30};
 const int kNotMasterNumRetries = 3;
 const Milliseconds kNotMasterRetryInterval{500};
 const BSONObj kReplMetadata(BSON(rpc::kReplSetMetadataFieldName << 1));
+const BSONObj kReplSecondaryOkMetadata{
+    BSON(rpc::kSecondaryOkFieldName << 1 << rpc::kReplSetMetadataFieldName << 1)};
+const BSONObj kSecondaryOkMetadata{BSON(rpc::kSecondaryOkFieldName << 1)};
+
+void updateReplSetMonitor(const std::shared_ptr<RemoteCommandTargeter>& targeter,
+                          const HostAndPort& remoteHost,
+                          const Status& remoteCommandStatus) {
+    if (ErrorCodes::NotMaster == remoteCommandStatus) {
+        targeter->markHostNotMaster(remoteHost);
+    } else if (ErrorCodes::isNetworkError(remoteCommandStatus.code())) {
+        targeter->markHostUnreachable(remoteHost);
+    }
+}
+
 }  // unnamed namespace
 
 ShardRegistry::ShardRegistry(std::unique_ptr<RemoteCommandTargeterFactory> targeterFactory,
@@ -329,13 +344,19 @@ OpTime ShardRegistry::getConfigOpTime() {
     return _configOpTime;
 }
 
-StatusWith<ShardRegistry::QueryResponse> ShardRegistry::exhaustiveFindOnConfigNode(
-    const HostAndPort& host,
+StatusWith<ShardRegistry::QueryResponse> ShardRegistry::exhaustiveFindOnConfig(
+    const ReadPreferenceSetting& readPref,
     const NamespaceString& nss,
     const BSONObj& query,
     const BSONObj& sort,
     boost::optional<long long> limit,
     boost::optional<repl::ReadConcernArgs> readConcern) {
+    const auto targeter = getConfigShard()->getTargeter();
+    const auto host = targeter->findHost(readPref);
+    if (!host.isOK()) {
+        return host.getStatus();
+    }
+
     // If for some reason the callback never gets invoked, we will return this status
     Status status = Status(ErrorCodes::InternalError, "Internal error running find command");
     QueryResponse response;
@@ -391,8 +412,13 @@ StatusWith<ShardRegistry::QueryResponse> ShardRegistry::exhaustiveFindOnConfigNo
     BSONObjBuilder findCmdBuilder;
     lpq->asFindCommand(&findCmdBuilder);
 
-    QueryFetcher fetcher(
-        _executor.get(), host, nss, findCmdBuilder.done(), fetcherCallback, kReplMetadata);
+    QueryFetcher fetcher(_executor.get(),
+                         host.getValue(),
+                         nss,
+                         findCmdBuilder.done(),
+                         fetcherCallback,
+                         readPref.pref == ReadPreference::PrimaryOnly ? kReplMetadata
+                                                                      : kReplSecondaryOkMetadata);
 
     Status scheduleStatus = fetcher.schedule();
     if (!scheduleStatus.isOK()) {
@@ -401,6 +427,8 @@ StatusWith<ShardRegistry::QueryResponse> ShardRegistry::exhaustiveFindOnConfigNo
 
     fetcher.wait();
 
+    updateReplSetMonitor(targeter, host.getValue(), status);
+
     if (!status.isOK()) {
         return status;
     }
@@ -410,12 +438,19 @@ StatusWith<ShardRegistry::QueryResponse> ShardRegistry::exhaustiveFindOnConfigNo
     return response;
 }
 
-StatusWith<BSONObj> ShardRegistry::runCommand(OperationContext* txn,
-                                              const HostAndPort& host,
-                                              const std::string& dbName,
-                                              const BSONObj& cmdObj) {
-    auto response =
-        _runCommandWithMetadata(_executor.get(), host, dbName, cmdObj, rpc::makeEmptyMetadata());
+StatusWith<BSONObj> ShardRegistry::runCommandOnShard(OperationContext* txn,
+                                                     const std::shared_ptr<Shard>& shard,
+                                                     const ReadPreferenceSetting& readPref,
+                                                     const std::string& dbName,
+                                                     const BSONObj& cmdObj) {
+    auto response = _runCommandWithMetadata(_executor.get(),
+                                            shard,
+                                            readPref,
+                                            dbName,
+                                            cmdObj,
+                                            readPref.pref == ReadPreference::PrimaryOnly
+                                                ? rpc::makeEmptyMetadata()
+                                                : kSecondaryOkMetadata);
     if (!response.isOK()) {
         return response.getStatus();
     }
@@ -423,12 +458,32 @@ StatusWith<BSONObj> ShardRegistry::runCommand(OperationContext* txn,
     return response.getValue().response;
 }
 
+StatusWith<BSONObj> ShardRegistry::runCommandOnShard(OperationContext* txn,
+                                                     ShardId shardId,
+                                                     const ReadPreferenceSetting& readPref,
+                                                     const std::string& dbName,
+                                                     const BSONObj& cmdObj) {
+    auto shard = getShard(txn, shardId);
+    if (!shard) {
+        return {ErrorCodes::ShardNotFound, str::stream() << "shard " << shardId << " not found"};
+    }
+    return runCommandOnShard(txn, shard, readPref, dbName, cmdObj);
+}
+
+
 StatusWith<BSONObj> ShardRegistry::runCommandForAddShard(OperationContext* txn,
-                                                         const HostAndPort& host,
+                                                         const std::shared_ptr<Shard>& shard,
+                                                         const ReadPreferenceSetting& readPref,
                                                          const std::string& dbName,
                                                          const BSONObj& cmdObj) {
-    auto status = _runCommandWithMetadata(
-        _executorForAddShard.get(), host, dbName, cmdObj, rpc::makeEmptyMetadata());
+    auto status = _runCommandWithMetadata(_executorForAddShard.get(),
+                                          shard,
+                                          readPref,
+                                          dbName,
+                                          cmdObj,
+                                          readPref.pref == ReadPreference::PrimaryOnly
+                                              ? rpc::makeEmptyMetadata()
+                                              : kSecondaryOkMetadata);
     if (!status.isOK()) {
         return status.getStatus();
     }
@@ -436,10 +491,16 @@ StatusWith<BSONObj> ShardRegistry::runCommandForAddShard(OperationContext* txn,
     return status.getValue().response;
 }
 
-StatusWith<BSONObj> ShardRegistry::runCommandOnConfig(const HostAndPort& host,
+StatusWith<BSONObj> ShardRegistry::runCommandOnConfig(const ReadPreferenceSetting& readPref,
                                                       const std::string& dbName,
                                                       const BSONObj& cmdObj) {
-    auto response = _runCommandWithMetadata(_executor.get(), host, dbName, cmdObj, kReplMetadata);
+    auto response = _runCommandWithMetadata(
+        _executor.get(),
+        getConfigShard(),
+        readPref,
+        dbName,
+        cmdObj,
+        readPref.pref == ReadPreference::PrimaryOnly ? kReplMetadata : kReplSecondaryOkMetadata);
 
     if (!response.isOK()) {
         return response.getStatus();
@@ -451,9 +512,8 @@ StatusWith<BSONObj> ShardRegistry::runCommandOnConfig(const HostAndPort& host,
 
 StatusWith<BSONObj> ShardRegistry::runCommandOnConfigWithNotMasterRetries(const std::string& dbname,
                                                                           const BSONObj& cmdObj) {
-    auto configShard = getConfigShard();
     auto response = _runCommandWithNotMasterRetries(
-        _executor.get(), configShard->getTargeter(), dbname, cmdObj, kReplMetadata);
+        _executor.get(), getConfigShard(), dbname, cmdObj, kReplMetadata);
 
     if (!response.isOK()) {
         return response.getStatus();
@@ -471,7 +531,7 @@ StatusWith<BSONObj> ShardRegistry::runCommandWithNotMasterRetries(OperationConte
     invariant(!shard->isConfig());
 
     auto response = _runCommandWithNotMasterRetries(
-        _executor.get(), shard->getTargeter(), dbname, cmdObj, rpc::makeEmptyMetadata());
+        _executor.get(), shard, dbname, cmdObj, rpc::makeEmptyMetadata());
     if (!response.isOK()) {
         return response.getStatus();
     }
@@ -481,28 +541,15 @@ StatusWith<BSONObj> ShardRegistry::runCommandWithNotMasterRetries(OperationConte
 
 StatusWith<ShardRegistry::CommandResponse> ShardRegistry::_runCommandWithNotMasterRetries(
     TaskExecutor* executor,
-    const std::shared_ptr<RemoteCommandTargeter>& targeter,
+    const std::shared_ptr<Shard>& shard,
     const std::string& dbname,
     const BSONObj& cmdObj,
     const BSONObj& metadata) {
-    const ReadPreferenceSetting readPref(ReadPreference::PrimaryOnly, TagSet{});
+    const ReadPreferenceSetting readPref{ReadPreference::PrimaryOnly};
 
     for (int i = 0; i < kNotMasterNumRetries; ++i) {
-        auto target = targeter->findHost(readPref);
-        if (!target.isOK()) {
-            if (ErrorCodes::NotMaster == target.getStatus()) {
-                if (i == kNotMasterNumRetries - 1) {
-                    // If we're out of retries don't bother sleeping, just return.
-                    return target.getStatus();
-                }
-                sleepmillis(durationCount<Milliseconds>(kNotMasterRetryInterval));
-                continue;
-            }
-            return target.getStatus();
-        }
-
         auto response =
-            _runCommandWithMetadata(executor, target.getValue(), dbname, cmdObj, metadata);
+            _runCommandWithMetadata(executor, shard, readPref, dbname, cmdObj, metadata);
         if (!response.isOK()) {
             return response.getStatus();
         }
@@ -510,7 +557,6 @@ StatusWith<ShardRegistry::CommandResponse> ShardRegistry::_runCommandWithNotMast
         Status commandStatus = getStatusFromCommandResult(response.getValue().response);
         if (ErrorCodes::NotMaster == commandStatus ||
             ErrorCodes::NotMasterNoSlaveOkCode == commandStatus) {
-            targeter->markHostNotMaster(target.getValue());
             if (i == kNotMasterNumRetries - 1) {
                 // If we're out of retries don't bother sleeping, just return.
                 return commandStatus;
@@ -527,14 +573,22 @@ StatusWith<ShardRegistry::CommandResponse> ShardRegistry::_runCommandWithNotMast
 
 StatusWith<ShardRegistry::CommandResponse> ShardRegistry::_runCommandWithMetadata(
     TaskExecutor* executor,
-    const HostAndPort& host,
+    const std::shared_ptr<Shard>& shard,
+    const ReadPreferenceSetting& readPref,
     const std::string& dbName,
     const BSONObj& cmdObj,
     const BSONObj& metadata) {
+    auto targeter = shard->getTargeter();
+    auto host = targeter->findHost(readPref);
+    if (!host.isOK()) {
+        return host.getStatus();
+    }
+
+    executor::RemoteCommandRequest request(
+        host.getValue(), dbName, cmdObj, metadata, kConfigCommandTimeout);
     StatusWith<executor::RemoteCommandResponse> responseStatus =
         Status(ErrorCodes::InternalError, "Internal error running command");
 
-    executor::RemoteCommandRequest request(host, dbName, cmdObj, metadata, kConfigCommandTimeout);
     auto callStatus =
         executor->scheduleRemoteCommand(request,
                                         [&responseStatus](const RemoteCommandCallbackArgs& args) {
@@ -547,11 +601,13 @@ StatusWith<ShardRegistry::CommandResponse> ShardRegistry::_runCommandWithMetadat
     // Block until the command is carried out
     executor->wait(callStatus.getValue());
 
+    updateReplSetMonitor(targeter, host.getValue(), responseStatus.getStatus());
     if (!responseStatus.isOK()) {
         return responseStatus.getStatus();
     }
 
     auto response = responseStatus.getValue();
+    updateReplSetMonitor(targeter, host.getValue(), getStatusFromCommandResult(response.data));
 
     CommandResponse cmdResponse;
     cmdResponse.response = response.data;
diff --git a/src/mongo/s/client/shard_registry.h b/src/mongo/s/client/shard_registry.h
index 611c78aae56..2780d9fe8c3 100644
--- a/src/mongo/s/client/shard_registry.h
+++ b/src/mongo/s/client/shard_registry.h
@@ -50,6 +50,7 @@ class OperationContext;
 class RemoteCommandTargeterFactory;
 class Shard;
 class ShardType;
+struct ReadPreferenceSetting;
 
 template <typename T>
 class StatusWith;
@@ -191,16 +192,16 @@ public:
     repl::OpTime getConfigOpTime();
 
     /**
-     * Executes 'find' command against the specified host and fetches *all* the results that
-     * the host will return until there are no more or until an error is returned.
-     * "host" must refer to a config server.
+     * Executes 'find' command against a config server matching the given read preference, and
+     * fetches *all* the results that the host will return until there are no more or until an error
+     * is returned.
      *
      * Returns either the complete set of results or an error, never partial results.
      *
      * Note: should never be used outside of CatalogManagerReplicaSet or DistLockCatalogImpl.
      */
-    StatusWith<QueryResponse> exhaustiveFindOnConfigNode(
-        const HostAndPort& host,
+    StatusWith<QueryResponse> exhaustiveFindOnConfig(
+        const ReadPreferenceSetting& readPref,
         const NamespaceString& nss,
         const BSONObj& query,
         const BSONObj& sort,
@@ -208,29 +209,38 @@ public:
         boost::optional<repl::ReadConcernArgs> readConcern);
 
     /**
-     * Runs a command against the specified host and returns the result.  It is the responsibility
-     * of the caller to check the returned BSON for command-specific failures.
+     * Runs a command against a host belonging to the specified shard and matching the given
+     * readPref, and returns the result.  It is the responsibility of the caller to check the
+     * returned BSON for command-specific failures.
      */
-    StatusWith<BSONObj> runCommand(OperationContext* txn,
-                                   const HostAndPort& host,
-                                   const std::string& dbName,
-                                   const BSONObj& cmdObj);
+    StatusWith<BSONObj> runCommandOnShard(OperationContext* txn,
+                                          const std::shared_ptr<Shard>& shard,
+                                          const ReadPreferenceSetting& readPref,
+                                          const std::string& dbName,
+                                          const BSONObj& cmdObj);
+    StatusWith<BSONObj> runCommandOnShard(OperationContext* txn,
+                                          ShardId shardId,
+                                          const ReadPreferenceSetting& readPref,
+                                          const std::string& dbName,
+                                          const BSONObj& cmdObj);
+
 
     /**
-     * Same as runCommand above but used for talking to nodes that are not yet in the ShardRegistry.
+     * Same as runCommandOnShard above but used for talking to nodes that are not yet in the
+     * ShardRegistry.
      */
     StatusWith<BSONObj> runCommandForAddShard(OperationContext* txn,
-                                              const HostAndPort& host,
+                                              const std::shared_ptr<Shard>& shard,
+                                              const ReadPreferenceSetting& readPref,
                                               const std::string& dbName,
                                               const BSONObj& cmdObj);
 
     /**
-     * Runs a command against the specified host and returns the result.  It is the responsibility
-     * of the caller to check the returned BSON for command-specific failures.
-     *
-     * "host" must refer to a config server node.
+     * Runs a command against a config server that matches the given read preference, and returns
+     * the result.  It is the responsibility of the caller to check the returned BSON for
+     * command-specific failures.
      */
-    StatusWith<BSONObj> runCommandOnConfig(const HostAndPort& host,
+    StatusWith<BSONObj> runCommandOnConfig(const ReadPreferenceSetting& readPref,
                                            const std::string& dbname,
                                            const BSONObj& cmdObj);
 
@@ -282,17 +292,17 @@ private:
      * of the caller to check the returned BSON for command-specific failures.
      */
     StatusWith<CommandResponse> _runCommandWithMetadata(executor::TaskExecutor* executor,
-                                                        const HostAndPort& host,
+                                                        const std::shared_ptr<Shard>& shard,
+                                                        const ReadPreferenceSetting& readPref,
                                                         const std::string& dbName,
                                                         const BSONObj& cmdObj,
                                                         const BSONObj& metadata);
 
-    StatusWith<CommandResponse> _runCommandWithNotMasterRetries(
-        executor::TaskExecutor* executor,
-        const std::shared_ptr<RemoteCommandTargeter>& targeter,
-        const std::string& dbname,
-        const BSONObj& cmdObj,
-        const BSONObj& metadata);
+    StatusWith<CommandResponse> _runCommandWithNotMasterRetries(executor::TaskExecutor* executor,
+                                                                const std::shared_ptr<Shard>& shard,
+                                                                const std::string& dbname,
+                                                                const BSONObj& cmdObj,
+                                                                const BSONObj& metadata);
 
     // Factory to obtain remote command targeters for shards
     const std::unique_ptr<RemoteCommandTargeterFactory> _targeterFactory;
diff --git a/src/mongo/s/commands/cluster_fsync_cmd.cpp b/src/mongo/s/commands/cluster_fsync_cmd.cpp
index cd4d182a2f3..0f4cea8c754 100644
--- a/src/mongo/s/commands/cluster_fsync_cmd.cpp
+++ b/src/mongo/s/commands/cluster_fsync_cmd.cpp
@@ -91,11 +91,12 @@ public:
                 continue;
             }
 
-            const auto shardHost = uassertStatusOK(
-                s->getTargeter()->findHost({ReadPreference::PrimaryOnly, TagSet::primaryOnly()}));
-
-            BSONObj x = uassertStatusOK(
-                grid.shardRegistry()->runCommand(txn, shardHost, "admin", BSON("fsync" << 1)));
+            BSONObj x = uassertStatusOK(grid.shardRegistry()->runCommandOnShard(
+                txn,
+                s,
+                ReadPreferenceSetting{ReadPreference::PrimaryOnly},
+                "admin",
+                BSON("fsync" << 1)));
 
             sub.append(s->getId(), x);
 
diff --git a/src/mongo/s/commands/cluster_list_databases_cmd.cpp b/src/mongo/s/commands/cluster_list_databases_cmd.cpp
index 0ef56e359f9..891ccb8fd4a 100644
--- a/src/mongo/s/commands/cluster_list_databases_cmd.cpp
+++ b/src/mongo/s/commands/cluster_list_databases_cmd.cpp
@@ -99,11 +99,12 @@ public:
                 continue;
             }
 
-            const auto shardHost = uassertStatusOK(s->getTargeter()->findHost(
-                {ReadPreference::PrimaryPreferred, TagSet::primaryOnly()}));
-
-            BSONObj x = uassertStatusOK(grid.shardRegistry()->runCommand(
-                txn, shardHost, "admin", BSON("listDatabases" << 1)));
+            BSONObj x = uassertStatusOK(grid.shardRegistry()->runCommandOnShard(
+                txn,
+                s,
+                ReadPreferenceSetting{ReadPreference::PrimaryPreferred},
+                "admin",
+                BSON("listDatabases" << 1)));
 
             BSONObjIterator j(x["databases"].Obj());
             while (j.more()) {
diff --git a/src/mongo/s/query/async_results_merger_test.cpp b/src/mongo/s/query/async_results_merger_test.cpp
index 75dfe2a2876..70e5d0e69a3 100644
--- a/src/mongo/s/query/async_results_merger_test.cpp
+++ b/src/mongo/s/query/async_results_merger_test.cpp
@@ -37,6 +37,7 @@
 #include "mongo/executor/network_interface_mock.h"
 #include "mongo/executor/task_executor.h"
 #include "mongo/executor/thread_pool_task_executor_test_fixture.h"
+#include "mongo/rpc/metadata/server_selection_metadata.h"
 #include "mongo/stdx/memory.h"
 #include "mongo/unittest/unittest.h"
 
@@ -1037,7 +1038,7 @@ TEST_F(AsyncResultsMergerTest, SendsSecondaryOkAsMetadata) {
     ASSERT_FALSE(arm->ready());
 
     BSONObj cmdRequestMetadata = getFirstPendingRequest().metadata;
-    ASSERT_EQ(cmdRequestMetadata, BSON("$secondaryOk" << 1));
+    ASSERT_EQ(cmdRequestMetadata, BSON(rpc::kSecondaryOkFieldName << 1));
 
     std::vector<CursorResponse> responses;
     std::vector<BSONObj> batch1 = {fromjson("{_id: 1}")};
diff --git a/src/mongo/s/shard_util.cpp b/src/mongo/s/shard_util.cpp
index 46afc889bc5..8b7ced7748e 100644
--- a/src/mongo/s/shard_util.cpp
+++ b/src/mongo/s/shard_util.cpp
@@ -42,19 +42,12 @@ namespace shardutil {
 StatusWith<long long> retrieveTotalShardSize(OperationContext* txn,
                                              ShardId shardId,
                                              ShardRegistry* shardRegistry) {
-    auto shard = shardRegistry->getShard(txn, shardId);
-    if (!shard) {
-        return {ErrorCodes::ShardNotFound, str::stream() << "shard " << shardId << " not found"};
-    }
-
-    auto shardHostStatus =
-        shard->getTargeter()->findHost({ReadPreference::PrimaryPreferred, TagSet::primaryOnly()});
-    if (!shardHostStatus.isOK()) {
-        return shardHostStatus.getStatus();
-    }
-
-    auto listDatabasesStatus = shardRegistry->runCommand(
-        txn, shardHostStatus.getValue(), "admin", BSON("listDatabases" << 1));
+    auto listDatabasesStatus =
+        shardRegistry->runCommandOnShard(txn,
+                                         shardId,
+                                         ReadPreferenceSetting{ReadPreference::PrimaryPreferred},
+                                         "admin",
+                                         BSON("listDatabases" << 1));
     if (!listDatabasesStatus.isOK()) {
         return listDatabasesStatus.getStatus();
     }
author	Andy Schwerin <schwerin@mongodb.com>	2015-10-02 17:44:17 -0400
committer	Andy Schwerin <schwerin@mongodb.com>	2015-10-06 12:45:03 -0400
commit	9267d348b98e3be67a85f219ba184c35f35fc309 (patch)
tree	2f5453f78ff8b15207f9c9df0fc0fffb1f42cb4f
parent	d9f2d8fda800fdc2cbd2be30413412c19a24f97a (diff)
download	mongo-9267d348b98e3be67a85f219ba184c35f35fc309.tar.gz