SERVER-49070: add and use FCV gating helpers

16 files changed, 78 insertions, 44 deletions

diff --git a/src/mongo/db/catalog/coll_mod.cpp b/src/mongo/db/catalog/coll_mod.cpp
index 25d9db7db51..f3c722afee0 100644
--- a/src/mongo/db/catalog/coll_mod.cpp
+++ b/src/mongo/db/catalog/coll_mod.cpp
@@ -233,18 +233,17 @@ StatusWith<CollModRequest> parseCollModRequest(OperationContext* opCtx,
                 continue;
             }
         } else if (fieldName == "validator" && !isView) {
-            // Save this to a variable to avoid reading the atomic variable multiple times.
-            const auto currentFCV = serverGlobalParams.featureCompatibility.getVersion();
-
             // If the feature compatibility version is not kLatest, and we are validating features
             // as master, ban the use of new agg features introduced in kLatest to prevent them from
             // being persisted in the catalog.
             boost::optional<ServerGlobalParams::FeatureCompatibility::Version>
                 maxFeatureCompatibilityVersion;
             // (Generic FCV reference): This FCV check should exist across LTS binary versions.
+            ServerGlobalParams::FeatureCompatibility::Version fcv;
             if (serverGlobalParams.validateFeaturesAsMaster.load() &&
-                currentFCV != ServerGlobalParams::FeatureCompatibility::kLatest) {
-                maxFeatureCompatibilityVersion = currentFCV;
+                serverGlobalParams.featureCompatibility.isLessThan(
+                    ServerGlobalParams::FeatureCompatibility::kLatest, &fcv)) {
+                maxFeatureCompatibilityVersion = fcv;
             }
             cmr.collValidator = coll->parseValidator(opCtx,
                                                      e.Obj().getOwned(),
diff --git a/src/mongo/db/catalog/database_impl.cpp b/src/mongo/db/catalog/database_impl.cpp
index 3b61a99f4cf..1bce91141fa 100644
--- a/src/mongo/db/catalog/database_impl.cpp
+++ b/src/mongo/db/catalog/database_impl.cpp
@@ -864,16 +864,15 @@ Status DatabaseImpl::userCreateNS(OperationContext* opCtx,
         boost::intrusive_ptr<ExpressionContext> expCtx(
             new ExpressionContext(opCtx, std::move(collator), nss));
 
-        // Save this to a variable to avoid reading the atomic variable multiple times.
-        const auto currentFCV = serverGlobalParams.featureCompatibility.getVersion();
-
         // If the feature compatibility version is not kLatest, and we are validating features as
         // master, ban the use of new agg features introduced in kLatest to prevent them from being
         // persisted in the catalog.
         // (Generic FCV reference): This FCV check should exist across LTS binary versions.
+        ServerGlobalParams::FeatureCompatibility::Version fcv;
         if (serverGlobalParams.validateFeaturesAsMaster.load() &&
-            currentFCV != ServerGlobalParams::FeatureCompatibility::kLatest) {
-            expCtx->maxFeatureCompatibilityVersion = currentFCV;
+            serverGlobalParams.featureCompatibility.isLessThan(
+                ServerGlobalParams::FeatureCompatibility::kLatest, &fcv)) {
+            expCtx->maxFeatureCompatibilityVersion = fcv;
         }
 
         // The match expression parser needs to know that we're parsing an expression for a
diff --git a/src/mongo/db/index/index_descriptor.cpp b/src/mongo/db/index/index_descriptor.cpp
index 6dddcf4c0d2..a16478bc4ac 100644
--- a/src/mongo/db/index/index_descriptor.cpp
+++ b/src/mongo/db/index/index_descriptor.cpp
@@ -179,8 +179,8 @@ IndexDescriptor::Comparison IndexDescriptor::compareIndexOptions(
 
     // The partialFilterExpression is only part of the index signature if FCV has been set to 4.6.
     // TODO SERVER-47766: remove these FCV checks after we branch for 4.7.
-    auto isFCV46 = serverGlobalParams.featureCompatibility.getVersion() ==
-        ServerGlobalParams::FeatureCompatibility::Version::kVersion451;
+    auto isFCV46 = serverGlobalParams.featureCompatibility.isGreaterThanOrEqualTo(
+        ServerGlobalParams::FeatureCompatibility::Version::kVersion451);
 
     // If we have a partial filter expression and the other index doesn't, or vice-versa, then the
     // two indexes are not equivalent. We therefore return Comparison::kDifferent immediately.
diff --git a/src/mongo/db/mongod_main.cpp b/src/mongo/db/mongod_main.cpp
index 9c3de78b56d..ee2aed80c34 100644
--- a/src/mongo/db/mongod_main.cpp
+++ b/src/mongo/db/mongod_main.cpp
@@ -1061,7 +1061,10 @@ void shutdownTask(const ShutdownTaskArgs& shutdownArgs) {
     }
 
     // TODO SERVER-49138: Remove this FCV check once we branch for 4.8.
-    if (serverGlobalParams.featureCompatibility.isVersion(
+    // We must FCV gate the Quiesce mode feature so that a 4.6 node entering Quiesce mode in a mixed
+    // 4.4/4.6 replica set does not delay a 4.4 node from finding a valid sync source.
+    if (serverGlobalParams.featureCompatibility.isVersionInitialized() &&
+        serverGlobalParams.featureCompatibility.isGreaterThanOrEqualTo(
             ServerGlobalParams::FeatureCompatibility::Version::kVersion451)) {
         if (auto replCoord = repl::ReplicationCoordinator::get(serviceContext);
             replCoord && replCoord->enterQuiesceModeIfSecondary(shutdownTimeout)) {
diff --git a/src/mongo/db/ops/insert.cpp b/src/mongo/db/ops/insert.cpp
index 9333440f060..91a405a18d9 100644
--- a/src/mongo/db/ops/insert.cpp
+++ b/src/mongo/db/ops/insert.cpp
@@ -174,8 +174,8 @@ StatusWith<BSONObj> fixDocumentForInsert(ServiceContext* service, const BSONObj&
 Status userAllowedWriteNS(const NamespaceString& ns) {
     // TODO (SERVER-49545): Remove the FCV check after branching for 4.8.
     if (ns.isSystemDotProfile() ||
-        (ns.isSystemDotViews() &&
-         serverGlobalParams.featureCompatibility.isVersion(
+        (ns.isSystemDotViews() && serverGlobalParams.featureCompatibility.isVersionInitialized() &&
+         serverGlobalParams.featureCompatibility.isGreaterThanOrEqualTo(
              ServerGlobalParams::FeatureCompatibility::Version::kVersion451))) {
         return Status(ErrorCodes::InvalidNamespace, str::stream() << "cannot write to " << ns);
     }
diff --git a/src/mongo/db/repl/initial_syncer.cpp b/src/mongo/db/repl/initial_syncer.cpp
index 7fc437c2b6b..ec21186276d 100644
--- a/src/mongo/db/repl/initial_syncer.cpp
+++ b/src/mongo/db/repl/initial_syncer.cpp
@@ -1087,8 +1087,7 @@ void InitialSyncer::_fcvFetcherCallback(const StatusWith<Fetcher::QueryResponse>
 
     // Changing the featureCompatibilityVersion during initial sync is unsafe.
     // (Generic FCV reference): This FCV check should exist across LTS binary versions.
-    if (version > ServerGlobalParams::FeatureCompatibility::kLastLTS &&
-        version < ServerGlobalParams::FeatureCompatibility::kLatest) {
+    if (serverGlobalParams.featureCompatibility.isUpgradingOrDowngrading(version)) {
         onCompletionGuard->setResultAndCancelRemainingWork_inlock(
             lock,
             Status(ErrorCodes::IncompatibleServerVersion,
diff --git a/src/mongo/db/repl/repl_set_heartbeat_args_v1.cpp b/src/mongo/db/repl/repl_set_heartbeat_args_v1.cpp
index c1bc9b7ac83..1da6ec13f11 100644
--- a/src/mongo/db/repl/repl_set_heartbeat_args_v1.cpp
+++ b/src/mongo/db/repl/repl_set_heartbeat_args_v1.cpp
@@ -179,7 +179,8 @@ void ReplSetHeartbeatArgsV1::addToBSON(BSONObjBuilder* builder) const {
     builder->appendIntOrLL(kTermFieldName, _term);
 
     // TODO SERVER-49382: Remove this FCV check after we branch for 4.7.
-    if (serverGlobalParams.featureCompatibility.isVersion(
+    if (serverGlobalParams.featureCompatibility.isVersionInitialized() &&
+        serverGlobalParams.featureCompatibility.isGreaterThanOrEqualTo(
             ServerGlobalParams::FeatureCompatibility::Version::kVersion451)) {
         builder->append(kPrimaryIdFieldName, _primaryId);
     }
diff --git a/src/mongo/db/repl/replication_coordinator_impl.cpp b/src/mongo/db/repl/replication_coordinator_impl.cpp
index 53fe1169ba0..52908aedbae 100644
--- a/src/mongo/db/repl/replication_coordinator_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl.cpp
@@ -3173,12 +3173,8 @@ Status ReplicationCoordinatorImpl::processReplSetFreeze(int secs, BSONObjBuilder
 }
 
 bool ReplicationCoordinatorImpl::_supportsAutomaticReconfig() const {
-    if (serverGlobalParams.featureCompatibility.getVersion() !=
-        ServerGlobalParams::FeatureCompatibility::Version::kVersion451) {
-        return false;
-    }
-
-    return true;
+    return serverGlobalParams.featureCompatibility.isGreaterThanOrEqualTo(
+        ServerGlobalParams::FeatureCompatibility::Version::kVersion451);
 }
 
 Status ReplicationCoordinatorImpl::processReplSetReconfig(OperationContext* opCtx,
diff --git a/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp b/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
index c4ebaad4ce5..c1365f31ee4 100644
--- a/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
+++ b/src/mongo/db/repl/replication_coordinator_impl_heartbeat.cpp
@@ -302,8 +302,8 @@ void ReplicationCoordinatorImpl::_handleHeartbeatResponse(
                 // binaries to have on-disk repl config with 'newlyAdded' fields.
                 invariant(
                     _supportsAutomaticReconfig() ||
-                    serverGlobalParams.featureCompatibility.getVersion() >
-                        ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo44);
+                    serverGlobalParams.featureCompatibility.isGreaterThan(
+                        ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo44));
 
                 const auto memId = mem->getId();
                 auto status = _replExecutor->scheduleWork(
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 20b238c4344..fbc5d0c6e51 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
@@ -339,8 +339,8 @@ StatusWith<ShardType> ShardingCatalogManager::_validateHostAsShard(
                                                 << connectionString.toString() << " as a shard");
     }
     // (Generic FCV reference): This FCV check should exist across LTS binary versions.
-    if (serverGlobalParams.featureCompatibility.getVersion() >
-        ServerGlobalParams::FeatureCompatibility::kLastLTS) {
+    if (serverGlobalParams.featureCompatibility.isGreaterThan(
+            ServerGlobalParams::FeatureCompatibility::kLastLTS)) {
         // If the cluster's FCV is kLatest, or upgrading to / downgrading from, the node being added
         // must be a version kLatest binary.
         invariant(maxWireVersion == WireVersion::LATEST_WIRE_VERSION);
diff --git a/src/mongo/db/server_options.h b/src/mongo/db/server_options.h
index 2b2f88dee47..4d239097d91 100644
--- a/src/mongo/db/server_options.h
+++ b/src/mongo/db/server_options.h
@@ -242,8 +242,44 @@ struct ServerGlobalParams {
             return _version.store(version);
         }
 
-        bool isVersion(Version version) {
-            return _version.load() == version;
+        bool isLessThanOrEqualTo(Version version, Version* versionReturn = nullptr) {
+            Version currentVersion = getVersion();
+            if (versionReturn != nullptr) {
+                *versionReturn = currentVersion;
+            }
+            return currentVersion <= version;
+        }
+
+        bool isGreaterThanOrEqualTo(Version version, Version* versionReturn = nullptr) {
+            Version currentVersion = getVersion();
+            if (versionReturn != nullptr) {
+                *versionReturn = currentVersion;
+            }
+            return currentVersion >= version;
+        }
+
+        bool isLessThan(Version version, Version* versionReturn = nullptr) {
+            Version currentVersion = getVersion();
+            if (versionReturn != nullptr) {
+                *versionReturn = currentVersion;
+            }
+            return currentVersion < version;
+        }
+
+        bool isGreaterThan(Version version, Version* versionReturn = nullptr) {
+            Version currentVersion = getVersion();
+            if (versionReturn != nullptr) {
+                *versionReturn = currentVersion;
+            }
+            return currentVersion > version;
+        }
+
+        // This function is to be used for generic FCV references only, and not for FCV-gating.
+        bool isUpgradingOrDowngrading(boost::optional<Version> version = boost::none) {
+            if (version == boost::none) {
+                version = getVersion();
+            }
+            return version != kLatest && version != kLastContinuous && version != kLastLTS;
         }
 
     private:
diff --git a/src/mongo/db/storage/storage_engine_impl.cpp b/src/mongo/db/storage/storage_engine_impl.cpp
index aad57d352e3..d739fb000dc 100644
--- a/src/mongo/db/storage/storage_engine_impl.cpp
+++ b/src/mongo/db/storage/storage_engine_impl.cpp
@@ -927,8 +927,9 @@ bool StorageEngineImpl::supportsOplogStones() const {
 
 bool StorageEngineImpl::supportsResumableIndexBuilds() const {
     return enableResumableIndexBuilds && supportsReadConcernMajority() && !isEphemeral() &&
-        serverGlobalParams.featureCompatibility.getVersion() ==
-        ServerGlobalParams::FeatureCompatibility::Version::kVersion451 &&
+        serverGlobalParams.featureCompatibility.isVersionInitialized() &&
+        serverGlobalParams.featureCompatibility.isGreaterThanOrEqualTo(
+            ServerGlobalParams::FeatureCompatibility::Version::kVersion451) &&
         !repl::ReplSettings::shouldRecoverFromOplogAsStandalone();
 }
 
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
index 3fa21ec4f8d..e027e67162a 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine.cpp
@@ -146,8 +146,8 @@ bool WiredTigerFileVersion::shouldDowngrade(bool readOnly,
             _startupVersion == StartupVersion::IS_42;
     }
 
-    if (serverGlobalParams.featureCompatibility.getVersion() !=
-        ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo44) {
+    if (serverGlobalParams.featureCompatibility.isGreaterThan(
+            ServerGlobalParams::FeatureCompatibility::Version::kFullyDowngradedTo44)) {
         // Only consider downgrading when FCV is set to kFullyDowngraded.
         // (This FCV gate must remain across binary version releases.)
         return false;
diff --git a/src/mongo/db/vector_clock.cpp b/src/mongo/db/vector_clock.cpp
index 92f060ac16a..b45badf38c3 100644
--- a/src/mongo/db/vector_clock.cpp
+++ b/src/mongo/db/vector_clock.cpp
@@ -160,9 +160,9 @@ public:
              BSONObjBuilder* out,
              LogicalTime time,
              Component component) const override {
-        const auto& fcv = serverGlobalParams.featureCompatibility;
-        if (fcv.isVersionInitialized() &&
-            fcv.getVersion() == ServerGlobalParams::FeatureCompatibility::Version::kVersion451) {
+        if (serverGlobalParams.featureCompatibility.isVersionInitialized() &&
+            serverGlobalParams.featureCompatibility.isGreaterThanOrEqualTo(
+                ServerGlobalParams::FeatureCompatibility::Version::kVersion451)) {
             return ActualFormat::out(service, opCtx, permitRefresh, out, time, component);
         }
         return false;
diff --git a/src/mongo/db/views/view_catalog.cpp b/src/mongo/db/views/view_catalog.cpp
index ad05c435d43..ee8e5198b17 100644
--- a/src/mongo/db/views/view_catalog.cpp
+++ b/src/mongo/db/views/view_catalog.cpp
@@ -328,16 +328,15 @@ StatusWith<stdx::unordered_set<NamespaceString>> ViewCatalog::_validatePipeline(
                               std::move(resolvedNamespaces),
                               boost::none);
 
-    // Save this to a variable to avoid reading the atomic variable multiple times.
-    auto currentFCV = serverGlobalParams.featureCompatibility.getVersion();
-
     // If the feature compatibility version is not kLatest, and we are validating features as
     // master, ban the use of new agg features introduced in kLatest to prevent them from being
     // persisted in the catalog.
     // (Generic FCV reference): This FCV check should exist across LTS binary versions.
+    ServerGlobalParams::FeatureCompatibility::Version fcv;
     if (serverGlobalParams.validateFeaturesAsMaster.load() &&
-        currentFCV != ServerGlobalParams::FeatureCompatibility::kLatest) {
-        expCtx->maxFeatureCompatibilityVersion = currentFCV;
+        serverGlobalParams.featureCompatibility.isLessThan(
+            ServerGlobalParams::FeatureCompatibility::kLatest, &fcv)) {
+        expCtx->maxFeatureCompatibilityVersion = fcv;
     }
 
     // The pipeline parser needs to know that we're parsing a pipeline for a view definition
diff --git a/src/mongo/s/mongos_main.cpp b/src/mongo/s/mongos_main.cpp
index 234a1a84c53..fcb9b6c0b2e 100644
--- a/src/mongo/s/mongos_main.cpp
+++ b/src/mongo/s/mongos_main.cpp
@@ -289,8 +289,9 @@ void cleanupTask(const ShutdownTaskArgs& shutdownArgs) {
         // so that clients can re-route their operations.
         //
         // TODO SERVER-49138: Remove this FCV check once we branch for 4.8.
-        if (serverGlobalParams.featureCompatibility.isVersion(
-                ServerGlobalParams::FeatureCompatibility::Version::kVersion451);
+        if (serverGlobalParams.featureCompatibility.isVersionInitialized() &&
+                serverGlobalParams.featureCompatibility.isGreaterThanOrEqualTo(
+                    ServerGlobalParams::FeatureCompatibility::Version::kVersion451);
             auto mongosTopCoord = MongosTopologyCoordinator::get(opCtx)) {
             mongosTopCoord->enterQuiesceModeAndWait(opCtx, quiesceTime);
         }