SERVER-46288 Reconfig in 4.2 style with the current config on FCV downgrade

- Refactoring doReplSetConfig to accept a callback.
- Use replset tag system to wait for config replication.
- Revert kConfigMajority write concern.
- Include all nodes including arbiters in config replication quorum.
- Reconfig with term -1 using the current config on downgrade.

2 files changed, 10 insertions, 0 deletions

diff --git a/src/mongo/embedded/replication_coordinator_embedded.cpp b/src/mongo/embedded/replication_coordinator_embedded.cpp
index fabaa6f64f5..0238e7ea547 100644
--- a/src/mongo/embedded/replication_coordinator_embedded.cpp
+++ b/src/mongo/embedded/replication_coordinator_embedded.cpp
@@ -346,6 +346,12 @@ Status ReplicationCoordinatorEmbedded::processReplSetReconfig(OperationContext*,
     UASSERT_NOT_IMPLEMENTED;
 }
 
+Status ReplicationCoordinatorEmbedded::doReplSetReconfig(OperationContext* opCtx,
+                                                         GetNewConfigFn getNewConfig,
+                                                         bool force) {
+    UASSERT_NOT_IMPLEMENTED;
+}
+
 Status ReplicationCoordinatorEmbedded::processReplSetInitiate(OperationContext*,
                                                               const BSONObj&,
                                                               BSONObjBuilder*) {
diff --git a/src/mongo/embedded/replication_coordinator_embedded.h b/src/mongo/embedded/replication_coordinator_embedded.h
index a0028c7591b..9bff367083c 100644
--- a/src/mongo/embedded/replication_coordinator_embedded.h
+++ b/src/mongo/embedded/replication_coordinator_embedded.h
@@ -190,6 +190,10 @@ public:
                                   const ReplSetReconfigArgs&,
                                   BSONObjBuilder*) override;
 
+    Status doReplSetReconfig(OperationContext* opCtx,
+                             GetNewConfigFn getNewConfig,
+                             bool force) override;
+
     Status processReplSetInitiate(OperationContext*, const BSONObj&, BSONObjBuilder*) override;
 
     Status processReplSetUpdatePosition(const repl::UpdatePositionArgs&, long long*) override;