SERVER-26139 Abandon snapshot after spawning a background index build

Also adds extra logging to help debug similar future issues.

4 files changed, 12 insertions, 3 deletions

diff --git a/src/mongo/db/catalog/index_catalog.cpp b/src/mongo/db/catalog/index_catalog.cpp
index e48040cb591..2315180d796 100644
--- a/src/mongo/db/catalog/index_catalog.cpp
+++ b/src/mongo/db/catalog/index_catalog.cpp
@@ -405,6 +405,8 @@ void IndexCatalog::IndexBuildBlock::fail() {
 void IndexCatalog::IndexBuildBlock::success() {
     Collection* collection = _catalog->_collection;
     fassert(17207, collection->ok());
+    NamespaceString ns(_indexNamespace);
+    invariant(_txn->lockState()->isDbLockedForMode(ns.db(), MODE_X));
 
     collection->getCatalogEntry()->indexBuildSuccess(_txn, _indexName);
 
@@ -414,6 +416,8 @@ void IndexCatalog::IndexBuildBlock::success() {
     fassert(17331, entry && entry == _entry);
 
     OperationContext* txn = _txn;
+    LOG(2) << "marking index " << _indexName << " as ready in snapshot id "
+           << txn->recoveryUnit()->getSnapshotId();
     _txn->recoveryUnit()->onCommit([txn, entry, collection] {
         // Note: this runs after the WUOW commits but before we release our X lock on the
         // collection. This means that any snapshot created after this must include the full index,
diff --git a/src/mongo/db/repl/oplog.cpp b/src/mongo/db/repl/oplog.cpp
index 16f655443f0..bac3bc31e95 100644
--- a/src/mongo/db/repl/oplog.cpp
+++ b/src/mongo/db/repl/oplog.cpp
@@ -758,6 +758,7 @@ Status applyOperation_inlock(OperationContext* txn,
                     // Wait for thread to start and register itself
                     IndexBuilder::waitForBgIndexStarting();
                 }
+                txn->recoveryUnit()->abandonSnapshot();
             } else {
                 IndexBuilder builder(indexSpec);
                 Status status = builder.buildInForeground(txn, db);
diff --git a/src/mongo/db/storage/snapshot.h b/src/mongo/db/storage/snapshot.h
index 6ce5b57e51d..b622c14d863 100644
--- a/src/mongo/db/storage/snapshot.h
+++ b/src/mongo/db/storage/snapshot.h
@@ -57,6 +57,10 @@ public:
         return _id != other._id;
     }
 
+    std::string toString() const {
+        return std::to_string(_id);
+    }
+
 private:
     uint64_t _id;
 };
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
index d02452ff1f0..67ea0f617ff 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_recovery_unit.cpp
@@ -203,10 +203,10 @@ void WiredTigerRecoveryUnit::_txnClose(bool commit) {
     WT_SESSION* s = _session->getSession();
     if (commit) {
         invariantWTOK(s->commit_transaction(s, NULL));
-        LOG(3) << "WT commit_transaction";
+        LOG(3) << "WT commit_transaction for snapshot id " << _mySnapshotId;
     } else {
         invariantWTOK(s->rollback_transaction(s, NULL));
-        LOG(3) << "WT rollback_transaction";
+        LOG(3) << "WT rollback_transaction for snapshot id " << _mySnapshotId;
     }
     _active = false;
     _mySnapshotId = nextSnapshotId.fetchAndAdd(1);
@@ -248,7 +248,7 @@ void WiredTigerRecoveryUnit::_txnOpen(OperationContext* opCtx) {
         invariantWTOK(s->begin_transaction(s, NULL));
     }
 
-    LOG(3) << "WT begin_transaction";
+    LOG(3) << "WT begin_transaction for snapshot id " << _mySnapshotId;
     _timer.reset();
     _active = true;
 }