SERVER-30076 Use the UUID of the transactions collection for rollback via refetch

5 files changed, 114 insertions, 60 deletions

diff --git a/src/mongo/db/repl/rs_rollback.cpp b/src/mongo/db/repl/rs_rollback.cpp
index 9532179b3d0..a6ac87e169a 100644
--- a/src/mongo/db/repl/rs_rollback.cpp
+++ b/src/mongo/db/repl/rs_rollback.cpp
@@ -256,19 +256,23 @@ Status rollback_internal::updateFixUpInfoFromLocalOplogEntry(FixUpInfo& fixUpInf
         invariant(sessionId);
         invariant(oplogEntry.getStatementId());
 
-        // TODO: SERVER-30076
-        // Once collection uuids replace namespace strings for rollback, this will need to be
-        // changed to the uuid of the session transaction table collection. Need to add
-        // txnDoc.uuid with the proper uuid.
-        //        DocID txnDoc;
-        //        BSONObjBuilder txnBob;
-        //        txnBob.append("_id", sessionId->toBSON());
-        //        txnDoc.ownedObj = txnBob.obj();
-        //        txnDoc._id = txnDoc.ownedObj.firstElement();
-        //        txnDoc.ns = NamespaceString::kSessionTransactionsTableNamespace.ns().c_str();
-        //
-        //        fixUpInfo.docsToRefetch.insert(txnDoc);
-        //        fixUpInfo.refetchTransactionDocs = true;
+        auto transactionTableUUID = fixUpInfo.transactionTableUUID;
+        if (transactionTableUUID) {
+            BSONObjBuilder txnBob;
+            txnBob.append("_id", sessionId->toBSON());
+            auto txnObj = txnBob.obj();
+
+            DocID txnDoc(txnObj, txnObj.firstElement(), transactionTableUUID.get());
+            txnDoc.ns = NamespaceString::kSessionTransactionsTableNamespace.ns();
+
+            fixUpInfo.docsToRefetch.insert(txnDoc);
+            fixUpInfo.refetchTransactionDocs = true;
+        } else {
+            throw RSFatalException(
+                str::stream() << NamespaceString::kSessionTransactionsTableNamespace.ns()
+                              << " does not have a UUID, but local op has a transaction number: "
+                              << redact(oplogEntry.toBSON()));
+        }
     }
 
     if (oplogEntry.getOpType() == OpTypeEnum::kCommand) {
@@ -1308,6 +1312,10 @@ Status _syncRollback(OperationContext* opCtx,
     uassert(
         40506, "Upstream node rolled back. Need to retry our rollback.", how.rbid == requiredRBID);
 
+    // Find the UUID of the transactions collection. An OperationContext is required because the
+    // UUID is not known at compile time, so the SessionCatalog needs to load the collection.
+    how.transactionTableUUID = SessionCatalog::getTransactionTableUUID(opCtx);
+
     log() << "Finding the Common Point";
     try {
 
diff --git a/src/mongo/db/repl/rs_rollback.h b/src/mongo/db/repl/rs_rollback.h
index b4659313608..74d59ae3c8f 100644
--- a/src/mongo/db/repl/rs_rollback.h
+++ b/src/mongo/db/repl/rs_rollback.h
@@ -276,6 +276,9 @@ struct FixUpInfo {
     stdx::unordered_map<UUID, std::pair<OpTime, NamespaceString>, UUID::Hash>
         collectionsToRemoveFromDropPendingCollections;
 
+    // The UUID of the transactions collection. Set at the beginning of rollback.
+    boost::optional<UUID> transactionTableUUID = boost::none;
+
     // True if rollback requires re-fetching documents in the session transaction table. If true,
     // after rollback the in-memory transaction table is cleared.
     bool refetchTransactionDocs = false;
diff --git a/src/mongo/db/repl/rs_rollback_test.cpp b/src/mongo/db/repl/rs_rollback_test.cpp
index 6555843ad26..ec966c4cb01 100644
--- a/src/mongo/db/repl/rs_rollback_test.cpp
+++ b/src/mongo/db/repl/rs_rollback_test.cpp
@@ -1975,53 +1975,78 @@ DEATH_TEST_F(RSRollbackTest, LocalEntryWithTxnNumberWithoutStmtIdIsFatal, "invar
                   RSFatalException);
 }
 
-// TODO: Uncomment this test once transactions have been updated to work with the proper
-// uuid. See SERVER-30076.
-// TEST(RSRollbackTest, LocalEntryWithTxnNumberAddsTransactionTableDocToBeRefetched) {
-//    FixUpInfo fui;
-//    auto entryWithoutTxnNumber =
-//        BSON("ts" << Timestamp(Seconds(1), 0) << "t" << 1LL << "h" << 1LL << "op"
-//                  << "i"
-//                  << "ui"
-//                  << UUID::gen()
-//                  << "ns"
-//                  << "test.t2"
-//                  << "o"
-//                  << BSON("_id" << 2 << "a" << 2));
-//    ASSERT_OK(updateFixUpInfoFromLocalOplogEntry(fui, entryWithoutTxnNumber));
-//
-//    // With no txnNumber present, no extra documents need to be refetched.
-//    ASSERT_EQ(fui.docsToRefetch.size(), 1U);
-//
-//    UUID uuid = UUID::gen();
-//    auto entryWithTxnNumber =
-//        BSON("ts" << Timestamp(Seconds(1), 0) << "t" << 1LL << "h" << 1LL << "op"
-//                  << "i"
-//                  << "ui"
-//                  << uuid
-//                  << "ns"
-//                  << "test.t"
-//                  << "o"
-//                  << BSON("_id" << 1 << "a" << 1)
-//                  << "txnNumber"
-//                  << 1LL
-//                  << "stmtId"
-//                  << 1
-//                  << "lsid"
-//                  << makeLogicalSessionIdForTest().toBSON());
-//    ASSERT_OK(updateFixUpInfoFromLocalOplogEntry(fui, entryWithTxnNumber));
-//
-//    // If txnNumber is present, the session transactions table document corresponding to the oplog
-//    // entry's sessionId also needs to be refetched.
-//    ASSERT_EQ(fui.docsToRefetch.size(), 3U);
-//
-//    DocID expectedTxnDoc;
-//    expectedTxnDoc.ownedObj = BSON("_id" << entryWithTxnNumber["lsid"]);
-//    expectedTxnDoc._id = expectedTxnDoc.ownedObj.firstElement();
-//    expectedTxnDoc.ns = NamespaceString::kSessionTransactionsTableNamespace.ns().c_str();
-//    expectedTxnDoc.uuid = uuid;
-//    ASSERT_TRUE(fui.docsToRefetch.find(expectedTxnDoc) != fui.docsToRefetch.end());
-//}
+TEST_F(RSRollbackTest, LocalEntryWithTxnNumberWithoutTxnTableUUIDIsFatal) {
+    // If txnNumber is present, but the transaction collection has no UUID, rollback fails.
+    UUID uuid = UUID::gen();
+    auto lsid = makeLogicalSessionIdForTest();
+    auto entryWithTxnNumber =
+        BSON("ts" << Timestamp(Seconds(1), 0) << "t" << 1LL << "h" << 1LL << "op"
+                  << "i"
+                  << "ui"
+                  << uuid
+                  << "ns"
+                  << "test.t"
+                  << "o"
+                  << BSON("_id" << 1 << "a" << 1)
+                  << "txnNumber"
+                  << 1LL
+                  << "stmtId"
+                  << 1
+                  << "lsid"
+                  << lsid.toBSON());
+
+    FixUpInfo fui;
+    ASSERT_THROWS(updateFixUpInfoFromLocalOplogEntry(fui, entryWithTxnNumber).ignore(),
+                  RSFatalException);
+}
+
+TEST_F(RSRollbackTest, LocalEntryWithTxnNumberAddsTransactionTableDocToBeRefetched) {
+    FixUpInfo fui;
+
+    // With no txnNumber present, no extra documents need to be refetched.
+    auto entryWithoutTxnNumber =
+        BSON("ts" << Timestamp(Seconds(1), 0) << "t" << 1LL << "h" << 1LL << "op"
+                  << "i"
+                  << "ui"
+                  << UUID::gen()
+                  << "ns"
+                  << "test.t2"
+                  << "o"
+                  << BSON("_id" << 2 << "a" << 2));
+
+    ASSERT_OK(updateFixUpInfoFromLocalOplogEntry(fui, entryWithoutTxnNumber));
+    ASSERT_EQ(fui.docsToRefetch.size(), 1U);
+
+    // If txnNumber is present, and the transaction table exists and has a UUID, the session
+    // transactions table document corresponding to the oplog entry's sessionId also needs to be
+    // refetched.
+    UUID uuid = UUID::gen();
+    auto lsid = makeLogicalSessionIdForTest();
+    auto entryWithTxnNumber =
+        BSON("ts" << Timestamp(Seconds(1), 0) << "t" << 1LL << "h" << 1LL << "op"
+                  << "i"
+                  << "ui"
+                  << uuid
+                  << "ns"
+                  << "test.t"
+                  << "o"
+                  << BSON("_id" << 1 << "a" << 1)
+                  << "txnNumber"
+                  << 1LL
+                  << "stmtId"
+                  << 1
+                  << "lsid"
+                  << lsid.toBSON());
+    UUID transactionTableUUID = UUID::gen();
+    fui.transactionTableUUID = transactionTableUUID;
+
+    ASSERT_OK(updateFixUpInfoFromLocalOplogEntry(fui, entryWithTxnNumber));
+    ASSERT_EQ(fui.docsToRefetch.size(), 3U);
+
+    auto expectedObj = BSON("_id" << lsid.toBSON());
+    DocID expectedTxnDoc(expectedObj, expectedObj.firstElement(), transactionTableUUID);
+    ASSERT_TRUE(fui.docsToRefetch.find(expectedTxnDoc) != fui.docsToRefetch.end());
+}
 
 TEST_F(RSRollbackTest, RollbackReturnsImmediatelyOnFailureToTransitionToRollback) {
     // On failing to transition to ROLLBACK, rollback() should return immediately and not call
diff --git a/src/mongo/db/session_catalog.cpp b/src/mongo/db/session_catalog.cpp
index e7b672aa1d5..4e0a28bb0ac 100644
--- a/src/mongo/db/session_catalog.cpp
+++ b/src/mongo/db/session_catalog.cpp
@@ -34,6 +34,7 @@
 
 #include <boost/optional.hpp>
 
+#include "mongo/db/db_raii.h"
 #include "mongo/db/dbdirectclient.h"
 #include "mongo/db/namespace_string.h"
 #include "mongo/db/operation_context.h"
@@ -91,6 +92,17 @@ SessionCatalog* SessionCatalog::get(ServiceContext* service) {
     return sessionTransactionTable.get_ptr();
 }
 
+boost::optional<UUID> SessionCatalog::getTransactionTableUUID(OperationContext* opCtx) {
+    AutoGetCollection autoColl(opCtx, NamespaceString::kSessionTransactionsTableNamespace, MODE_IS);
+
+    const auto coll = autoColl.getCollection();
+    if (coll == nullptr) {
+        return boost::none;
+    }
+
+    return coll->uuid();
+}
+
 void SessionCatalog::onStepUp(OperationContext* opCtx) {
     DBDirectClient client(opCtx);
 
diff --git a/src/mongo/db/session_catalog.h b/src/mongo/db/session_catalog.h
index b4c4d6b3775..27aeb059669 100644
--- a/src/mongo/db/session_catalog.h
+++ b/src/mongo/db/session_catalog.h
@@ -75,6 +75,12 @@ public:
     static SessionCatalog* get(ServiceContext* service);
 
     /**
+     * Fetches the UUID of the transaction table, or an empty optional if the collection does not
+     * exist or has no UUID. Acquires a lock on the collection. Required for rollback via refetch.
+     */
+    static boost::optional<UUID> getTransactionTableUUID(OperationContext* opCtx);
+
+    /**
      * Invoked when the node enters the primary state. Ensures that the transactions collection is
      * created. Throws on severe exceptions due to which it is not safe to continue the step-up
      * process.