From 1ea94501e41b3d30c460e122e04d8d25ca51a2a7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=A4kel=C3=A4?= <markus.makela@mariadb.com>
Date: Tue, 12 Jun 2018 22:16:45 +0300
Subject: [PATCH] Prefer servers that are not busy executing session commands

Readwritesplit now prefers servers that are not busy executing session
commands. This should give the best responsiveness for reads.
---
 .../routing/readwritesplit/rwsplit_route_stmt.cc    | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/server/modules/routing/readwritesplit/rwsplit_route_stmt.cc b/server/modules/routing/readwritesplit/rwsplit_route_stmt.cc
index 123aee722..ffcfac699 100644
--- a/server/modules/routing/readwritesplit/rwsplit_route_stmt.cc
+++ b/server/modules/routing/readwritesplit/rwsplit_route_stmt.cc
@@ -63,6 +63,19 @@ static SRWBackend compare_backends(SRWBackend a, SRWBackend b, select_criteria_t
         return a;
     }
 
+    // Prefer servers that are not busy executing session commands
+    bool a_busy = a->has_session_commands();
+    bool b_busy = b->has_session_commands();
+
+    if (a_busy && !b_busy)
+    {
+        return b;
+    }
+    else if (!a_busy && b_busy)
+    {
+        return a;
+    }
+
     return p(a, b) <= 0 ? a : b;
 }