SERVER-50264: Better FCV const correctness

12 files changed, 30 insertions, 27 deletions

diff --git a/src/mongo/db/commands/feature_compatibility_version.cpp b/src/mongo/db/commands/feature_compatibility_version.cpp
index d4d57344d22..6c93d22d318 100644
--- a/src/mongo/db/commands/feature_compatibility_version.cpp
+++ b/src/mongo/db/commands/feature_compatibility_version.cpp
@@ -266,7 +266,7 @@ void FeatureCompatibilityVersion::initializeForStartup(OperationContext* opCtx)
     }
 
     auto version = swVersion.getValue();
-    serverGlobalParams.featureCompatibility.setVersion(version);
+    serverGlobalParams.mutableFeatureCompatibility.setVersion(version);
     FeatureCompatibilityVersion::updateMinWireVersion();
 
     // On startup, if the version is in an upgrading or downgrading state, print a warning.
diff --git a/src/mongo/db/fcv_op_observer.cpp b/src/mongo/db/fcv_op_observer.cpp
index 3b75c0a8e97..d5a94048cc5 100644
--- a/src/mongo/db/fcv_op_observer.cpp
+++ b/src/mongo/db/fcv_op_observer.cpp
@@ -52,7 +52,7 @@ using FeatureCompatibilityParams = ServerGlobalParams::FeatureCompatibility;
 
 void FcvOpObserver::_setVersion(OperationContext* opCtx,
                                 ServerGlobalParams::FeatureCompatibility::Version newVersion) {
-    serverGlobalParams.featureCompatibility.setVersion(newVersion);
+    serverGlobalParams.mutableFeatureCompatibility.setVersion(newVersion);
     FeatureCompatibilityVersion::updateMinWireVersion();
 
     // (Generic FCV reference): This FCV check should exist across LTS binary versions.
diff --git a/src/mongo/db/repl/initial_syncer.cpp b/src/mongo/db/repl/initial_syncer.cpp
index 7aa35351c99..d91141560ac 100644
--- a/src/mongo/db/repl/initial_syncer.cpp
+++ b/src/mongo/db/repl/initial_syncer.cpp
@@ -632,7 +632,7 @@ void InitialSyncer::_startInitialSyncAttemptCallback(
                 "Resetting feature compatibility version to last-lts. If the sync source is in "
                 "latest feature compatibility version, we will find out when we clone the "
                 "server configuration collection (admin.system.version)");
-    serverGlobalParams.featureCompatibility.reset();
+    serverGlobalParams.mutableFeatureCompatibility.reset();
 
     // Clear the oplog buffer.
     _oplogBuffer->clear(makeOpCtx().get());
diff --git a/src/mongo/db/repl/initial_syncer_test.cpp b/src/mongo/db/repl/initial_syncer_test.cpp
index 0ec082420af..4bf9cebc028 100644
--- a/src/mongo/db/repl/initial_syncer_test.cpp
+++ b/src/mongo/db/repl/initial_syncer_test.cpp
@@ -4042,7 +4042,7 @@ OplogEntry InitialSyncerTest::doInitialSyncWithOneBatch() {
 
 void InitialSyncerTest::doSuccessfulInitialSyncWithOneBatch() {
     auto lastOp = doInitialSyncWithOneBatch();
-    serverGlobalParams.featureCompatibility.reset();
+    serverGlobalParams.mutableFeatureCompatibility.reset();
     ASSERT_OK(_lastApplied.getStatus());
     ASSERT_EQUALS(lastOp.getOpTime(), _lastApplied.getValue().opTime);
     ASSERT_EQUALS(lastOp.getWallClockTime(), _lastApplied.getValue().wallTime);
diff --git a/src/mongo/db/repl/oplog_applier_impl_test_fixture.cpp b/src/mongo/db/repl/oplog_applier_impl_test_fixture.cpp
index 61eec974350..cb390508c6c 100644
--- a/src/mongo/db/repl/oplog_applier_impl_test_fixture.cpp
+++ b/src/mongo/db/repl/oplog_applier_impl_test_fixture.cpp
@@ -128,7 +128,7 @@ void OplogApplierImplTest::setUp() {
     // test fixture does not create a featureCompatibilityVersion document from which to initialize
     // the server parameter.
     // (Generic FCV reference): This FCV reference should exist across LTS binary versions.
-    serverGlobalParams.featureCompatibility.setVersion(
+    serverGlobalParams.mutableFeatureCompatibility.setVersion(
         ServerGlobalParams::FeatureCompatibility::kLatest);
 
     // This is necessary to generate ghost timestamps for index builds that are not 0, since 0 is an
diff --git a/src/mongo/db/s/sharding_mongod_test_fixture.cpp b/src/mongo/db/s/sharding_mongod_test_fixture.cpp
index ce0c23c09c6..4b73a742e02 100644
--- a/src/mongo/db/s/sharding_mongod_test_fixture.cpp
+++ b/src/mongo/db/s/sharding_mongod_test_fixture.cpp
@@ -138,7 +138,7 @@ ShardingMongodTestFixture::ShardingMongodTestFixture() {
     // Set the highest FCV because otherwise it defaults to the lower FCV. This way we default to
     // testing this release's code, not backwards compatibility code.
     // (Generic FCV reference): This FCV reference should exist across LTS binary versions.
-    serverGlobalParams.featureCompatibility.setVersion(
+    serverGlobalParams.mutableFeatureCompatibility.setVersion(
         ServerGlobalParams::FeatureCompatibility::kLatest);
 }
 
diff --git a/src/mongo/db/server_options.h b/src/mongo/db/server_options.h
index 9cff03225e1..057133d2124 100644
--- a/src/mongo/db/server_options.h
+++ b/src/mongo/db/server_options.h
@@ -232,15 +232,7 @@ struct ServerGlobalParams {
             return _version.load();
         }
 
-        void reset() {
-            _version.store(Version::kUnsetDefault44Behavior);
-        }
-
-        void setVersion(Version version) {
-            return _version.store(version);
-        }
-
-        bool isLessThanOrEqualTo(Version version, Version* versionReturn = nullptr) {
+        bool isLessThanOrEqualTo(Version version, Version* versionReturn = nullptr) const {
             Version currentVersion = getVersion();
             if (versionReturn != nullptr) {
                 *versionReturn = currentVersion;
@@ -248,7 +240,7 @@ struct ServerGlobalParams {
             return currentVersion <= version;
         }
 
-        bool isGreaterThanOrEqualTo(Version version, Version* versionReturn = nullptr) {
+        bool isGreaterThanOrEqualTo(Version version, Version* versionReturn = nullptr) const {
             Version currentVersion = getVersion();
             if (versionReturn != nullptr) {
                 *versionReturn = currentVersion;
@@ -256,7 +248,7 @@ struct ServerGlobalParams {
             return currentVersion >= version;
         }
 
-        bool isLessThan(Version version, Version* versionReturn = nullptr) {
+        bool isLessThan(Version version, Version* versionReturn = nullptr) const {
             Version currentVersion = getVersion();
             if (versionReturn != nullptr) {
                 *versionReturn = currentVersion;
@@ -264,7 +256,7 @@ struct ServerGlobalParams {
             return currentVersion < version;
         }
 
-        bool isGreaterThan(Version version, Version* versionReturn = nullptr) {
+        bool isGreaterThan(Version version, Version* versionReturn = nullptr) const {
             Version currentVersion = getVersion();
             if (versionReturn != nullptr) {
                 *versionReturn = currentVersion;
@@ -273,17 +265,28 @@ struct ServerGlobalParams {
         }
 
         // This function is to be used for generic FCV references only, and not for FCV-gating.
-        bool isUpgradingOrDowngrading(boost::optional<Version> version = boost::none) {
+        bool isUpgradingOrDowngrading(boost::optional<Version> version = boost::none) const {
             if (version == boost::none) {
                 version = getVersion();
             }
             return version != kLatest && version != kLastContinuous && version != kLastLTS;
         }
 
+        void reset() {
+            _version.store(Version::kUnsetDefault44Behavior);
+        }
+
+        void setVersion(Version version) {
+            return _version.store(version);
+        }
+
     private:
         AtomicWord<Version> _version{Version::kUnsetDefault44Behavior};
 
-    } featureCompatibility;
+    } mutableFeatureCompatibility;
+
+    // Const reference for featureCompatibilityVersion checks.
+    const FeatureCompatibility& featureCompatibility = mutableFeatureCompatibility;
 
     // Feature validation differs depending on the role of a mongod in a replica set. Replica set
     // primaries can accept user-initiated writes and validate based on the feature compatibility
diff --git a/src/mongo/dbtests/dbtests.cpp b/src/mongo/dbtests/dbtests.cpp
index 3661ecdc5ed..0ecc021f82d 100644
--- a/src/mongo/dbtests/dbtests.cpp
+++ b/src/mongo/dbtests/dbtests.cpp
@@ -184,7 +184,7 @@ int dbtestsMain(int argc, char** argv) {
 
     mongo::runGlobalInitializersOrDie(std::vector<std::string>(argv, argv + argc));
     // (Generic FCV reference): This FCV reference should exist across LTS binary versions.
-    serverGlobalParams.featureCompatibility.setVersion(
+    serverGlobalParams.mutableFeatureCompatibility.setVersion(
         ServerGlobalParams::FeatureCompatibility::kLatest);
     repl::ReplSettings replSettings;
     replSettings.setOplogSizeBytes(10 * 1024 * 1024);
diff --git a/src/mongo/s/mongos_main.cpp b/src/mongo/s/mongos_main.cpp
index 28d4e1b79b4..eaaa36b3fa1 100644
--- a/src/mongo/s/mongos_main.cpp
+++ b/src/mongo/s/mongos_main.cpp
@@ -883,7 +883,7 @@ MONGO_INITIALIZER_WITH_PREREQUISITES(SetFeatureCompatibilityVersionLatest,
                                      ("EndStartupOptionStorage"))
 // (Generic FCV reference): This FCV reference should exist across LTS binary versions.
 (InitializerContext* context) {
-    serverGlobalParams.featureCompatibility.setVersion(
+    serverGlobalParams.mutableFeatureCompatibility.setVersion(
         ServerGlobalParams::FeatureCompatibility::kLatest);
     return Status::OK();
 }
diff --git a/src/mongo/shell/mongo_main.cpp b/src/mongo/shell/mongo_main.cpp
index ecdca584ab1..cb947fc76b1 100644
--- a/src/mongo/shell/mongo_main.cpp
+++ b/src/mongo/shell/mongo_main.cpp
@@ -118,7 +118,7 @@ MONGO_INITIALIZER_WITH_PREREQUISITES(SetFeatureCompatibilityVersionLatest,
                                      ("EndStartupOptionSetup"))
 // (Generic FCV reference): This FCV reference should exist across LTS binary versions.
 (InitializerContext* context) {
-    mongo::serverGlobalParams.featureCompatibility.setVersion(
+    mongo::serverGlobalParams.mutableFeatureCompatibility.setVersion(
         ServerGlobalParams::FeatureCompatibility::kLatest);
     return Status::OK();
 }
diff --git a/src/mongo/unittest/ensure_fcv.h b/src/mongo/unittest/ensure_fcv.h
index bcba036e417..a0e6e19ed8d 100644
--- a/src/mongo/unittest/ensure_fcv.h
+++ b/src/mongo/unittest/ensure_fcv.h
@@ -43,10 +43,10 @@ public:
     using Version = ServerGlobalParams::FeatureCompatibility::Version;
     EnsureFCV(Version version)
         : _origVersion(serverGlobalParams.featureCompatibility.getVersion()) {
-        serverGlobalParams.featureCompatibility.setVersion(version);
+        serverGlobalParams.mutableFeatureCompatibility.setVersion(version);
     }
     ~EnsureFCV() {
-        serverGlobalParams.featureCompatibility.setVersion(_origVersion);
+        serverGlobalParams.mutableFeatureCompatibility.setVersion(_origVersion);
     }
 
 private:
diff --git a/src/mongo/unittest/unittest.cpp b/src/mongo/unittest/unittest.cpp
index 2e8dafe95c3..0d28c50999e 100644
--- a/src/mongo/unittest/unittest.cpp
+++ b/src/mongo/unittest/unittest.cpp
@@ -156,11 +156,11 @@ namespace {
 // with a meaningful value will trigger failures as of SERVER-32630.
 // (Generic FCV reference): This FCV reference should exist across LTS binary versions.
 void setUpFCV() {
-    serverGlobalParams.featureCompatibility.setVersion(
+    serverGlobalParams.mutableFeatureCompatibility.setVersion(
         ServerGlobalParams::FeatureCompatibility::kLatest);
 }
 void tearDownFCV() {
-    serverGlobalParams.featureCompatibility.reset();
+    serverGlobalParams.mutableFeatureCompatibility.reset();
 }
 
 struct TestSuiteEnvironment {