SERVER-51733 ShardLocal::createIndexOnConfig() falls back on hybrid index build if collection is not empty

2 files changed, 31 insertions, 11 deletions

diff --git a/src/mongo/db/s/shard_local.cpp b/src/mongo/db/s/shard_local.cpp
index 9d6c9a2d4df..fd48ebdad78 100644
--- a/src/mongo/db/s/shard_local.cpp
+++ b/src/mongo/db/s/shard_local.cpp
@@ -27,6 +27,8 @@
  *    it in the license file.
  */
 
+#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kSharding
+
 #include "mongo/platform/basic.h"
 
 #include "mongo/db/s/shard_local.h"
@@ -41,6 +43,7 @@
 #include "mongo/db/repl/repl_set_config.h"
 #include "mongo/db/repl/replication_coordinator.h"
 #include "mongo/db/server_options.h"
+#include "mongo/logv2/log.h"
 #include "mongo/util/assert_util.h"
 #include "mongo/util/scopeguard.h"
 
@@ -161,14 +164,29 @@ Status ShardLocal::createIndexOnConfig(OperationContext* opCtx,
             return Status::OK();
         }
 
-        writeConflictRetry(opCtx, "ShardLocal::createIndexOnConfig", ns.ns(), [&] {
-            WriteUnitOfWork wunit(opCtx);
-            auto fromMigrate = true;
-            CollectionWriter collWriter(opCtx, collection->uuid());
-            IndexBuildsCoordinator::get(opCtx)->createIndexesOnEmptyCollection(
-                opCtx, collWriter, indexSpecs, fromMigrate);
-            wunit.commit();
-        });
+        auto fromMigrate = true;
+        if (!collection->isEmpty(opCtx)) {
+            // We typically create indexes on config/admin collections for sharding while setting up
+            // a sharded cluster, so we do not expect to see data in the collection.
+            // Therefore, it is ok to log this index build.
+            const auto& indexSpec = indexSpecs[0];
+            LOGV2(5173300,
+                  "Creating index on sharding collection with existing data",
+                  "ns"_attr = ns,
+                  "uuid"_attr = collection->uuid(),
+                  "index"_attr = indexSpec);
+            auto indexConstraints = IndexBuildsManager::IndexConstraints::kEnforce;
+            IndexBuildsCoordinator::get(opCtx)->createIndex(
+                opCtx, collection->uuid(), indexSpec, indexConstraints, fromMigrate);
+        } else {
+            writeConflictRetry(opCtx, "ShardLocal::createIndexOnConfig", ns.ns(), [&] {
+                WriteUnitOfWork wunit(opCtx);
+                CollectionWriter collWriter(opCtx, collection->uuid());
+                IndexBuildsCoordinator::get(opCtx)->createIndexesOnEmptyCollection(
+                    opCtx, collWriter, indexSpecs, fromMigrate);
+                wunit.commit();
+            });
+        }
     } catch (const DBException& e) {
         return e.toStatus();
     }
diff --git a/src/mongo/db/s/shard_local_test.cpp b/src/mongo/db/s/shard_local_test.cpp
index c551347b2bf..200043c20df 100644
--- a/src/mongo/db/s/shard_local_test.cpp
+++ b/src/mongo/db/s/shard_local_test.cpp
@@ -41,7 +41,6 @@
 #include "mongo/db/service_context_d_test_fixture.h"
 #include "mongo/db/write_concern_options.h"
 #include "mongo/s/client/shard_registry.h"
-#include "mongo/unittest/death_test.h"
 
 namespace mongo {
 namespace {
@@ -272,7 +271,7 @@ TEST_F(ShardLocalTest, CreateIndex) {
     ASSERT_EQ(2U, indexes.size());
 }
 
-DEATH_TEST_REGEX_F(ShardLocalTest, CreateIndexNonEmptyCollection, "Invariant failure.*isEmpty") {
+TEST_F(ShardLocalTest, CreateIndexNonEmptyCollection) {
     NamespaceString nss("config.foo");
 
     ASSERT_EQUALS(ErrorCodes::NamespaceNotFound, getIndexes(nss).getStatus());
@@ -281,7 +280,10 @@ DEATH_TEST_REGEX_F(ShardLocalTest, CreateIndexNonEmptyCollection, "Invariant fai
     DBDirectClient dbDirectClient(_opCtx.get());
     dbDirectClient.insert(nss.toString(), BSON("_id" << 1 << "a" << 1));
 
-    _shardLocal->createIndexOnConfig(_opCtx.get(), nss, BSON("a" << 1), false).ignore();
+    auto status = _shardLocal->createIndexOnConfig(_opCtx.get(), nss, BSON("a" << 1), false);
+    ASSERT_OK(status);
+    auto indexes = unittest::assertGet(getIndexes(nss));
+    ASSERT_EQ(2U, indexes.size()) << BSON("indexes" << indexes);
 }
 
 }  // namespace