mariadb/server-tools/instance-manager/guardian.cc

/* Copyright (C) 2004 MySQL AB

   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; either version 2 of the License, or
   (at your option) any later version.

   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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */


#ifdef __GNUC__
#pragma implementation
#endif

#include "guardian.h"
#include "instance_map.h"
#include <string.h>

C_MODE_START

pthread_handler_decl(guardian, arg)
{
  Guardian_thread *guardian_thread= (Guardian_thread *) arg;
  guardian_thread->run();
  return 0;
}

C_MODE_END


Guardian_thread::Guardian_thread(Thread_registry &thread_registry_arg,
                                 Instance_map *instance_map_arg,
                                 uint monitoring_interval_arg) :
  Guardian_thread_args(thread_registry_arg, instance_map_arg,
                       monitoring_interval_arg),
  thread_info(pthread_self())
{
  pthread_mutex_init(&LOCK_guardian, 0);
  thread_registry.register_thread(&thread_info);
  init_alloc_root(&alloc, MEM_ROOT_BLOCK_SIZE, 0);
  guarded_instances= NULL;
}


Guardian_thread::~Guardian_thread()
{
  /* delay guardian destruction to the moment when no one needs it */
  pthread_mutex_lock(&LOCK_guardian);
  free_root(&alloc, MYF(0));
  thread_registry.unregister_thread(&thread_info);
  pthread_mutex_unlock(&LOCK_guardian);
  pthread_mutex_destroy(&LOCK_guardian);
}


/*
  Run guardian thread

  SYNOPSYS
    run()

  DESCRIPTION

    Check for all guarded instances and restart them if needed. If everything
    is fine go and sleep for some time.
*/

void Guardian_thread::run()
{
  Instance *instance;
  LIST *loop;
  int i= 0;

  my_thread_init();

  while (!thread_registry.is_shutdown())
  {
    pthread_mutex_lock(&LOCK_guardian);
    loop= guarded_instances;
    while (loop != NULL)
    {
      instance= (Instance *) loop->data;
      /* instance-> start already checks whether instance is running */
      instance->start();
      loop= loop->next;
    }
    pthread_mutex_unlock(&LOCK_guardian);
    sleep(monitoring_interval);
  }

  my_thread_end();
}


/*
  Start instance guarding

  SYNOPSYS
    guard()
    instance_name      the name of the instance to be guarded
    name_len           the length of the name

  DESCRIPTION

    The instance is added to the list of guarded instances.

  RETURN
    0 - ok
    1 - error occured
*/

int Guardian_thread::guard(const char *instance_name, uint name_len)
{
  LIST *node;
  Instance *instance;

  node= (LIST *) alloc_root(&alloc, sizeof(LIST));
  if (node == NULL)
    return 1;
  instance= instance_map->find(instance_name, name_len);
  /* we store the pointers to instances from the instance_map's MEM_ROOT */
  node->data= (void *) instance;

  pthread_mutex_lock(&LOCK_guardian);
  guarded_instances= list_add(guarded_instances, node);
  pthread_mutex_unlock(&LOCK_guardian);

  return 0;
}


/*
  TODO: perhaps it would make sense to create a pool of the LIST elements
  elements and give them upon request. Now we are loosing a bit of memory when
  guarded instance was stopped and then restarted (since we cannot free just
  a piece of the MEM_ROOT).
*/

int Guardian_thread::stop_guard(const char *instance_name, uint name_len)
{
  LIST *node;
  Instance *instance;

  instance= instance_map->find(instance_name, name_len);

  pthread_mutex_lock(&LOCK_guardian);
  node= guarded_instances;

  while (node != NULL)
  {
    /*
      We compare only pointers, as we always use pointers from the
      instance_map's MEM_ROOT.
    */
    if ((Instance *) node->data == instance)
    {
      guarded_instances= list_delete(guarded_instances, node);
      pthread_mutex_unlock(&LOCK_guardian);
      return 0;
    }
    else
      node= node->next;
  }
  pthread_mutex_unlock(&LOCK_guardian);
  /* if there is nothing to delete it is also fine */
  return 0;
}