SERVER-39419 Stepdown interrupting a running dropDatabase command could leave unclean state

jstests/noPassthrough/step_down_during_drop_database.js

@@ -0,0 +1,60 @@
+/**
+ * Tests that performing a stepdown on the primary during a dropDatabase command doesn't have any
+ * negative effects when the new primary runs the same dropDatabase command while the old primary
+ * is still in the midst of dropping the database.
+ *
+ * @tags: [requires_replication]
+ */
+(function() {
+    "use strict";
+
+    load("jstests/libs/check_log.js");
+
+    const dbName = "test";
+    const collName = "coll";
+
+    const replSet = new ReplSetTest({nodes: 2});
+    replSet.startSet();
+    replSet.initiate();
+
+    let primary = replSet.getPrimary();
+    let testDB = primary.getDB(dbName);
+
+    const size = 5;
+    jsTest.log("Creating " + size + " test documents.");
+    var bulk = testDB.getCollection(collName).initializeUnorderedBulkOp();
+    for (var i = 0; i < size; ++i) {
+        bulk.insert({i: i});
+    }
+    assert.writeOK(bulk.execute());
+    replSet.awaitReplication();
+
+    const failpoint = "dropDatabaseHangAfterAllCollectionsDrop";
+    assert.commandWorked(primary.adminCommand({configureFailPoint: failpoint, mode: "alwaysOn"}));
+
+    // Run the dropDatabase command and stepdown the primary while it is running.
+    const awaitShell = startParallelShell(() => {
+        db.dropDatabase();
+    }, testDB.getMongo().port);
+
+    // Ensure the dropDatabase command has begun before stepping down.
+    checkLog.contains(primary,
+                      "dropDatabase - fail point dropDatabaseHangAfterAllCollectionsDrop " +
+                          "enabled. Blocking until fail point is disabled.");
+
+    assert.commandWorked(testDB.adminCommand({replSetStepDown: 60, force: true}));
+    replSet.waitForState(primary, ReplSetTest.State.SECONDARY);
+
+    assert.commandWorked(primary.adminCommand({configureFailPoint: failpoint, mode: "off"}));
+    awaitShell();
+
+    primary = replSet.getPrimary();
+    testDB = primary.getDB(dbName);
+
+    // Run dropDatabase on the new primary. The secondary (formerly the primary) should be able to
+    // drop the database too.
+    testDB.dropDatabase();
+    replSet.awaitReplication();
+
+    replSet.stopSet();
+})();

src/mongo/db/catalog/database.h

@@ -152,8 +152,6 @@ public:
      * Sets the 'drop-pending' state of this Database.
      * This is done at the beginning of a dropDatabase operation and is used to reject subsequent
      * collection creation requests on this database.
-     * Throws a UserAssertion if this is called on a Database that is already in a 'drop-pending'
-     * state.
      * The database must be locked in MODE_X when calling this function.
      */
     virtual void setDropPending(OperationContext* opCtx, bool dropPending) = 0;

src/mongo/db/catalog/database_impl.cpp

@@ -370,10 +370,6 @@ Status DatabaseImpl::setProfilingLevel(OperationContext* opCtx, int newLevel) {
 void DatabaseImpl::setDropPending(OperationContext* opCtx, bool dropPending) {
     if (dropPending) {
         invariant(opCtx->lockState()->isDbLockedForMode(name(), MODE_X));
-        uassert(ErrorCodes::DatabaseDropPending,
-                str::stream() << "Unable to drop database " << name()
-                              << " because it is already in the process of being dropped.",
-                !_dropPending);
         _dropPending = true;
     } else {
         invariant(opCtx->lockState()->isDbLockedForMode(name(), MODE_IX));

src/mongo/db/catalog/database_test.cpp

@@ -128,13 +128,8 @@ TEST_F(DatabaseTest, SetDropPendingThrowsExceptionIfDatabaseIsAlreadyInADropPend
         db->setDropPending(_opCtx.get(), true);
         ASSERT_TRUE(db->isDropPending(_opCtx.get()));
 
-        ASSERT_THROWS_CODE_AND_WHAT(
-            db->setDropPending(_opCtx.get(), true),
-            AssertionException,
-            ErrorCodes::DatabaseDropPending,
-            (StringBuilder() << "Unable to drop database " << _nss.db()
-                             << " because it is already in the process of being dropped.")
-                .stringData());
+        db->setDropPending(_opCtx.get(), true);
+        ASSERT_TRUE(db->isDropPending(_opCtx.get()));
 
         db->setDropPending(_opCtx.get(), false);
         ASSERT_FALSE(db->isDropPending(_opCtx.get()));