MaxScale/include/maxscale/monitor.hh

#pragma once
/*
 * 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: 2020-01-01
 *
 * 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.
 */

#include <maxscale/cppdefs.hh>
#include <maxscale/monitor.h>
#include <maxscale/semaphore.hh>
#include <maxscale/thread.h>

namespace maxscale
{

class MonitorInstance : public  MXS_MONITOR_INSTANCE
{
public:
    MonitorInstance(const MonitorInstance&) = delete;
    MonitorInstance& operator = (const MonitorInstance&) = delete;

    virtual ~MonitorInstance();

    bool start(const MXS_CONFIG_PARAMETER* param);
    void stop();

protected:
    MonitorInstance(MXS_MONITOR* pMonitor);

    const std::string& script() const { return m_script; }
    uint64_t           events() const { return m_events; }

    /**
     * @brief Update server information
     *
     * The implementation should probe the server in question and update
     * the server status bits.
     */
    virtual void update_server_status(MXS_MONITORED_SERVER* pMonitored_server) = 0;

    /**
     * @brief Check whether the monitor has sufficient rights
     *
     * The implementation should check whether the monitor user has sufficient
     * rights to access the servers. The default implementation returns True.
     *
     * @return True, if the monitor user has sufficient rights, false otherwise.
     */
    virtual bool has_sufficient_permissions() const;

    /**
     * @brief Configure the monitor.
     *
     * When the monitor is started, this function will be called in order
     * to allow the concrete implementation to configure itself from
     * configuration parameters. The default implementation does nothing.
     */
    virtual void configure(const MXS_CONFIG_PARAMETER* pParams);

    /**
     * @brief Monitor the servers
     *
     * This function is called once per monitor round, and the concrete
     * implementation should probe all servers, i.e. call @c update_server_status
     * on each server.
     *
     * The default implementation will:
     *   - Not call @update_server_status for a server that is in maintenance.
     *   - Before calling, update the previous status of the server.
     *   - After the call, update the error count of the server.
     */
    virtual void tick();

    MXS_MONITOR*          m_monitor;  /**< The generic monitor structure. */
    MXS_MONITORED_SERVER* m_master;   /**< Master server */

private:
    int32_t     m_status;    /**< The current status 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. */
    std::string m_script;    /**< Launchable script. */
    uint64_t    m_events;    /**< Enabled monitor events. */
    Semaphore   m_semaphore; /**< Semaphore for synchronizing with monitor thread. */

    void main();

    static void main(void* pArg);
};

/**
 * The purpose of the template MonitorApi is to provide an implementation
 * of the monitor C-API. The template is instantiated with a class that
 * provides the actual behaviour of a monitor.
 */
template<class MonitorInstance>
class MonitorApi
{
public:
    MonitorApi() = delete;
    MonitorApi(const MonitorApi&) = delete;
    MonitorApi& operator = (const MonitorApi&) = delete;

    static MXS_MONITOR_INSTANCE* createInstance(MXS_MONITOR* pMonitor)
    {
        MonitorInstance* pInstance = NULL;
        MXS_EXCEPTION_GUARD(pInstance = MonitorInstance::create(pMonitor));
        return pInstance;
    }

    static void destroyInstance(MXS_MONITOR_INSTANCE* pInstance)
    {
        MXS_EXCEPTION_GUARD(static_cast<MonitorInstance*>(pInstance)->destroy());
    }

    static bool startMonitor(MXS_MONITOR_INSTANCE* pInstance,
                             const MXS_CONFIG_PARAMETER* pParams)
    {
        bool started = false;
        MXS_EXCEPTION_GUARD(started = static_cast<MonitorInstance*>(pInstance)->start(pParams));
        return started;
    }

    static void stopMonitor(MXS_MONITOR_INSTANCE* pInstance)
    {
        MXS_EXCEPTION_GUARD(static_cast<MonitorInstance*>(pInstance)->stop());
    }

    static void diagnostics(const MXS_MONITOR_INSTANCE* pInstance, DCB* pDcb)
    {
        MXS_EXCEPTION_GUARD(static_cast<const MonitorInstance*>(pInstance)->diagnostics(pDcb));
    }

    static json_t* diagnostics_json(const MXS_MONITOR_INSTANCE* pInstance)
    {
        json_t* pJson = NULL;
        MXS_EXCEPTION_GUARD(pJson = static_cast<const MonitorInstance*>(pInstance)->diagnostics_json());
        return pJson;
    }

    static MXS_MONITOR_API s_api;
};

template<class MonitorInstance>
MXS_MONITOR_API MonitorApi<MonitorInstance>::s_api =
{
    &MonitorApi<MonitorInstance>::createInstance,
    &MonitorApi<MonitorInstance>::destroyInstance,
    &MonitorApi<MonitorInstance>::startMonitor,
    &MonitorApi<MonitorInstance>::stopMonitor,
    &MonitorApi<MonitorInstance>::diagnostics,
    &MonitorApi<MonitorInstance>::diagnostics_json,
};

}