wsrep-lib/include/wsrep/client_service.hpp

//
// Copyright (C) 2018 Codership Oy <info@codership.com>
//

/** @file client_service.hpp
 *
 * This file will define a `callback` abstract interface for a
 * DBMS client session service. The interface will define methods
 * which will be called by the wsrep-lib.
 */

#ifndef WSREP_CLIENT_SERVICE_HPP
#define WSREP_CLIENT_SERVICE_HPP

#include "buffer.hpp"
#include "provider.hpp"
#include "mutex.hpp"
#include "lock.hpp"

namespace wsrep
{
    class transaction;
    class client_service
    {
    public:
        client_service() { }

        /**
         * Return true if two pahase commit is required for transaction
         * to commit.
         */
        virtual bool do_2pc() const = 0;

        /**
         * Return true if the current transaction has been interrupted
         * by the DBMS.
         */
        virtual bool interrupted() const = 0;

        /**
         * Reset possible global or thread local parameters associated
         * to the thread.
         */
        virtual void reset_globals() = 0;

        /**
         * Store possible global or thread local parameters associated
         * to the thread.
         */
        virtual void store_globals() = 0;

        /**
         * Set up a data for replication.
         */
        virtual int prepare_data_for_replication() = 0;

        /**
         * Clean up after transcation has been terminated.
         */
        virtual void cleanup_transaction() = 0;

        //
        // Streaming
        //
        /**
         * Return true if current statement is allowed for streaming,
         * otherwise false.
         */
        virtual bool statement_allowed_for_streaming() const = 0;
        virtual size_t bytes_generated() const = 0;
        virtual int prepare_fragment_for_replication(wsrep::mutable_buffer&) = 0;
        virtual void remove_fragments() = 0;

        virtual int commit(const wsrep::ws_handle&, const wsrep::ws_meta&) = 0;
        //
        // Rollback
        //
        /**
         * Perform brute force rollback.
         *
         * This method may be called from two contexts, either from
         * client state methods when the BF abort condition is detected,
         * or from the background rollbacker thread. The task for this
         * method is to release all reasources held by the client
         * after BF abort so that the high priority thread can continue
         * applying.
         */
        virtual int bf_rollback() = 0;

        //
        // Interface to global server state
        //

        /**
         * Forcefully shut down the DBMS process or replication system.
         * This may be called in situations where
         * the process may encounter a situation where data integrity
         * may not be guaranteed or other unrecoverable condition is
         * encontered.
         */
        virtual void emergency_shutdown() = 0;

        // Replaying
        /**
         * Notify that the client will replay.
         *
         * @todo This should not be visible to DBMS level, should be
         * handled internally by wsrep-lib.
         */
        virtual void will_replay() = 0;

        /**
         * Replay the current transaction. The implementation must put
         * the caller Client Context into applying mode and call
         * client_state::replay().
         *
         * @todo This should not be visible to DBMS level, should be
         * handled internally by wsrep-lib.
         */
        virtual enum wsrep::provider::status replay() = 0;

        /**
         * Wait until all replaying transactions have been finished
         * replaying.
         *
         * @todo This should not be visible to DBMS level, should be
         * handled internally by wsrep-lib.
         */
        virtual void wait_for_replayers(wsrep::unique_lock<wsrep::mutex>&) = 0;

        // Streaming replication
        /**
         * Append a write set fragment into fragment storage.
         */
        virtual int append_fragment(const wsrep::transaction&, int flag, const wsrep::const_buffer&) = 0;

        //
        // Debug interface
        //
        /**
         * Enter debug sync point.
         *
         * @params sync_point Name of the debug sync point.
         */
        virtual void debug_sync(const char* sync_point) = 0;

        /**
         * Forcefully kill the process if the crash_point has
         * been enabled.
         */
        virtual void debug_crash(const char* crash_point) = 0;
    };

    /**
     * Debug callback methods. These methods are called only in
     * builds that have WITH_DEBUG defined.
     */
    class client_debug_callback
    {
    public:
    };
}

#endif // WSREP_CLIENT_SERVICE_HPP