mariadb/sql/wsrep_hton.cc

/* Copyright 2008-2015 Codership Oy <http://www.codership.com>

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335 USA */

#include <mysqld.h>
#include "sql_base.h"
#include "rpl_filter.h"
#include <sql_class.h>
#include "wsrep_mysqld.h"
#include "wsrep_binlog.h"
#include "wsrep_xid.h"
#include <cstdio>
#include <cstdlib>
#include "debug_sync.h"

extern handlerton *binlog_hton;
extern int binlog_close_connection(handlerton *hton, THD *thd);
extern ulonglong thd_to_trx_id(THD *thd);

extern "C" int thd_binlog_format(const MYSQL_THD thd);
// todo: share interface with ha_innodb.c

/*
  Cleanup after local transaction commit/rollback, replay or TOI.
*/
void wsrep_cleanup_transaction(THD *thd)
{
  if (!WSREP(thd)) return;

  if (wsrep_emulate_bin_log) thd_binlog_trx_reset(thd);
  thd->wsrep_ws_handle.trx_id= WSREP_UNDEFINED_TRX_ID;
  thd->wsrep_trx_meta.gtid= WSREP_GTID_UNDEFINED;
  thd->wsrep_trx_meta.depends_on= WSREP_SEQNO_UNDEFINED;
  thd->wsrep_exec_mode= LOCAL_STATE;
  thd->wsrep_affected_rows= 0;
  thd->wsrep_skip_wsrep_GTID= false;
  thd->wsrep_split_flag= false;
  return;
}

/*
  wsrep hton
*/
handlerton *wsrep_hton;


/*
  Registers wsrep hton at commit time if transaction has registered htons
  for supported engine types.

  Hton should not be registered for TOTAL_ORDER operations.

  Registration is needed for both LOCAL_MODE and REPL_RECV transactions to run
  commit in 2pc so that wsrep position gets properly recorded in storage
  engines.

  Note that all hton calls should immediately return for threads that are
  in REPL_RECV mode as their states are controlled by wsrep appliers or
  replaying code. Only threads in LOCAL_MODE should run wsrep callbacks
  from hton methods.
*/
void wsrep_register_hton(THD* thd, bool all)
{
  if (WSREP(thd) && thd->wsrep_exec_mode != TOTAL_ORDER &&
      !thd->wsrep_apply_toi)
  {
    if (thd->wsrep_exec_mode == LOCAL_STATE      &&
        (thd_sql_command(thd) == SQLCOM_OPTIMIZE ||
        thd_sql_command(thd) == SQLCOM_ANALYZE   ||
        thd_sql_command(thd) == SQLCOM_REPAIR)   &&
            thd->lex->no_write_to_binlog == 1)
    {
        WSREP_DEBUG("Skipping wsrep_register_hton for LOCAL sql admin command : %s",
                thd->query());
        return;
    }

    THD_TRANS *trans=all ? &thd->transaction.all : &thd->transaction.stmt;
    for (Ha_trx_info *i= trans->ha_list; i; i = i->next())
    {
      if ((i->ht()->db_type == DB_TYPE_INNODB) ||
	  (i->ht()->db_type == DB_TYPE_TOKUDB))
      {
        trans_register_ha(thd, all, wsrep_hton);

        /* follow innodb read/write settting
         * but, as an exception: CTAS with empty result set will not be
         * replicated unless we declare wsrep hton as read/write here
	 */
        if (i->is_trx_read_write() ||
            (thd->lex->sql_command == SQLCOM_CREATE_TABLE &&
             thd->wsrep_exec_mode == LOCAL_STATE))
        {
          thd->ha_data[wsrep_hton->slot].ha_info[all].set_trx_read_write();
        }
        break;
      }
    }
  }
}

/*
  Calls wsrep->post_commit() for locally executed transactions that have
  got seqno from provider (must commit) and don't require replaying.
 */
void wsrep_post_commit(THD* thd, bool all)
{
  if (!WSREP(thd)) return;

  switch (thd->wsrep_exec_mode)
  {
    case LOCAL_COMMIT:
    {
      DBUG_ASSERT(thd->wsrep_trx_meta.gtid.seqno != WSREP_SEQNO_UNDEFINED);
      if (wsrep && wsrep->post_commit(wsrep, &thd->wsrep_ws_handle))
      {
        DBUG_PRINT("wsrep", ("set committed fail"));
        WSREP_WARN("set committed fail: %llu %d",
                   (long long)thd->real_id, thd->get_stmt_da()->status());
      }
      wsrep_cleanup_transaction(thd);
      break;
    }
    case LOCAL_STATE:
    {
      /* non-InnoDB statements may have populated events in stmt cache
        => cleanup
      */
      WSREP_DEBUG("cleanup transaction for LOCAL_STATE");
      /*
        Run post-rollback hook to clean up in the case if
        some keys were populated for the transaction in provider
        but during commit time there was no write set to replicate.
        This may happen when client sets the SAVEPOINT and immediately
        rolls back to savepoint after first operation.
      */
      if (all && thd->wsrep_conflict_state != MUST_REPLAY &&
          wsrep && wsrep->post_rollback(wsrep, &thd->wsrep_ws_handle))
      {
        WSREP_WARN("post_rollback fail: %llu %d",
		(long long)thd->thread_id, thd->get_stmt_da()->status());
      }
      wsrep_cleanup_transaction(thd);
      break;
    }
    default: break;
  }
}

/*
  wsrep exploits binlog's caches even if binlogging itself is not
  activated. In such case connection close needs calling
  actual binlog's method.
  Todo: split binlog hton from its caches to use ones by wsrep
  without referring to binlog's stuff.
*/
static int
wsrep_close_connection(handlerton*  hton, THD* thd)
{
  DBUG_ENTER("wsrep_close_connection");

  if (thd->wsrep_exec_mode == REPL_RECV)
  {
    DBUG_RETURN(0);
  }

  if (wsrep_emulate_bin_log && thd_get_ha_data(thd, binlog_hton) != NULL)
    binlog_hton->close_connection (binlog_hton, thd);
  DBUG_RETURN(0);
}

/*
  prepare/wsrep_run_wsrep_commit can fail in two ways
  - certification test or an equivalent. As a result,
    the current transaction just rolls back
    Error codes:
           WSREP_TRX_CERT_FAIL, WSREP_TRX_SIZE_EXCEEDED, WSREP_TRX_ERROR
  - a post-certification failure makes this server unable to
    commit its own WS and therefore the server must abort
*/
static int wsrep_prepare(handlerton *hton, THD *thd, bool all)
{
  DBUG_ENTER("wsrep_prepare");

  if (thd->wsrep_exec_mode == REPL_RECV)
  {
    DBUG_RETURN(0);
  }

  DBUG_ASSERT(thd->ha_data[wsrep_hton->slot].ha_info[all].is_trx_read_write());
  DBUG_ASSERT(thd->wsrep_exec_mode == LOCAL_STATE);
  DBUG_ASSERT(thd->wsrep_trx_meta.gtid.seqno == WSREP_SEQNO_UNDEFINED);

  if ((all ||
      !thd_test_options(thd, OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN)) &&
      (thd->variables.wsrep_on && !wsrep_trans_cache_is_empty(thd)))
  {
    int res= wsrep_run_wsrep_commit(thd, all);
    if (res != 0)
    {
      if (res == WSREP_TRX_SIZE_EXCEEDED)
        res= EMSGSIZE;
      else
        res= EDEADLK;                           // for a better error message
    }
    DBUG_RETURN (res);
  }
  DBUG_RETURN(0);
}

/*
  Empty callbacks to support SAVEPOINT callbacks.
*/

static int wsrep_savepoint_set(handlerton *hton, THD *thd,  void *sv)
{
  DBUG_ENTER("wsrep_savepoint_set");
  DBUG_RETURN(0);
}

static int wsrep_savepoint_rollback(handlerton *hton, THD *thd, void *sv)
{
  DBUG_ENTER("wsrep_savepoint_rollback");
  DBUG_RETURN(0);
}

static int wsrep_rollback(handlerton *hton, THD *thd, bool all)
{
  DBUG_ENTER("wsrep_rollback");

  if (thd->wsrep_exec_mode == REPL_RECV)
  {
    DBUG_RETURN(0);
  }

  mysql_mutex_lock(&thd->LOCK_thd_data);
  switch (thd->wsrep_exec_mode)
  {
  case TOTAL_ORDER:
  case REPL_RECV:
      mysql_mutex_unlock(&thd->LOCK_thd_data);
      WSREP_DEBUG("Avoiding wsrep rollback for failed DDL: %s", thd->query());
      DBUG_RETURN(0);
  default: break;
  }

  if ((all || !thd_test_options(thd, OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN)) &&
      thd->variables.wsrep_on && thd->wsrep_conflict_state != MUST_REPLAY)
  {
    if (wsrep && wsrep->post_rollback(wsrep, &thd->wsrep_ws_handle))
    {
      DBUG_PRINT("wsrep", ("setting rollback fail"));
      WSREP_ERROR("settting rollback fail: thd: %llu, schema: %s, SQL: %s",
                  (long long)thd->real_id, (thd->db ? thd->db : "(null)"),
                  thd->query());
    }
    wsrep_cleanup_transaction(thd);
  }
  mysql_mutex_unlock(&thd->LOCK_thd_data);
  DBUG_RETURN(0);
}

int wsrep_commit(handlerton *hton, THD *thd, bool all)
{
  DBUG_ENTER("wsrep_commit");

  if (thd->wsrep_exec_mode == REPL_RECV)
  {
    DBUG_RETURN(0);
  }

  mysql_mutex_lock(&thd->LOCK_thd_data);
  if ((all || !thd_test_options(thd, OPTION_NOT_AUTOCOMMIT | OPTION_BEGIN)) &&
      (thd->variables.wsrep_on && thd->wsrep_conflict_state != MUST_REPLAY))
  {
    if (thd->wsrep_exec_mode == LOCAL_COMMIT)
    {
      DBUG_ASSERT(thd->ha_data[wsrep_hton->slot].ha_info[all].is_trx_read_write());
      /*
        Call to wsrep->post_commit() (moved to wsrep_post_commit()) must
        be done only after commit has done for all involved htons.
      */
      DBUG_PRINT("wsrep", ("commit"));
    }
    else
    {
      /*
        Transaction didn't go through wsrep->pre_commit() so just roll back
        possible changes to clean state.
      */
      if (WSREP_PROVIDER_EXISTS) {
        if (wsrep && wsrep->post_rollback(wsrep, &thd->wsrep_ws_handle))
        {
          DBUG_PRINT("wsrep", ("setting rollback fail"));
          WSREP_ERROR("settting rollback fail: thd: %llu, schema: %s, SQL: %s",
                      (long long)thd->real_id, (thd->db ? thd->db : "(null)"),
                      thd->query());
        }
      }
      wsrep_cleanup_transaction(thd);
    }
  }
  mysql_mutex_unlock(&thd->LOCK_thd_data);
  DBUG_RETURN(0);
}


extern Rpl_filter* binlog_filter;
extern my_bool opt_log_slave_updates;

enum wsrep_trx_status
wsrep_run_wsrep_commit(THD *thd, bool all)
{
  int rcode= -1;
  size_t data_len= 0;
  IO_CACHE *cache;
  int replay_round= 0;
  DBUG_ENTER("wsrep_run_wsrep_commit");

  if (thd->get_stmt_da()->is_error()) {
    WSREP_DEBUG("commit issue, error: %d %s",
                thd->get_stmt_da()->sql_errno(), thd->get_stmt_da()->message());
  }

  DEBUG_SYNC(thd, "wsrep_before_replication");

  if (thd->slave_thread && !opt_log_slave_updates) DBUG_RETURN(WSREP_TRX_OK);

  if (thd->wsrep_exec_mode == REPL_RECV) {

    mysql_mutex_lock(&thd->LOCK_thd_data);
    if (thd->wsrep_conflict_state == MUST_ABORT) {
      if (wsrep_debug)
        WSREP_INFO("WSREP: must abort for BF");
      DBUG_PRINT("wsrep", ("BF apply commit fail"));
      thd->wsrep_conflict_state = NO_CONFLICT;
      mysql_mutex_unlock(&thd->LOCK_thd_data);
      //
      // TODO: test all calls of the rollback.
      // rollback must happen automagically innobase_rollback(hton, thd, 1);
      //
      DBUG_RETURN(WSREP_TRX_ERROR);
    }
    mysql_mutex_unlock(&thd->LOCK_thd_data);
  }

  if (thd->wsrep_exec_mode != LOCAL_STATE) DBUG_RETURN(WSREP_TRX_OK);

  if (thd->wsrep_consistency_check == CONSISTENCY_CHECK_RUNNING) {
    WSREP_DEBUG("commit for consistency check: %s", thd->query());
    DBUG_RETURN(WSREP_TRX_OK);
  }

  DBUG_PRINT("wsrep", ("replicating commit"));

  mysql_mutex_lock(&thd->LOCK_thd_data);
  if (thd->wsrep_conflict_state == MUST_ABORT) {
    DBUG_PRINT("wsrep", ("replicate commit fail"));
    thd->wsrep_conflict_state = ABORTED;
    mysql_mutex_unlock(&thd->LOCK_thd_data);
    if (wsrep_debug) {
      WSREP_INFO("innobase_commit, abort %s",
                 (thd->query()) ? thd->query() : "void");
    }
    DBUG_RETURN(WSREP_TRX_CERT_FAIL);
  }

  mysql_mutex_lock(&LOCK_wsrep_replaying);

  while (wsrep_replaying > 0                       &&
         thd->wsrep_conflict_state == NO_CONFLICT  &&
         thd->killed == NOT_KILLED            &&
         !shutdown_in_progress)
  {

    mysql_mutex_unlock(&LOCK_wsrep_replaying);
    mysql_mutex_unlock(&thd->LOCK_thd_data);

    mysql_mutex_lock(&thd->mysys_var->mutex);
    thd_proc_info(thd, "wsrep waiting on replaying");
    thd->mysys_var->current_mutex= &LOCK_wsrep_replaying;
    thd->mysys_var->current_cond=  &COND_wsrep_replaying;
    mysql_mutex_unlock(&thd->mysys_var->mutex);

    mysql_mutex_lock(&LOCK_wsrep_replaying);
    // Using timedwait is a hack to avoid deadlock in case if BF victim
    // misses the signal.
    struct timespec wtime = {0, 1000000};
    mysql_cond_timedwait(&COND_wsrep_replaying, &LOCK_wsrep_replaying,
			 &wtime);

    if (replay_round++ % 100000 == 0)
      WSREP_DEBUG("commit waiting for replaying: replayers %d, thd: %lld "
                  "conflict: %d (round: %d)",
		  wsrep_replaying, (longlong) thd->thread_id,
                  thd->wsrep_conflict_state, replay_round);

    mysql_mutex_unlock(&LOCK_wsrep_replaying);

    mysql_mutex_lock(&thd->mysys_var->mutex);
    thd->mysys_var->current_mutex= 0;
    thd->mysys_var->current_cond=  0;
    mysql_mutex_unlock(&thd->mysys_var->mutex);

    mysql_mutex_lock(&thd->LOCK_thd_data);
    mysql_mutex_lock(&LOCK_wsrep_replaying);
  }
  mysql_mutex_unlock(&LOCK_wsrep_replaying);

  if (thd->wsrep_conflict_state == MUST_ABORT) {
    DBUG_PRINT("wsrep", ("replicate commit fail"));
    thd->wsrep_conflict_state = ABORTED;
    mysql_mutex_unlock(&thd->LOCK_thd_data);
    WSREP_DEBUG("innobase_commit abort after replaying wait %s",
                (thd->query()) ? thd->query() : "void");
    DBUG_RETURN(WSREP_TRX_CERT_FAIL);
  }

  wsrep_thd_set_query_state(thd, QUERY_COMMITTING);
  mysql_mutex_unlock(&thd->LOCK_thd_data);

  cache = get_trans_log(thd);
  rcode = 0;
  if (cache) {
    thd->binlog_flush_pending_rows_event(true);
    rcode = wsrep_write_cache(wsrep, thd, cache, &data_len);
    if (WSREP_OK != rcode) {
      WSREP_ERROR("rbr write fail, data_len: %zu, %d", data_len, rcode);
      DBUG_RETURN(WSREP_TRX_SIZE_EXCEEDED);
    }
  }

  if (data_len == 0)
  {
    if (thd->get_stmt_da()->is_ok()              &&
        thd->get_stmt_da()->affected_rows() > 0  &&
        !binlog_filter->is_on())
    {
      WSREP_DEBUG("empty rbr buffer, query: %s, "
                 "affected rows: %llu, "
                 "changed tables: %d, "
                 "sql_log_bin: %d, "
                 "wsrep status (%d %d %d)",
                 thd->query(), thd->get_stmt_da()->affected_rows(),
                 stmt_has_updated_trans_table(thd), thd->variables.sql_log_bin,
                 thd->wsrep_exec_mode, thd->wsrep_query_state,
                 thd->wsrep_conflict_state);
    }
    else
    {
      WSREP_DEBUG("empty rbr buffer, query: %s", thd->query());
    }
    wsrep_thd_set_query_state(thd, QUERY_EXEC);
    DBUG_RETURN(WSREP_TRX_OK);
  }

  if (WSREP_UNDEFINED_TRX_ID == thd->wsrep_ws_handle.trx_id)
  {
    /*
      Async replication slave may have applied some non-innodb workload,
      and then has written replication "meta data" into gtid_slave_pos
      innodb table. Writes to gtid_slave_pos must not be replicated,
      but this activity has caused that innodb hton is registered for this
       transaction, but no wsrep keys have been appended.
       We enter in this code path, because IO cache has events for non-innodb
       tables.
       => we should not treat it an error if trx is not introduced for provider
    */
    if (thd->system_thread == SYSTEM_THREAD_SLAVE_SQL)
    {
      WSREP_DEBUG("skipping wsrep replication for async slave, error not raised");
      DBUG_RETURN(WSREP_TRX_OK);
    }

    WSREP_WARN("SQL statement was ineffective  thd: %llu  buf: %zu\n"
               "schema: %s \n"
	       "QUERY: %s\n"
	       " => Skipping replication",
	       (ulonglong) thd->thread_id, data_len,
               (thd->db ? thd->db : "(null)"), thd->query());

    rcode = WSREP_TRX_FAIL;
  }
  else if (!rcode)
  {
    if (WSREP_OK == rcode && wsrep)
      rcode = wsrep->pre_commit(wsrep,
                                (wsrep_conn_id_t)thd->thread_id,
                                &thd->wsrep_ws_handle,
                                WSREP_FLAG_COMMIT |
                                ((thd->wsrep_PA_safe) ?
                                 0ULL : WSREP_FLAG_PA_UNSAFE),
                                &thd->wsrep_trx_meta);

    if (rcode == WSREP_TRX_MISSING) {
      WSREP_WARN("Transaction missing in provider, thd: %lld  schema: %s  SQL: %s",
                 (longlong) thd->thread_id,
                 (thd->db ? thd->db : "(null)"), thd->query());
      rcode = WSREP_TRX_FAIL;
    } else if (rcode == WSREP_BF_ABORT) {
      WSREP_DEBUG("thd: %lld  seqno: %lld  BF aborted by provider, will replay",
                  (longlong) thd->thread_id,
                  (longlong) thd->wsrep_trx_meta.gtid.seqno);
      mysql_mutex_lock(&thd->LOCK_thd_data);
      thd->wsrep_conflict_state = MUST_REPLAY;
      DBUG_ASSERT(wsrep_thd_trx_seqno(thd) > 0);
      mysql_mutex_unlock(&thd->LOCK_thd_data);
      mysql_mutex_lock(&LOCK_wsrep_replaying);
      wsrep_replaying++;
      WSREP_DEBUG("replaying increased: %d, thd: %lld",
                  wsrep_replaying, (longlong) thd->thread_id);
      mysql_mutex_unlock(&LOCK_wsrep_replaying);
    }
  } else {
    WSREP_ERROR("I/O error reading from thd's binlog iocache: "
                "errno=%d, io cache code=%d", my_errno, cache->error);
    DBUG_ASSERT(0); // failure like this can not normally happen
    DBUG_RETURN(WSREP_TRX_ERROR);
  }

  mysql_mutex_lock(&thd->LOCK_thd_data);

  DEBUG_SYNC(thd, "wsrep_after_replication");

  switch(rcode) {
  case 0:
    /*
      About MUST_ABORT: We assume that even if thd conflict state was set
      to MUST_ABORT, underlying transaction was not rolled back or marked
      as deadlock victim in QUERY_COMMITTING state. Conflict state is
      set to NO_CONFLICT and commit proceeds as usual.
    */
    if (thd->wsrep_conflict_state == MUST_ABORT)
        thd->wsrep_conflict_state= NO_CONFLICT;

    if (thd->wsrep_conflict_state != NO_CONFLICT)
    {
      WSREP_WARN("thd: %llu  seqno: %lld  conflict state %d after post commit",
                 (longlong) thd->thread_id,
                 (longlong) thd->wsrep_trx_meta.gtid.seqno,
                 thd->wsrep_conflict_state);
    }
    thd->wsrep_exec_mode= LOCAL_COMMIT;
    DBUG_ASSERT(thd->wsrep_trx_meta.gtid.seqno != WSREP_SEQNO_UNDEFINED);
    /* Override XID iff it was generated by mysql */
    if (thd->transaction.xid_state.xid.get_my_xid())
    {
      wsrep_xid_init(&thd->transaction.xid_state.xid,
                     thd->wsrep_trx_meta.gtid.uuid,
                     thd->wsrep_trx_meta.gtid.seqno);
    }
    DBUG_PRINT("wsrep", ("replicating commit success"));
    break;
  case WSREP_BF_ABORT:
    DBUG_ASSERT(thd->wsrep_trx_meta.gtid.seqno != WSREP_SEQNO_UNDEFINED);
    /* fall through */
  case WSREP_TRX_FAIL:
    WSREP_DEBUG("commit failed for reason: %d", rcode);
    DBUG_PRINT("wsrep", ("replicating commit fail"));

    wsrep_thd_set_query_state(thd, QUERY_EXEC);

    if (thd->wsrep_conflict_state == MUST_ABORT) {
      thd->wsrep_conflict_state= ABORTED;
    }
    else
    {
      WSREP_DEBUG("conflict state: %d", thd->wsrep_conflict_state);
      if (thd->wsrep_conflict_state == NO_CONFLICT)
      {
        thd->wsrep_conflict_state = CERT_FAILURE;
        WSREP_LOG_CONFLICT(NULL, thd, FALSE);
      }
    }
    mysql_mutex_unlock(&thd->LOCK_thd_data);

    DBUG_RETURN(WSREP_TRX_CERT_FAIL);

  case WSREP_SIZE_EXCEEDED:
    WSREP_ERROR("transaction size exceeded");
    mysql_mutex_unlock(&thd->LOCK_thd_data);
    DBUG_RETURN(WSREP_TRX_SIZE_EXCEEDED);
  case WSREP_CONN_FAIL:
    WSREP_ERROR("connection failure");
    mysql_mutex_unlock(&thd->LOCK_thd_data);
    DBUG_RETURN(WSREP_TRX_ERROR);
  default:
    WSREP_ERROR("unknown connection failure");
    mysql_mutex_unlock(&thd->LOCK_thd_data);
    DBUG_RETURN(WSREP_TRX_ERROR);
  }

  wsrep_thd_set_query_state(thd, QUERY_EXEC);
  mysql_mutex_unlock(&thd->LOCK_thd_data);

  DBUG_RETURN(WSREP_TRX_OK);
}


static int wsrep_hton_init(void *p)
{
  wsrep_hton= (handlerton *)p;
  //wsrep_hton->state=opt_bin_log ? SHOW_OPTION_YES : SHOW_OPTION_NO;
  wsrep_hton->state= SHOW_OPTION_YES;
  wsrep_hton->db_type=(legacy_db_type)0;
  wsrep_hton->savepoint_offset= sizeof(my_off_t);
  wsrep_hton->close_connection= wsrep_close_connection;
  wsrep_hton->savepoint_set= wsrep_savepoint_set;
  wsrep_hton->savepoint_rollback= wsrep_savepoint_rollback;
  wsrep_hton->commit= wsrep_commit;
  wsrep_hton->rollback= wsrep_rollback;
  wsrep_hton->prepare= wsrep_prepare;
  wsrep_hton->flags= HTON_NOT_USER_SELECTABLE | HTON_HIDDEN; // todo: fix flags
  return 0;
}


struct st_mysql_storage_engine wsrep_storage_engine=
{ MYSQL_HANDLERTON_INTERFACE_VERSION };


maria_declare_plugin(wsrep)
{
  MYSQL_STORAGE_ENGINE_PLUGIN,
  &wsrep_storage_engine,
  "wsrep",
  "Codership Oy",
  "A pseudo storage engine to represent transactions in multi-master "
  "synchornous replication",
  PLUGIN_LICENSE_GPL,
  wsrep_hton_init, /* Plugin Init */
  NULL, /* Plugin Deinit */
  0x0100 /* 1.0 */,
  NULL,                       /* status variables                */
  NULL,                       /* system variables                */
  "1.0",         /* string version */
  MariaDB_PLUGIN_MATURITY_STABLE /* maturity */
}
maria_declare_plugin_end;