sandesh_state_machine.h

/*
 * Copyright (c) 2013 Juniper Networks, Inc. All rights reserved.
 */

//
// sandesh_state_machine.h
//
// Sandesh state machine based on boost::statechart
//

#ifndef __SANDESH_STATE_MACHINE_H__
#define __SANDESH_STATE_MACHINE_H__

#include <boost/asio.hpp>
#include <boost/ptr_container/ptr_map.hpp>
#include <boost/statechart/state_machine.hpp>
#include <tbb/mutex.h>
#include <tbb/atomic.h>

#include <base/queue_task.h>
#include <base/timer.h>
#include <io/tcp_session.h>

#include <sandesh/sandesh_statistics.h>

namespace sc = boost::statechart;

namespace ssm {

struct Idle;
struct Active;
struct Established;
struct ServerInit;
struct EvStart;

typedef enum {
    IDLE        = 0,
    ACTIVE      = 1,
    ESTABLISHED = 2,
    SERVER_INIT = 3,
} SsmState;

} // namespace ssm

class SandeshSession;
class TcpSession;
class SandeshConnection;
class SandeshStateMachine;
class SandeshUVE;
class SandeshStateMachineStats;
class SandeshGeneratorStats;
class SandeshMessageStatistics;
class SandeshMessageBuilder;

typedef boost::function<bool(SandeshStateMachine *)> EvValidate;

class SandeshStateMachine :
        public sc::state_machine<SandeshStateMachine, ssm::Idle> {
public:
    static const int kIdleHoldTime = 5000; //5 sec .. specified in milliseconds
    static const int kQueueSize = 200 * 1024 * 1024; // 200 MB
        
    SandeshStateMachine(const char *prefix, SandeshConnection *connection);
    ~SandeshStateMachine();

    void Initialize();
    void SetAdminState(bool down);
    void SetDeferDequeue(bool defer);

    // State transitions
    template <class Ev> void OnIdle(const Ev &event);

    // In state reactions
    template <class Ev> void ReleaseSandesh(const Ev &event);
    template <class Ev> void DeleteTcpSession(const Ev &event);
    template <class Ev> void ProcessMessage(const Ev &event);

    void StartIdleHoldTimer();
    void CancelIdleHoldTimer();
    bool IdleHoldTimerRunning();
    void IdleHoldTimerFired();

    // Feed session events into the state machine.
    void OnSessionEvent(TcpSession *session, TcpSession::Event event);

    // Receive Passive Open.
    void PassiveOpen(SandeshSession *session);

    // Send SandeshUVEs to collector
    void SandeshUVESend(SandeshUVE *usnh);

    // Receive incoming sandesh message
    void OnSandeshMessage(SandeshSession *session, const std::string &msg);

    // In established state, the SM accepts updates to resource state
    void ResourceUpdate(bool rsc);

    const std::string &StateName() const;
    const std::string &LastStateName() const;

    // getters and setters
    SandeshConnection *connection() { return connection_; }

    void DeleteSession(SandeshSession *session);
    void set_session(SandeshSession *session);
    void clear_session();
    SandeshSession *session();

    void set_state(ssm::SsmState state) {
        last_state_ = state;
        state_ = state;
        state_since_ = UTCTimestampUsec();
    }
    ssm::SsmState get_state() const { return state_; }

    bool get_resource() const { return resource_; }
    void set_resource(bool r) { resource_ = r; }

    int idle_hold_time() const { return idle_hold_time_; }
    void reset_idle_hold_time() { idle_hold_time_ = 0; }
    void set_idle_hold_time(int idle_hold_time) {
        idle_hold_time_ = idle_hold_time;
    }

    void set_last_event(const std::string &event) {
        tbb::mutex::scoped_lock lock(smutex_);
        last_event_ = event;
        last_event_at_ = UTCTimestampUsec();
    }
    const std::string last_event() const {
        tbb::mutex::scoped_lock lock(smutex_);
        return last_event_;
    }
    void reset_last_info() {
        tbb::mutex::scoped_lock lock(smutex_);
        last_state_ = ssm::IDLE;
        last_event_ = "";
    }

    void Shutdown(void);
    void unconsumed_event(const sc::event_base &event);
    const char *prefix() { return prefix_; }

    void SetGeneratorKey(const std::string &generator) {
        generator_key_ = generator;
    }
    const std::string &generator_key() const {
        return generator_key_;
    }
    void SetQueueWaterMarkInfo(Sandesh::QueueWaterMarkInfo &wm);
    void ResetQueueWaterMarkInfo();
    bool GetQueueCount(uint64_t &queue_count) const;
    bool GetMessageDropLevel(std::string &drop_level) const;
    bool GetStatistics(SandeshStateMachineStats &stats, 
                       SandeshGeneratorStats &msg_stats);

private:
    friend class SandeshServerStateMachineTest;
    friend class SandeshClientStateMachineTest;

    struct EventContainer {
        boost::intrusive_ptr<const sc::event_base> event;
        EvValidate validate;
    };

    friend class WorkQueue<EventContainer>;
    friend bool GetEvSandeshMessageRecvSize(EventContainer *ec,
        size_t *msg_size);

    void TimerErrorHandler(std::string name, std::string error);
    bool IdleHoldTimerExpired();

    template <typename Ev> void Enqueue(const Ev &event);
    bool DequeueEvent(EventContainer &ec);
    bool LogEvent(const sc::event_base *event);
    void UpdateRxMsgStats(const std::string &msg_name,
        size_t msg_size);
    void UpdateRxMsgFailStats(const std::string &msg_name,
        size_t msg_size, SandeshRxDropReason::type dreason);
    void UpdateEventDequeue(const sc::event_base &event);
    void UpdateEventDequeueFail(const sc::event_base &event);
    void UpdateEventEnqueue(const sc::event_base &event);
    void UpdateEventEnqueueFail(const sc::event_base &event);
    void UpdateEventStats(const sc::event_base &event, bool enqueue, bool fail);
    void SetSandeshMessageDropLevel(size_t queue_count,
        SandeshLevel::type level, boost::function<void (void)> cb);
    void SetDeferSessionReader(bool defer_reader);

    const char *prefix_;
    typedef WorkQueue<EventContainer> EventQueue;
    EventQueue work_queue_;
    SandeshConnection *connection_;
    SandeshSession *session_;
    Timer *idle_hold_timer_;
    int idle_hold_time_;
    bool deleted_;
    tbb::atomic<ssm::SsmState> state_;
    bool resource_;
    ssm::SsmState last_state_;
    uint64_t state_since_;
    std::string last_event_;
    uint64_t last_event_at_;

    std::string generator_key_;
    mutable tbb::mutex smutex_;
    SandeshEventStatistics event_stats_;
    SandeshMessageStatistics message_stats_;
    SandeshMessageBuilder *builder_;
    SandeshLevel::type message_drop_level_;
            
    DISALLOW_COPY_AND_ASSIGN(SandeshStateMachine);
};

template<>
size_t SandeshStateMachine::EventQueue::AtomicIncrementQueueCount(
    SandeshStateMachine::EventContainer *entry);

template<>
size_t SandeshStateMachine::EventQueue::AtomicDecrementQueueCount(
    SandeshStateMachine::EventContainer *entry);

#endif // __SANDESH_STATE_MACHINE_H__