MXS-1467: Create csmon

Added the csmon monitor which supports both old and new ColumnStore
servers. As older server versions aren't able to express their role, the
master needs to be designated by the user. When a ColumnStore version is
released that supports the mcsSystemPrimary() function, the master can be
automatically found.

server/modules/monitor/CMakeLists.txt

@@ -4,3 +4,4 @@ add_subdirectory(grmon)
 add_subdirectory(mariadbmon)
 add_subdirectory(mmmon)
 add_subdirectory(ndbclustermon)
+add_subdirectory(csmon)

server/modules/monitor/csmon/CMakeLists.txt

@@ -0,0 +1,4 @@
+add_library(csmon SHARED csmon.cc)
+target_link_libraries(csmon maxscale-common)
+set_target_properties(csmon PROPERTIES VERSION "1.0.0")
+install_module(csmon core)

server/modules/monitor/csmon/csmon.cc

@@ -0,0 +1,141 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2022-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#define MXS_MODULE_NAME "csmon"
+
+#include "csmon.hh"
+
+#include <regex>
+#include <vector>
+#include <string>
+
+#include <maxscale/modinfo.h>
+#include <maxscale/mysql_utils.h>
+
+namespace
+{
+
+constexpr const char* alive_query = "SELECT mcsSystemReady() = 1 && mcsSystemReadOnly() <> 2";
+constexpr const char* role_query = "SELECT mcsSystemPrimary()";
+
+// Helper for extracting string results from queries
+static std::string do_query(MXS_MONITORED_SERVER* srv, const char* query)
+{
+    std::string rval;
+    MYSQL_RES* result;
+
+    if (mxs_mysql_query(srv->con, query) == 0 && (result = mysql_store_result(srv->con)))
+    {
+        MYSQL_ROW row = mysql_fetch_row(result);
+
+        if (row && row[0])
+        {
+            rval = row[0];
+        }
+
+        mysql_free_result(result);
+    }
+    else
+    {
+        mon_report_query_error(srv);
+    }
+
+    return rval;
+}
+
+// Returns a numeric version similar to mysql_get_server_version
+int get_cs_version(MXS_MONITORED_SERVER* srv)
+{
+    std::string result = do_query(srv, "SELECT @@version_comment");
+    std::regex re("Columnstore ([0-9]*)[.]([0-9]*)[.]([0-9]*)-[0-9]*");
+    std::smatch match;
+    int rval = 0;
+
+    if (std::regex_match(result, match, re) && match.size() == 4)
+    {
+        rval = atoi(match[1].str().c_str()) * 10000 + atoi(match[2].str().c_str()) * 100
+            + atoi(match[3].str().c_str());
+    }
+
+    return rval;
+}
+}
+
+CsMonitor::CsMonitor(MXS_MONITOR* monitor)
+    : maxscale::MonitorInstanceSimple(monitor)
+    , m_primary(config_get_server(monitor->parameters, "primary"))
+{
+}
+
+CsMonitor::~CsMonitor()
+{
+}
+
+// static
+CsMonitor* CsMonitor::create(MXS_MONITOR* monitor)
+{
+    return new CsMonitor(monitor);
+}
+
+bool CsMonitor::has_sufficient_permissions() const
+{
+    return check_monitor_permissions(m_monitor, alive_query);
+}
+
+void CsMonitor::update_server_status(MXS_MONITORED_SERVER* srv)
+{
+    monitor_clear_pending_status(srv, SERVER_MASTER | SERVER_SLAVE | SERVER_RUNNING);
+    int status = 0;
+
+    if (do_query(srv, alive_query) == "1")
+    {
+        status |= SERVER_RUNNING;
+
+        if (get_cs_version(srv) >= 10107)
+        {
+            // 1.1.7 should support the mcsSystemPrimary function
+            // TODO: Update when the actual release is out
+            status |= do_query(srv, role_query) == "1" ? SERVER_MASTER : SERVER_SLAVE;
+        }
+        else
+        {
+            status |= srv->server == m_primary ? SERVER_MASTER : SERVER_SLAVE;
+        }
+    }
+
+    monitor_set_pending_status(srv, status);
+}
+
+extern "C" MXS_MODULE* MXS_CREATE_MODULE()
+{
+    static MXS_MODULE info =
+    {
+        MXS_MODULE_API_MONITOR,
+        MXS_MODULE_BETA_RELEASE,
+        MXS_MONITOR_VERSION,
+        "MariaDB ColumnStore monitor",
+        "V1.0.0",
+        MXS_NO_MODULE_CAPABILITIES,
+        &maxscale::MonitorApi<CsMonitor>::s_api,
+        NULL,   /* Process init. */
+        NULL,   /* Process finish. */
+        NULL,   /* Thread init. */
+        NULL,   /* Thread finish. */
+        {
+            {"primary", MXS_MODULE_PARAM_SERVER},
+            {MXS_END_MODULE_PARAMS}
+        }
+    };
+
+    return &info;
+}

server/modules/monitor/csmon/csmon.hh

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2018 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2022-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+#pragma once
+
+#include <maxscale/ccdefs.hh>
+#include <maxscale/monitor.hh>
+
+class CsMonitor : public maxscale::MonitorInstanceSimple
+{
+public:
+    CsMonitor(const CsMonitor&) = delete;
+    CsMonitor& operator=(const CsMonitor&) = delete;
+
+    ~CsMonitor();
+    static CsMonitor* create(MXS_MONITOR* monitor);
+
+protected:
+    bool has_sufficient_permissions() const;
+    void update_server_status(MXS_MONITORED_SERVER* monitored_server);
+
+private:
+    CsMonitor(MXS_MONITOR* monitor);
+
+    SERVER* m_primary;
+};