Add is_active helper to Backend

The Backend now provides a helper function for checking if the SERFER_REF
is still active.

Also renamed the close_type enum values.

include/maxscale/backend.hh

@@ -36,8 +36,8 @@ public:
      */
     enum close_type
     {
-        NORMAL,
-        FATAL
+        CLOSE_NORMAL,
+        CLOSE_FATAL
     };
 
     /**
@@ -125,7 +125,7 @@ public:
      *
      * This will close all active connections created by the backend.
      */
-    void close(close_type type = NORMAL);
+    void close(close_type type = CLOSE_NORMAL);
 
     /**
      * @brief Get a pointer to the internal DCB
@@ -182,6 +182,13 @@ public:
      */
     bool in_use() const;
 
+    /**
+     * @brief Check if the backend server reference is active
+     *
+     * @return True if the server reference is active
+     */
+    bool is_active() const;
+
     /**
      * @brief Check if backend is waiting for a result
      *

server/core/backend.cc

@@ -53,7 +53,7 @@ void Backend::close(close_type type)
             clear_state(IN_USE);
             set_state(CLOSED);
 
-            if (type == FATAL)
+            if (type == CLOSE_FATAL)
             {
                 set_state(FATAL_FAILURE);
             }
@@ -248,6 +248,11 @@ bool Backend::in_use() const
     return m_state & IN_USE;
 }
 
+bool Backend::is_active() const
+{
+    return SERVER_REF_IS_ACTIVE(m_backend);
+}
+
 bool Backend::is_waiting_result() const
 {
     return m_state & WAITING_RESULT;