SERVER-43310 Always route a sharded cluster's createIndexes call through a replica set's primary node

(cherry picked from commit bbca8dbaf5a32ece935d2a14a8d7f94da41378e3)

4 files changed, 24 insertions, 2 deletions

diff --git a/buildscripts/resmokeconfig/suites/sharding_last_stable_mongos_and_mixed_shards.yml b/buildscripts/resmokeconfig/suites/sharding_last_stable_mongos_and_mixed_shards.yml
index 7a8f821bacd..03701533b38 100644
--- a/buildscripts/resmokeconfig/suites/sharding_last_stable_mongos_and_mixed_shards.yml
+++ b/buildscripts/resmokeconfig/suites/sharding_last_stable_mongos_and_mixed_shards.yml
@@ -146,6 +146,8 @@ selector:
   - jstests/sharding/enable_sharding_with_primary.js
   # Enable when SERVER-44733 is backported
   - jstests/sharding/change_streams_update_lookup_shard_metadata_missing.js
+  # Enable if SERVER-43310 is backported to 4.0
+  - jstests/sharding/cluster_create_indexes_always_routes_through_primary.js
 
 executor:
   config:
diff --git a/jstests/sharding/cluster_create_indexes_always_routes_through_primary.js b/jstests/sharding/cluster_create_indexes_always_routes_through_primary.js
new file mode 100644
index 00000000000..6c661e0abac
--- /dev/null
+++ b/jstests/sharding/cluster_create_indexes_always_routes_through_primary.js
@@ -0,0 +1,20 @@
+// Ensure that a call to createIndexes in a sharded cluster will route to the primary, even when
+// setSlaveOk() is set to true.
+(function() {
+'use strict';
+
+let st = new ShardingTest({shards: {rs0: {nodes: 2}}});
+const testDBName = jsTestName();
+const collName = 'coll';
+const testDB = st.s.getDB(testDBName);
+
+assert.commandWorked(testDB.adminCommand({enableSharding: testDBName}));
+assert.commandWorked(
+    testDB.adminCommand({shardCollection: testDB[collName].getFullName(), key: {x: 1}}));
+
+st.s.setSlaveOk(true);
+assert.commandWorked(
+    testDB.runCommand({createIndexes: collName, indexes: [{key: {a: 1}, name: "index"}]}));
+
+st.stop();
+})();
diff --git a/src/mongo/db/sessions_collection_config_server.cpp b/src/mongo/db/sessions_collection_config_server.cpp
index f89916aace2..f04bef414ce 100644
--- a/src/mongo/db/sessions_collection_config_server.cpp
+++ b/src/mongo/db/sessions_collection_config_server.cpp
@@ -82,7 +82,7 @@ Status SessionsCollectionConfigServer::_generateIndexesIfNeeded(OperationContext
         scatterGatherOnlyVersionIfUnsharded(opCtx,
                                             NamespaceString::kLogicalSessionsNamespace,
                                             SessionsCollection::generateCreateIndexesCmd(),
-                                            ReadPreferenceSetting::get(opCtx),
+                                            ReadPreferenceSetting(ReadPreference::PrimaryOnly),
                                             Shard::RetryPolicy::kNoRetry);
         return Status::OK();
     } catch (const DBException& ex) {
diff --git a/src/mongo/s/commands/cluster_create_indexes_cmd.cpp b/src/mongo/s/commands/cluster_create_indexes_cmd.cpp
index 31e0d36625a..c0fad9aa46d 100644
--- a/src/mongo/s/commands/cluster_create_indexes_cmd.cpp
+++ b/src/mongo/s/commands/cluster_create_indexes_cmd.cpp
@@ -77,7 +77,7 @@ public:
             opCtx,
             nss,
             CommandHelpers::filterCommandRequestForPassthrough(cmdObj),
-            ReadPreferenceSetting::get(opCtx),
+            ReadPreferenceSetting(ReadPreference::PrimaryOnly),
             Shard::RetryPolicy::kNoRetry,
             {ErrorCodes::CannotImplicitlyCreateCollection});