SERVER-39847 Migrating session info can trigger fassert when destination shard has transaction history truncated by oplog

(cherry picked from commit 1466c2b24eef41805dfac73e2fb43256d6d8fae7)

2 files changed, 71 insertions, 21 deletions

diff --git a/src/mongo/db/s/session_catalog_migration_destination_test.cpp b/src/mongo/db/s/session_catalog_migration_destination_test.cpp
index 8cbaa4108e3..49da1334126 100644
--- a/src/mongo/db/s/session_catalog_migration_destination_test.cpp
+++ b/src/mongo/db/s/session_catalog_migration_destination_test.cpp
@@ -33,6 +33,7 @@
 #include "mongo/client/connection_string.h"
 #include "mongo/client/remote_command_targeter_mock.h"
 #include "mongo/db/concurrency/d_concurrency.h"
+#include "mongo/db/db_raii.h"
 #include "mongo/db/dbdirectclient.h"
 #include "mongo/db/initialize_operation_session_info.h"
 #include "mongo/db/logical_session_cache_noop.h"
@@ -1518,13 +1519,14 @@ TEST_F(SessionCatalogMigrationDestinationTest, OplogEntriesWithIncompleteHistory
                        sessionInfo,                   // session info
                        Date_t::now(),                 // wall clock time
                        kIncompleteHistoryStmtId),     // statement id
-        makeOplogEntry(OpTime(Timestamp(60, 2), 1),   // optime
-                       OpTypeEnum::kInsert,           // op type
-                       BSON("x" << 60),               // o
-                       boost::none,                   // o2
-                       sessionInfo,                   // session info
-                       Date_t::now(),                 // wall clock time
-                       5)};                           // statement id
+        // This will get ignored since previous entry will make the history 'incomplete'.
+        makeOplogEntry(OpTime(Timestamp(60, 2), 1),  // optime
+                       OpTypeEnum::kInsert,          // op type
+                       BSON("x" << 60),              // o
+                       boost::none,                  // o2
+                       sessionInfo,                  // session info
+                       Date_t::now(),                // wall clock time
+                       5)};                          // statement id
 
     SessionCatalogMigrationDestination sessionMigration(kFromShard, migrationId());
     sessionMigration.start(getServiceContext());
@@ -1545,19 +1547,12 @@ TEST_F(SessionCatalogMigrationDestinationTest, OplogEntriesWithIncompleteHistory
     TransactionHistoryIterator historyIter(session->getLastWriteOpTime(2));
 
     ASSERT_TRUE(historyIter.hasNext());
-    checkOplogWithNestedOplog(oplogEntries[2], historyIter.next(opCtx));
-
-    ASSERT_TRUE(historyIter.hasNext());
     checkOplog(oplogEntries[1], historyIter.next(opCtx));
 
     ASSERT_TRUE(historyIter.hasNext());
     checkOplogWithNestedOplog(oplogEntries[0], historyIter.next(opCtx));
 
     ASSERT_FALSE(historyIter.hasNext());
-
-    checkStatementExecuted(opCtx, session.get(), 2, 23, oplogEntries[0]);
-    checkStatementExecuted(opCtx, session.get(), 2, 5, oplogEntries[2]);
-    ASSERT_THROWS(session->checkStatementExecuted(opCtx, 2, 38), AssertionException);
 }
 
 TEST_F(SessionCatalogMigrationDestinationTest,
@@ -1645,5 +1640,61 @@ TEST_F(SessionCatalogMigrationDestinationTest,
     }
 }
 
+TEST_F(SessionCatalogMigrationDestinationTest, MigratingKnownStmtWhileOplogTruncated) {
+    auto opCtx = operationContext();
+    const StmtId kStmtId = 45;
+    OperationSessionInfo sessionInfo;
+    sessionInfo.setSessionId(makeLogicalSessionIdForTest());
+    sessionInfo.setTxnNumber(19);
+
+    insertDocWithSessionInfo(sessionInfo, kNs, BSON("_id" << 46), kStmtId);
+
+    auto getLastWriteOpTime = [&]() {
+        auto c1 = getServiceContext()->makeClient("c1");
+        AlternativeClientRegion acr(c1);
+        auto innerOpCtx = cc().makeOperationContext();
+        auto session = getSessionWithTxn(innerOpCtx.get(), *sessionInfo.getSessionId(), 19);
+        return session->getLastWriteOpTime(19);
+    };
+
+    auto lastOpTimeBeforeMigrate = getLastWriteOpTime();
+
+    {
+        AutoGetCollection oplogColl(opCtx, NamespaceString::kRsOplogNamespace, MODE_X);
+        ASSERT_OK(oplogColl.getCollection()->truncate(opCtx));  // Empties the oplog collection.
+    }
+
+    {
+        // Confirm that oplog is indeed empty.
+        DBDirectClient client(opCtx);
+        auto result = client.findOne(NamespaceString::kRsOplogNamespace.ns(), {});
+        ASSERT_TRUE(result.isEmpty());
+    }
+
+    auto sameStmtOplog = makeOplogEntry(OpTime(Timestamp(100, 2), 1),  // optime
+                                        OpTypeEnum::kInsert,           // op type
+                                        BSON("_id" << 46),             // o
+                                        boost::none,                   // o2
+                                        sessionInfo,                   // session info
+                                        Date_t::now(),                 // wall clock time
+                                        kStmtId);                      // statement id
+
+    SessionCatalogMigrationDestination sessionMigration(kFromShard, migrationId());
+    sessionMigration.start(getServiceContext());
+    sessionMigration.finish();
+
+    returnOplog({sameStmtOplog});
+
+    // migration always fetches at least twice to transition from committing to done.
+    returnOplog({});
+    returnOplog({});
+
+    sessionMigration.join();
+
+    ASSERT_TRUE(SessionCatalogMigrationDestination::State::Done == sessionMigration.getState());
+
+    ASSERT_EQ(lastOpTimeBeforeMigrate, getLastWriteOpTime());
+}
+
 }  // namespace
 }  // namespace mongo
diff --git a/src/mongo/db/session.cpp b/src/mongo/db/session.cpp
index a6ceba98b45..659ca1c3cc4 100644
--- a/src/mongo/db/session.cpp
+++ b/src/mongo/db/session.cpp
@@ -445,18 +445,17 @@ bool Session::onMigrateBeginOnPrimary(OperationContext* opCtx, TxnNumber txnNumb
             return false;
         }
     } catch (const DBException& ex) {
-        // If the transaction chain was truncated on the recipient shard, then we are most likely
-        // copying from a session that hasn't been touched on the recipient shard for a very long
-        // time but could be recent on the donor.
-        //
-        // We continue copying regardless to get the entire transaction from the donor.
-        if (ex.code() != ErrorCodes::IncompleteTransactionHistory) {
-            throw;
+        // If the transaction chain is incomplete because oplog was truncated, just ignore the
+        // incoming oplog and don't attempt to 'patch up' the missing pieces.
+        if (ex.code() == ErrorCodes::IncompleteTransactionHistory) {
+            return false;
         }
 
         if (stmtId == kIncompleteHistoryStmtId) {
             return false;
         }
+
+        throw;
     }
 
     return true;