From fd0c156655c6c2f3aaa61bf4d74c84c96d2664b4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=A4kel=C3=A4?= <markus.makela@mariadb.com>
Date: Thu, 19 Sep 2019 13:18:06 +0300
Subject: [PATCH] MXS-2564: Reconnect only when necessary

By doing the reconnection only when a new query arrives, we prevent the
excessive reconnecting that is done when a server's actual and monitored
states are in conflict.
---
 .../routing/readwritesplit/rwsplitsession.cc  | 35 ++++---------------
 .../routing/readwritesplit/rwsplitsession.hh  |  8 +++++
 2 files changed, 14 insertions(+), 29 deletions(-)

diff --git a/server/modules/routing/readwritesplit/rwsplitsession.cc b/server/modules/routing/readwritesplit/rwsplitsession.cc
index aad2e8a20..0cc70e97d 100644
--- a/server/modules/routing/readwritesplit/rwsplitsession.cc
+++ b/server/modules/routing/readwritesplit/rwsplitsession.cc
@@ -1175,39 +1175,16 @@ bool RWSplitSession::handle_error_new_connection(DCB* backend_dcb, GWBUF* errmsg
         route_stored_query();
     }
 
-    bool succp = false;
-    /**
-     * Try to get replacement slave or at least the minimum
-     * number of slave connections for router session.
-     */
-    if (m_recv_sescmd > 0 && m_config.disable_sescmd_history)
-    {
-        for (const auto& a : m_backends)
-        {
-            if (a->in_use())
-            {
-                succp = true;
-                break;
-            }
-        }
+    bool ok = can_recover_servers() || have_open_connections();
 
-        if (!succp)
-        {
-            MXS_ERROR("Unable to continue session as all connections have failed, "
-                      "last server to fail was '%s'.", backend->name());
-        }
-    }
-    else
+    if (!ok)
     {
-        succp = m_router->select_connect_backend_servers(ses,
-                                                         m_backends,
-                                                         m_current_master,
-                                                         &m_sescmd_list,
-                                                         &m_expected_responses,
-                                                         connection_type::SLAVE);
+        MXS_ERROR("Unable to continue session as all connections have failed and "
+                  "new connections cannot be created. Last server to fail was '%s'.",
+                  backend->name());
     }
 
-    return succp;
+    return ok;
 }
 
 /**
diff --git a/server/modules/routing/readwritesplit/rwsplitsession.hh b/server/modules/routing/readwritesplit/rwsplitsession.hh
index 9da56dcf2..ded4b20b5 100644
--- a/server/modules/routing/readwritesplit/rwsplitsession.hh
+++ b/server/modules/routing/readwritesplit/rwsplitsession.hh
@@ -293,6 +293,14 @@ private:
         return !m_config.disable_sescmd_history || m_recv_sescmd == 0;
     }
 
+    inline bool have_open_connections() const
+    {
+        return std::any_of(
+            m_backends.begin(), m_backends.end(), [](const mxs::SRWBackend& b) {
+                return b->in_use();
+            });
+    }
+
     inline bool is_large_query(GWBUF* buf)
     {
         uint32_t buflen = gwbuf_length(buf);