SERVER-48525 Forbid dropping config.transactions when there are prepared transactions

(cherry picked from commit d520082a3f8568b9303ab7e37c111d436d1dd50b)

2 files changed, 23 insertions, 1 deletions

diff --git a/jstests/core/txns/no_writes_to_config_transactions_with_prepared_transaction.js b/jstests/core/txns/no_writes_to_config_transactions_with_prepared_transaction.js
index 79bc3bac28d..4302a131c36 100644
--- a/jstests/core/txns/no_writes_to_config_transactions_with_prepared_transaction.js
+++ b/jstests/core/txns/no_writes_to_config_transactions_with_prepared_transaction.js
@@ -70,11 +70,17 @@ transactionEntry = config.transactions.findOne();
 assert(transactionEntry);
 
 jsTestLog("Test that dropping config.transactions fails when there is a prepared transaction" +
-          " on the session");
+          " present");
+jsTestLog("[1] collection drop in the same session");
 assert.commandFailedWithCode(assert.throws(function() {
                                               sessionConfigDB.transactions.drop();
                                           }),
                                           [4852500, 40528]);
+jsTestLog("[2] collection drop not in a session");
+assert.commandFailedWithCode(assert.throws(function() {
+                                              config.transactions.drop();
+                                          }),
+                                          4852500);
 
 jsTestLog("Test that we can prepare a transaction on a different session");
 const session2 = db.getMongo().startSession({causalConsistency: false});
diff --git a/src/mongo/db/op_observer_impl.cpp b/src/mongo/db/op_observer_impl.cpp
index 05b3bb2a35a..1b7bb32b676 100644
--- a/src/mongo/db/op_observer_impl.cpp
+++ b/src/mongo/db/op_observer_impl.cpp
@@ -742,6 +742,22 @@ repl::OpTime OpObserverImpl::onDropCollection(OperationContext* opCtx,
     if (collectionName.coll() == DurableViewCatalog::viewsCollectionName()) {
         DurableViewCatalog::onSystemViewsCollectionDrop(opCtx, collectionName);
     } else if (collectionName == NamespaceString::kSessionTransactionsTableNamespace) {
+        // Disallow this drop if there are currently prepared transactions.
+        const auto sessionCatalog = SessionCatalog::get(opCtx);
+        SessionKiller::Matcher matcherAllSessions(
+            KillAllSessionsByPatternSet{makeKillAllSessionsByPattern(opCtx)});
+        bool noPreparedTxns = true;
+        sessionCatalog->scanSessions(matcherAllSessions, [&](const ObservableSession& session) {
+            auto txnParticipant = TransactionParticipant::get(session);
+            if (txnParticipant.transactionIsPrepared()) {
+                noPreparedTxns = false;
+            }
+        });
+        uassert(4852500,
+                "Unable to drop transactions table (config.transactions) while prepared "
+                "transactions are present.",
+                noPreparedTxns);
+
         MongoDSessionCatalog::invalidateAllSessions(opCtx);
     } else if (collectionName == NamespaceString::kConfigSettingsNamespace) {
         ReadWriteConcernDefaults::get(opCtx).invalidate();