SERVER-42920 remove storage engine knowledge of mmap

Author: haleyConnelly

src/mongo/db/storage/README.md

@@ -34,9 +34,9 @@ indexes.
 #### Record Identities
 A RecordId is a unique identifier, assigned by the storage engine, for a specific document or entry
 in a record store at a given time. For storage engines based in the KVEngine the record identity is
-fixed, but other storage engines, such as MMAPv1, may change it when updating a document. Note that
-changing record ids can be very expensive, as indexes map to the RecordId. A single document with a
-large array may have thousands of index entries, resulting in very expensive updates.
+fixed, but other storage engines may change it when updating a document. Note that changing record
+ids can be very expensive, as indexes map to the RecordId. A single document with a large array may
+have thousands of index entries, resulting in very expensive updates.
 
 #### Cloning and bulk operations
 Currently all cloning, [initial sync][] and other operations are done in terms of operating on
@@ -74,10 +74,10 @@ Storage engines must ensure that atomicity and isolation guarantees span all rec
 otherwise the guarantee of atomic updates on a document and all its indexes would be violated.
 
 #### Isolation
-Storage engines must provide snapshot isolation, either through locking (as is the case for the
-MMAPv1 engine), through multi-version concurrency control (MVCC) or otherwise. The first read
-implicitly establishes the snapshot. Operations can always see all changes they make in the context
-of a recovery unit, but other operations cannot until a successful commit.
+Storage engines must provide snapshot isolation, either through locking, through multi-version
+concurrency control (MVCC) or otherwise. The first read implicitly establishes the snapshot.
+Operations can always see all changes they make in the context of a recovery unit, but other
+operations cannot until a successful commit.
 
 #### Durability
 Once a transaction is committed, it is not necessarily durable: if, and only if the server fails,

src/mongo/db/storage/durable_catalog.h

@@ -131,9 +131,8 @@ class DurableCatalog {
                                   StringData idxName,
                                   long long newExpireSeconds) = 0;
 
-    /**
-     * Compare the UUID argument to the UUID obtained from the metadata. Return true if they
-     * are equal, false otherwise. uuid can become a CollectionUUID once MMAPv1 is removed.
+    /** Compares the UUID argument to the UUID obtained from the metadata. Returns true if they are
+     * equal, false otherwise.
      */
     virtual bool isEqualToMetadataUUID(OperationContext* opCtx,
                                        NamespaceString ns,

src/mongo/db/storage/durable_catalog_feature_tracker.h

@@ -48,9 +48,6 @@ class RecordStore;
  * When a new feature is enabled on a collection or index in the data files, a bit is set in one of
  * the fields of the document. Older versions won't recognize this bit and will fail to start up as
  * a result.
- *
- * The inserted document serves a similar purpose to the DataFileVersion class used with the MMAPv1
- * storage engine.
  */
 class DurableCatalogImpl::FeatureTracker {
 public:

src/mongo/db/storage/record_store.h

@@ -157,13 +157,9 @@ class RecordCursor {
 };
 
 /**
- * Adds explicit seeking of records. This functionality is separated out from RecordCursor,
- * because some cursors, such as repair cursors, are not required to support seeking.
- *
- * Warning: MMAPv1 cannot detect if RecordIds are valid. Therefore callers should only pass
- * potentially deleted RecordIds to seek methods if they know that MMAPv1 is not the current
- * storage engine. All new storage engines must support detecting the existence of Records.
- *
+ * Adds explicit seeking of records. This functionality is separated out from RecordCursor, because
+ * some cursors are not required to support seeking. All storage engines must support detecting the
+ * existence of Records.
  */
 class SeekableRecordCursor : public RecordCursor {
 public:
@@ -202,7 +198,6 @@ class SeekableRecordCursor : public RecordCursor {
  *
  * This class must be thread-safe for document-level locking storage engines. In addition, for
  * storage engines implementing the KVEngine some methods must be thread safe, see DurableCatalog.
- * Only for MMAPv1 is this class not thread-safe.
  */
 class RecordStore {
     RecordStore(const RecordStore&) = delete;
@@ -288,10 +283,6 @@ class RecordStore {
      *
      * In general prefer RecordCursor::seekExact since it can avoid copying data in more
      * storageEngines.
-     *
-     * Warning: MMAPv1 cannot detect if RecordIds are valid. Therefore callers should only pass
-     * potentially deleted RecordIds to seek methods if they know that MMAPv1 is not the current
-     * storage engine. All new storage engines must support detecting the existence of Records.
      */
     virtual bool findRecord(OperationContext* opCtx, const RecordId& loc, RecordData* out) const {
         auto cursor = getCursor(opCtx);

src/mongo/db/storage/storage_engine_init.cpp

@@ -87,18 +87,6 @@ void initializeStorageEngine(ServiceContext* service, const StorageEngineInitFla
     }
 
     if (auto existingStorageEngine = StorageEngineMetadata::getStorageEngineForPath(dbpath)) {
-        if (*existingStorageEngine == "mmapv1" ||
-            (storageGlobalParams.engineSetByUser && storageGlobalParams.engine == "mmapv1")) {
-            log() << startupWarningsLog;
-            log() << "** WARNING: Support for MMAPV1 storage engine has been deprecated and will be"
-                  << startupWarningsLog;
-            log() << "**          removed in version 4.2. Please plan to migrate to the wiredTiger"
-                  << startupWarningsLog;
-            log() << "**          storage engine." << startupWarningsLog;
-            log() << "**          See http://dochub.mongodb.org/core/deprecated-mmapv1";
-            log() << startupWarningsLog;
-        }
-
         if (storageGlobalParams.engineSetByUser) {
             // Verify that the name of the user-supplied storage engine matches the contents of
             // the metadata file.
@@ -121,25 +109,6 @@ void initializeStorageEngine(ServiceContext* service, const StorageEngineInitFla
                   << " storage engine to '" << *existingStorageEngine << "'.";
             storageGlobalParams.engine = *existingStorageEngine;
         }
-    } else if (!storageGlobalParams.engineSetByUser) {
-        // Ensure the default storage engine is available with this build of mongod.
-        uassert(28663,
-                str::stream()
-                    << "Cannot start server. The default storage engine '"
-                    << storageGlobalParams.engine
-                    << "' is not available with this build of mongod. Please specify a different"
-                    << " storage engine explicitly, e.g. --storageEngine=mmapv1.",
-                isRegisteredStorageEngine(service, storageGlobalParams.engine));
-    } else if (storageGlobalParams.engineSetByUser && storageGlobalParams.engine == "mmapv1") {
-        log() << startupWarningsLog;
-        log() << "** WARNING: You have explicitly specified 'MMAPV1' storage engine in your"
-              << startupWarningsLog;
-        log() << "**          config file or as a command line option.  Support for the MMAPV1"
-              << startupWarningsLog;
-        log() << "**          storage engine has been deprecated and will be removed in"
-              << startupWarningsLog;
-        log() << "**          version 4.2. See http://dochub.mongodb.org/core/deprecated-mmapv1";
-        log() << startupWarningsLog;
     }
 
     const StorageEngine::Factory* factory =

src/mongo/db/storage/storage_engine_metadata_test.cpp

@@ -255,18 +255,6 @@ TEST(StorageEngineMetadataTest, StorageEngineForPath_NoDataFilesExist) {
     ASSERT_FALSE(storageEngine);
 }
 
-// Override the active storage engine with "mmapv1" when the metadata file specifies "mmapv1".
-TEST(StorageEngineMetadataTest, StorageEngineForPath_MetadataFile_mmapv1) {
-    TempDir tempDir("StorageEngineMetadataTest_StorageEngineForPath_MetadataFile_mmapv1");
-    {
-        StorageEngineMetadata metadata(tempDir.path());
-        metadata.setStorageEngine("mmapv1");
-        ASSERT_OK(metadata.write());
-    }
-    ASSERT_EQUALS(std::string("mmapv1"),
-                  StorageEngineMetadata::getStorageEngineForPath(tempDir.path()));
-}
-
 // Override the active storage engine whatever the metadata file specifies.
 TEST(StorageEngineMetadataTest, StorageEngineForPath_MetadataFile_someEngine) {
     TempDir tempDir("StorageEngineMetadataTest_StorageEngineForPath_MetadataFile_someEngine");