From 446a3fac1538a6cd61f87f8da1e76965e5925b7b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Markus=20M=C3=A4kel=C3=A4?= <markus.makela@mariadb.com>
Date: Thu, 10 Oct 2019 08:57:38 +0300
Subject: [PATCH] MXS-2720: Fix service session count

The number of sessions wasn't always incremented but it was always
decremented. This happened primarily when authentication failed. By making
the management of the counters a part of the object lifecycle, this
problem goes away.
---
 server/core/session.cc                     | 10 ++++++----
 server/modules/filter/test/mock_session.cc |  2 +-
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/server/core/session.cc b/server/core/session.cc
index 75514cc41..6fb196241 100644
--- a/server/core/session.cc
+++ b/server/core/session.cc
@@ -244,7 +244,6 @@ static MXS_SESSION* session_alloc_body(SERVICE* service,
                  session->client_dcb->remote);
     }
     mxb::atomic::add(&service->stats.n_sessions, 1, mxb::atomic::RELAXED);
-    mxb::atomic::add(&service->stats.n_current, 1, mxb::atomic::RELAXED);
 
     // Store the session in the client DCB even if the session creation fails.
     // It will be freed later on when the DCB is closed.
@@ -383,9 +382,6 @@ static void session_final_free(MXS_SESSION* ses)
 
     session->state = SESSION_STATE_TO_BE_FREED;
 
-    mxb::atomic::add(&session->service->stats.n_current, -1, mxb::atomic::RELAXED);
-    mxb_assert(session->service->stats.n_current >= 0);
-
     if (session->client_dcb)
     {
         dcb_free_all_memory(session->client_dcb);
@@ -1265,6 +1261,9 @@ Session::Session(SERVICE* service)
     {
         m_retain_last_statements = this_unit.retain_last_statements;
     }
+
+    mxb::atomic::add(&service->stats.n_current, 1, mxb::atomic::RELAXED);
+    mxb_assert(service->stats.n_current >= 0);
 }
 
 Session::~Session()
@@ -1279,6 +1278,9 @@ Session::~Session()
         f.filter->obj->closeSession(f.instance, f.session);
         f.filter->obj->freeSession(f.instance, f.session);
     }
+
+    mxb::atomic::add(&service->stats.n_current, -1, mxb::atomic::RELAXED);
+    mxb_assert(service->stats.n_current >= 0);
 }
 
 namespace
diff --git a/server/modules/filter/test/mock_session.cc b/server/modules/filter/test/mock_session.cc
index 29686de51..83513a122 100644
--- a/server/modules/filter/test/mock_session.cc
+++ b/server/modules/filter/test/mock_session.cc
@@ -17,7 +17,6 @@ namespace
 {
 
 SERVICE dummy_service;
-
 }
 
 namespace maxscale
@@ -44,6 +43,7 @@ Session::Session(Client* pClient)
     strcpy(m_mysql_session.db, "dummy");
 
     m_client_dcb.data = &m_mysql_session;
+    service = &dummy_service;
 }
 
 Session::~Session()