plugin/semisync/semisync_slave_plugin.cc

/* Copyright (C) 2007 Google Inc.
   Copyright (c) 2008, 2021, Oracle and/or its affiliates.
   Copyright (c) 2008, 2021, Oracle and/or its affiliates.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License, version 2.0,
   as published by the Free Software Foundation.

   This program is also distributed with certain software (including
   but not limited to OpenSSL) that is licensed under separate terms,
   as designated in a particular file or component or in included license
   documentation.  The authors of MySQL hereby grant you an additional
   permission to link the program and your derivative works with the
   separately licensed software that they have included with MySQL.

   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, version 2.0, 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 St, Fifth Floor, Boston, MA  02110-1301  USA */


#include "semisync_slave.h"
#include <mysql.h>
#include <mysqld_error.h>

ReplSemiSyncSlave repl_semisync;

/*
  indicate whether or not the slave should send a reply to the master.

  This is set to true in repl_semi_slave_read_event if the current
  event read is the last event of a transaction. And the value is
  checked in repl_semi_slave_queue_event.
*/
bool semi_sync_need_reply= false;

C_MODE_START

int repl_semi_reset_slave(Binlog_relay_IO_param *param)
{
  // TODO: reset semi-sync slave status here
  return 0;
}

int repl_semi_slave_request_dump(Binlog_relay_IO_param *param,
				 uint32 flags)
{
  MYSQL *mysql= param->mysql;
  MYSQL_RES *res= 0;
#ifndef NDEBUG
  MYSQL_ROW row= NULL;
#endif
  const char *query;
  uint mysql_error= 0;

  if (!repl_semisync.getSlaveEnabled())
    return 0;

  /* Check if master server has semi-sync plugin installed */
  query= "SELECT @@global.rpl_semi_sync_master_enabled";
  if (mysql_real_query(mysql, query, static_cast<ulong>(strlen(query))) ||
      !(res= mysql_store_result(mysql)))
  {
    mysql_error= mysql_errno(mysql);
    if (mysql_error != ER_UNKNOWN_SYSTEM_VARIABLE)
    {
      sql_print_error("Execution failed on master: %s; error %d", query, mysql_error);
      return 1;
    }
  }
  else
  {
#ifndef NDEBUG
    row=
#endif
      mysql_fetch_row(res);
  }

  assert(mysql_error == ER_UNKNOWN_SYSTEM_VARIABLE ||
         strtoul(row[0], 0, 10) == 0 || strtoul(row[0], 0, 10) == 1);

  if (mysql_error == ER_UNKNOWN_SYSTEM_VARIABLE)
  {
    /* Master does not support semi-sync */
    sql_print_warning("Master server does not support semi-sync, "
                      "fallback to asynchronous replication");
    rpl_semi_sync_slave_status= 0;
    mysql_free_result(res);
    return 0;
  }
  mysql_free_result(res);

  /*
    Tell master dump thread that we want to do semi-sync
    replication
  */
  query= "SET @rpl_semi_sync_slave= 1";
  if (mysql_real_query(mysql, query, static_cast<ulong>(strlen(query))))
  {
    sql_print_error("Set 'rpl_semi_sync_slave=1' on master failed");
    return 1;
  }
  mysql_free_result(mysql_store_result(mysql));
  rpl_semi_sync_slave_status= 1;
  return 0;
}

int repl_semi_slave_read_event(Binlog_relay_IO_param *param,
			       const char *packet, unsigned long len,
			       const char **event_buf, unsigned long *event_len)
{
  if (rpl_semi_sync_slave_status)
    return repl_semisync.slaveReadSyncHeader(packet, len,
					     &semi_sync_need_reply,
					     event_buf, event_len);
  *event_buf= packet;
  *event_len= len;
  return 0;
}

int repl_semi_slave_queue_event(Binlog_relay_IO_param *param,
				const char *event_buf,
				unsigned long event_len,
				uint32 flags)
{
  if (rpl_semi_sync_slave_status && semi_sync_need_reply)
  {
    /*
      We deliberately ignore the error in slaveReply, such error
      should not cause the slave IO thread to stop, and the error
      messages are already reported.
    */
    (void) repl_semisync.slaveReply(param->mysql,
                                    param->master_log_name,
                                    param->master_log_pos);
  }
  return 0;
}

int repl_semi_slave_io_start(Binlog_relay_IO_param *param)
{
  return repl_semisync.slaveStart(param);
}

int repl_semi_slave_io_end(Binlog_relay_IO_param *param)
{
  return repl_semisync.slaveStop(param);
}

int repl_semi_slave_sql_start(Binlog_relay_IO_param *param)
{
  return 0;
}

int repl_semi_slave_sql_stop(Binlog_relay_IO_param *param, bool aborted)
{
  return 0;
}

C_MODE_END

static void fix_rpl_semi_sync_slave_enabled(MYSQL_THD thd,
					    SYS_VAR *var,
					    void *ptr,
					    const void *val)
{
  *(char *)ptr= *(char *)val;
  repl_semisync.setSlaveEnabled(rpl_semi_sync_slave_enabled != 0);
  return;
}

static void fix_rpl_semi_sync_trace_level(MYSQL_THD thd,
					  SYS_VAR *var,
					  void *ptr,
					  const void *val)
{
  *(unsigned long *)ptr= *(unsigned long *)val;
  repl_semisync.setTraceLevel(rpl_semi_sync_slave_trace_level);
  return;
}

/* plugin system variables */
static MYSQL_SYSVAR_BOOL(enabled, rpl_semi_sync_slave_enabled,
  PLUGIN_VAR_OPCMDARG,
 "Enable semi-synchronous replication slave (disabled by default). ",
  NULL,				   // check
  &fix_rpl_semi_sync_slave_enabled, // update
  0);

static MYSQL_SYSVAR_ULONG(trace_level, rpl_semi_sync_slave_trace_level,
  PLUGIN_VAR_OPCMDARG,
 "The tracing level for semi-sync replication.",
  NULL,				  // check
  &fix_rpl_semi_sync_trace_level, // update
  32, 0, ~0UL, 1);

static SYS_VAR* semi_sync_slave_system_vars[]= {
  MYSQL_SYSVAR(enabled),
  MYSQL_SYSVAR(trace_level),
  NULL,
};


/* plugin status variables */
static SHOW_VAR semi_sync_slave_status_vars[]= {
  {"Rpl_semi_sync_slave_status",
   (char*) &rpl_semi_sync_slave_status, SHOW_BOOL, SHOW_SCOPE_GLOBAL},
  {NULL, NULL, SHOW_BOOL, SHOW_SCOPE_GLOBAL},
};

Binlog_relay_IO_observer relay_io_observer = {
  sizeof(Binlog_relay_IO_observer), // len

  repl_semi_slave_io_start,	// start
  repl_semi_slave_io_end,	// stop
  repl_semi_slave_sql_start,    // start sql thread
  repl_semi_slave_sql_stop,     // stop sql thread
  repl_semi_slave_request_dump,	// request_transmit
  repl_semi_slave_read_event,	// after_read_event
  repl_semi_slave_queue_event,	// after_queue_event
  repl_semi_reset_slave,	// reset
};

static int semi_sync_slave_plugin_init(void *p)
{
  if (repl_semisync.initObject())
    return 1;
  if (register_binlog_relay_io_observer(&relay_io_observer, p))
    return 1;
  return 0;
}

static int semi_sync_slave_plugin_deinit(void *p)
{
  if (unregister_binlog_relay_io_observer(&relay_io_observer, p))
    return 1;
  return 0;
}


struct Mysql_replication semi_sync_slave_plugin= {
  MYSQL_REPLICATION_INTERFACE_VERSION
};

/*
  Plugin library descriptor
*/
mysql_declare_plugin(semi_sync_slave)
{
  MYSQL_REPLICATION_PLUGIN,
  &semi_sync_slave_plugin,
  "rpl_semi_sync_slave",
  "He Zhenxing",
  "Semi-synchronous replication slave",
  PLUGIN_LICENSE_GPL,
  semi_sync_slave_plugin_init, /* Plugin Init */
  semi_sync_slave_plugin_deinit, /* Plugin Deinit */
  0x0100 /* 1.0 */,
  semi_sync_slave_status_vars,	/* status variables */
  semi_sync_slave_system_vars,	/* system variables */
  NULL,                         /* config options */
  0,                            /* flags */
}
mysql_declare_plugin_end;