Merge branch '2.3' into 2.4

BUILD/install_test_build_deps.sh

@@ -16,14 +16,17 @@ then
   echo "deb http://mirror.netinch.com/pub/mariadb/repo/10.3/ubuntu/ ${UBUNTU_CODENAME} main" > mariadb.list
   sudo cp mariadb.list /etc/apt/sources.list.d/
   sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 0xF1656F24C74CD1D8
+  export DEBIAN_FRONTEND=noninteractive
   sudo apt-get update
-  sudo apt-get install -y --force-yes \
-                 git wget build-essential \
-                 libssl-dev mariadb-client php perl \
-                 coreutils libjansson-dev zlib1g-dev \
-                 mariadb-test python python-pip cmake \
-                 libpam0g-dev libsqlite3-dev \
-                 libcurl4-gnutls-dev
+  sudo -E apt-get -q -o Dpkg::Options::=--force-confold \
+       -o Dpkg::Options::=--force-confdef \
+       -y --force-yes \
+       install \
+       git wget build-essential \
+       libssl-dev mariadb-client php perl \
+       coreutils libjansson-dev zlib1g-dev \
+       mariadb-test python python-pip cmake libpam0g-dev \
+       libsqlite3-dev libcurl4-gnutls-dev
   sudo apt-get install -y --force-yes openjdk-8-jdk
   sudo apt-get install -y --force-yes php-mysql
   if [ $? != 0 ]

server/modules/filter/throttlefilter/throttlesession.cc

@@ -96,6 +96,7 @@ int ThrottleSession::real_routeQuery(GWBUF* buffer, bool is_delayed)
             MXS_NOTICE("Query throttling Session %ld user %s, throttling limit reached. Disconnect.",
                        m_pSession->ses_id,
                        m_pSession->client_dcb->user);
+            gwbuf_free(buffer);
             return false;   // disconnect
         }
     }

server/modules/routing/readwritesplit/rwsplit_route_stmt.cc

@@ -553,9 +553,19 @@ bool RWSplitSession::route_session_write(GWBUF* querybuf, uint8_t command, uint3
             }
             else
             {
-                MXS_ERROR("Failed to execute session command in %s (%s)",
-                          backend->name(),
-                          backend->uri());
+                backend->close();
+
+                if (m_config.master_failure_mode == RW_FAIL_INSTANTLY && backend == m_current_master)
+                {
+                    MXS_ERROR("Failed to execute session command in Master: %s (%s)",
+                              backend->name(), backend->uri());
+                    return false;
+                }
+                else
+                {
+                    MXS_ERROR("Failed to execute session command in %s (%s)",
+                              backend->name(), backend->uri());
+                }
             }
         }
     }