~drizzle-trunk/drizzle/development

/* Copyright (C) 2007 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; 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/*

  Implementation for the thread scheduler

*/

#ifdef USE_PRAGMA_INTERFACE

#pragma implementation

#endif

#include <mysql_priv.h>

#include "event.h"

/*

  'Dummy' functions to be used when we don't need any handling for a scheduler

  event

 */

static bool init_dummy(void) {return 0;}

static void post_kill_dummy(THD *thd __attribute__((unused))) {}

static void end_dummy(void) {}

static bool end_thread_dummy(THD *thd __attribute__((unused)),

                             bool cache_thread __attribute__((unused)))

{ return 0; }

/*

  Initialize default scheduler with dummy functions so that setup functions

  only need to declare those that are relvant for their usage

*/

scheduler_functions::scheduler_functions()

  :init(init_dummy),

   init_new_connection_thread(init_new_connection_handler_thread),

   add_connection(0),                           // Must be defined

   post_kill_notification(post_kill_dummy),

   end_thread(end_thread_dummy), end(end_dummy)

{}

static uint created_threads, killed_threads;

static bool kill_pool_threads;

static struct event thd_add_event;

static struct event thd_kill_event;

static pthread_mutex_t LOCK_thd_add;    /* protects thds_need_adding */

static LIST *thds_need_adding;    /* list of thds to add to libevent queue */

static int thd_add_pipe[2]; /* pipe to signal add a connection to libevent*/

static int thd_kill_pipe[2]; /* pipe to signal kill a connection in libevent */

/*

  LOCK_event_loop protects the non-thread safe libevent calls (event_add and 

  event_del) and thds_need_processing and thds_waiting_for_io.

*/

static pthread_mutex_t LOCK_event_loop;

static LIST *thds_need_processing; /* list of thds that needs some processing */

static LIST *thds_waiting_for_io; /* list of thds with added events */

pthread_handler_t libevent_thread_proc(void *arg);

static void libevent_end();

static bool libevent_needs_immediate_processing(THD *thd);

static void libevent_connection_close(THD *thd);

static bool libevent_should_close_connection(THD* thd);

static void libevent_thd_add(THD* thd);

void libevent_io_callback(int Fd, short Operation, void *ctx);

void libevent_add_thd_callback(int Fd, short Operation, void *ctx);

void libevent_kill_thd_callback(int Fd, short Operation, void *ctx);

/*

  Create a pipe and set to non-blocking.

  Returns true if there is an error.

*/

static bool init_pipe(int pipe_fds[])

{

  int flags;

  return pipe(pipe_fds) < 0 ||

          (flags= fcntl(pipe_fds[0], F_GETFL)) == -1 ||

          fcntl(pipe_fds[0], F_SETFL, flags | O_NONBLOCK) == -1;

          (flags= fcntl(pipe_fds[1], F_GETFL)) == -1 ||

          fcntl(pipe_fds[1], F_SETFL, flags | O_NONBLOCK) == -1;

}

/*

  thd_scheduler keeps the link between THD and events.

  It's embedded in the THD class.

*/

thd_scheduler::thd_scheduler()

  : logged_in(false), io_event(NULL), thread_attached(false)

{  

  dbug_explain_buf[0]= 0;

}

thd_scheduler::~thd_scheduler()

{

  my_free(io_event, MYF(MY_ALLOW_ZERO_PTR));

}

bool thd_scheduler::init(THD *parent_thd)

{

  io_event=

    (struct event*)my_malloc(sizeof(*io_event),MYF(MY_ZEROFILL|MY_WME));

  if (!io_event)

  {

    sql_print_error("Memory allocation error in thd_scheduler::init\n");

    return true;

  }

  event_set(io_event, parent_thd->net.vio->sd, EV_READ, 

            libevent_io_callback, (void*)parent_thd);

  list.data= parent_thd;

  return false;

}

/*

  Attach/associate the connection with the OS thread, for command processing.

*/

bool thd_scheduler::thread_attach()

{

  assert(!thread_attached);

  THD* thd = (THD*)list.data;

  if (libevent_should_close_connection(thd) ||

      setup_connection_thread_globals(thd))

  {

    return true;

  }

  my_errno= 0;

  thd->mysys_var->abort= 0;

  thread_attached= true;

  swap_dbug_explain();

  return false;

}

/*

  Detach/disassociate the connection with the OS thread.

*/

void thd_scheduler::thread_detach()

{

  if (thread_attached)

  {

    THD* thd = (THD*)list.data;

    thd->mysys_var= NULL;

    thread_attached= false;

    swap_dbug_explain();

  }

}

/*

  Swap the THD's dbug explain_buffer with the OS thread's dbug explain buffer.

  This is used to preserve the SESSION DEBUG variable, which is mapped to the OS 

  thread during a command, but each command is handled by a different thread.

*/

void thd_scheduler::swap_dbug_explain()

{

  char buffer[sizeof(dbug_explain_buf)];

  memcpy(dbug_explain_buf, buffer, sizeof(buffer));

}

/**

  Create all threads for the thread pool

  NOTES

    After threads are created we wait until all threads has signaled that

    they have started before we return

  RETURN

    0  ok

    1  We got an error creating the thread pool

       In this case we will abort all created threads

*/

static bool libevent_init(void)

{

  uint i;

  event_init();

  created_threads= 0;

  killed_threads= 0;

  kill_pool_threads= false;

  pthread_mutex_init(&LOCK_event_loop, NULL);

  pthread_mutex_init(&LOCK_thd_add, NULL);

  /* set up the pipe used to add new thds to the event pool */

  if (init_pipe(thd_add_pipe))

  {

    sql_print_error("init_pipe(thd_add_pipe) error in libevent_init\n");

    return(1);

  }

  /* set up the pipe used to kill thds in the event queue */

  if (init_pipe(thd_kill_pipe))

  {

    sql_print_error("init_pipe(thd_kill_pipe) error in libevent_init\n");

    close(thd_add_pipe[0]);

    close(thd_add_pipe[1]);

    return(1);

  }

  event_set(&thd_add_event, thd_add_pipe[0], EV_READ|EV_PERSIST,

            libevent_add_thd_callback, NULL);

  event_set(&thd_kill_event, thd_kill_pipe[0], EV_READ|EV_PERSIST,

            libevent_kill_thd_callback, NULL);

 if (event_add(&thd_add_event, NULL) || event_add(&thd_kill_event, NULL))

 {

   sql_print_error("thd_add_event event_add error in libevent_init\n");

   libevent_end();

   return(1);

 }

  /* Set up the thread pool */

  created_threads= killed_threads= 0;

  pthread_mutex_lock(&LOCK_thread_count);

  for (i= 0; i < thread_pool_size; i++)

  {

    pthread_t thread;

    int error;

    if ((error= pthread_create(&thread, &connection_attrib,

                               libevent_thread_proc, 0)))

    {

      sql_print_error("Can't create completion port thread (error %d)",

                      error);

      pthread_mutex_unlock(&LOCK_thread_count);

      libevent_end();                      // Cleanup

      return(true);

    }

  }

  /* Wait until all threads are created */

  while (created_threads != thread_pool_size)

    pthread_cond_wait(&COND_thread_count,&LOCK_thread_count);

  pthread_mutex_unlock(&LOCK_thread_count);

  return(false);

}

/*

  This is called when data is ready on the socket.

  NOTES

    This is only called by the thread that owns LOCK_event_loop.

    We add the thd that got the data to thds_need_processing, and 

    cause the libevent event_loop() to terminate. Then this same thread will

    return from event_loop and pick the thd value back up for processing.

*/

void libevent_io_callback(int, short, void *ctx)

{    

  safe_mutex_assert_owner(&LOCK_event_loop);

  THD *thd= (THD*)ctx;

  thds_waiting_for_io= list_delete(thds_waiting_for_io, &thd->scheduler.list);

  thds_need_processing= list_add(thds_need_processing, &thd->scheduler.list);

}

/*

  This is called when we have a thread we want to be killed.

  NOTES

    This is only called by the thread that owns LOCK_event_loop.

*/

void libevent_kill_thd_callback(int Fd, short, void*)

{    

  safe_mutex_assert_owner(&LOCK_event_loop);

  /* clear the pending events */

  char c;

  while (read(Fd, &c, sizeof(c)) == sizeof(c))

  {}

  LIST* list= thds_waiting_for_io;

  while (list)

  {

    THD *thd= (THD*)list->data;

    list= list_rest(list);

    if (thd->killed == THD::KILL_CONNECTION)

    {

      /*

        Delete from libevent and add to the processing queue.

      */

      event_del(thd->scheduler.io_event);

      thds_waiting_for_io= list_delete(thds_waiting_for_io,

                                       &thd->scheduler.list);

      thds_need_processing= list_add(thds_need_processing,

                                     &thd->scheduler.list);

    }

  }

}

/*

  This is used to add connections to the pool. This callback is invoked from

  the libevent event_loop() call whenever the thd_add_pipe[1] pipe has a byte

  written to it.

  NOTES

    This is only called by the thread that owns LOCK_event_loop.

*/

void libevent_add_thd_callback(int Fd, short, void *)

{ 

  safe_mutex_assert_owner(&LOCK_event_loop);

  /* clear the pending events */

  char c;

  while (read(Fd, &c, sizeof(c)) == sizeof(c))

  {}

  pthread_mutex_lock(&LOCK_thd_add);

  while (thds_need_adding)

  {

    /* pop the first thd off the list */

    THD* thd= (THD*)thds_need_adding->data;

    thds_need_adding= list_delete(thds_need_adding, thds_need_adding);

    pthread_mutex_unlock(&LOCK_thd_add);

    if (!thd->scheduler.logged_in || libevent_should_close_connection(thd))

    {

      /*

        Add thd to thds_need_processing list. If it needs closing we'll close

        it outside of event_loop().

      */

      thds_need_processing= list_add(thds_need_processing,

                                     &thd->scheduler.list);

    }

    else

    {

      /* Add to libevent */

      if (event_add(thd->scheduler.io_event, NULL))

      {

        sql_print_error("event_add error in libevent_add_thd_callback\n");

        libevent_connection_close(thd);

      } 

      else

      {

        thds_waiting_for_io= list_add(thds_waiting_for_io,

                                      &thd->scheduler.list);

      }

    }

    pthread_mutex_lock(&LOCK_thd_add);

  }

  pthread_mutex_unlock(&LOCK_thd_add);

}

/**

  Notify the thread pool about a new connection

  NOTES

    LOCK_thread_count is locked on entry. This function MUST unlock it!

*/

static void libevent_add_connection(THD *thd)

{

  if (thd->scheduler.init(thd))

  {

    sql_print_error("Scheduler init error in libevent_add_new_connection\n");

    pthread_mutex_unlock(&LOCK_thread_count);

    libevent_connection_close(thd);

    return;

  }

  threads.append(thd);

  libevent_thd_add(thd);

  pthread_mutex_unlock(&LOCK_thread_count);

  return;

}

/**

  @brief Signal a waiting connection it's time to die.

  @details This function will signal libevent the THD should be killed.

    Either the global LOCK_thd_count or the THD's LOCK_delete must be locked

    upon entry.

  @param[in]  thd The connection to kill

*/

static void libevent_post_kill_notification(THD *)

{

  /*

    Note, we just wake up libevent with an event that a THD should be killed,

    It will search its list of thds for thd->killed ==  KILL_CONNECTION to

    find the THDs it should kill.

    So we don't actually tell it which one and we don't actually use the

    THD being passed to us, but that's just a design detail that could change

    later.

  */

  char c= 0;

  write(thd_kill_pipe[1], &c, sizeof(c));

}

/*

  Close and delete a connection.

*/

static void libevent_connection_close(THD *thd)

{

  thd->killed= THD::KILL_CONNECTION;          // Avoid error messages

  if (thd->net.vio->sd >= 0)                  // not already closed

  {

    end_connection(thd);

    close_connection(thd, 0, 1);

  }

  thd->scheduler.thread_detach();

  unlink_thd(thd);   /* locks LOCK_thread_count and deletes thd */

  pthread_mutex_unlock(&LOCK_thread_count);

  return;

}

/*

  Returns true if we should close and delete a THD connection.

*/

static bool libevent_should_close_connection(THD* thd)

{

  return thd->net.error ||

         thd->net.vio == 0 ||

         thd->killed == THD::KILL_CONNECTION;

}

/*

  libevent_thread_proc is the outer loop of each thread in the thread pool.

  These procs only return/terminate on shutdown (kill_pool_threads == true).

*/

pthread_handler_t libevent_thread_proc(void *arg __attribute__((unused)))

{

  if (init_new_connection_handler_thread())

  {

    my_thread_global_end();

    sql_print_error("libevent_thread_proc: my_thread_init() failed\n");

    exit(1);

  }

  /*

    Signal libevent_init() when all threads has been created and are ready to

    receive events.

  */

  (void) pthread_mutex_lock(&LOCK_thread_count);

  created_threads++;

  if (created_threads == thread_pool_size)

    (void) pthread_cond_signal(&COND_thread_count);

  (void) pthread_mutex_unlock(&LOCK_thread_count);

  for (;;)

  {

    THD *thd= NULL;

    (void) pthread_mutex_lock(&LOCK_event_loop);

    /* get thd(s) to process */

    while (!thds_need_processing)

    {

      if (kill_pool_threads)

      {

        /* the flag that we should die has been set */

        (void) pthread_mutex_unlock(&LOCK_event_loop);

        goto thread_exit;

      }

      event_loop(EVLOOP_ONCE);

    }

    /* pop the first thd off the list */

    thd= (THD*)thds_need_processing->data;

    thds_need_processing= list_delete(thds_need_processing,

                                      thds_need_processing);

    (void) pthread_mutex_unlock(&LOCK_event_loop);

    /* now we process the connection (thd) */

    /* set up the thd<->thread links. */

    thd->thread_stack= (char*) &thd;

    if (thd->scheduler.thread_attach())

    {

      libevent_connection_close(thd);

      continue;

    }

    /* is the connection logged in yet? */

    if (!thd->scheduler.logged_in)

    {

      if (login_connection(thd))

      {

        /* Failed to log in */

        libevent_connection_close(thd);

        continue;

      }

      else

      {

        /* login successful */

        thd->scheduler.logged_in= true;

        prepare_new_connection_state(thd);

        if (!libevent_needs_immediate_processing(thd))

          continue; /* New connection is now waiting for data in libevent*/

      }

    }

    do

    {

      /* Process a query */

      if (do_command(thd))

      {

        libevent_connection_close(thd);

        break;

      }

    } while (libevent_needs_immediate_processing(thd));

  }

thread_exit:

  (void) pthread_mutex_lock(&LOCK_thread_count);

  killed_threads++;

  pthread_cond_broadcast(&COND_thread_count);

  (void) pthread_mutex_unlock(&LOCK_thread_count);

  my_thread_end();

  pthread_exit(0);

  return(0);                               /* purify: deadcode */

}

/*

  Returns true if the connection needs immediate processing and false if 

  instead it's queued for libevent processing or closed,

*/

static bool libevent_needs_immediate_processing(THD *thd)

{

  if (libevent_should_close_connection(thd))

  {

    libevent_connection_close(thd);

    return false;

  }

  /*

    If more data in the socket buffer, return true to process another command.

    Note: we cannot add for event processing because the whole request might

    already be buffered and we wouldn't receive an event.

  */

  if (thd->net.vio == 0 || thd->net.vio->read_pos < thd->net.vio->read_end)

    return true;

  thd->scheduler.thread_detach();

  libevent_thd_add(thd);

  return false;

}

/*

  Adds a THD to queued for libevent processing.

  This call does not actually register the event with libevent.

  Instead, it places the THD onto a queue and signals libevent by writing

  a byte into thd_add_pipe, which will cause our libevent_add_thd_callback to

  be invoked which will find the THD on the queue and add it to libevent.

*/

static void libevent_thd_add(THD* thd)

{

  char c=0;

  pthread_mutex_lock(&LOCK_thd_add);

  /* queue for libevent */

  thds_need_adding= list_add(thds_need_adding, &thd->scheduler.list);

  /* notify libevent */

  write(thd_add_pipe[1], &c, sizeof(c));

  pthread_mutex_unlock(&LOCK_thd_add);

}

/**

  Wait until all pool threads have been deleted for clean shutdown

*/

static void libevent_end()

{

  (void) pthread_mutex_lock(&LOCK_thread_count);

  kill_pool_threads= true;

  while (killed_threads != created_threads)

  {

    /* wake up the event loop */

    char c= 0;

    write(thd_add_pipe[1], &c, sizeof(c));

    pthread_cond_wait(&COND_thread_count, &LOCK_thread_count);

  }

  (void) pthread_mutex_unlock(&LOCK_thread_count);

  event_del(&thd_add_event);

  close(thd_add_pipe[0]);

  close(thd_add_pipe[1]);

  event_del(&thd_kill_event);

  close(thd_kill_pipe[0]);

  close(thd_kill_pipe[1]);

  (void) pthread_mutex_destroy(&LOCK_event_loop);

  (void) pthread_mutex_destroy(&LOCK_thd_add);

  return;

}

void pool_of_threads_scheduler(scheduler_functions* func)

{

  func->max_threads= thread_pool_size;

  func->init= libevent_init;

  func->end=  libevent_end;

  func->post_kill_notification= libevent_post_kill_notification;

  func->add_connection= libevent_add_connection;

}