1 files changed, 55 insertions, 36 deletions

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 f03ee603838..d10ba0288d3 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
@@ -84,6 +84,7 @@ using CallbackHandle = executor::TaskExecutor::CallbackHandle;
 using CallbackArgs = executor::TaskExecutor::CallbackArgs;
 using RemoteCommandCallbackArgs = executor::TaskExecutor::RemoteCommandCallbackArgs;
 using RemoteCommandCallbackFn = executor::TaskExecutor::RemoteCommandCallbackFn;
+using FeatureCompatibilityParams = ServerGlobalParams::FeatureCompatibility;
 
 const ReadPreferenceSetting kConfigReadSelector(ReadPreference::Nearest, TagSet{});
 
@@ -338,23 +339,24 @@ StatusWith<ShardType> ShardingCatalogManager::_validateHostAsShard(
                                                 << "field when attempting to add "
                                                 << connectionString.toString() << " as a shard");
     }
+    const auto currentFcv = serverGlobalParams.featureCompatibility.getVersion();
     // (Generic FCV reference): These FCV checks should exist across LTS binary versions.
-    if (serverGlobalParams.featureCompatibility.isGreaterThanOrEqualTo(
-            ServerGlobalParams::FeatureCompatibility::kLatest) ||
-        serverGlobalParams.featureCompatibility.isUpgradingOrDowngrading()) {
-        // If the cluster's FCV is kLatest, or upgrading to / downgrading from, the node being added
-        // must be a version kLatest binary.
+    if (currentFcv == FeatureCompatibilityParams::kLatest ||
+        currentFcv == FeatureCompatibilityParams::kDowngradingFromLatestToLastContinuous ||
+        currentFcv == FeatureCompatibilityParams::kDowngradingFromLatestToLastLTS ||
+        currentFcv == FeatureCompatibilityParams::kUpgradingFromLastContinuousToLatest ||
+        currentFcv == FeatureCompatibilityParams::kUpgradingFromLastLTSToLatest) {
+        // If the cluster's FCV is kLatest, or upgrading to / downgrading from kLatest, the node
+        // being added must be a version kLatest binary.
         invariant(maxWireVersion == WireVersion::LATEST_WIRE_VERSION);
-    } else if (serverGlobalParams.featureCompatibility.isGreaterThanOrEqualTo(
-                   ServerGlobalParams::FeatureCompatibility::kLastContinuous)) {
-        // If we are using the kLastContinuous FCV, the node being added must be of the
-        // last-continuous or latest binary version.
+    } else if (currentFcv == FeatureCompatibilityParams::kLastContinuous ||
+               currentFcv == FeatureCompatibilityParams::kUpgradingFromLastLTSToLastContinuous) {
+        // If we are using the kLastContinuous  or upgrading to kLastContinuous FCV, the node being
+        // added must be of the last-continuous or latest binary version.
         invariant(maxWireVersion >= WireVersion::LAST_CONT_WIRE_VERSION);
     } else {
-        // If we are using the kLastLTS FCV, the node being added must be of the last-lts or latest
-        // binary version.
-        invariant(maxWireVersion == WireVersion::LAST_LTS_WIRE_VERSION ||
-                  maxWireVersion == WireVersion::LATEST_WIRE_VERSION);
+        // (Generic FCV reference): These FCV checks should exist across LTS binary versions.
+        invariant(currentFcv == FeatureCompatibilityParams::kLastLTS);
     }
 
     // Check whether there is a master. If there isn't, the replica set may not have been
@@ -656,32 +658,49 @@ StatusWith<std::string> ShardingCatalogManager::addShard(
         invariant(!opCtx->lockState()->isLocked());
         Lock::SharedLock lk(opCtx->lockState(), FeatureCompatibilityVersion::fcvLock);
 
-        BSONObjBuilder setFCVBuilder;
-        // (Generic FCV reference): These FCV checks should exist across LTS binary versions.
-        switch (serverGlobalParams.featureCompatibility.getVersion()) {
-            case ServerGlobalParams::FeatureCompatibility::kLatest:
-            case ServerGlobalParams::FeatureCompatibility::Version::kUpgradingFrom44To47: {
-                SetFeatureCompatibilityVersion setLatestCmd(
-                    ServerGlobalParams::FeatureCompatibility::kLatest);
-                // The serialize function generated by IDL requires the DB name to be set.
-                setLatestCmd.setDbName(NamespaceString::kAdminDb);
-                setLatestCmd.serialize({}, &setFCVBuilder);
-                break;
-            }
-            default:
+        // Get the target version that the newly added shard should be set to.
+        const FeatureCompatibilityParams::Version setVersion = [] {
+            const auto currentFcv = serverGlobalParams.featureCompatibility.getVersion();
+            // (Generic FCV reference): These FCV checks should exist across LTS binary versions.
+            if (currentFcv == FeatureCompatibilityParams::kLatest ||
+                currentFcv == FeatureCompatibilityParams::kUpgradingFromLastContinuousToLatest ||
+                currentFcv == FeatureCompatibilityParams::kUpgradingFromLastLTSToLatest) {
+                return FeatureCompatibilityParams::kLatest;
+            } else if (currentFcv == FeatureCompatibilityParams::kLastContinuous ||
+                       currentFcv ==
+                           FeatureCompatibilityParams::kDowngradingFromLatestToLastContinuous ||
+                       currentFcv ==
+                           FeatureCompatibilityParams::kUpgradingFromLastLTSToLastContinuous) {
+                // (Generic FCV reference): These FCV checks should exist across LTS binary
+                // versions.
+                return FeatureCompatibilityParams::kLastContinuous;
+            } else {
                 // (Generic FCV reference): This FCV reference should exist across LTS binary
                 // versions.
-                SetFeatureCompatibilityVersion setLastLTSCmd(
-                    ServerGlobalParams::FeatureCompatibility::kLastLTS);
-                // The serialize function generated by IDL requires the DB name to be set.
-                setLastLTSCmd.setDbName(NamespaceString::kAdminDb);
-                setLastLTSCmd.serialize({}, &setFCVBuilder);
-                break;
+                invariant(currentFcv ==
+                              FeatureCompatibilityParams::kDowngradingFromLatestToLastLTS ||
+                          currentFcv == FeatureCompatibilityParams::kLastLTS);
+                return FeatureCompatibilityParams::kLastLTS;
+            }
+        }();
+
+        SetFeatureCompatibilityVersion setFcvCmd(setVersion);
+        setFcvCmd.setDbName(NamespaceString::kAdminDb);
+        // TODO (SERVER-50954): Remove this FCV check once 4.4 is no longer the last LTS
+        // version.
+        if (serverGlobalParams.featureCompatibility.isGreaterThanOrEqualTo(
+                FeatureCompatibilityParams::Version::kVersion47)) {
+            // fromConfigServer is a new parameter added to 4.8 with intention to be backported
+            // to 4.7.
+            setFcvCmd.setFromConfigServer(true);
         }
-        setFCVBuilder.append(WriteConcernOptions::kWriteConcernField,
-                             opCtx->getWriteConcern().toBSON());
-        auto versionResponse = _runCommandForAddShard(
-            opCtx, targeter.get(), NamespaceString::kAdminDb, setFCVBuilder.obj());
+
+        auto versionResponse =
+            _runCommandForAddShard(opCtx,
+                                   targeter.get(),
+                                   NamespaceString::kAdminDb,
+                                   setFcvCmd.toBSON(BSON(WriteConcernOptions::kWriteConcernField
+                                                         << opCtx->getWriteConcern().toBSON())));
         if (!versionResponse.isOK()) {
             return versionResponse.getStatus();
         }