SERVER-34739 Migrate to 1 connpool in ARS

Migrate to 1 connection pool in mongos.

This change involves the introduction of a transport layer baton, which
improves perf for a particular transport layer when doing local
scatter/gather operations.

1 files changed, 6 insertions, 3 deletions

diff --git a/src/mongo/transport/session.h b/src/mongo/transport/session.h
index bfe45a6cbe2..304c8f11da4 100644
--- a/src/mongo/transport/session.h
+++ b/src/mongo/transport/session.h
@@ -44,6 +44,8 @@ namespace transport {
 
 class TransportLayer;
 class Session;
+class Baton;
+using BatonHandle = std::shared_ptr<Baton>;
 
 using SessionHandle = std::shared_ptr<Session>;
 using ConstSessionHandle = std::shared_ptr<const Session>;
@@ -103,7 +105,7 @@ public:
      * Source (receive) a new Message from the remote host for this Session.
      */
     virtual StatusWith<Message> sourceMessage() = 0;
-    virtual Future<Message> asyncSourceMessage() = 0;
+    virtual Future<Message> asyncSourceMessage(const transport::BatonHandle& handle = nullptr) = 0;
 
     /**
      * Sink (send) a Message to the remote host for this Session.
@@ -111,14 +113,15 @@ public:
      * Async version will keep the buffer alive until the operation completes.
      */
     virtual Status sinkMessage(Message message) = 0;
-    virtual Future<void> asyncSinkMessage(Message message) = 0;
+    virtual Future<void> asyncSinkMessage(Message message,
+                                          const transport::BatonHandle& handle = nullptr) = 0;
 
     /**
      * Cancel any outstanding async operations. There is no way to cancel synchronous calls.
      * Futures will finish with an ErrorCodes::CallbackCancelled error if they haven't already
      * completed.
      */
-    virtual void cancelAsyncOperations() = 0;
+    virtual void cancelAsyncOperations(const transport::BatonHandle& handle = nullptr) = 0;
 
     /**
     * This should only be used to detect when the remote host has disappeared without