SERVER-37030 Make internal reads ignore prepare conflicts by default

4 files changed, 19 insertions, 15 deletions

diff --git a/src/mongo/db/read_concern.cpp b/src/mongo/db/read_concern.cpp
index 6184548f7b0..d2f18637fac 100644
--- a/src/mongo/db/read_concern.cpp
+++ b/src/mongo/db/read_concern.cpp
@@ -206,10 +206,12 @@ Status waitForReadConcern(OperationContext* opCtx,
                           bool allowAfterClusterTime) {
     // If we are in a direct client within a transaction, then we may be holding locks, so it is
     // illegal to wait for read concern. This is fine, since the outer operation should have handled
-    // waiting for read concern.
+    // waiting for read concern. We don't want to ignore prepare conflicts because snapshot reads
+    // should block on prepared transactions.
     auto txnParticipant = TransactionParticipant::get(opCtx);
     if (opCtx->getClient()->isInDirectClient() && txnParticipant &&
         txnParticipant->inMultiDocumentTransaction()) {
+        opCtx->recoveryUnit()->setIgnorePrepared(false);
         return Status::OK();
     }
 
@@ -304,6 +306,8 @@ Status waitForReadConcern(OperationContext* opCtx,
     }
 
     if (atClusterTime) {
+        opCtx->recoveryUnit()->setIgnorePrepared(false);
+
         // TODO(SERVER-34620): We should be using Session::setSpeculativeTransactionReadOpTime when
         // doing speculative execution with atClusterTime.
         opCtx->recoveryUnit()->setTimestampReadSource(RecoveryUnit::ReadSource::kProvided,
@@ -339,12 +343,12 @@ Status waitForReadConcern(OperationContext* opCtx,
     }
 
     // Only snapshot, linearizable and afterClusterTime reads should block on prepared transactions.
-    // We don't ignore prepare conflicts if we are in a direct client in case this overrides
-    // behavior set by a higher-level operation.
     if (readConcernArgs.getLevel() != repl::ReadConcernLevel::kSnapshotReadConcern &&
         readConcernArgs.getLevel() != repl::ReadConcernLevel::kLinearizableReadConcern &&
-        !afterClusterTime && !atClusterTime && !opCtx->getClient()->isInDirectClient()) {
+        !afterClusterTime && !atClusterTime) {
         opCtx->recoveryUnit()->setIgnorePrepared(true);
+    } else {
+        opCtx->recoveryUnit()->setIgnorePrepared(false);
     }
 
     return Status::OK();
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_begin_transaction_block.h b/src/mongo/db/storage/wiredtiger/wiredtiger_begin_transaction_block.h
index 6052e1df6d3..73441b8f038 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_begin_transaction_block.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_begin_transaction_block.h
@@ -47,7 +47,7 @@ public:
     // Whether or not to ignore prepared transactions.
     enum class IgnorePrepared {
         kNoIgnore,  // Do not ignore prepared transactions and return prepare conflicts.
-        kIgnore     // Ignore prepared transactions and show prepared, but uncommitted data.
+        kIgnore     // Ignore prepare conflicts, but don't show prepared data.
     };
 
     // Whether or not to round up to the oldest timestamp when the read timestamp is behind it.
@@ -57,7 +57,7 @@ public:
     };
 
     WiredTigerBeginTxnBlock(WT_SESSION* session,
-                            IgnorePrepared ignorePrepared = IgnorePrepared::kNoIgnore);
+                            IgnorePrepared ignorePrepared = IgnorePrepared::kIgnore);
     WiredTigerBeginTxnBlock(WT_SESSION* session, const char* config);
     ~WiredTigerBeginTxnBlock();
 
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h
index 585f01ece25..66c1e78033f 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.h
@@ -181,10 +181,10 @@ private:
     // When 'true', data read from disk should not be kept in the storage engine cache.
     bool _readOnce = false;
 
-    // Ignoring prepared transactions will not return prepare conflicts and allow seeing prepared,
-    // but uncommitted data.
+    // Ignoring prepared transactions will not return prepare conflicts and will not allow seeing
+    // prepared data.
     WiredTigerBeginTxnBlock::IgnorePrepared _ignorePrepared{
-        WiredTigerBeginTxnBlock::IgnorePrepared::kNoIgnore};
+        WiredTigerBeginTxnBlock::IgnorePrepared::kIgnore};
     Timestamp _commitTimestamp;
     Timestamp _prepareTimestamp;
     boost::optional<Timestamp> _lastTimestampSet;
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit_test.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit_test.cpp
index 63b0f95ee26..8e3cb105036 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit_test.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit_test.cpp
@@ -211,7 +211,7 @@ TEST_F(WiredTigerRecoveryUnitTestFixture, CreateAndCheckForCachePressure) {
 }
 
 TEST_F(WiredTigerRecoveryUnitTestFixture,
-       LocalReadOnADocumentBeingPreparedTriggersPrepareConflict) {
+       LocalReadOnADocumentBeingPreparedWithoutIgnoringPreparedTriggersPrepareConflict) {
     // Prepare but don't commit a transaction
     ru1->beginUnitOfWork(clientAndCtx1.second.get());
     WT_CURSOR* cursor;
@@ -222,8 +222,9 @@ TEST_F(WiredTigerRecoveryUnitTestFixture,
     ru1->setPrepareTimestamp({1, 1});
     ru1->prepareUnitOfWork();
 
-    // Transaction read default triggers WT_PREPARE_CONFLICT
+    // Transaction read that does not ignore prepare conflicts triggers WT_PREPARE_CONFLICT
     ru2->beginUnitOfWork(clientAndCtx2.second.get());
+    ru2->setIgnorePrepared(false);
     getCursor(ru2, &cursor);
     cursor->set_key(cursor, "key");
     int ret = cursor->search(cursor);
@@ -234,7 +235,7 @@ TEST_F(WiredTigerRecoveryUnitTestFixture,
 }
 
 TEST_F(WiredTigerRecoveryUnitTestFixture,
-       AvailableReadOnADocumentBeingPreparedDoesNotTriggerPrepareConflict) {
+       LocalReadOnADocumentBeingPreparedDoesntTriggerPrepareConflict) {
     // Prepare but don't commit a transaction
     ru1->beginUnitOfWork(clientAndCtx1.second.get());
     WT_CURSOR* cursor;
@@ -245,10 +246,9 @@ TEST_F(WiredTigerRecoveryUnitTestFixture,
     ru1->setPrepareTimestamp({1, 1});
     ru1->prepareUnitOfWork();
 
-    // Transaction that should ignore prepared transactions won't trigger
-    // WT_PREPARE_CONFLICT
+    // Transaction read default ignores prepare conflicts but should not be able to read
+    // data from the prepared transaction.
     ru2->beginUnitOfWork(clientAndCtx2.second.get());
-    ru2->setIgnorePrepared(true);
     getCursor(ru2, &cursor);
     cursor->set_key(cursor, "key");
     int ret = cursor->search(cursor);