From a55019774d9e0b1ea6ae71e73886cea8a26a925c Mon Sep 17 00:00:00 2001
From: Johan Wikman <johan.wikman@mariadb.com>
Date: Mon, 28 May 2018 10:17:30 +0300
Subject: [PATCH] MXS-1775 Expose the state of the monitor

---
 include/maxscale/monitor.hh | 16 +++++++++++++++-
 server/core/monitor.cc      | 20 ++++++++++++--------
 2 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/include/maxscale/monitor.hh b/include/maxscale/monitor.hh
index 54fa26fed..e53877bb1 100644
--- a/include/maxscale/monitor.hh
+++ b/include/maxscale/monitor.hh
@@ -28,6 +28,20 @@ public:
 
     virtual ~MonitorInstance();
 
+    /**
+     * @brief Current state of the monitor.
+     *
+     * Note that in principle the state of the monitor may already have
+     * changed when the current state is returned. The state can be fully
+     * trusted only if it is asked in a context when it is known that nobody
+     * else can affect it.
+     *
+     * @return @c MXS_MONITOR_RUNNING if the monitor is running,
+     *         @c MXS_MONITOR_STOPPING if the monitor is stopping, and
+     *         @c MXS_MONITOR_STOPPED of the monitor is stopped.
+     */
+    int32_t state() const;
+
     /**
      * @brief Starts the monitor.
      *
@@ -143,7 +157,7 @@ protected:
     MXS_MONITORED_SERVER* m_master;   /**< Master server */
 
 private:
-    int32_t     m_status;    /**< The current status of the monitor. */
+    int32_t     m_state;     /**< The current state of the monitor. */
     THREAD      m_thread;    /**< The thread handle of the monitoring thread. */
     int32_t     m_shutdown;  /**< Non-zero if the monitor should shut down. */
     bool        m_checked;   /**< Whether server access has been checked. */
diff --git a/server/core/monitor.cc b/server/core/monitor.cc
index 982c10c08..0f216459f 100644
--- a/server/core/monitor.cc
+++ b/server/core/monitor.cc
@@ -2546,7 +2546,7 @@ namespace maxscale
 MonitorInstance::MonitorInstance(MXS_MONITOR* pMonitor)
     : m_monitor(pMonitor)
     , m_master(NULL)
-    , m_status(MXS_MONITOR_STOPPED)
+    , m_state(MXS_MONITOR_STOPPED)
     , m_thread(0)
     , m_shutdown(0)
     , m_checked(false)
@@ -2559,15 +2559,21 @@ MonitorInstance::~MonitorInstance()
     ss_dassert(!m_thread);
 }
 
+int32_t MonitorInstance::state() const
+{
+    return atomic_load_int32(&m_state);
+}
+
 void MonitorInstance::stop()
 {
     // This is always called in single-thread context.
     ss_dassert(m_thread);
-    ss_dassert(m_status == MXS_MONITOR_RUNNING);
+    ss_dassert(m_state == MXS_MONITOR_RUNNING);
 
-    atomic_store_int32(&m_status, MXS_MONITOR_STOPPING);
+    atomic_store_int32(&m_state, MXS_MONITOR_STOPPING);
     atomic_store_int32(&m_shutdown, 1);
     thread_wait(m_thread);
+    atomic_store_int32(&m_state, MXS_MONITOR_STOPPED);
 
     m_thread = 0;
     m_shutdown = 0;
@@ -2616,7 +2622,7 @@ bool MonitorInstance::start(const MXS_CONFIG_PARAMETER* pParams)
 
     ss_dassert(!m_shutdown);
     ss_dassert(!m_thread);
-    ss_dassert(m_status == MXS_MONITOR_STOPPED);
+    ss_dassert(m_state == MXS_MONITOR_STOPPED);
 
     if (!m_checked)
     {
@@ -2648,7 +2654,7 @@ bool MonitorInstance::start(const MXS_CONFIG_PARAMETER* pParams)
                 // state has been updated.
                 m_semaphore.wait();
 
-                started = (atomic_load_int32(&m_status) == MXS_MONITOR_RUNNING);
+                started = (atomic_load_int32(&m_state) == MXS_MONITOR_RUNNING);
 
                 if (!started)
                 {
@@ -2793,13 +2799,11 @@ void MonitorInstance::main(void* pArg)
 
     if (mysql_thread_init() == 0)
     {
-        atomic_store_int32(&pThis->m_status, MXS_MONITOR_RUNNING);
+        atomic_store_int32(&pThis->m_state, MXS_MONITOR_RUNNING);
         pThis->m_semaphore.post();
 
         pThis->main();
 
-        atomic_store_int32(&pThis->m_status, MXS_MONITOR_STOPPED);
-
         mysql_thread_end();
     }
     else