SERVER-32645 Create a shim helper framework.

The `MONGO_DECLARE_SHIM`, `MONGO_DEFINE_SHIM`, and `MONGO_REGISTER_SHIM`
macros can be used to create specialized types which are customization
and auto-registration points for late-binding functions.  In some
sense they work like weak-symbols; however, they also are useful for
tracking dependencies upon shimmed-out implementations.

78 files changed, 354 insertions, 660 deletions

diff --git a/src/mongo/db/catalog/SConscript b/src/mongo/db/catalog/SConscript
index c2f57ca82a4..5ed9e0ad896 100644
--- a/src/mongo/db/catalog/SConscript
+++ b/src/mongo/db/catalog/SConscript
@@ -130,6 +130,7 @@ env.Library(
         "database.cpp",
     ],
     LIBDEPS=[
+        '$BUILD_DIR/mongo/base',
     ],
 )
 
diff --git a/src/mongo/db/catalog/catalog_control.cpp b/src/mongo/db/catalog/catalog_control.cpp
index 684862b6a9f..f97cb254d72 100644
--- a/src/mongo/db/catalog/catalog_control.cpp
+++ b/src/mongo/db/catalog/catalog_control.cpp
@@ -56,7 +56,7 @@ void closeCatalog(OperationContext* opCtx) {
     // Close all databases.
     log() << "closeCatalog: closing all databases";
     constexpr auto reason = "closing databases for closeCatalog";
-    dbHolder().closeAll(opCtx, reason);
+    DatabaseHolder::getDatabaseHolder().closeAll(opCtx, reason);
 
     // Close the storage engine's catalog.
     log() << "closeCatalog: closing storage engine catalog";
@@ -145,7 +145,7 @@ void openCatalog(OperationContext* opCtx) {
     storageEngine->listDatabases(&databasesToOpen);
     for (auto&& dbName : databasesToOpen) {
         LOG(1) << "openCatalog: dbholder reopening database " << dbName;
-        auto db = dbHolder().openDb(opCtx, dbName);
+        auto db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName);
         invariant(db, str::stream() << "failed to reopen database " << dbName);
 
         std::list<std::string> collections;
diff --git a/src/mongo/db/catalog/collection.cpp b/src/mongo/db/catalog/collection.cpp
index 13bb493e5a6..915980a34d3 100644
--- a/src/mongo/db/catalog/collection.cpp
+++ b/src/mongo/db/catalog/collection.cpp
@@ -70,56 +70,14 @@ namespace mongo {
 // Emit the vtable in this TU
 Collection::Impl::~Impl() = default;
 
-namespace {
-stdx::function<Collection::factory_function_type> factory;
-}  // namespace
+MONGO_DEFINE_SHIM(Collection::makeImpl);
 
-void Collection::registerFactory(decltype(factory) newFactory) {
-    factory = std::move(newFactory);
-}
+MONGO_DEFINE_SHIM(Collection::parseValidationLevel);
 
-auto Collection::makeImpl(Collection* _this,
-                          OperationContext* const opCtx,
-                          const StringData fullNS,
-                          OptionalCollectionUUID uuid,
-                          CollectionCatalogEntry* const details,
-                          RecordStore* const recordStore,
-                          DatabaseCatalogEntry* const dbce) -> std::unique_ptr<Impl> {
-    return factory(_this, opCtx, fullNS, uuid, details, recordStore, dbce);
-}
+MONGO_DEFINE_SHIM(Collection::parseValidationAction);
 
 void Collection::TUHook::hook() noexcept {}
 
-
-namespace {
-stdx::function<decltype(Collection::parseValidationLevel)> parseValidationLevelImpl;
-}  // namespace
-
-void Collection::registerParseValidationLevelImpl(
-    stdx::function<decltype(parseValidationLevel)> impl) {
-    parseValidationLevelImpl = std::move(impl);
-}
-
-auto Collection::parseValidationLevel(const StringData data) -> StatusWith<ValidationLevel> {
-    return parseValidationLevelImpl(data);
-}
-
-namespace {
-stdx::function<decltype(Collection::parseValidationAction)> parseValidationActionImpl;
-}  // namespace
-
-void Collection::registerParseValidationActionImpl(
-    stdx::function<decltype(parseValidationAction)> impl) {
-    parseValidationActionImpl = std::move(impl);
-}
-
-auto Collection::parseValidationAction(const StringData data) -> StatusWith<ValidationAction> {
-    return parseValidationActionImpl(data);
-}
-}  // namespace mongo
-
-
-namespace mongo {
 std::string CompactOptions::toString() const {
     std::stringstream ss;
     ss << "paddingMode: ";
diff --git a/src/mongo/db/catalog/collection.h b/src/mongo/db/catalog/collection.h
index 042c7a3a0c5..9c41f8478f3 100644
--- a/src/mongo/db/catalog/collection.h
+++ b/src/mongo/db/catalog/collection.h
@@ -330,19 +330,16 @@ public:
         virtual const CollatorInterface* getDefaultCollator() const = 0;
     };
 
-private:
-    static std::unique_ptr<Impl> makeImpl(Collection* _this,
-                                          OperationContext* opCtx,
-                                          StringData fullNS,
-                                          OptionalCollectionUUID uuid,
-                                          CollectionCatalogEntry* details,
-                                          RecordStore* recordStore,
-                                          DatabaseCatalogEntry* dbce);
-
 public:
-    using factory_function_type = decltype(makeImpl);
-
-    static void registerFactory(stdx::function<factory_function_type> factory);
+    static MONGO_DECLARE_SHIM((Collection * _this,
+                               OperationContext* opCtx,
+                               StringData fullNS,
+                               OptionalCollectionUUID uuid,
+                               CollectionCatalogEntry* details,
+                               RecordStore* recordStore,
+                               DatabaseCatalogEntry* dbce,
+                               PrivateTo<Collection>)
+                                  ->std::unique_ptr<Impl>) makeImpl;
 
     explicit inline Collection(OperationContext* const opCtx,
                                const StringData fullNS,
@@ -350,7 +347,8 @@ public:
                                CollectionCatalogEntry* const details,  // does not own
                                RecordStore* const recordStore,         // does not own
                                DatabaseCatalogEntry* const dbce)       // does not own
-        : _pimpl(makeImpl(this, opCtx, fullNS, uuid, details, recordStore, dbce)) {
+        : _pimpl(makeImpl(
+              this, opCtx, fullNS, uuid, details, recordStore, dbce, PrivateCall<Collection>{})) {
         this->_impl().init(opCtx);
     }
 
@@ -627,13 +625,8 @@ public:
             opCtx, validator, allowedFeatures, maxFeatureCompatibilityVersion);
     }
 
-    static StatusWith<ValidationLevel> parseValidationLevel(StringData);
-    static StatusWith<ValidationAction> parseValidationAction(StringData);
-
-    static void registerParseValidationLevelImpl(
-        stdx::function<decltype(parseValidationLevel)> impl);
-    static void registerParseValidationActionImpl(
-        stdx::function<decltype(parseValidationAction)> impl);
+    static MONGO_DECLARE_SHIM((StringData)->StatusWith<ValidationLevel>) parseValidationLevel;
+    static MONGO_DECLARE_SHIM((StringData)->StatusWith<ValidationAction>) parseValidationAction;
 
     /**
      * Sets the validator for this collection.
diff --git a/src/mongo/db/catalog/collection_impl.cpp b/src/mongo/db/catalog/collection_impl.cpp
index 74909e46f0c..f08d5be410e 100644
--- a/src/mongo/db/catalog/collection_impl.cpp
+++ b/src/mongo/db/catalog/collection_impl.cpp
@@ -76,34 +76,30 @@
 
 namespace mongo {
 
-namespace {
-MONGO_INITIALIZER(InitializeCollectionFactory)(InitializerContext* const) {
-    Collection::registerFactory(
-        [](Collection* const _this,
-           OperationContext* const opCtx,
-           const StringData fullNS,
-           OptionalCollectionUUID uuid,
-           CollectionCatalogEntry* const details,
-           RecordStore* const recordStore,
-           DatabaseCatalogEntry* const dbce) -> std::unique_ptr<Collection::Impl> {
-            return stdx::make_unique<CollectionImpl>(
-                _this, opCtx, fullNS, uuid, details, recordStore, dbce);
-        });
-    return Status::OK();
+MONGO_REGISTER_SHIM(Collection::makeImpl)
+(Collection* const _this,
+ OperationContext* const opCtx,
+ const StringData fullNS,
+ OptionalCollectionUUID uuid,
+ CollectionCatalogEntry* const details,
+ RecordStore* const recordStore,
+ DatabaseCatalogEntry* const dbce,
+ PrivateTo<Collection>)
+    ->std::unique_ptr<Collection::Impl> {
+    return std::make_unique<CollectionImpl>(_this, opCtx, fullNS, uuid, details, recordStore, dbce);
 }
 
-MONGO_INITIALIZER(InitializeParseValidationLevelImpl)(InitializerContext* const) {
-    Collection::registerParseValidationLevelImpl(
-        [](const StringData data) { return CollectionImpl::parseValidationLevel(data); });
-    return Status::OK();
+MONGO_REGISTER_SHIM(Collection::parseValidationLevel)
+(const StringData data)->StatusWith<Collection::ValidationLevel> {
+    return CollectionImpl::parseValidationLevel(data);
 }
 
-MONGO_INITIALIZER(InitializeParseValidationActionImpl)(InitializerContext* const) {
-    Collection::registerParseValidationActionImpl(
-        [](const StringData data) { return CollectionImpl::parseValidationAction(data); });
-    return Status::OK();
+MONGO_REGISTER_SHIM(Collection::parseValidationAction)
+(const StringData data)->StatusWith<Collection::ValidationAction> {
+    return CollectionImpl::parseValidationAction(data);
 }
 
+namespace {
 // Used below to fail during inserts.
 MONGO_FP_DECLARE(failCollectionInserts);
 
diff --git a/src/mongo/db/catalog/collection_info_cache.cpp b/src/mongo/db/catalog/collection_info_cache.cpp
index 4bd1e4715f7..0a36bb07448 100644
--- a/src/mongo/db/catalog/collection_info_cache.cpp
+++ b/src/mongo/db/catalog/collection_info_cache.cpp
@@ -33,20 +33,9 @@
 #include "mongo/db/catalog/collection_info_cache.h"
 
 namespace mongo {
-namespace {
-stdx::function<CollectionInfoCache::factory_function_type> factory;
-}  // namespace
-
 CollectionInfoCache::Impl::~Impl() = default;
 
-void CollectionInfoCache::registerFactory(decltype(factory) newFactory) {
-    factory = std::move(newFactory);
-}
-
-auto CollectionInfoCache::makeImpl(Collection* const collection, const NamespaceString& ns)
-    -> std::unique_ptr<Impl> {
-    return factory(collection, ns);
-}
+MONGO_DEFINE_SHIM(CollectionInfoCache::makeImpl);
 
 void CollectionInfoCache::TUHook::hook() noexcept {}
 }  // namespace mongo
diff --git a/src/mongo/db/catalog/collection_info_cache.h b/src/mongo/db/catalog/collection_info_cache.h
index 9bc07e80c61..6fb0fa5278e 100644
--- a/src/mongo/db/catalog/collection_info_cache.h
+++ b/src/mongo/db/catalog/collection_info_cache.h
@@ -28,6 +28,7 @@
 
 #pragma once
 
+#include "mongo/base/shim.h"
 #include "mongo/db/collection_index_usage_tracker.h"
 #include "mongo/db/query/plan_cache.h"
 #include "mongo/db/query/query_settings.h"
@@ -69,16 +70,15 @@ public:
                                    const std::set<std::string>& indexesUsed) = 0;
     };
 
-private:
-    static std::unique_ptr<Impl> makeImpl(Collection* collection, const NamespaceString& ns);
 
 public:
-    using factory_function_type = decltype(makeImpl);
-
-    static void registerFactory(stdx::function<factory_function_type> factory);
+    static MONGO_DECLARE_SHIM((Collection * collection,
+                               const NamespaceString& ns,
+                               PrivateTo<CollectionInfoCache>)
+                                  ->std::unique_ptr<Impl>) makeImpl;
 
     explicit inline CollectionInfoCache(Collection* const collection, const NamespaceString& ns)
-        : _pimpl(makeImpl(collection, ns)) {}
+        : _pimpl(makeImpl(collection, ns, PrivateCall<CollectionInfoCache>{})) {}
 
     inline ~CollectionInfoCache() = default;
 
diff --git a/src/mongo/db/catalog/collection_info_cache_impl.cpp b/src/mongo/db/catalog/collection_info_cache_impl.cpp
index b3366f70ae2..d23da8c5a81 100644
--- a/src/mongo/db/catalog/collection_info_cache_impl.cpp
+++ b/src/mongo/db/catalog/collection_info_cache_impl.cpp
@@ -49,15 +49,11 @@
 #include "mongo/util/log.h"
 
 namespace mongo {
-namespace {
-MONGO_INITIALIZER(InitializeCollectionInfoCacheFactory)(InitializerContext* const) {
-    CollectionInfoCache::registerFactory(
-        [](Collection* const collection, const NamespaceString& ns) {
-            return stdx::make_unique<CollectionInfoCacheImpl>(collection, ns);
-        });
-    return Status::OK();
+MONGO_REGISTER_SHIM(CollectionInfoCache::makeImpl)
+(Collection* const collection, const NamespaceString& ns, PrivateTo<CollectionInfoCache>)
+    ->std::unique_ptr<CollectionInfoCache::Impl> {
+    return std::make_unique<CollectionInfoCacheImpl>(collection, ns);
 }
-}  // namespace
 
 CollectionInfoCacheImpl::CollectionInfoCacheImpl(Collection* collection, const NamespaceString& ns)
     : _collection(collection),
diff --git a/src/mongo/db/catalog/collection_info_cache_impl.h b/src/mongo/db/catalog/collection_info_cache_impl.h
index 58be19ed045..38e03f68a7b 100644
--- a/src/mongo/db/catalog/collection_info_cache_impl.h
+++ b/src/mongo/db/catalog/collection_info_cache_impl.h
@@ -30,6 +30,7 @@
 
 #include "mongo/db/catalog/collection_info_cache.h"
 
+#include "mongo/base/shim.h"
 #include "mongo/db/collection_index_usage_tracker.h"
 #include "mongo/db/query/plan_cache.h"
 #include "mongo/db/query/query_settings.h"
diff --git a/src/mongo/db/catalog/create_collection.cpp b/src/mongo/db/catalog/create_collection.cpp
index 950420fa787..f8258d36f07 100644
--- a/src/mongo/db/catalog/create_collection.cpp
+++ b/src/mongo/db/catalog/create_collection.cpp
@@ -101,8 +101,8 @@ Status createCollection(OperationContext* opCtx,
 
         // Create collection.
         const bool createDefaultIndexes = true;
-        status =
-            userCreateNS(opCtx, ctx.db(), nss.ns(), options, kind, createDefaultIndexes, idIndex);
+        status = Database::userCreateNS(
+            opCtx, ctx.db(), nss.ns(), options, kind, createDefaultIndexes, idIndex);
 
         if (!status.isOK()) {
             return status;
@@ -137,7 +137,7 @@ Status createCollectionForApplyOps(OperationContext* opCtx,
     auto newCmd = cmdObj;
 
     auto* const serviceContext = opCtx->getServiceContext();
-    auto* const db = dbHolder().get(opCtx, dbName);
+    auto* const db = DatabaseHolder::getDatabaseHolder().get(opCtx, dbName);
 
     // If a UUID is given, see if we need to rename a collection out of the way, and whether the
     // collection already exists under a different name. If so, rename it into place. As this is
diff --git a/src/mongo/db/catalog/database.cpp b/src/mongo/db/catalog/database.cpp
index 527c9e847ab..a9963a2dc7d 100644
--- a/src/mongo/db/catalog/database.cpp
+++ b/src/mongo/db/catalog/database.cpp
@@ -36,66 +36,13 @@
 namespace mongo {
 Database::Impl::~Impl() = default;
 
-namespace {
-stdx::function<Database::factory_function_type> factory;
-}  // namespace
-
-void Database::registerFactory(decltype(factory) newFactory) {
-    factory = std::move(newFactory);
-}
-
-auto Database::makeImpl(Database* const this_,
-                        OperationContext* const opCtx,
-                        const StringData name,
-                        DatabaseCatalogEntry* const dbEntry) -> std::unique_ptr<Impl> {
-    return factory(this_, opCtx, name, dbEntry);
-}
+MONGO_DEFINE_SHIM(Database::makeImpl);
 
 void Database::TUHook::hook() noexcept {}
 
-namespace {
-stdx::function<decltype(Database::dropDatabase)> dropDatabaseImpl;
-}
-
-void Database::dropDatabase(OperationContext* const opCtx, Database* const db) {
-    return dropDatabaseImpl(opCtx, db);
-}
+MONGO_DEFINE_SHIM(Database::dropDatabase);
 
-void Database::registerDropDatabaseImpl(stdx::function<decltype(dropDatabase)> impl) {
-    dropDatabaseImpl = std::move(impl);
-}
+MONGO_DEFINE_SHIM(Database::userCreateNS);
 
-namespace {
-stdx::function<decltype(userCreateNS)> userCreateNSImpl;
-stdx::function<decltype(dropAllDatabasesExceptLocal)> dropAllDatabasesExceptLocalImpl;
-}  // namespace
+MONGO_DEFINE_SHIM(Database::dropAllDatabasesExceptLocal);
 }  // namespace mongo
-
-auto mongo::userCreateNS(OperationContext* const opCtx,
-                         Database* const db,
-                         const StringData ns,
-                         const BSONObj options,
-                         const CollectionOptions::ParseKind parseKind,
-                         const bool createDefaultIndexes,
-                         const BSONObj& idIndex) -> Status {
-    return userCreateNSImpl(opCtx, db, ns, options, parseKind, createDefaultIndexes, idIndex);
-}
-
-void mongo::registerUserCreateNSImpl(stdx::function<decltype(userCreateNS)> impl) {
-    userCreateNSImpl = std::move(impl);
-}
-
-void mongo::dropAllDatabasesExceptLocal(OperationContext* const opCtx) {
-    return dropAllDatabasesExceptLocalImpl(opCtx);
-}
-
-/**
- * Registers an implementation of `dropAllDatabaseExceptLocal` for use by library clients.
- * This is necessary to allow `catalog/database` to be a vtable edge.
- * @param impl Implementation of `dropAllDatabaseExceptLocal` to install.
- * @note This call is not thread safe.
- */
-void mongo::registerDropAllDatabasesExceptLocalImpl(
-    stdx::function<decltype(dropAllDatabasesExceptLocal)> impl) {
-    dropAllDatabasesExceptLocalImpl = std::move(impl);
-}
diff --git a/src/mongo/db/catalog/database.h b/src/mongo/db/catalog/database.h
index e5fab444357..2a5e281c1b5 100644
--- a/src/mongo/db/catalog/database.h
+++ b/src/mongo/db/catalog/database.h
@@ -31,6 +31,8 @@
 #include <memory>
 #include <string>
 
+#include "mongo/base/shim.h"
+#include "mongo/base/status.h"
 #include "mongo/base/string_data.h"
 #include "mongo/bson/bsonobj.h"
 #include "mongo/db/catalog/collection.h"
@@ -45,6 +47,7 @@
 #include "mongo/util/string_map.h"
 
 namespace mongo {
+
 /**
  * Represents a logical database containing Collections.
  *
@@ -123,16 +126,34 @@ public:
         virtual const CollectionMap& collections() const = 0;
     };
 
-private:
-    static std::unique_ptr<Impl> makeImpl(Database* _this,
-                                          OperationContext* opCtx,
-                                          StringData name,
-                                          DatabaseCatalogEntry* dbEntry);
-
 public:
-    using factory_function_type = decltype(makeImpl);
+    static MONGO_DECLARE_SHIM((OperationContext * opCtx)->void) dropAllDatabasesExceptLocal;
 
-    static void registerFactory(stdx::function<factory_function_type> factory);
+    /**
+     * Creates the namespace 'ns' in the database 'db' according to 'options'. If
+     * 'createDefaultIndexes'
+     * is true, creates the _id index for the collection (and the system indexes, in the case of
+     * system
+     * collections). Creates the collection's _id index according to 'idIndex', if it is non-empty.
+     * When
+     * 'idIndex' is empty, creates the default _id index.
+     */
+    static MONGO_DECLARE_SHIM(
+        (OperationContext * opCtx,
+         Database* db,
+         StringData ns,
+         BSONObj options,
+         CollectionOptions::ParseKind parseKind = CollectionOptions::parseForCommand,
+         bool createDefaultIndexes = true,
+         const BSONObj& idIndex = BSONObj())
+            ->Status) userCreateNS;
+
+    static MONGO_DECLARE_SHIM((Database * this_,
+                               OperationContext* opCtx,
+                               StringData name,
+                               DatabaseCatalogEntry*,
+                               PrivateTo<Database>)
+                                  ->std::unique_ptr<Impl>) makeImpl;
 
     /**
      * Iterating over a Database yields Collection* pointers.
@@ -182,7 +203,7 @@ public:
     explicit inline Database(OperationContext* const opCtx,
                              const StringData name,
                              DatabaseCatalogEntry* const dbEntry)
-        : _pimpl(makeImpl(this, opCtx, name, dbEntry)) {
+        : _pimpl(makeImpl(this, opCtx, name, dbEntry, PrivateCall<Database>{})) {
         this->_impl().init(opCtx);
     }
 
@@ -335,17 +356,7 @@ public:
      *
      * Must be called with the specified database locked in X mode.
      */
-    static void dropDatabase(OperationContext* opCtx, Database* db);
-
-    /**
-     * Registers an implementation of `Database::dropDatabase` for use by library clients.
-     * This is necessary to allow `catalog/database` to be a vtable edge.
-     * @param impl Implementation of `dropDatabase` to install.
-     * @note This call is not thread safe.
-     */
-    static void registerDropDatabaseImpl(stdx::function<decltype(dropDatabase)> impl);
-
-    // static Status validateDBName( StringData dbname );
+    static MONGO_DECLARE_SHIM((OperationContext * opCtx, Database* db)->void) dropDatabase;
 
     inline const NamespaceString& getSystemIndexesName() const {
         return this->_impl().getSystemIndexesName();
@@ -395,37 +406,4 @@ private:
 
     std::unique_ptr<Impl> _pimpl;
 };
-
-void dropAllDatabasesExceptLocal(OperationContext* opCtx);
-
-/**
- * Registers an implementation of `dropAllDatabaseExceptLocal` for use by library clients.
- * This is necessary to allow `catalog/database` to be a vtable edge.
- * @param impl Implementation of `dropAllDatabaseExceptLocal` to install.
- * @note This call is not thread safe.
- */
-void registerDropAllDatabasesExceptLocalImpl(
-    stdx::function<decltype(dropAllDatabasesExceptLocal)> impl);
-
-/**
- * Creates the namespace 'ns' in the database 'db' according to 'options'. If 'createDefaultIndexes'
- * is true, creates the _id index for the collection (and the system indexes, in the case of system
- * collections). Creates the collection's _id index according to 'idIndex', if it is non-empty. When
- * 'idIndex' is empty, creates the default _id index.
- */
-Status userCreateNS(OperationContext* opCtx,
-                    Database* db,
-                    StringData ns,
-                    BSONObj options,
-                    CollectionOptions::ParseKind parseKind = CollectionOptions::parseForCommand,
-                    bool createDefaultIndexes = true,
-                    const BSONObj& idIndex = BSONObj());
-
-/**
- * Registers an implementation of `userCreateNS` for use by library clients.
- * This is necessary to allow `catalog/database` to be a vtable edge.
- * @param impl Implementation of `userCreateNS` to install.
- * @note This call is not thread safe.
- */
-void registerUserCreateNSImpl(stdx::function<decltype(userCreateNS)> impl);
 }  // namespace mongo
diff --git a/src/mongo/db/catalog/database_holder.cpp b/src/mongo/db/catalog/database_holder.cpp
index 0b0c4336662..b40577d797f 100644
--- a/src/mongo/db/catalog/database_holder.cpp
+++ b/src/mongo/db/catalog/database_holder.cpp
@@ -36,32 +36,9 @@ namespace mongo {
 
 DatabaseHolder::Impl::~Impl() = default;
 
-namespace {
-stdx::function<DatabaseHolder::factory_function_type> factory;
-}  // namespace
-
-void DatabaseHolder::registerFactory(decltype(factory) newFactory) {
-    factory = std::move(newFactory);
-}
-
-auto DatabaseHolder::makeImpl() -> std::unique_ptr<Impl> {
-    return factory();
-}
-
 void DatabaseHolder::TUHook::hook() noexcept {}
 
-namespace {
-stdx::function<decltype(dbHolder)> dbHolderImpl;
-}  // namespace
-}  // namespace mongo
-
-// The `mongo::` prefix is necessary to placate MSVC -- it is unable to properly identify anonymous
-// nested namespace members in `decltype` expressions when defining functions using scope-resolution
-// syntax.
-void mongo::registerDbHolderImpl(decltype(mongo::dbHolderImpl) impl) {
-    dbHolderImpl = std::move(impl);
-}
+MONGO_DEFINE_SHIM(DatabaseHolder::makeImpl);
+MONGO_DEFINE_SHIM(DatabaseHolder::getDatabaseHolder);
 
-auto mongo::dbHolder() -> DatabaseHolder& {
-    return dbHolderImpl();
-}
+}  // namespace mongo
diff --git a/src/mongo/db/catalog/database_holder.h b/src/mongo/db/catalog/database_holder.h
index 0edde9cfccf..3af319ab963 100644
--- a/src/mongo/db/catalog/database_holder.h
+++ b/src/mongo/db/catalog/database_holder.h
@@ -31,6 +31,7 @@
 #include <set>
 #include <string>
 
+#include "mongo/base/shim.h"
 #include "mongo/base/string_data.h"
 #include "mongo/db/namespace_string.h"
 #include "mongo/stdx/functional.h"
@@ -62,17 +63,14 @@ public:
         virtual std::set<std::string> getNamesWithConflictingCasing(StringData name) = 0;
     };
 
-private:
-    static std::unique_ptr<Impl> makeImpl();
-
 public:
-    using factory_function_type = decltype(makeImpl);
+    static MONGO_DECLARE_SHIM(()->DatabaseHolder&) getDatabaseHolder;
 
-    static void registerFactory(stdx::function<factory_function_type> factory);
+    static MONGO_DECLARE_SHIM((PrivateTo<DatabaseHolder>)->std::unique_ptr<Impl>) makeImpl;
 
     inline ~DatabaseHolder() = default;
 
-    inline explicit DatabaseHolder() : _pimpl(makeImpl()) {}
+    inline explicit DatabaseHolder() : _pimpl(makeImpl(PrivateCall<DatabaseHolder>{})) {}
 
     /**
      * Retrieves an already opened database or returns NULL. Must be called with the database
@@ -147,7 +145,4 @@ private:
 
     std::unique_ptr<Impl> _pimpl;
 };
-
-extern DatabaseHolder& dbHolder();
-extern void registerDbHolderImpl(stdx::function<decltype(dbHolder)> impl);
 }  // namespace mongo
diff --git a/src/mongo/db/catalog/database_holder_impl.cpp b/src/mongo/db/catalog/database_holder_impl.cpp
index d5b5560df67..df70ef25c27 100644
--- a/src/mongo/db/catalog/database_holder_impl.cpp
+++ b/src/mongo/db/catalog/database_holder_impl.cpp
@@ -50,32 +50,29 @@
 
 namespace mongo {
 namespace {
-
-DatabaseHolder* _dbHolder = nullptr;
-
-DatabaseHolder& dbHolderImpl() {
-    return *_dbHolder;
-}
+std::unique_ptr<DatabaseHolder> dbHolderStorage;
 
 GlobalInitializerRegisterer dbHolderImplInitializer("InitializeDbHolderimpl",
-                                                    {"InitializeDatabaseHolderFactory"},
                                                     [](InitializerContext* const) {
-                                                        _dbHolder = new DatabaseHolder();
-                                                        registerDbHolderImpl(dbHolderImpl);
+                                                        dbHolderStorage =
+                                                            std::make_unique<DatabaseHolder>();
                                                         return Status::OK();
                                                     },
                                                     [](DeinitializerContext* const) {
-                                                        delete _dbHolder;
-                                                        _dbHolder = nullptr;
+                                                        dbHolderStorage = nullptr;
                                                         return Status::OK();
                                                     });
+}  // namespace
 
-MONGO_INITIALIZER(InitializeDatabaseHolderFactory)(InitializerContext* const) {
-    DatabaseHolder::registerFactory([] { return stdx::make_unique<DatabaseHolderImpl>(); });
-    return Status::OK();
+MONGO_REGISTER_SHIM(DatabaseHolder::getDatabaseHolder)
+()->DatabaseHolder& {
+    return *dbHolderStorage;
 }
 
-}  // namespace
+MONGO_REGISTER_SHIM(DatabaseHolder::makeImpl)
+(PrivateTo<DatabaseHolder>)->std::unique_ptr<DatabaseHolder::Impl> {
+    return std::make_unique<DatabaseHolderImpl>();
+}
 
 using std::set;
 using std::size_t;
diff --git a/src/mongo/db/catalog/database_holder_mock.cpp b/src/mongo/db/catalog/database_holder_mock.cpp
index 694091f8afc..561713fb555 100644
--- a/src/mongo/db/catalog/database_holder_mock.cpp
+++ b/src/mongo/db/catalog/database_holder_mock.cpp
@@ -33,23 +33,15 @@
 #include "mongo/stdx/memory.h"
 
 namespace mongo {
-namespace {
 
-DatabaseHolder& dbHolderImpl() {
+MONGO_REGISTER_SHIM(DatabaseHolder::getDatabaseHolder)()->DatabaseHolder& {
     static DatabaseHolder _dbHolder;
     return _dbHolder;
 }
 
-MONGO_INITIALIZER_WITH_PREREQUISITES(InitializeDbHolderimpl, ("InitializeDatabaseHolderFactory"))
-(InitializerContext* const) {
-    registerDbHolderImpl(dbHolderImpl);
-    return Status::OK();
+MONGO_REGISTER_SHIM(DatabaseHolder::makeImpl)
+(PrivateTo<DatabaseHolder>)->std::unique_ptr<DatabaseHolder::Impl> {
+    return stdx::make_unique<DatabaseHolderMock>();
 }
 
-MONGO_INITIALIZER(InitializeDatabaseHolderFactory)(InitializerContext* const) {
-    DatabaseHolder::registerFactory([] { return stdx::make_unique<DatabaseHolderMock>(); });
-    return Status::OK();
-}
-
-}  // namespace
 }  // namespace mongo
diff --git a/src/mongo/db/catalog/database_impl.cpp b/src/mongo/db/catalog/database_impl.cpp
index 038061c36b8..44e229aaf26 100644
--- a/src/mongo/db/catalog/database_impl.cpp
+++ b/src/mongo/db/catalog/database_impl.cpp
@@ -78,16 +78,17 @@
 #include "mongo/util/log.h"
 
 namespace mongo {
-namespace {
-MONGO_INITIALIZER(InitializeDatabaseFactory)(InitializerContext* const) {
-    Database::registerFactory([](Database* const this_,
-                                 OperationContext* const opCtx,
-                                 const StringData name,
-                                 DatabaseCatalogEntry* const dbEntry) {
-        return stdx::make_unique<DatabaseImpl>(this_, opCtx, name, dbEntry);
-    });
-    return Status::OK();
+MONGO_REGISTER_SHIM(Database::makeImpl)
+(Database* const this_,
+ OperationContext* const opCtx,
+ const StringData name,
+ DatabaseCatalogEntry* const dbEntry,
+ PrivateTo<Database>)
+    ->std::unique_ptr<Database::Impl> {
+    return stdx::make_unique<DatabaseImpl>(this_, opCtx, name, dbEntry);
 }
+
+namespace {
 MONGO_FP_DECLARE(hangBeforeLoggingCreateCollection);
 }  // namespace
 
@@ -865,7 +866,7 @@ void DatabaseImpl::dropDatabase(OperationContext* opCtx, Database* db) {
         Top::get(serviceContext).collectionDropped(coll->ns().ns(), true);
     }
 
-    dbHolder().close(opCtx, name, "database dropped");
+    DatabaseHolder::getDatabaseHolder().close(opCtx, name, "database dropped");
 
     auto const storageEngine = serviceContext->getGlobalStorageEngine();
     writeConflictRetry(opCtx, "dropDatabase", name, [&] {
@@ -896,7 +897,7 @@ StatusWith<NamespaceString> DatabaseImpl::makeUniqueCollectionNamespace(
     if (!_uniqueCollectionNamespacePseudoRandom) {
         Timestamp ts;
         _uniqueCollectionNamespacePseudoRandom =
-            stdx::make_unique<PseudoRandom>(Date_t::now().asInt64());
+            std::make_unique<PseudoRandom>(Date_t::now().asInt64());
     }
 
     const auto charsToChooseFrom =
@@ -936,60 +937,19 @@ StatusWith<NamespaceString> DatabaseImpl::makeUniqueCollectionNamespace(
                       << " attempts due to namespace conflicts with existing collections.");
 }
 
-namespace {
-MONGO_INITIALIZER(InitializeDropDatabaseImpl)(InitializerContext* const) {
-    Database::registerDropDatabaseImpl(DatabaseImpl::dropDatabase);
-    return Status::OK();
-}
-MONGO_INITIALIZER(InitializeUserCreateNSImpl)(InitializerContext* const) {
-    registerUserCreateNSImpl(userCreateNSImpl);
-    return Status::OK();
-}
-
-MONGO_INITIALIZER(InitializeDropAllDatabasesExceptLocalImpl)(InitializerContext* const) {
-    registerDropAllDatabasesExceptLocalImpl(dropAllDatabasesExceptLocalImpl);
-    return Status::OK();
+MONGO_REGISTER_SHIM(Database::dropDatabase)(OperationContext* opCtx, Database* db)->void {
+    return DatabaseImpl::dropDatabase(opCtx, db);
 }
-}  // namespace
-}  // namespace mongo
-
-void mongo::dropAllDatabasesExceptLocalImpl(OperationContext* opCtx) {
-    Lock::GlobalWrite lk(opCtx);
-
-    vector<string> n;
-    StorageEngine* storageEngine = opCtx->getServiceContext()->getGlobalStorageEngine();
-    storageEngine->listDatabases(&n);
-
-    if (n.size() == 0)
-        return;
-    log() << "dropAllDatabasesExceptLocal " << n.size();
-
-    repl::ReplicationCoordinator::get(opCtx)->dropAllSnapshots();
-
-    for (const auto& dbName : n) {
-        if (dbName != "local") {
-            writeConflictRetry(opCtx, "dropAllDatabasesExceptLocal", dbName, [&opCtx, &dbName] {
-                Database* db = dbHolder().get(opCtx, dbName);
 
-                // This is needed since dropDatabase can't be rolled back.
-                // This is safe be replaced by "invariant(db);dropDatabase(opCtx, db);" once fixed
-                if (db == nullptr) {
-                    log() << "database disappeared after listDatabases but before drop: " << dbName;
-                } else {
-                    DatabaseImpl::dropDatabase(opCtx, db);
-                }
-            });
-        }
-    }
-}
-
-auto mongo::userCreateNSImpl(OperationContext* opCtx,
-                             Database* db,
-                             StringData ns,
-                             BSONObj options,
-                             CollectionOptions::ParseKind parseKind,
-                             bool createDefaultIndexes,
-                             const BSONObj& idIndex) -> Status {
+MONGO_REGISTER_SHIM(Database::userCreateNS)
+(OperationContext* opCtx,
+ Database* db,
+ StringData ns,
+ BSONObj options,
+ CollectionOptions::ParseKind parseKind,
+ bool createDefaultIndexes,
+ const BSONObj& idIndex)
+    ->Status {
     invariant(db);
 
     LOG(1) << "create collection " << ns << ' ' << options;
@@ -1088,3 +1048,34 @@ auto mongo::userCreateNSImpl(OperationContext* opCtx,
 
     return Status::OK();
 }
+
+MONGO_REGISTER_SHIM(Database::dropAllDatabasesExceptLocal)(OperationContext* opCtx)->void {
+    Lock::GlobalWrite lk(opCtx);
+
+    vector<string> n;
+    StorageEngine* storageEngine = opCtx->getServiceContext()->getGlobalStorageEngine();
+    storageEngine->listDatabases(&n);
+
+    if (n.size() == 0)
+        return;
+    log() << "dropAllDatabasesExceptLocal " << n.size();
+
+    repl::ReplicationCoordinator::get(opCtx)->dropAllSnapshots();
+
+    for (const auto& dbName : n) {
+        if (dbName != "local") {
+            writeConflictRetry(opCtx, "dropAllDatabasesExceptLocal", dbName, [&opCtx, &dbName] {
+                Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, dbName);
+
+                // This is needed since dropDatabase can't be rolled back.
+                // This is safe be replaced by "invariant(db);dropDatabase(opCtx, db);" once fixed
+                if (db == nullptr) {
+                    log() << "database disappeared after listDatabases but before drop: " << dbName;
+                } else {
+                    DatabaseImpl::dropDatabase(opCtx, db);
+                }
+            });
+        }
+    }
+}
+}  // namespace mongo
diff --git a/src/mongo/db/catalog/database_impl.h b/src/mongo/db/catalog/database_impl.h
index e2102e3154b..8a341037778 100644
--- a/src/mongo/db/catalog/database_impl.h
+++ b/src/mongo/db/catalog/database_impl.h
@@ -309,18 +309,4 @@ private:
 
 void dropAllDatabasesExceptLocalImpl(OperationContext* opCtx);
 
-/**
- * Creates the namespace 'ns' in the database 'db' according to 'options'. If 'createDefaultIndexes'
- * is true, creates the _id index for the collection (and the system indexes, in the case of system
- * collections). Creates the collection's _id index according to 'idIndex', if it is non-empty. When
- * 'idIndex' is empty, creates the default _id index.
- */
-Status userCreateNSImpl(OperationContext* opCtx,
-                        Database* db,
-                        StringData ns,
-                        BSONObj options,
-                        CollectionOptions::ParseKind parseKind = CollectionOptions::parseForCommand,
-                        bool createDefaultIndexes = true,
-                        const BSONObj& idIndex = BSONObj());
-
 }  // namespace mongo
diff --git a/src/mongo/db/catalog/index_catalog.cpp b/src/mongo/db/catalog/index_catalog.cpp
index 4d9288e841d..7a2a28a241a 100644
--- a/src/mongo/db/catalog/index_catalog.cpp
+++ b/src/mongo/db/catalog/index_catalog.cpp
@@ -37,19 +37,7 @@
 namespace mongo {
 IndexCatalog::Impl::~Impl() = default;
 
-namespace {
-IndexCatalog::factory_function_type factory;
-}  // namespace
-
-void IndexCatalog::registerFactory(decltype(factory) newFactory) {
-    factory = std::move(newFactory);
-}
-
-auto IndexCatalog::makeImpl(IndexCatalog* const this_,
-                            Collection* const collection,
-                            const int maxNumIndexesAllowed) -> std::unique_ptr<Impl> {
-    return factory(this_, collection, maxNumIndexesAllowed);
-}
+MONGO_DEFINE_SHIM(IndexCatalog::makeImpl);
 
 void IndexCatalog::TUHook::hook() noexcept {}
 
@@ -63,38 +51,11 @@ IndexCatalogEntry* IndexCatalog::_setupInMemoryStructures(
 
 IndexCatalog::IndexIterator::Impl::~Impl() = default;
 
-namespace {
-IndexCatalog::IndexIterator::factory_function_type iteratorFactory;
-}  // namespace
-
-void IndexCatalog::IndexIterator::registerFactory(decltype(iteratorFactory) newFactory) {
-    iteratorFactory = std::move(newFactory);
-}
-
-auto IndexCatalog::IndexIterator::makeImpl(OperationContext* const opCtx,
-                                           const IndexCatalog* const cat,
-                                           const bool includeUnfinishedIndexes)
-    -> std::unique_ptr<Impl> {
-    return iteratorFactory(opCtx, cat, includeUnfinishedIndexes);
-}
+MONGO_DEFINE_SHIM(IndexCatalog::IndexIterator::makeImpl);
 
 void IndexCatalog::IndexIterator::TUHook::hook() noexcept {}
 
-namespace {
-stdx::function<decltype(IndexCatalog::fixIndexKey)> fixIndexKeyImpl;
-}  // namespace
-
-void IndexCatalog::registerFixIndexKeyImpl(decltype(fixIndexKeyImpl) impl) {
-    fixIndexKeyImpl = std::move(impl);
-}
-
-BSONObj IndexCatalog::fixIndexKey(const BSONObj& key) {
-    return fixIndexKeyImpl(key);
-}
-
-namespace {
-stdx::function<decltype(IndexCatalog::prepareInsertDeleteOptions)> prepareInsertDeleteOptionsImpl;
-}  // namespace
+MONGO_DEFINE_SHIM(IndexCatalog::fixIndexKey);
 
 std::string::size_type IndexCatalog::getLongestIndexNameLength(OperationContext* opCtx) const {
     IndexCatalog::IndexIterator it = getIndexIterator(opCtx, true);
@@ -107,14 +68,5 @@ std::string::size_type IndexCatalog::getLongestIndexNameLength(OperationContext*
     return longestIndexNameLength;
 }
 
-void IndexCatalog::prepareInsertDeleteOptions(OperationContext* const opCtx,
-                                              const IndexDescriptor* const desc,
-                                              InsertDeleteOptions* const options) {
-    return prepareInsertDeleteOptionsImpl(opCtx, desc, options);
-}
-
-void IndexCatalog::registerPrepareInsertDeleteOptionsImpl(
-    stdx::function<decltype(prepareInsertDeleteOptions)> impl) {
-    prepareInsertDeleteOptionsImpl = std::move(impl);
-}
+MONGO_DEFINE_SHIM(IndexCatalog::prepareInsertDeleteOptions);
 }  // namespace mongo
diff --git a/src/mongo/db/catalog/index_catalog.h b/src/mongo/db/catalog/index_catalog.h
index 5e5b17281e2..bb9902f91cd 100644
--- a/src/mongo/db/catalog/index_catalog.h
+++ b/src/mongo/db/catalog/index_catalog.h
@@ -32,6 +32,7 @@
 #include <vector>
 
 #include "mongo/base/clonable_ptr.h"
+#include "mongo/base/shim.h"
 #include "mongo/db/catalog/index_catalog_entry.h"
 #include "mongo/db/index/multikey_paths.h"
 #include "mongo/db/jsobj.h"
@@ -76,20 +77,20 @@ public:
             virtual IndexCatalogEntry* catalogEntry(const IndexDescriptor* desc) = 0;
         };
 
-    private:
-        static std::unique_ptr<Impl> makeImpl(OperationContext* opCtx,
-                                              const IndexCatalog* cat,
-                                              bool includeUnfinishedIndexes);
+        static MONGO_DECLARE_SHIM((OperationContext * opCtx,
+                                   const IndexCatalog* cat,
+                                   bool includeUnfinishedIndexes,
+                                   PrivateTo<IndexIterator>)
+                                      ->std::unique_ptr<Impl>) makeImpl;
 
+    private:
         explicit inline IndexIterator(OperationContext* const opCtx,
                                       const IndexCatalog* const cat,
                                       const bool includeUnfinishedIndexes)
-            : _pimpl(makeImpl(opCtx, cat, includeUnfinishedIndexes)) {}
+            : _pimpl(makeImpl(opCtx, cat, includeUnfinishedIndexes, PrivateCall<IndexIterator>{})) {
+        }
 
     public:
-        using factory_function_type = stdx::function<decltype(makeImpl)>;
-        static void registerFactory(factory_function_type factory);
-
         inline ~IndexIterator() = default;
 
         inline IndexIterator(const IndexIterator& copy) = default;
@@ -255,19 +256,17 @@ public:
         friend IndexCatalog;
     };
 
-private:
-    static std::unique_ptr<Impl> makeImpl(IndexCatalog* this_,
-                                          Collection* collection,
-                                          int maxNumIndexesAllowed);
-
 public:
-    using factory_function_type = stdx::function<decltype(makeImpl)>;
-    static void registerFactory(factory_function_type factory);
+    static MONGO_DECLARE_SHIM((IndexCatalog * this_,
+                               Collection* collection,
+                               int maxNumIndexesAllowed,
+                               PrivateTo<IndexCatalog>)
+                                  ->std::unique_ptr<Impl>) makeImpl;
 
     inline ~IndexCatalog() = default;
 
     explicit inline IndexCatalog(Collection* const collection, const int maxNumIndexesAllowed)
-        : _pimpl(makeImpl(this, collection, maxNumIndexesAllowed)) {}
+        : _pimpl(makeImpl(this, collection, maxNumIndexesAllowed, PrivateCall<IndexCatalog>{})) {}
 
     inline IndexCatalog(IndexCatalog&&) = delete;
     inline IndexCatalog& operator=(IndexCatalog&&) = delete;
@@ -538,18 +537,15 @@ public:
 
     // public static helpers
 
-    static BSONObj fixIndexKey(const BSONObj& key);
-    static void registerFixIndexKeyImpl(stdx::function<decltype(fixIndexKey)> impl);
+    static MONGO_DECLARE_SHIM((const BSONObj& key)->BSONObj) fixIndexKey;
 
     /**
      * Fills out 'options' in order to indicate whether to allow dups or relax
      * index constraints, as needed by replication.
      */
-    static void prepareInsertDeleteOptions(OperationContext* opCtx,
-                                           const IndexDescriptor* desc,
-                                           InsertDeleteOptions* options);
-    static void registerPrepareInsertDeleteOptionsImpl(
-        stdx::function<decltype(prepareInsertDeleteOptions)> impl);
+    static MONGO_DECLARE_SHIM(
+        (OperationContext * opCtx, const IndexDescriptor* desc, InsertDeleteOptions* options)->void)
+        prepareInsertDeleteOptions;
 
 private:
     inline const Collection* _getCollection() const {
diff --git a/src/mongo/db/catalog/index_catalog_entry.cpp b/src/mongo/db/catalog/index_catalog_entry.cpp
index 94a05fde7ac..1972c2237d4 100644
--- a/src/mongo/db/catalog/index_catalog_entry.cpp
+++ b/src/mongo/db/catalog/index_catalog_entry.cpp
@@ -38,22 +38,7 @@
 namespace mongo {
 IndexCatalogEntry::Impl::~Impl() = default;
 
-namespace {
-stdx::function<IndexCatalogEntry::factory_function_type> factory;
-}  // namespace
-
-void IndexCatalogEntry::registerFactory(decltype(factory) newFactory) {
-    factory = std::move(newFactory);
-}
-
-auto IndexCatalogEntry::makeImpl(IndexCatalogEntry* const this_,
-                                 OperationContext* const opCtx,
-                                 const StringData ns,
-                                 CollectionCatalogEntry* const collection,
-                                 std::unique_ptr<IndexDescriptor> descriptor,
-                                 CollectionInfoCache* const infoCache) -> std::unique_ptr<Impl> {
-    return factory(this_, opCtx, ns, collection, std::move(descriptor), infoCache);
-}
+MONGO_DEFINE_SHIM(IndexCatalogEntry::makeImpl);
 
 void IndexCatalogEntry::TUHook::hook() noexcept {}
 
@@ -62,7 +47,13 @@ IndexCatalogEntry::IndexCatalogEntry(OperationContext* opCtx,
                                      CollectionCatalogEntry* collection,
                                      std::unique_ptr<IndexDescriptor> descriptor,
                                      CollectionInfoCache* infoCache)
-    : _pimpl(makeImpl(this, opCtx, ns, collection, std::move(descriptor), infoCache)) {}
+    : _pimpl(makeImpl(this,
+                      opCtx,
+                      ns,
+                      collection,
+                      std::move(descriptor),
+                      infoCache,
+                      PrivateCall<IndexCatalogEntry>{})) {}
 
 void IndexCatalogEntry::init(std::unique_ptr<IndexAccessMethod> accessMethod) {
     return this->_impl().init(std::move(accessMethod));
diff --git a/src/mongo/db/catalog/index_catalog_entry.h b/src/mongo/db/catalog/index_catalog_entry.h
index fecfd197bb1..20d748c9846 100644
--- a/src/mongo/db/catalog/index_catalog_entry.h
+++ b/src/mongo/db/catalog/index_catalog_entry.h
@@ -32,6 +32,7 @@
 #include <string>
 
 #include "mongo/base/owned_pointer_vector.h"
+#include "mongo/base/shim.h"
 #include "mongo/bson/ordering.h"
 #include "mongo/bson/timestamp.h"
 #include "mongo/db/index/multikey_paths.h"
@@ -102,18 +103,15 @@ public:
         virtual void setMinimumVisibleSnapshot(Timestamp name) = 0;
     };
 
-private:
-    static std::unique_ptr<Impl> makeImpl(IndexCatalogEntry* this_,
-                                          OperationContext* opCtx,
-                                          StringData ns,
-                                          CollectionCatalogEntry* collection,
-                                          std::unique_ptr<IndexDescriptor> descriptor,
-                                          CollectionInfoCache* infoCache);
-
 public:
-    using factory_function_type = decltype(makeImpl);
-
-    static void registerFactory(stdx::function<factory_function_type> factory);
+    static MONGO_DECLARE_SHIM((IndexCatalogEntry * this_,
+                               OperationContext* opCtx,
+                               StringData ns,
+                               CollectionCatalogEntry* collection,
+                               std::unique_ptr<IndexDescriptor> descriptor,
+                               CollectionInfoCache* infoCache,
+                               PrivateTo<IndexCatalogEntry>)
+                                  ->std::unique_ptr<Impl>) makeImpl;
 
     explicit IndexCatalogEntry(
         OperationContext* opCtx,
diff --git a/src/mongo/db/catalog/index_catalog_entry_impl.cpp b/src/mongo/db/catalog/index_catalog_entry_impl.cpp
index 5e717b97e71..1ef395b85b4 100644
--- a/src/mongo/db/catalog/index_catalog_entry_impl.cpp
+++ b/src/mongo/db/catalog/index_catalog_entry_impl.cpp
@@ -53,20 +53,18 @@
 #include "mongo/util/scopeguard.h"
 
 namespace mongo {
-namespace {
-MONGO_INITIALIZER(InitializeIndexCatalogEntryFactory)(InitializerContext* const) {
-    IndexCatalogEntry::registerFactory([](IndexCatalogEntry* const this_,
-                                          OperationContext* const opCtx,
-                                          const StringData ns,
-                                          CollectionCatalogEntry* const collection,
-                                          std::unique_ptr<IndexDescriptor> descriptor,
-                                          CollectionInfoCache* const infoCache) {
-        return stdx::make_unique<IndexCatalogEntryImpl>(
-            this_, opCtx, ns, collection, std::move(descriptor), infoCache);
-    });
-    return Status::OK();
+MONGO_REGISTER_SHIM(IndexCatalogEntry::makeImpl)
+(IndexCatalogEntry* const this_,
+ OperationContext* const opCtx,
+ const StringData ns,
+ CollectionCatalogEntry* const collection,
+ std::unique_ptr<IndexDescriptor> descriptor,
+ CollectionInfoCache* const infoCache,
+ PrivateTo<IndexCatalogEntry>)
+    ->std::unique_ptr<IndexCatalogEntry::Impl> {
+    return std::make_unique<IndexCatalogEntryImpl>(
+        this_, opCtx, ns, collection, std::move(descriptor), infoCache);
 }
-}  // namespace
 
 using std::string;
 
diff --git a/src/mongo/db/catalog/index_catalog_impl.cpp b/src/mongo/db/catalog/index_catalog_impl.cpp
index e19773b34fd..76bb7aa4b8a 100644
--- a/src/mongo/db/catalog/index_catalog_impl.cpp
+++ b/src/mongo/db/catalog/index_catalog_impl.cpp
@@ -70,38 +70,33 @@
 #include "mongo/util/represent_as.h"
 
 namespace mongo {
-namespace {
-MONGO_INITIALIZER(InitializeIndexCatalogFactory)(InitializerContext* const) {
-    IndexCatalog::registerFactory([](
-        IndexCatalog* const this_, Collection* const collection, const int maxNumIndexesAllowed) {
-        return stdx::make_unique<IndexCatalogImpl>(this_, collection, maxNumIndexesAllowed);
-    });
-    return Status::OK();
+MONGO_REGISTER_SHIM(IndexCatalog::makeImpl)
+(IndexCatalog* const this_,
+ Collection* const collection,
+ const int maxNumIndexesAllowed,
+ PrivateTo<IndexCatalog>)
+    ->std::unique_ptr<IndexCatalog::Impl> {
+    return std::make_unique<IndexCatalogImpl>(this_, collection, maxNumIndexesAllowed);
 }
 
-MONGO_INITIALIZER(InitializeIndexCatalogIndexIteratorFactory)(InitializerContext* const) {
-    IndexCatalog::IndexIterator::registerFactory([](OperationContext* const opCtx,
-                                                    const IndexCatalog* const cat,
-                                                    const bool includeUnfinishedIndexes) {
-        return stdx::make_unique<IndexCatalogImpl::IndexIteratorImpl>(
-            opCtx, cat, includeUnfinishedIndexes);
-    });
-    return Status::OK();
+MONGO_REGISTER_SHIM(IndexCatalog::IndexIterator::makeImpl)
+(OperationContext* const opCtx,
+ const IndexCatalog* const cat,
+ const bool includeUnfinishedIndexes,
+ PrivateTo<IndexCatalog::IndexIterator>)
+    ->std::unique_ptr<IndexCatalog::IndexIterator::Impl> {
+    return std::make_unique<IndexCatalogImpl::IndexIteratorImpl>(
+        opCtx, cat, includeUnfinishedIndexes);
 }
-
-MONGO_INITIALIZER(InitializeFixIndexKeyImpl)(InitializerContext* const) {
-    IndexCatalog::registerFixIndexKeyImpl(&IndexCatalogImpl::fixIndexKey);
-    return Status::OK();
+MONGO_REGISTER_SHIM(IndexCatalog::fixIndexKey)(const BSONObj& key)->BSONObj {
+    return IndexCatalogImpl::fixIndexKey(key);
 }
 
-MONGO_INITIALIZER(InitializePrepareInsertDeleteOptionsImpl)(InitializerContext* const) {
-    IndexCatalog::registerPrepareInsertDeleteOptionsImpl(
-        &IndexCatalogImpl::prepareInsertDeleteOptions);
-    return Status::OK();
+MONGO_REGISTER_SHIM(IndexCatalog::prepareInsertDeleteOptions)
+(OperationContext* opCtx, const IndexDescriptor* desc, InsertDeleteOptions* options)->void {
+    return IndexCatalogImpl::prepareInsertDeleteOptions(opCtx, desc, options);
 }
 
-}  // namespace
-
 using std::unique_ptr;
 using std::endl;
 using std::string;
diff --git a/src/mongo/db/catalog/index_consistency.cpp b/src/mongo/db/catalog/index_consistency.cpp
index f1237212a1b..7caf6e1ed86 100644
--- a/src/mongo/db/catalog/index_consistency.cpp
+++ b/src/mongo/db/catalog/index_consistency.cpp
@@ -506,7 +506,7 @@ uint32_t IndexConsistency::_hashKeyString(const KeyString& ks, int indexNumber)
 
 Status IndexConsistency::_throwExceptionIfError() {
 
-    Database* database = dbHolder().get(_opCtx, _nss.db());
+    Database* database = DatabaseHolder::getDatabaseHolder().get(_opCtx, _nss.db());
 
     // Ensure the database still exists.
     if (!database) {
diff --git a/src/mongo/db/catalog/index_create.cpp b/src/mongo/db/catalog/index_create.cpp
index 06f9676ca4b..1f4c169000c 100644
--- a/src/mongo/db/catalog/index_create.cpp
+++ b/src/mongo/db/catalog/index_create.cpp
@@ -57,19 +57,7 @@
 namespace mongo {
 MultiIndexBlock::Impl::~Impl() = default;
 
-namespace {
-stdx::function<MultiIndexBlock::factory_function_type> factory;
-}  // namespace
-
-void MultiIndexBlock::registerFactory(decltype(factory) newFactory) {
-    factory = std::move(newFactory);
-}
-
-auto MultiIndexBlock::makeImpl(OperationContext* const opCtx, Collection* const collection)
-    -> std::unique_ptr<Impl> {
-    return factory(opCtx, collection);
-}
-
+MONGO_DEFINE_SHIM(MultiIndexBlock::makeImpl);
 
 void MultiIndexBlock::TUHook::hook() noexcept {}
 }  // namespace mongo
diff --git a/src/mongo/db/catalog/index_create.h b/src/mongo/db/catalog/index_create.h
index 56c85609a1f..acdf744da9e 100644
--- a/src/mongo/db/catalog/index_create.h
+++ b/src/mongo/db/catalog/index_create.h
@@ -114,12 +114,11 @@ private:
         return *this->_pimpl;
     }
 
-    static std::unique_ptr<Impl> makeImpl(OperationContext* opCtx, Collection* collection);
-
 public:
-    using factory_function_type = decltype(makeImpl);
-
-    static void registerFactory(stdx::function<factory_function_type> factory);
+    static MONGO_DECLARE_SHIM((OperationContext * opCtx,
+                               Collection* collection,
+                               PrivateTo<MultiIndexBlock>)
+                                  ->std::unique_ptr<Impl>) makeImpl;
 
     inline ~MultiIndexBlock() = default;
 
@@ -127,7 +126,7 @@ public:
      * Neither pointer is owned.
      */
     inline explicit MultiIndexBlock(OperationContext* const opCtx, Collection* const collection)
-        : _pimpl(makeImpl(opCtx, collection)) {}
+        : _pimpl(makeImpl(opCtx, collection, PrivateCall<MultiIndexBlock>{})) {}
 
     /**
      * By default we ignore the 'background' flag in specs when building an index. If this is
diff --git a/src/mongo/db/catalog/index_create_impl_servers.cpp b/src/mongo/db/catalog/index_create_impl_servers.cpp
index 5fab9ebee48..541a19a0434 100644
--- a/src/mongo/db/catalog/index_create_impl_servers.cpp
+++ b/src/mongo/db/catalog/index_create_impl_servers.cpp
@@ -41,14 +41,12 @@ class MultiIndexBlockImplServers : public MultiIndexBlockImpl {
         return spec["background"].trueValue();
     }
 };
+}  // namespace
 
-MONGO_INITIALIZER(InitializeMultiIndexBlockFactory)(InitializerContext* const) {
-    MultiIndexBlock::registerFactory(
-        [](OperationContext* const opCtx, Collection* const collection) {
-            return stdx::make_unique<MultiIndexBlockImplServers>(opCtx, collection);
-        });
-    return Status::OK();
+MONGO_REGISTER_SHIM(MultiIndexBlock::makeImpl)
+(OperationContext* const opCtx, Collection* const collection, PrivateTo<MultiIndexBlock>)
+    ->std::unique_ptr<MultiIndexBlock::Impl> {
+    return std::make_unique<MultiIndexBlockImplServers>(opCtx, collection);
 }
 
-}  // namespace
 }  // namespace mongo
diff --git a/src/mongo/db/catalog/rename_collection.cpp b/src/mongo/db/catalog/rename_collection.cpp
index fd5d2df9706..0d7722093e6 100644
--- a/src/mongo/db/catalog/rename_collection.cpp
+++ b/src/mongo/db/catalog/rename_collection.cpp
@@ -152,7 +152,7 @@ Status renameCollectionCommon(OperationContext* opCtx,
                                     << target.ns());
     }
 
-    Database* const sourceDB = dbHolder().get(opCtx, source.db());
+    Database* const sourceDB = DatabaseHolder::getDatabaseHolder().get(opCtx, source.db());
     if (sourceDB) {
         DatabaseShardingState::get(sourceDB).checkDbVersion(opCtx);
     }
@@ -180,7 +180,7 @@ Status renameCollectionCommon(OperationContext* opCtx,
 
     BackgroundOperation::assertNoBgOpInProgForNs(source.ns());
 
-    Database* const targetDB = dbHolder().openDb(opCtx, target.db());
+    Database* const targetDB = DatabaseHolder::getDatabaseHolder().openDb(opCtx, target.db());
 
     // Check if the target namespace exists and if dropTarget is true.
     // Return a non-OK status if target exists and dropTarget is not true or if the collection
diff --git a/src/mongo/db/catalog/uuid_catalog.cpp b/src/mongo/db/catalog/uuid_catalog.cpp
index 3ec994d7ef0..0a50cadfa71 100644
--- a/src/mongo/db/catalog/uuid_catalog.cpp
+++ b/src/mongo/db/catalog/uuid_catalog.cpp
@@ -92,7 +92,7 @@ repl::OpTime UUIDCatalogObserver::onRenameCollection(OperationContext* opCtx,
     if (!uuid)
         return {};
     auto getNewCollection = [opCtx, toCollection] {
-        auto db = dbHolder().get(opCtx, toCollection.db());
+        auto db = DatabaseHolder::getDatabaseHolder().get(opCtx, toCollection.db());
         auto newColl = db->getCollection(opCtx, toCollection);
         invariant(newColl);
         return newColl;
diff --git a/src/mongo/db/catalog_raii.cpp b/src/mongo/db/catalog_raii.cpp
index bdb49ef8c6c..2763bad080c 100644
--- a/src/mongo/db/catalog_raii.cpp
+++ b/src/mongo/db/catalog_raii.cpp
@@ -59,7 +59,7 @@ AutoGetDb::AutoGetDb(OperationContext* opCtx, StringData dbName, LockMode mode,
     : _dbLock(opCtx, dbName, mode, deadline), _db([&] {
           uassertLockTimeout(
               str::stream() << "database " << dbName, mode, deadline, _dbLock.isLocked());
-          return dbHolder().get(opCtx, dbName);
+          return DatabaseHolder::getDatabaseHolder().get(opCtx, dbName);
       }()) {
     if (_db) {
         DatabaseShardingState::get(_db).checkDbVersion(opCtx);
@@ -159,7 +159,7 @@ AutoGetOrCreateDb::AutoGetOrCreateDb(OperationContext* opCtx,
             _autoDb.emplace(opCtx, dbName, MODE_X, deadline);
         }
 
-        _db = dbHolder().openDb(opCtx, dbName, &_justCreated);
+        _db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName, &_justCreated);
     }
 
     DatabaseShardingState::get(_db).checkDbVersion(opCtx);
diff --git a/src/mongo/db/catalog_raii.h b/src/mongo/db/catalog_raii.h
index 081e566e7de..1d0b1e9238f 100644
--- a/src/mongo/db/catalog_raii.h
+++ b/src/mongo/db/catalog_raii.h
@@ -40,7 +40,8 @@ namespace mongo {
 
 /**
  * RAII-style class, which acquires a lock on the specified database in the requested mode and
- * obtains a reference to the database. Used as a shortcut for calls to dbHolder().get().
+ * obtains a reference to the database. Used as a shortcut for calls to
+ * DatabaseHolder::getDatabaseHolder().get().
  *
  * Use this when you want to do a database-level operation, like read a list of all collections, or
  * drop a collection.
@@ -152,9 +153,9 @@ private:
 /**
  * RAII-style class, which acquires a lock on the specified database in the requested mode and
  * obtains a reference to the database, creating it was non-existing. Used as a shortcut for
- * calls to dbHolder().openDb(), taking care of locking details. The requested mode must be
- * MODE_IX or MODE_X. If the database needs to be created, the lock will automatically be
- * reacquired as MODE_X.
+ * calls to DatabaseHolder::getDatabaseHolder().openDb(), taking care of locking details. The
+ * requested mode must be MODE_IX or MODE_X. If the database needs to be created, the lock will
+ * automatically be reacquired as MODE_X.
  *
  * Use this when you are about to perform a write, and want to create the database if it doesn't
  * already exist.
diff --git a/src/mongo/db/cloner.cpp b/src/mongo/db/cloner.cpp
index 4c1971b8585..8af7e4f452d 100644
--- a/src/mongo/db/cloner.cpp
+++ b/src/mongo/db/cloner.cpp
@@ -1,6 +1,3 @@
-
-// cloner.cpp - copy a database (export/import basically)
-
 /**
 *    Copyright (C) 2008 10gen Inc.
 *
@@ -156,7 +153,7 @@ struct Cloner::Fun {
                 repl::ReplicationCoordinator::get(opCtx)->canAcceptWritesFor(opCtx, to_collection));
 
         // Make sure database still exists after we resume from the temp release
-        Database* db = dbHolder().openDb(opCtx, _dbName);
+        Database* db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, _dbName);
 
         bool createdCollection = false;
         Collection* collection = NULL;
@@ -172,13 +169,14 @@ struct Cloner::Fun {
 
                 WriteUnitOfWork wunit(opCtx);
                 const bool createDefaultIndexes = true;
-                Status s = userCreateNS(opCtx,
-                                        db,
-                                        to_collection.toString(),
-                                        from_options,
-                                        CollectionOptions::parseForCommand,
-                                        createDefaultIndexes,
-                                        fixIndexSpec(to_collection.db().toString(), from_id_index));
+                Status s = Database::userCreateNS(
+                    opCtx,
+                    db,
+                    to_collection.toString(),
+                    from_options,
+                    CollectionOptions::parseForCommand,
+                    createDefaultIndexes,
+                    fixIndexSpec(to_collection.db().toString(), from_id_index));
                 verify(s.isOK());
                 wunit.commit();
                 collection = db->getCollection(opCtx, to_collection);
@@ -214,7 +212,7 @@ struct Cloner::Fun {
                 }
 
                 // TODO: SERVER-16598 abort if original db or collection is gone.
-                db = dbHolder().get(opCtx, _dbName);
+                db = DatabaseHolder::getDatabaseHolder().get(opCtx, _dbName);
                 uassert(28593,
                         str::stream() << "Database " << _dbName << " dropped while cloning",
                         db != NULL);
@@ -372,7 +370,7 @@ void Cloner::copyIndexes(OperationContext* opCtx,
 
     // We are under lock here again, so reload the database in case it may have disappeared
     // during the temp release
-    Database* db = dbHolder().openDb(opCtx, toDBName);
+    Database* db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, toDBName);
 
     Collection* collection = db->getCollection(opCtx, to_collection);
     if (!collection) {
@@ -381,7 +379,7 @@ void Cloner::copyIndexes(OperationContext* opCtx,
 
             WriteUnitOfWork wunit(opCtx);
             const bool createDefaultIndexes = true;
-            Status s = userCreateNS(
+            Status s = Database::userCreateNS(
                 opCtx,
                 db,
                 to_collection.toString(),
@@ -479,7 +477,7 @@ bool Cloner::copyCollection(OperationContext* opCtx,
             !opCtx->writesAreReplicated() ||
                 repl::ReplicationCoordinator::get(opCtx)->canAcceptWritesFor(opCtx, nss));
 
-    Database* db = dbHolder().openDb(opCtx, dbname);
+    Database* db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbname);
 
     if (shouldCreateCollection) {
         bool result = writeConflictRetry(opCtx, "createCollection", ns, [&] {
@@ -487,7 +485,7 @@ bool Cloner::copyCollection(OperationContext* opCtx,
 
             WriteUnitOfWork wunit(opCtx);
             const bool createDefaultIndexes = true;
-            Status status = userCreateNS(
+            Status status = Database::userCreateNS(
                 opCtx, db, ns, options, optionsParser, createDefaultIndexes, idIndexSpec);
             if (!status.isOK()) {
                 errmsg = status.toString();
@@ -567,7 +565,7 @@ Status Cloner::createCollectionsForDb(
     const std::vector<CreateCollectionParams>& createCollectionParams,
     const std::string& dbName,
     const CloneOptions& opts) {
-    Database* db = dbHolder().openDb(opCtx, dbName);
+    Database* db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName);
     invariant(opCtx->lockState()->isDbLockedForMode(dbName, MODE_X));
 
     auto collCount = 0;
@@ -639,13 +637,13 @@ Status Cloner::createCollectionsForDb(
                 auto options = optionsBuilder.obj();
 
                 Status createStatus =
-                    userCreateNS(opCtx,
-                                 db,
-                                 nss.ns(),
-                                 options,
-                                 CollectionOptions::parseForStorage,
-                                 createDefaultIndexes,
-                                 fixIndexSpec(nss.db().toString(), params.idIndexSpec));
+                    Database::userCreateNS(opCtx,
+                                           db,
+                                           nss.ns(),
+                                           options,
+                                           CollectionOptions::parseForStorage,
+                                           createDefaultIndexes,
+                                           fixIndexSpec(nss.db().toString(), params.idIndexSpec));
                 if (!createStatus.isOK()) {
                     return createStatus;
                 }
diff --git a/src/mongo/db/commands/create_indexes.cpp b/src/mongo/db/commands/create_indexes.cpp
index eb3b197278f..bf1edf90884 100644
--- a/src/mongo/db/commands/create_indexes.cpp
+++ b/src/mongo/db/commands/create_indexes.cpp
@@ -269,9 +269,9 @@ public:
                        str::stream() << "Not primary while creating indexes in " << ns.ns()));
         }
 
-        Database* db = dbHolder().get(opCtx, ns.db());
+        Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, ns.db());
         if (!db) {
-            db = dbHolder().openDb(opCtx, ns.db());
+            db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, ns.db());
         }
         DatabaseShardingState::get(db).checkDbVersion(opCtx);
 
@@ -393,7 +393,7 @@ public:
                     str::stream() << "Not primary while completing index build in " << dbname,
                     repl::ReplicationCoordinator::get(opCtx)->canAcceptWritesFor(opCtx, ns));
 
-            Database* db = dbHolder().get(opCtx, ns.db());
+            Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, ns.db());
             if (db) {
                 DatabaseShardingState::get(db).checkDbVersion(opCtx);
             }
diff --git a/src/mongo/db/commands/dbcommands.cpp b/src/mongo/db/commands/dbcommands.cpp
index 34e2ed22f5b..ed753c7392a 100644
--- a/src/mongo/db/commands/dbcommands.cpp
+++ b/src/mongo/db/commands/dbcommands.cpp
@@ -210,7 +210,7 @@ public:
 
         // Closing a database requires a global lock.
         Lock::GlobalWrite lk(opCtx);
-        auto db = dbHolder().get(opCtx, dbname);
+        auto db = DatabaseHolder::getDatabaseHolder().get(opCtx, dbname);
         if (db) {
             if (db->isDropPending(opCtx)) {
                 return CommandHelpers::appendCommandStatus(
@@ -221,7 +221,8 @@ public:
             }
         } else {
             // If the name doesn't make an exact match, check for a case insensitive match.
-            std::set<std::string> otherCasing = dbHolder().getNamesWithConflictingCasing(dbname);
+            std::set<std::string> otherCasing =
+                DatabaseHolder::getDatabaseHolder().getNamesWithConflictingCasing(dbname);
             if (otherCasing.empty()) {
                 // Database doesn't exist. Treat this as a success (historical behavior).
                 return true;
@@ -255,7 +256,7 @@ public:
             opCtx, engine, dbname, preserveClonedFilesOnFailure, backupOriginalFiles);
 
         // Open database before returning
-        dbHolder().openDb(opCtx, dbname);
+        DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbname);
         return CommandHelpers::appendCommandStatus(result, status);
     }
 } cmdRepairDatabase;
diff --git a/src/mongo/db/commands/dbcommands_d.cpp b/src/mongo/db/commands/dbcommands_d.cpp
index a0b4be7ebd1..90ab6c70bfa 100644
--- a/src/mongo/db/commands/dbcommands_d.cpp
+++ b/src/mongo/db/commands/dbcommands_d.cpp
@@ -128,7 +128,7 @@ protected:
             if (!db) {
                 // When setting the profiling level, create the database if it didn't already exist.
                 // When just reading the profiling level, we do not create the database.
-                db = dbHolder().openDb(opCtx, dbName);
+                db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName);
             }
             uassertStatusOK(db->setProfilingLevel(opCtx, profilingLevel));
         }
diff --git a/src/mongo/db/commands/find_and_modify.cpp b/src/mongo/db/commands/find_and_modify.cpp
index 5190d97bf1f..3a36c306626 100644
--- a/src/mongo/db/commands/find_and_modify.cpp
+++ b/src/mongo/db/commands/find_and_modify.cpp
@@ -480,8 +480,8 @@ public:
                     if (!collection) {
                         uassertStatusOK(userAllowedCreateNS(nsString.db(), nsString.coll()));
                         WriteUnitOfWork wuow(opCtx);
-                        uassertStatusOK(
-                            userCreateNS(opCtx, autoDb->getDb(), nsString.ns(), BSONObj()));
+                        uassertStatusOK(Database::userCreateNS(
+                            opCtx, autoDb->getDb(), nsString.ns(), BSONObj()));
                         wuow.commit();
 
                         collection = autoDb->getDb()->getCollection(opCtx, nsString);
diff --git a/src/mongo/db/commands/mr.cpp b/src/mongo/db/commands/mr.cpp
index 476fd6b5d3e..c743a951ba5 100644
--- a/src/mongo/db/commands/mr.cpp
+++ b/src/mongo/db/commands/mr.cpp
@@ -393,7 +393,8 @@ void State::dropTempCollections() {
 
         writeConflictRetry(_opCtx, "M/R dropTempCollections", _config.incLong.ns(), [this] {
             Lock::DBLock lk(_opCtx, _config.incLong.db(), MODE_X);
-            if (Database* db = dbHolder().get(_opCtx, _config.incLong.ns())) {
+            if (Database* db =
+                    DatabaseHolder::getDatabaseHolder().get(_opCtx, _config.incLong.ns())) {
                 WriteUnitOfWork wunit(_opCtx);
                 uassertStatusOK(db->dropCollection(_opCtx, _config.incLong.ns()));
                 wunit.commit();
@@ -653,7 +654,7 @@ unsigned long long _collectionCount(OperationContext* opCtx,
     // If the global write lock is held, we must avoid using AutoGetCollectionForReadCommand as it
     // may lead to deadlock when waiting for a majority snapshot to be committed. See SERVER-24596.
     if (callerHoldsGlobalLock) {
-        Database* db = dbHolder().get(opCtx, nss.ns());
+        Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, nss.ns());
         if (db) {
             coll = db->getCollection(opCtx, nss);
         }
diff --git a/src/mongo/db/commands/resize_oplog.cpp b/src/mongo/db/commands/resize_oplog.cpp
index d82c4321695..726cf043b5d 100644
--- a/src/mongo/db/commands/resize_oplog.cpp
+++ b/src/mongo/db/commands/resize_oplog.cpp
@@ -87,7 +87,7 @@ public:
              BSONObjBuilder& result) {
         const NamespaceString nss("local", "oplog.rs");
         Lock::GlobalWrite global(opCtx);
-        Database* database = dbHolder().get(opCtx, nss.db());
+        Database* database = DatabaseHolder::getDatabaseHolder().get(opCtx, nss.db());
         if (!database) {
             return CommandHelpers::appendCommandStatus(
                 result, Status(ErrorCodes::NamespaceNotFound, "database local does not exist"));
diff --git a/src/mongo/db/commands/restart_catalog_command.cpp b/src/mongo/db/commands/restart_catalog_command.cpp
index a3aefcd3168..f840f7954bc 100644
--- a/src/mongo/db/commands/restart_catalog_command.cpp
+++ b/src/mongo/db/commands/restart_catalog_command.cpp
@@ -95,7 +95,7 @@ public:
         std::vector<std::string> allDbs;
         getGlobalServiceContext()->getGlobalStorageEngine()->listDatabases(&allDbs);
         for (auto&& dbName : allDbs) {
-            const auto db = dbHolder().get(opCtx, dbName);
+            const auto db = DatabaseHolder::getDatabaseHolder().get(opCtx, dbName);
             if (db->isDropPending(opCtx)) {
                 return CommandHelpers::appendCommandStatus(
                     result,
diff --git a/src/mongo/db/db.cpp b/src/mongo/db/db.cpp
index 745d235926a..743a4aef4a4 100644
--- a/src/mongo/db/db.cpp
+++ b/src/mongo/db/db.cpp
@@ -222,7 +222,7 @@ void logStartup(OperationContext* opCtx) {
     if (!collection) {
         BSONObj options = BSON("capped" << true << "size" << 10 * 1024 * 1024);
         repl::UnreplicatedWritesBlock uwb(opCtx);
-        uassertStatusOK(userCreateNS(opCtx, db, startupLogCollectionName.ns(), options));
+        uassertStatusOK(Database::userCreateNS(opCtx, db, startupLogCollectionName.ns(), options));
         collection = db->getCollection(opCtx, startupLogCollectionName);
     }
     invariant(collection);
diff --git a/src/mongo/db/db_raii.cpp b/src/mongo/db/db_raii.cpp
index dbecb09a07f..59d49c5943b 100644
--- a/src/mongo/db/db_raii.cpp
+++ b/src/mongo/db/db_raii.cpp
@@ -281,7 +281,8 @@ AutoGetCollectionForReadCommand::AutoGetCollectionForReadCommand(
 }
 
 OldClientContext::OldClientContext(OperationContext* opCtx, const std::string& ns, bool doVersion)
-    : OldClientContext(opCtx, ns, doVersion, dbHolder().get(opCtx, ns), false) {}
+    : OldClientContext(
+          opCtx, ns, doVersion, DatabaseHolder::getDatabaseHolder().get(opCtx, ns), false) {}
 
 OldClientContext::OldClientContext(
     OperationContext* opCtx, const std::string& ns, bool doVersion, Database* db, bool justCreated)
@@ -289,7 +290,7 @@ OldClientContext::OldClientContext(
     if (!_db) {
         const auto dbName = nsToDatabaseSubstring(ns);
         invariant(_opCtx->lockState()->isDbLockedForMode(dbName, MODE_X));
-        _db = dbHolder().openDb(_opCtx, dbName, &_justCreated);
+        _db = DatabaseHolder::getDatabaseHolder().openDb(_opCtx, dbName, &_justCreated);
         invariant(_db);
     }
 
diff --git a/src/mongo/db/index_builder.cpp b/src/mongo/db/index_builder.cpp
index ab927cfc54b..d915fc6590b 100644
--- a/src/mongo/db/index_builder.cpp
+++ b/src/mongo/db/index_builder.cpp
@@ -98,7 +98,7 @@ void IndexBuilder::run() {
     Lock::DBLock dlk(opCtx.get(), ns.db(), MODE_X);
     OldClientContext ctx(opCtx.get(), ns.getSystemIndexesCollection());
 
-    Database* db = dbHolder().get(opCtx.get(), ns.db().toString());
+    Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx.get(), ns.db().toString());
 
     Status status = _build(opCtx.get(), db, true, &dlk);
     if (!status.isOK()) {
@@ -210,7 +210,7 @@ Status IndexBuilder::_build(OperationContext* opCtx,
 
     if (allowBackgroundBuilding) {
         dbLock->relockWithMode(MODE_X);
-        Database* reloadDb = dbHolder().get(opCtx, ns.db());
+        Database* reloadDb = DatabaseHolder::getDatabaseHolder().get(opCtx, ns.db());
         fassert(28553, reloadDb);
         fassert(28554, reloadDb->getCollection(opCtx, ns));
     }
diff --git a/src/mongo/db/keypattern.cpp b/src/mongo/db/keypattern.cpp
index ffc2a1f8e71..37c7f69631f 100644
--- a/src/mongo/db/keypattern.cpp
+++ b/src/mongo/db/keypattern.cpp
@@ -1,5 +1,3 @@
-// @file keypattern.cpp
-
 /**
 *    Copyright (C) 2012 10gen Inc.
 *
diff --git a/src/mongo/db/op_observer_impl.cpp b/src/mongo/db/op_observer_impl.cpp
index a92d5753d27..c572c9c65a1 100644
--- a/src/mongo/db/op_observer_impl.cpp
+++ b/src/mongo/db/op_observer_impl.cpp
@@ -660,7 +660,7 @@ void OpObserverImpl::onCollMod(OperationContext* opCtx,
     // catalog are all present and equal, unless the collection is system.indexes or
     // system.namespaces (see SERVER-29926, SERVER-30095).
     invariant(opCtx->lockState()->isDbLockedForMode(nss.db(), MODE_X));
-    Database* db = dbHolder().get(opCtx, nss.db());
+    Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, nss.db());
     // Some unit tests call the op observer on an unregistered Database.
     if (!db) {
         return;
diff --git a/src/mongo/db/ops/write_ops_exec.cpp b/src/mongo/db/ops/write_ops_exec.cpp
index 7edfd3d09d4..c401349d2c5 100644
--- a/src/mongo/db/ops/write_ops_exec.cpp
+++ b/src/mongo/db/ops/write_ops_exec.cpp
@@ -212,7 +212,7 @@ void makeCollection(OperationContext* opCtx, const NamespaceString& ns) {
         if (!db.getDb()->getCollection(opCtx, ns)) {  // someone else may have beat us to it.
             uassertStatusOK(userAllowedCreateNS(ns.db(), ns.coll()));
             WriteUnitOfWork wuow(opCtx);
-            uassertStatusOK(userCreateNS(opCtx, db.getDb(), ns.ns(), BSONObj()));
+            uassertStatusOK(Database::userCreateNS(opCtx, db.getDb(), ns.ns(), BSONObj()));
             wuow.commit();
         }
     });
diff --git a/src/mongo/db/query/plan_executor.cpp b/src/mongo/db/query/plan_executor.cpp
index 54d56cfb313..2deec30fd5f 100644
--- a/src/mongo/db/query/plan_executor.cpp
+++ b/src/mongo/db/query/plan_executor.cpp
@@ -446,7 +446,7 @@ std::shared_ptr<CappedInsertNotifier> PlanExecutor::getCappedInsertNotifier() {
     // We can only wait if we have a collection; otherwise we should retry immediately when
     // we hit EOF.
     dassert(_opCtx->lockState()->isCollectionLockedForMode(_nss.ns(), MODE_IS));
-    auto db = dbHolder().get(_opCtx, _nss.db());
+    auto db = DatabaseHolder::getDatabaseHolder().get(_opCtx, _nss.db());
     invariant(db);
     auto collection = db->getCollection(_opCtx, _nss);
     invariant(collection);
diff --git a/src/mongo/db/repair_database.cpp b/src/mongo/db/repair_database.cpp
index 93773d7fdc4..7c106ec1d62 100644
--- a/src/mongo/db/repair_database.cpp
+++ b/src/mongo/db/repair_database.cpp
@@ -266,14 +266,14 @@ Status repairDatabase(OperationContext* opCtx,
     }
 
     // Close the db and invalidate all current users and caches.
-    dbHolder().close(opCtx, dbName, "database closed for repair");
+    DatabaseHolder::getDatabaseHolder().close(opCtx, dbName, "database closed for repair");
     ON_BLOCK_EXIT([&dbName, &opCtx] {
         try {
             // Ensure that we don't trigger an exception when attempting to take locks.
             UninterruptibleLockGuard noInterrupt(opCtx->lockState());
 
             // Open the db after everything finishes.
-            auto db = dbHolder().openDb(opCtx, dbName);
+            auto db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName);
 
             // Set the minimum snapshot for all Collections in this db. This ensures that readers
             // using majority readConcern level can only use the collections after their repaired
diff --git a/src/mongo/db/repair_database_and_check_version.cpp b/src/mongo/db/repair_database_and_check_version.cpp
index 37baffa3ab4..523e635fbe4 100644
--- a/src/mongo/db/repair_database_and_check_version.cpp
+++ b/src/mongo/db/repair_database_and_check_version.cpp
@@ -76,11 +76,11 @@ Status restoreMissingFeatureCompatibilityVersionDocument(OperationContext* opCtx
 
     // If the admin database, which contains the server configuration collection with the
     // featureCompatibilityVersion document, does not exist, create it.
-    Database* db = dbHolder().get(opCtx, fcvNss.db());
+    Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, fcvNss.db());
     if (!db) {
         log() << "Re-creating admin database that was dropped.";
     }
-    db = dbHolder().openDb(opCtx, fcvNss.db());
+    db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, fcvNss.db());
     invariant(db);
 
     // If the server configuration collection, which contains the FCV document, does not exist, then
@@ -136,7 +136,7 @@ Status ensureAllCollectionsHaveUUIDs(OperationContext* opCtx,
     bool isMmapV1 = opCtx->getServiceContext()->getGlobalStorageEngine()->isMmapV1();
     std::vector<NamespaceString> nonReplicatedCollNSSsWithoutUUIDs;
     for (const auto& dbName : dbNames) {
-        Database* db = dbHolder().openDb(opCtx, dbName);
+        Database* db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName);
         invariant(db);
         for (auto collectionIt = db->begin(); collectionIt != db->end(); ++collectionIt) {
             Collection* coll = *collectionIt;
@@ -318,7 +318,7 @@ StatusWith<bool> repairDatabasesAndCheckVersion(OperationContext* opCtx) {
         // Attempt to restore the featureCompatibilityVersion document if it is missing.
         NamespaceString fcvNSS(NamespaceString::kServerConfigurationNamespace);
 
-        Database* db = dbHolder().get(opCtx, fcvNSS.db());
+        Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, fcvNSS.db());
         Collection* versionColl;
         BSONObj featureCompatibilityVersion;
         if (!db || !(versionColl = db->getCollection(opCtx, fcvNSS)) ||
@@ -349,7 +349,7 @@ StatusWith<bool> repairDatabasesAndCheckVersion(OperationContext* opCtx) {
         // it is fine to not open the "local" database and populate the catalog entries because we
         // won't attempt to drop the temporary collections anyway.
         Lock::DBLock dbLock(opCtx, kSystemReplSetCollection.db(), MODE_X);
-        dbHolder().openDb(opCtx, kSystemReplSetCollection.db());
+        DatabaseHolder::getDatabaseHolder().openDb(opCtx, kSystemReplSetCollection.db());
     }
 
     const repl::ReplSettings& replSettings =
@@ -377,7 +377,7 @@ StatusWith<bool> repairDatabasesAndCheckVersion(OperationContext* opCtx) {
         }
         LOG(1) << "    Recovering database: " << dbName;
 
-        Database* db = dbHolder().openDb(opCtx, dbName);
+        Database* db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName);
         invariant(db);
 
         // First thing after opening the database is to check for file compatibility,
diff --git a/src/mongo/db/repl/apply_ops.cpp b/src/mongo/db/repl/apply_ops.cpp
index 3a732c407ec..81ebf365c62 100644
--- a/src/mongo/db/repl/apply_ops.cpp
+++ b/src/mongo/db/repl/apply_ops.cpp
@@ -137,7 +137,7 @@ Status _applyOps(OperationContext* opCtx,
             invariant(opCtx->lockState()->isW());
             invariant(*opType != 'c');
 
-            auto db = dbHolder().get(opCtx, nss.ns());
+            auto db = DatabaseHolder::getDatabaseHolder().get(opCtx, nss.ns());
             if (!db) {
                 // Retry in non-atomic mode, since MMAP cannot implicitly create a new database
                 // within an active WriteUnitOfWork.
@@ -339,7 +339,7 @@ Status _checkPrecondition(OperationContext* opCtx,
         BSONObj realres = db.findOne(nss.ns(), preCondition["q"].Obj());
 
         // Get collection default collation.
-        Database* database = dbHolder().get(opCtx, nss.db());
+        Database* database = DatabaseHolder::getDatabaseHolder().get(opCtx, nss.db());
         if (!database) {
             return {ErrorCodes::NamespaceNotFound, "database in ns does not exist: " + nss.ns()};
         }
diff --git a/src/mongo/db/repl/oplog.cpp b/src/mongo/db/repl/oplog.cpp
index 6e083990f4e..2c6f4395590 100644
--- a/src/mongo/db/repl/oplog.cpp
+++ b/src/mongo/db/repl/oplog.cpp
@@ -227,7 +227,7 @@ void createIndexForApplyOps(OperationContext* opCtx,
                             IncrementOpsAppliedStatsFn incrementOpsAppliedStats,
                             OplogApplication::Mode mode) {
     // Check if collection exists.
-    Database* db = dbHolder().get(opCtx, indexNss.ns());
+    Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, indexNss.ns());
     auto indexCollection = db ? db->getCollection(opCtx, indexNss) : nullptr;
     uassert(ErrorCodes::NamespaceNotFound,
             str::stream() << "Failed to create index due to missing collection: " << indexNss.ns(),
@@ -1516,7 +1516,7 @@ Status applyCommand_inlock(OperationContext* opCtx,
         return {ErrorCodes::InvalidNamespace, "invalid ns: " + std::string(nss.ns())};
     }
     {
-        Database* db = dbHolder().get(opCtx, nss.ns());
+        Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, nss.ns());
         if (db && !db->getCollection(opCtx, nss) && db->getViewCatalog()->lookup(opCtx, nss.ns())) {
             return {ErrorCodes::CommandNotSupportedOnView,
                     str::stream() << "applyOps not supported on view:" << nss.ns()};
diff --git a/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp b/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
index bb87c7312d7..1fb7bea1adf 100644
--- a/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
+++ b/src/mongo/db/repl/replication_coordinator_external_state_impl.cpp
@@ -394,7 +394,7 @@ Status ReplicationCoordinatorExternalStateImpl::runRepairOnLocalDB(OperationCont
         Status status = repairDatabase(opCtx, engine, localDbName, false, false);
 
         // Open database before returning
-        dbHolder().openDb(opCtx, localDbName);
+        DatabaseHolder::getDatabaseHolder().openDb(opCtx, localDbName);
     } catch (const DBException& ex) {
         return ex.toStatus();
     }
@@ -787,7 +787,7 @@ void ReplicationCoordinatorExternalStateImpl::_dropAllTempCollections(OperationC
         if (*it == "local")
             continue;
         LOG(2) << "Removing temporary collections from " << *it;
-        Database* db = dbHolder().get(opCtx, *it);
+        Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, *it);
         // Since we must be holding the global lock during this function, if listDatabases
         // returned this dbname, we should be able to get a reference to it - it can't have
         // been dropped.
diff --git a/src/mongo/db/repl/rollback_impl.cpp b/src/mongo/db/repl/rollback_impl.cpp
index e92b0c9ab2d..6e96e6d0237 100644
--- a/src/mongo/db/repl/rollback_impl.cpp
+++ b/src/mongo/db/repl/rollback_impl.cpp
@@ -857,7 +857,7 @@ void RollbackImpl::_resetDropPendingState(OperationContext* opCtx) {
     opCtx->getServiceContext()->getGlobalStorageEngine()->listDatabases(&dbNames);
     for (const auto& dbName : dbNames) {
         Lock::DBLock dbLock(opCtx, dbName, MODE_X);
-        Database* db = dbHolder().openDb(opCtx, dbName);
+        Database* db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName);
         checkForIdIndexesAndDropPendingCollections(opCtx, db);
     }
 }
diff --git a/src/mongo/db/repl/rollback_test_fixture.cpp b/src/mongo/db/repl/rollback_test_fixture.cpp
index 2e9c4f47889..b0d49b1473a 100644
--- a/src/mongo/db/repl/rollback_test_fixture.cpp
+++ b/src/mongo/db/repl/rollback_test_fixture.cpp
@@ -102,8 +102,8 @@ void RollbackTest::tearDown() {
     SessionCatalog::get(_serviceContextMongoDTest.getServiceContext())->reset_forTest();
 
     // We cannot unset the global replication coordinator because ServiceContextMongoD::tearDown()
-    // calls dropAllDatabasesExceptLocal() which requires the replication coordinator to clear all
-    // snapshots.
+    // calls Databse::dropAllDatabasesExceptLocal() which requires the replication coordinator to
+    // clear all snapshots.
     _serviceContextMongoDTest.tearDown();
 
     // ServiceContextMongoD::tearDown() does not destroy service context so it is okay
@@ -179,7 +179,7 @@ Collection* RollbackTest::_createCollection(OperationContext* opCtx,
                                             const CollectionOptions& options) {
     Lock::DBLock dbLock(opCtx, nss.db(), MODE_X);
     mongo::WriteUnitOfWork wuow(opCtx);
-    auto db = dbHolder().openDb(opCtx, nss.db());
+    auto db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, nss.db());
     ASSERT_TRUE(db);
     db->dropCollection(opCtx, nss.ns()).transitional_ignore();
     auto coll = db->createCollection(opCtx, nss.ns(), options);
diff --git a/src/mongo/db/repl/rs_rollback.cpp b/src/mongo/db/repl/rs_rollback.cpp
index 3e9944988ba..eae8c70a468 100644
--- a/src/mongo/db/repl/rs_rollback.cpp
+++ b/src/mongo/db/repl/rs_rollback.cpp
@@ -844,7 +844,7 @@ void rollbackRenameCollection(OperationContext* opCtx, UUID uuid, RenameCollecti
     log() << "Attempting to rename collection with UUID: " << uuid << ", from: " << info.renameFrom
           << ", to: " << info.renameTo;
     Lock::DBLock dbLock(opCtx, dbName, MODE_X);
-    auto db = dbHolder().openDb(opCtx, dbName);
+    auto db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName);
     invariant(db);
 
     auto status = renameCollectionForRollback(opCtx, info.renameTo, uuid);
@@ -1138,7 +1138,7 @@ void rollback_internal::syncFixUp(OperationContext* opCtx,
 
             Lock::DBLock dbLock(opCtx, nss.db(), MODE_X);
 
-            auto db = dbHolder().openDb(opCtx, nss.db().toString());
+            auto db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, nss.db().toString());
             invariant(db);
 
             Collection* collection = UUIDCatalog::get(opCtx).lookupCollectionByUUID(uuid);
diff --git a/src/mongo/db/repl/rs_rollback_test.cpp b/src/mongo/db/repl/rs_rollback_test.cpp
index b4858df9cba..93a47ec8044 100644
--- a/src/mongo/db/repl/rs_rollback_test.cpp
+++ b/src/mongo/db/repl/rs_rollback_test.cpp
@@ -357,7 +357,7 @@ int _testRollbackDelete(OperationContext* opCtx,
 
     Lock::DBLock dbLock(opCtx, "test", MODE_S);
     Lock::CollectionLock collLock(opCtx->lockState(), "test.t", MODE_S);
-    auto db = dbHolder().get(opCtx, "test");
+    auto db = DatabaseHolder::getDatabaseHolder().get(opCtx, "test");
     ASSERT_TRUE(db);
     auto collection = db->getCollection(opCtx, "test.t");
     if (!collection) {
@@ -1777,7 +1777,7 @@ TEST_F(RSRollbackTest, RollbackCreateCollectionCommand) {
                            _replicationProcess.get()));
     {
         Lock::DBLock dbLock(_opCtx.get(), "test", MODE_S);
-        auto db = dbHolder().get(_opCtx.get(), "test");
+        auto db = DatabaseHolder::getDatabaseHolder().get(_opCtx.get(), "test");
         ASSERT_TRUE(db);
         ASSERT_FALSE(db->getCollection(_opCtx.get(), "test.t"));
     }
diff --git a/src/mongo/db/repl/storage_interface_impl.cpp b/src/mongo/db/repl/storage_interface_impl.cpp
index e4a53344305..cd9dbcc1fd1 100644
--- a/src/mongo/db/repl/storage_interface_impl.cpp
+++ b/src/mongo/db/repl/storage_interface_impl.cpp
@@ -370,7 +370,7 @@ Status StorageInterfaceImpl::insertDocuments(OperationContext* opCtx,
 }
 
 Status StorageInterfaceImpl::dropReplicatedDatabases(OperationContext* opCtx) {
-    dropAllDatabasesExceptLocal(opCtx);
+    Database::dropAllDatabasesExceptLocal(opCtx);
     return Status::OK();
 }
 
diff --git a/src/mongo/db/repl/sync_tail.cpp b/src/mongo/db/repl/sync_tail.cpp
index 1dd997ce5a8..b70f3c56793 100644
--- a/src/mongo/db/repl/sync_tail.cpp
+++ b/src/mongo/db/repl/sync_tail.cpp
@@ -542,7 +542,7 @@ private:
         CollectionProperties collProperties;
 
         Lock::DBLock dbLock(opCtx, nsToDatabaseSubstring(ns), MODE_IS);
-        auto db = dbHolder().get(opCtx, ns);
+        auto db = DatabaseHolder::getDatabaseHolder().get(opCtx, ns);
         if (!db) {
             return collProperties;
         }
diff --git a/src/mongo/db/repl/sync_tail_test.cpp b/src/mongo/db/repl/sync_tail_test.cpp
index 3740407529a..d995e4f61e2 100644
--- a/src/mongo/db/repl/sync_tail_test.cpp
+++ b/src/mongo/db/repl/sync_tail_test.cpp
@@ -193,7 +193,7 @@ auto createCollectionWithUuid(OperationContext* opCtx, const NamespaceString& ns
 void createDatabase(OperationContext* opCtx, StringData dbName) {
     Lock::GlobalWrite globalLock(opCtx);
     bool justCreated;
-    Database* db = dbHolder().openDb(opCtx, dbName, &justCreated);
+    Database* db = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName, &justCreated);
     ASSERT_TRUE(db);
     ASSERT_TRUE(justCreated);
 }
@@ -991,7 +991,8 @@ TEST_F(SyncTailTest, MultiInitialSyncApplyIgnoresUpdateOperationIfDocumentIsMiss
     {
         Lock::GlobalWrite globalLock(_opCtx.get());
         bool justCreated = false;
-        Database* db = dbHolder().openDb(_opCtx.get(), nss.db(), &justCreated);
+        Database* db =
+            DatabaseHolder::getDatabaseHolder().openDb(_opCtx.get(), nss.db(), &justCreated);
         ASSERT_TRUE(db);
         ASSERT_TRUE(justCreated);
     }
diff --git a/src/mongo/db/s/implicit_create_collection.cpp b/src/mongo/db/s/implicit_create_collection.cpp
index c15fc331d41..0ad6e536658 100644
--- a/src/mongo/db/s/implicit_create_collection.cpp
+++ b/src/mongo/db/s/implicit_create_collection.cpp
@@ -93,7 +93,7 @@ public:
             // Take the DBLock and CollectionLock directly rather than using AutoGetCollection
             // (which calls AutoGetDb) to avoid doing database and shard version checks.
             Lock::DBLock dbLock(opCtx, _ns.db(), MODE_IS);
-            const auto db = dbHolder().get(opCtx, _ns.db());
+            const auto db = DatabaseHolder::getDatabaseHolder().get(opCtx, _ns.db());
             if (db) {
                 Lock::CollectionLock collLock(opCtx->lockState(), _ns.ns(), MODE_IS);
                 if (db->getCollection(opCtx, _ns.ns())) {
diff --git a/src/mongo/db/s/migration_destination_manager.cpp b/src/mongo/db/s/migration_destination_manager.cpp
index 06721587c68..b1545848bd5 100644
--- a/src/mongo/db/s/migration_destination_manager.cpp
+++ b/src/mongo/db/s/migration_destination_manager.cpp
@@ -677,13 +677,13 @@ void MigrationDestinationManager::_migrateDriver(OperationContext* opCtx,
             // options.
             WriteUnitOfWork wuow(opCtx);
             const bool createDefaultIndexes = true;
-            Status status = userCreateNS(opCtx,
-                                         db,
-                                         _nss.ns(),
-                                         donorOptions,
-                                         CollectionOptions::parseForStorage,
-                                         createDefaultIndexes,
-                                         donorIdIndexSpec);
+            Status status = Database::userCreateNS(opCtx,
+                                                   db,
+                                                   _nss.ns(),
+                                                   donorOptions,
+                                                   CollectionOptions::parseForStorage,
+                                                   createDefaultIndexes,
+                                                   donorIdIndexSpec);
             if (!status.isOK()) {
                 warning() << "failed to create collection [" << _nss << "] "
                           << " with options " << donorOptions << ": " << redact(status);
diff --git a/src/mongo/db/s/shard_filtering_metadata_refresh.cpp b/src/mongo/db/s/shard_filtering_metadata_refresh.cpp
index be2d5ad9db5..90c776cae58 100644
--- a/src/mongo/db/s/shard_filtering_metadata_refresh.cpp
+++ b/src/mongo/db/s/shard_filtering_metadata_refresh.cpp
@@ -213,7 +213,7 @@ void forceDatabaseRefresh(OperationContext* opCtx, const StringData dbName) {
             // Take the DBLock directly rather than using AutoGetDb, to prevent a recursive call
             // into checkDbVersion().
             Lock::DBLock dbLock(opCtx, dbName, MODE_IS);
-            const auto db = dbHolder().get(opCtx, dbName);
+            const auto db = DatabaseHolder::getDatabaseHolder().get(opCtx, dbName);
             if (!db) {
                 log() << "Database " << dbName
                       << " has been dropped; not caching the refreshed databaseVersion";
@@ -234,7 +234,7 @@ void forceDatabaseRefresh(OperationContext* opCtx, const StringData dbName) {
 
         // The cached version is older than the refreshed version; update the cached version.
         Lock::DBLock dbLock(opCtx, dbName, MODE_X);
-        const auto db = dbHolder().get(opCtx, dbName);
+        const auto db = DatabaseHolder::getDatabaseHolder().get(opCtx, dbName);
         if (!db) {
             log() << "Database " << dbName
                   << " has been dropped; not caching the refreshed databaseVersion";
diff --git a/src/mongo/db/service_context_d_test_fixture.cpp b/src/mongo/db/service_context_d_test_fixture.cpp
index d42641381e9..df3811421d4 100644
--- a/src/mongo/db/service_context_d_test_fixture.cpp
+++ b/src/mongo/db/service_context_d_test_fixture.cpp
@@ -99,7 +99,7 @@ void ServiceContextMongoDTest::_doTest() {
 }
 
 void ServiceContextMongoDTest::_dropAllDBs(OperationContext* opCtx) {
-    dropAllDatabasesExceptLocal(opCtx);
+    Database::dropAllDatabasesExceptLocal(opCtx);
 
     Lock::GlobalWrite lk(opCtx);
     AutoGetDb autoDBLocal(opCtx, "local", MODE_X);
@@ -111,10 +111,11 @@ void ServiceContextMongoDTest::_dropAllDBs(OperationContext* opCtx) {
         });
     }
 
-    // dropAllDatabasesExceptLocal() does not close empty databases. However the holder still
-    // allocates resources to track these empty databases. These resources not released by
-    // dropAllDatabasesExceptLocal() will be leaked at exit unless we call DatabaseHolder::closeAll.
-    dbHolder().closeAll(opCtx, "all databases dropped");
+    // Database::dropAllDatabasesExceptLocal() does not close empty databases. However the holder
+    // still allocates resources to track these empty databases. These resources not released by
+    // Database::dropAllDatabasesExceptLocal() will be leaked at exit unless we call
+    // DatabaseHolder::closeAll.
+    DatabaseHolder::getDatabaseHolder().closeAll(opCtx, "all databases dropped");
 }
 
 }  // namespace mongo
diff --git a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_btree_impl_test.cpp b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_btree_impl_test.cpp
index 49cbc6d1762..700628c4331 100644
--- a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_btree_impl_test.cpp
+++ b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_btree_impl_test.cpp
@@ -1,5 +1,3 @@
-// ephemeral_for_test_btree_impl_test.cpp
-
 /**
  *    Copyright (C) 2014 MongoDB Inc.
  *
diff --git a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_engine_test.cpp b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_engine_test.cpp
index 949cdc5f670..154daa7c9cd 100644
--- a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_engine_test.cpp
+++ b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_engine_test.cpp
@@ -1,5 +1,3 @@
-// ephemeral_for_test_engine_test.cpp
-
 /**
  *    Copyright (C) 2014 MongoDB Inc.
  *
diff --git a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_init.cpp b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_init.cpp
index b52507c20df..1c5fff52e8b 100644
--- a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_init.cpp
+++ b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_init.cpp
@@ -1,5 +1,3 @@
-// ephemeral_for_test_init.cpp
-
 /**
  *    Copyright (C) 2014 MongoDB Inc.
  *
diff --git a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_record_store_test.cpp b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_record_store_test.cpp
index 29f97fd98d6..602311e4ce4 100644
--- a/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_record_store_test.cpp
+++ b/src/mongo/db/storage/ephemeral_for_test/ephemeral_for_test_record_store_test.cpp
@@ -1,5 +1,3 @@
-// ephemeral_for_test_record_store_test.cpp
-
 /**
  *    Copyright (C) 2014 MongoDB Inc.
  *
diff --git a/src/mongo/db/storage/kv/kv_engine_test_harness.cpp b/src/mongo/db/storage/kv/kv_engine_test_harness.cpp
index 4ca06132c0c..e0eebfaa73d 100644
--- a/src/mongo/db/storage/kv/kv_engine_test_harness.cpp
+++ b/src/mongo/db/storage/kv/kv_engine_test_harness.cpp
@@ -1,5 +1,3 @@
-// kv_engine_test_harness.cpp
-
 /**
  *    Copyright (C) 2014 MongoDB Inc.
  *
diff --git a/src/mongo/db/storage/kv/kv_engine_test_harness.h b/src/mongo/db/storage/kv/kv_engine_test_harness.h
index 592e11b2a32..64edb26da44 100644
--- a/src/mongo/db/storage/kv/kv_engine_test_harness.h
+++ b/src/mongo/db/storage/kv/kv_engine_test_harness.h
@@ -1,5 +1,3 @@
-// kv_engine_test_harness.h
-
 /**
  *    Copyright (C) 2014 MongoDB Inc.
  *
diff --git a/src/mongo/db/storage/mmap_v1/btree/btree_interface_test.cpp b/src/mongo/db/storage/mmap_v1/btree/btree_interface_test.cpp
index 59bde328780..b49fd70ec26 100644
--- a/src/mongo/db/storage/mmap_v1/btree/btree_interface_test.cpp
+++ b/src/mongo/db/storage/mmap_v1/btree/btree_interface_test.cpp
@@ -1,5 +1,3 @@
-// btree_interface_test.cpp
-
 /**
  *    Copyright (C) 2014 MongoDB Inc.
  *
diff --git a/src/mongo/db/storage/mmap_v1/mmap_v1_database_catalog_entry.cpp b/src/mongo/db/storage/mmap_v1/mmap_v1_database_catalog_entry.cpp
index 75ca4cda551..31440e91bc5 100644
--- a/src/mongo/db/storage/mmap_v1/mmap_v1_database_catalog_entry.cpp
+++ b/src/mongo/db/storage/mmap_v1/mmap_v1_database_catalog_entry.cpp
@@ -408,7 +408,7 @@ void MMAPV1DatabaseCatalogEntry::invalidateSystemCollectionRecord(
     // violation, but at this point we're not going to add more MMAPv1 specific interfaces.
     StringData dbName = systemCollectionNamespace.db();
     invariant(opCtx->lockState()->isDbLockedForMode(dbName, MODE_X));
-    Database* db = dbHolder().get(opCtx, dbName);
+    Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, dbName);
     Collection* systemCollection = db->getCollection(opCtx, systemCollectionNamespace);
     systemCollection->getCursorManager()->invalidateDocument(opCtx, record, INVALIDATION_DELETION);
 }
diff --git a/src/mongo/db/storage/mmap_v1/mmap_v1_record_store_test.cpp b/src/mongo/db/storage/mmap_v1/mmap_v1_record_store_test.cpp
index dff4fab6f08..3a1e71fad40 100644
--- a/src/mongo/db/storage/mmap_v1/mmap_v1_record_store_test.cpp
+++ b/src/mongo/db/storage/mmap_v1/mmap_v1_record_store_test.cpp
@@ -1,5 +1,3 @@
-// mmap_v1_record_store_test.cpp
-
 /**
  *    Copyright (C) 2014 MongoDB Inc.
  *
diff --git a/src/mongo/db/storage/mmap_v1/repair_database.cpp b/src/mongo/db/storage/mmap_v1/repair_database.cpp
index 73114b71362..416ff14063e 100644
--- a/src/mongo/db/storage/mmap_v1/repair_database.cpp
+++ b/src/mongo/db/storage/mmap_v1/repair_database.cpp
@@ -312,7 +312,7 @@ Status MMAPV1Engine::repairDatabase(OperationContext* opCtx,
             new RepairFileDeleter(opCtx, dbName, reservedPathString, reservedPath));
 
     {
-        Database* originalDatabase = dbHolder().openDb(opCtx, dbName);
+        Database* originalDatabase = DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName);
         if (originalDatabase == NULL) {
             return Status(ErrorCodes::NamespaceNotFound, "database does not exist to repair");
         }
@@ -454,7 +454,7 @@ Status MMAPV1Engine::repairDatabase(OperationContext* opCtx,
         repairFileDeleter->success();
 
     // Close the database so we can rename/delete the original data files
-    dbHolder().close(opCtx, dbName, "database closed for repair");
+    DatabaseHolder::getDatabaseHolder().close(opCtx, dbName, "database closed for repair");
 
     if (backupOriginalFiles) {
         _renameForBackup(dbName, reservedPath);
@@ -480,7 +480,7 @@ Status MMAPV1Engine::repairDatabase(OperationContext* opCtx,
     }
 
     // Reopen the database so it's discoverable
-    dbHolder().openDb(opCtx, dbName);
+    DatabaseHolder::getDatabaseHolder().openDb(opCtx, dbName);
 
     return Status::OK();
 }
diff --git a/src/mongo/db/storage/sorted_data_interface_test_harness.h b/src/mongo/db/storage/sorted_data_interface_test_harness.h
index e6f9443fd23..5966755397e 100644
--- a/src/mongo/db/storage/sorted_data_interface_test_harness.h
+++ b/src/mongo/db/storage/sorted_data_interface_test_harness.h
@@ -1,5 +1,3 @@
-// sorted_data_interface_test_harness.h
-
 /**
  *    Copyright (C) 2014 MongoDB Inc.
  *
@@ -136,4 +134,4 @@ inline void removeFromIndex(unowned_ptr<HarnessHelper> harness,
 inline std::unique_ptr<SortedDataInterfaceHarnessHelper> newSortedDataInterfaceHarnessHelper() {
     return dynamic_ptr_cast<SortedDataInterfaceHarnessHelper>(newHarnessHelper());
 }
-}
+}  // namespace mongo
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine_test.cpp
index fbf55d41b3c..f5ac70627cc 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_kv_engine_test.cpp
@@ -1,5 +1,3 @@
-// wiredtiger_kv_engine_test.cpp
-
 /**
  *    Copyright (C) 2014 MongoDB Inc.
  *
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_record_store_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_record_store_test.cpp
index c42744ff769..50d0b2a2548 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_record_store_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_prefixed_record_store_test.cpp
@@ -251,4 +251,4 @@ TEST(WiredTigerRecordStoreTest, PrefixedSeekingCursor) {
 }
 
 }  // namespace
-}  // mongo
+}  // namespace mongo
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_standard_record_store_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_standard_record_store_test.cpp
index 9650fe4a021..4041187ce36 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_standard_record_store_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_standard_record_store_test.cpp
@@ -451,4 +451,4 @@ TEST_F(SizeStorerValidateTest, InvalidSizeStorerAtCreation) {
 }
 
 }  // namespace
-}  // mongo
+}  // namespace mongo
diff --git a/src/mongo/db/views/durable_view_catalog.cpp b/src/mongo/db/views/durable_view_catalog.cpp
index 270bd1ce9c0..199c201f07c 100644
--- a/src/mongo/db/views/durable_view_catalog.cpp
+++ b/src/mongo/db/views/durable_view_catalog.cpp
@@ -54,7 +54,7 @@ namespace mongo {
 
 void DurableViewCatalog::onExternalChange(OperationContext* opCtx, const NamespaceString& name) {
     dassert(opCtx->lockState()->isDbLockedForMode(name.db(), MODE_IX));
-    Database* db = dbHolder().get(opCtx, name.db());
+    Database* db = DatabaseHolder::getDatabaseHolder().get(opCtx, name.db());
 
     if (db) {
         opCtx->recoveryUnit()->onCommit([db]() { db->getViewCatalog()->invalidate(); });