SERVER-19464 Add a way to explicitly kill a DBClientCursor before destruction

(cherry picked from commit 0476dec3ae310f768ae7fd31418a4c8aa7c24506)

Conflicts:
	src/mongo/client/dbclientcursor.h

2 files changed, 19 insertions, 0 deletions

diff --git a/src/mongo/client/dbclientcursor.cpp b/src/mongo/client/dbclientcursor.cpp
index d3ec7160ca3..33fccef8945 100644
--- a/src/mongo/client/dbclientcursor.cpp
+++ b/src/mongo/client/dbclientcursor.cpp
@@ -365,6 +365,10 @@ void DBClientCursor::attach(AScopedConnection* conn) {
 }
 
 DBClientCursor::~DBClientCursor() {
+    kill();
+}
+
+void DBClientCursor::kill() {
     DESTRUCTOR_GUARD(
 
         if (cursorId && _ownCursor && !inShutdown()) {
@@ -397,6 +401,9 @@ DBClientCursor::~DBClientCursor() {
         }
 
         );
+
+    // Mark this cursor as dead since we can't do any getMores.
+    cursorId = 0;
 }
 
 
diff --git a/src/mongo/client/dbclientcursor.h b/src/mongo/client/dbclientcursor.h
index a1c903d157e..b076106489d 100644
--- a/src/mongo/client/dbclientcursor.h
+++ b/src/mongo/client/dbclientcursor.h
@@ -249,6 +249,18 @@ public:
         Batch() : m(new Message()), nReturned(), pos(), data() {}
     };
 
+    /**
+     * Marks this object as dead and sends the KillCursors message to the server.
+     *
+     * Any errors that result from this are swallowed since this is typically performed as part of
+     * cleanup and a failure to kill the cursor should not result in a failure of the operation
+     * using the cursor.
+     *
+     * Killing an already killed or exhausted cursor does nothing, so it is safe to always call this
+     * if you want to ensure that a cursor is killed.
+     */
+    void kill();
+
 private:
     friend class DBClientBase;
     friend class DBClientConnection;