SERVER-32957 part 1: mongos will now destroy kill pending cursors on checkin

1 files changed, 21 insertions, 17 deletions

diff --git a/src/mongo/s/query/cluster_cursor_manager.h b/src/mongo/s/query/cluster_cursor_manager.h
index 923e6914953..4f172cb9715 100644
--- a/src/mongo/s/query/cluster_cursor_manager.h
+++ b/src/mongo/s/query/cluster_cursor_manager.h
@@ -127,10 +127,11 @@ public:
      * A PinnedCursor can either be in a state where it owns a cursor, or can be in a null state
      * where it owns no cursor.  If a cursor is owned, the underlying cursor can be iterated with
      * next(), and the underlying cursor can be returned to the manager with the returnCursor()
-     * method (and after it is returned, no cursor will be owned).
+     * method (and after it is returned, no cursor will be owned). When a PinnedCursor is created,
+     * the underlying cursor is attached to the current OperationContext.
      *
-     * Invoking the PinnedCursor's destructor while it owns a cursor will kill and return the
-     * cursor.
+     * Invoking the PinnedCursor's destructor while it owns a cursor will kill, detach from the
+     * current OperationContext, and return the cursor.
      */
     class PinnedCursor {
         MONGO_DISALLOW_COPYING(PinnedCursor);
@@ -167,17 +168,6 @@ public:
         StatusWith<ClusterQueryResult> next(RouterExecStage::ExecContext);
 
         /**
-         * Sets the operation context for the cursor. Must be called before the first call to
-         * next().
-         */
-        void reattachToOperationContext(OperationContext* opCtx);
-
-        /**
-         * Detaches the cursor from its current OperationContext.
-         */
-        void detachFromOperationContext();
-
-        /**
          * Returns whether or not the underlying cursor is tailing a capped collection.  Cannot be
          * called after returnCursor() is called.  A cursor must be owned.
          */
@@ -191,8 +181,9 @@ public:
         bool isTailableAndAwaitData() const;
 
         /**
-         * Transfers ownership of the underlying cursor back to the manager.  A cursor must be
-         * owned, and a cursor will no longer be owned after this method completes.
+         * Transfers ownership of the underlying cursor back to the manager, and detaches it from
+         * the current OperationContext. A cursor must be owned, and a cursor will no longer be
+         * owned after this method completes.
          *
          * If 'Exhausted' is passed, the manager will de-register and destroy the cursor after it
          * is returned.
@@ -310,6 +301,8 @@ public:
      * returns an error Status with code CursorInUse.  If the given cursor is not registered or has
      * a pending kill, returns an error Status with code CursorNotFound.
      *
+     * Checking out a cursor will attach it to the given operation context.
+     *
      * 'authChecker' is function that will be called with the list of users authorized to use this
      * cursor. This function should check whether the current client is also authorized to use this
      * cursor, and if not, return an error status, which will cause checkOutCursor to fail.
@@ -342,9 +335,12 @@ public:
      * If the given cursor is not registered, returns an error Status with code CursorNotFound.
      * Otherwise, marks the cursor as 'kill pending' and returns Status::OK().
      *
+     * A thread which is currently using a cursor may not call killCursor() on it, but rather
+     * should kill the cursor by checking it back into the manager in the exhausted state.
+     *
      * Does not block.
      */
-    Status killCursor(const NamespaceString& nss, CursorId cursorId);
+    Status killCursor(OperationContext* opCtx, const NamespaceString& nss, CursorId cursorId);
 
     /**
      * Informs the manager that all mortal cursors with a 'last active' time equal to or earlier
@@ -445,6 +441,14 @@ private:
                        CursorState cursorState);
 
     /**
+     * Will detach a cursor, release the lock and then call kill() on it.
+     */
+    void detachAndKillCursor(stdx::unique_lock<stdx::mutex> lk,
+                             OperationContext* opCtx,
+                             const NamespaceString& nss,
+                             CursorId cursorId);
+
+    /**
      * Returns a pointer to the CursorEntry for the given cursor.  If the given cursor is not
      * registered, returns null.
      *