MXS-2424 Refactor for further changes

In subsequent change(s) persisted node information will be used
as a last resort to connect to a Clustrix node.

server/modules/monitor/clustrixmon/clustrixmonitor.cc

@@ -274,41 +274,64 @@ void ClustrixMonitor::choose_hub(Clustrix::Softfailed softfailed)
 {
     mxb_assert(!m_pHub_con);
 
-    SERVER* pHub_server = nullptr;
-    MYSQL* pHub_con = nullptr;
-
     set<string> ips;
 
-    // First we check the dynamic servers, in case there are.
+    // First we check the dynamic servers, in case there are,
-    for (auto it = m_nodes.begin(); !pHub_con && (it != m_nodes.end()); ++it)
+    if (!choose_dynamic_hub(softfailed, ips))
+    {
+        // then we check the bootstrap servers, and
+        if (!choose_bootstrap_hub(softfailed, ips))
+        {
+            // finally, if all else fails, we check servers that have been persisted.
+            // In practise we will only get here at startup (no dynamic servers)
+            // if the bootstrap servers cannot be contacted.
+            choose_persisted_hub(softfailed, ips);
+        }
+    }
+
+    if (m_pHub_con)
+    {
+        MXS_NOTICE("%s: Monitoring Clustrix cluster state using node %s:%d.",
+                   name(), m_pHub_server->address, m_pHub_server->port);
+    }
+    else
+    {
+        MXS_ERROR("%s: Could not connect to any server or no server that could "
+                  "be connected to was part of the quorum.", name());
+    }
+}
+
+bool ClustrixMonitor::choose_dynamic_hub(Clustrix::Softfailed softfailed, std::set<string>& ips_checked)
+{
+    for (auto it = m_nodes.begin(); !m_pHub_con && (it != m_nodes.end()); ++it)
     {
         auto& element = *it;
         ClustrixNode& node = element.second;
 
-        if (node.can_be_used_as_hub(name(), m_settings.conn_settings))
+        if (node.can_be_used_as_hub(name(), m_settings.conn_settings, softfailed))
         {
-            pHub_con = node.release_connection();
+            m_pHub_con = node.release_connection();
-            pHub_server = node.server();
+            m_pHub_server = node.server();
         }
 
-        ips.insert(node.ip());
+        ips_checked.insert(node.ip());
     }
 
-    if (!pHub_con)
+    return m_pHub_con != nullptr;
-    {
+}
-        // If that fails, then we check the bootstrap servers, but only if
-        // it was not checked above.
 
-        for (auto it = m_servers.begin(); !pHub_con && (it != m_servers.end()); ++it)
+bool ClustrixMonitor::choose_bootstrap_hub(Clustrix::Softfailed softfailed, std::set<string>& ips_checked)
+{
+    for (auto it = m_servers.begin(); !m_pHub_con && (it != m_servers.end()); ++it)
     {
         MonitorServer& ms = **it;
 
-            if (ips.find(ms.server->address) == ips.end())
+        if (ips_checked.find(ms.server->address) == ips_checked.end())
         {
             if (Clustrix::ping_or_connect_to_hub(name(), m_settings.conn_settings, softfailed, ms))
             {
-                    pHub_con = ms.con;
+                m_pHub_con = ms.con;
-                    pHub_server = ms.server;
+                m_pHub_server = ms.server;
             }
             else if (ms.con)
             {
@@ -318,24 +341,14 @@ void ClustrixMonitor::choose_hub(Clustrix::Softfailed softfailed)
             ms.con = nullptr;
         }
     }
+
+    return m_pHub_con != nullptr;
 }
 
-    if (pHub_con)
+bool ClustrixMonitor::choose_persisted_hub(Clustrix::Softfailed softfailed, std::set<string>& ips_checked)
 {
-        MXS_NOTICE("%s: Monitoring Clustrix cluster state using node %s:%d.",
+    // TODO: Check persisted servers.
-                   name(), pHub_server->address, pHub_server->port);
+    return false;
-
-        m_pHub_con = pHub_con;
-        m_pHub_server = pHub_server;
-
-        mxb_assert(m_pHub_con);
-        mxb_assert(m_pHub_con);
-    }
-    else
-    {
-        MXS_ERROR("%s: Could not connect to any server or no server that could "
-                  "be connected to was part of the quorum.", name());
-    }
 }
 
 void ClustrixMonitor::refresh_nodes()

server/modules/monitor/clustrixmon/clustrixmonitor.hh

@@ -14,6 +14,7 @@
 
 #include "clustrixmon.hh"
 #include <map>
+#include <set>
 #include <sqlite3.h>
 #include <maxscale/monitor.hh>
 #include <maxbase/http.hh>
@@ -87,6 +88,11 @@ private:
     void check_cluster(Clustrix::Softfailed softfailed);
     void check_hub(Clustrix::Softfailed softfailed);
     void choose_hub(Clustrix::Softfailed softfailed);
+
+    bool choose_dynamic_hub(Clustrix::Softfailed softfailed, std::set<std::string>& ips_checked);
+    bool choose_bootstrap_hub(Clustrix::Softfailed softfailed, std::set<std::string>& ips_checked);
+    bool choose_persisted_hub(Clustrix::Softfailed softfailed, std::set<std::string>& ips_checked);
+
     void refresh_nodes();
     bool check_cluster_membership(std::map<int, ClustrixMembership>* pMemberships);
 

server/modules/monitor/clustrixmon/clustrixnode.cc

@@ -15,11 +15,11 @@
 #include "clustrix.hh"
 
 bool ClustrixNode::can_be_used_as_hub(const char* zName,
-                                      const mxs::MonitorServer::ConnectionSettings& settings)
+                                      const mxs::MonitorServer::ConnectionSettings& settings,
+                                      Clustrix::Softfailed softfailed)
 {
     mxb_assert(m_pServer);
-    bool rv = Clustrix::ping_or_connect_to_hub(zName, settings, Clustrix::Softfailed::REJECT,
+    bool rv = Clustrix::ping_or_connect_to_hub(zName, settings, softfailed, *m_pServer, &m_pCon);
-                                               *m_pServer, &m_pCon);
 
     if (!rv)
     {

server/modules/monitor/clustrixmon/clustrixnode.hh

@@ -161,7 +161,8 @@ public:
     }
 
     bool can_be_used_as_hub(const char* zName,
-                            const mxs::MonitorServer::ConnectionSettings& settings);
+                            const mxs::MonitorServer::ConnectionSettings& settings,
+                            Clustrix::Softfailed softfailed);
 
     SERVER* server() const
     {