SERVER-33179 Remove featureCompatibilityVersion 3.4

3 files changed, 19 insertions, 34 deletions

diff --git a/src/mongo/db/s/config/configsvr_shard_collection_command.cpp b/src/mongo/db/s/config/configsvr_shard_collection_command.cpp
index 1ad8459f3f1..4dc2b459384 100644
--- a/src/mongo/db/s/config/configsvr_shard_collection_command.cpp
+++ b/src/mongo/db/s/config/configsvr_shard_collection_command.cpp
@@ -643,11 +643,6 @@ void migrateAndFurtherSplitInitialChunks(OperationContext* opCtx,
 
 boost::optional<UUID> getUUIDFromPrimaryShard(const NamespaceString& nss,
                                               ScopedDbConnection& conn) {
-    // UUIDs were introduced in featureCompatibilityVersion 3.6.
-    if (!serverGlobalParams.featureCompatibility.isSchemaVersion36()) {
-        return boost::none;
-    }
-
     // Obtain the collection's UUID from the primary shard's listCollections response.
     BSONObj res;
     {
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 79489af4c9e..5d93e1d7a62 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
@@ -340,20 +340,14 @@ StatusWith<ShardType> ShardingCatalogManager::_validateHostAsShard(
     }
     if (serverGlobalParams.featureCompatibility.getVersion() >
         ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo36) {
-        // If FCV 4.0, or upgrading to / downgrading from, wire version must be LATEST.
+        // If the cluster's FCV is 4.0, or upgrading to / downgrading from, the node being added
+        // must be a v4.0 binary.
         invariant(maxWireVersion == WireVersion::LATEST_WIRE_VERSION);
-    } else if (serverGlobalParams.featureCompatibility.getVersion() >
-                   ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo34 &&
-               serverGlobalParams.featureCompatibility.getVersion() <=
-                   ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo36) {
-        // If FCV 3.6, or upgrading to / downgrading from, wire version must be v3.6
-        // LATEST_WIRE_VERSION or greater.
-        invariant(maxWireVersion >= WireVersion::LATEST_WIRE_VERSION - 1);
     } else {
-        // If FCV 3.4, wire version cannot be less than v3.4 LATEST_WIRE_VERSION.
+        // If the cluster's FCV is 3.6, the node being added must be a v3.6 or v4.0 binary.
         invariant(serverGlobalParams.featureCompatibility.getVersion() ==
-                  ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo34);
-        invariant(maxWireVersion >= WireVersion::LATEST_WIRE_VERSION - 2);
+                  ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo36);
+        invariant(maxWireVersion >= WireVersion::LATEST_WIRE_VERSION - 1);
     }
 
     // Check whether there is a master. If there isn't, the replica set may not have been
diff --git a/src/mongo/db/s/migration_destination_manager.cpp b/src/mongo/db/s/migration_destination_manager.cpp
index a29bbc368bf..ac2746f180a 100644
--- a/src/mongo/db/s/migration_destination_manager.cpp
+++ b/src/mongo/db/s/migration_destination_manager.cpp
@@ -561,25 +561,21 @@ void MigrationDestinationManager::_migrateDriver(OperationContext* opCtx,
             donorOptionsBob.appendElements(entry["options"].Obj());
         }
 
-        if (serverGlobalParams.featureCompatibility.isSchemaVersion36()) {
-            BSONObj info;
-            if (entry["info"].isABSONObj()) {
-                info = entry["info"].Obj();
-            }
-            if (info["uuid"].eoo()) {
-                setStateFailWarn(str::stream()
-                                 << "The donor shard did not return a UUID for collection "
-                                 << _nss.ns()
-                                 << " as part of its listCollections response: "
-                                 << entry
-                                 << ", but this node expects to see a UUID since its "
-                                    "feature compatibility version is 3.6. Please follow "
-                                    "the online documentation to set the same feature "
-                                    "compatibility version across the cluster.");
-                return;
-            }
-            donorOptionsBob.append(info["uuid"]);
+        BSONObj info;
+        if (entry["info"].isABSONObj()) {
+            info = entry["info"].Obj();
+        }
+        if (info["uuid"].eoo()) {
+            setStateFailWarn(str::stream()
+                             << "The donor shard did not return a UUID for collection "
+                             << _nss.ns()
+                             << " as part of its listCollections response: "
+                             << entry
+                             << ", but this node expects to see a UUID.");
+            return;
         }
+        donorOptionsBob.append(info["uuid"]);
+
         donorOptions = donorOptionsBob.obj();
     }