fail-monitor/monitor.hpp

#pragma once

#include <sdbusplus/bus.hpp>

namespace phosphor
{
namespace unit
{
namespace failure
{

/**
 * @class Monitor
 *
 * This class will analyze a unit to see if it is in the failed
 * state.  If it is, it will either start or stop a target unit.
 *
 * The use case is for running from the OnFailure directive in a
 * unit file.  If that unit keeps failing and restarting, it will
 * eventually exceed its rate limits and stop being restarted.
 * This application will allow another unit to be started when that
 * occurs.
 */
class Monitor
{
    public:

        /**
         * The valid actions - either starting or stopping a unit
         */
        enum class Action
        {
            start,
            stop
        };

        Monitor() = delete;
        Monitor(const Monitor&) = delete;
        Monitor(Monitor&&) = default;
        Monitor& operator=(const Monitor&) = delete;
        Monitor& operator=(Monitor&&) = default;
        ~Monitor() = default;

        /**
         * Constructor
         *
         * @param[in] sourceUnit - the source unit
         * @param[in] targetUnit - the target unit
         * @param[in] action - the action to run on the target
         */
        Monitor(const std::string& sourceUnit,
                const std::string& targetUnit,
                Action action) :
            bus(std::move(sdbusplus::bus::new_default())),
            source(sourceUnit),
            target(targetUnit),
            action(action)
            {
            }

        /**
         * Analyzes the source unit to check if it is in a failed state.
         * If it is, then it runs the action on the target unit.
         */
        void analyze();

    private:

        /**
         * Returns the dbus object path of the source unit
         */
        std::string getSourceUnitPath();

        /**
         * Says if the unit object passed in has an
         * ActiveState property equal to 'failed'.
         *
         * @param[in] path - the unit object path to check
         *
         * @return - true if this unit is in the failed state
         */
        bool inFailedState(const std::string&& path);

        /**
         * Runs the action on the target unit.
         */
        void runTargetAction();

        /**
         * The dbus object
         */
        sdbusplus::bus::bus bus;

        /**
         * The source unit
         */
        const std::string source;

        /**
         * The target unit
         */
        const std::string target;

        /**
         * The action to run on the target if the source
         * unit is in failed state.
         */
        const Action action;
};

}
}
}