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/*
Copyright (c) 2013, 2019, Oracle and/or its affiliates. All rights reserved.
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 <stddef.h>
#include <sys/types.h>
#include <list>
#include <new>
#include "my_compiler.h"
#include "my_dbug.h"
#include "my_inttypes.h"
#include "my_loglevel.h"
#include "my_macros.h"
#include "my_psi_config.h"
#include "my_thread.h"
#include "mysql/components/services/log_builtins.h"
#include "mysql/components/services/mysql_cond_bits.h"
#include "mysql/components/services/mysql_mutex_bits.h"
#include "mysql/components/services/psi_cond_bits.h"
#include "mysql/components/services/psi_mutex_bits.h"
#include "mysql/components/services/psi_thread_bits.h"
#include "mysql/psi/mysql_cond.h"
#include "mysql/psi/mysql_mutex.h"
#include "mysql/psi/mysql_socket.h"
#include "mysql/psi/mysql_thread.h"
#include "mysql/psi/psi_base.h"
#include "mysql_com.h"
#include "mysqld_error.h" // ER_*
#include "pfs_thread_provider.h"
#include "sql/conn_handler/channel_info.h" // Channel_info
#include "sql/conn_handler/connection_handler_impl.h"
#include "sql/conn_handler/connection_handler_manager.h" // Connection_handler_manager
#include "sql/log.h" // Error_log_throttle
#include "sql/mysqld.h" // max_connections
#include "sql/mysqld_thd_manager.h" // Global_THD_manager
#include "sql/protocol_classic.h"
#include "sql/sql_class.h" // THD
#include "sql/sql_connect.h" // close_connection
#include "sql/sql_error.h"
#include "sql/sql_parse.h" // do_command
#include "sql/sql_thd_internal_api.h" // thd_set_thread_stack
#include "thr_mutex.h"
#include "ppi/ppi_thread.h"
// Initialize static members
ulong Per_thread_connection_handler::blocked_pthread_count = 0;
ulong Per_thread_connection_handler::slow_launch_threads = 0;
ulong Per_thread_connection_handler::max_blocked_pthreads = 0;
bool Per_thread_connection_handler::shrink_cache = false;
std::list<Channel_info *>
*Per_thread_connection_handler ::waiting_channel_info_list = NULL;
mysql_mutex_t Per_thread_connection_handler::LOCK_thread_cache;
mysql_cond_t Per_thread_connection_handler::COND_thread_cache;
mysql_cond_t Per_thread_connection_handler::COND_flush_thread_cache;
// Error log throttle for the thread creation failure in add_connection method.
static Error_log_throttle create_thd_err_log_throttle(
Log_throttle ::LOG_THROTTLE_WINDOW_SIZE, ERROR_LEVEL, 0,
"connection_handler",
"Error log throttle: %10lu"
" 'Can't create thread to"
" handle new connection'"
" error(s) suppressed");
/*
Number of pthreads currently being woken up to handle new connections.
Protected by LOCK_thread_cache.
*/
static uint wake_pthread = 0;
#ifdef HAVE_PSI_INTERFACE
static PSI_mutex_key key_LOCK_thread_cache;
static PSI_mutex_info all_per_thread_mutexes[] = {
{&key_LOCK_thread_cache, "LOCK_thread_cache", PSI_FLAG_SINGLETON, 0,
PSI_DOCUMENT_ME}};
static PSI_cond_key key_COND_thread_cache;
static PSI_cond_key key_COND_flush_thread_cache;
static PSI_cond_info all_per_thread_conds[] = {
{&key_COND_thread_cache, "COND_thread_cache", PSI_FLAG_SINGLETON, 0,
PSI_DOCUMENT_ME},
{&key_COND_flush_thread_cache, "COND_flush_thread_cache",
PSI_FLAG_SINGLETON, 0, PSI_DOCUMENT_ME}};
#endif
void Per_thread_connection_handler::init() {
#ifdef HAVE_PSI_INTERFACE
int count = static_cast<int>(array_elements(all_per_thread_mutexes));
mysql_mutex_register("sql", all_per_thread_mutexes, count);
count = static_cast<int>(array_elements(all_per_thread_conds));
mysql_cond_register("sql", all_per_thread_conds, count);
#endif
mysql_mutex_init(key_LOCK_thread_cache, &LOCK_thread_cache,
MY_MUTEX_INIT_FAST);
mysql_cond_init(key_COND_thread_cache, &COND_thread_cache);
mysql_cond_init(key_COND_flush_thread_cache, &COND_flush_thread_cache);
waiting_channel_info_list = new (std::nothrow) std::list<Channel_info *>;
DBUG_ASSERT(waiting_channel_info_list != NULL);
}
void Per_thread_connection_handler::destroy() {
if (waiting_channel_info_list != NULL) {
delete waiting_channel_info_list;
waiting_channel_info_list = NULL;
mysql_mutex_destroy(&LOCK_thread_cache);
mysql_cond_destroy(&COND_thread_cache);
mysql_cond_destroy(&COND_flush_thread_cache);
}
}
/**
Block the current pthread for reuse by new connections.
@retval NULL Too many pthreads blocked already or shutdown in progress.
@retval !NULL Pointer to Channel_info object representing the new connection
to be served by this pthread.
*/
Channel_info *Per_thread_connection_handler::block_until_new_connection() {
Channel_info *new_conn = NULL;
mysql_mutex_lock(&LOCK_thread_cache);
if (blocked_pthread_count < max_blocked_pthreads && !shrink_cache) {
/* Don't kill the pthread, just block it for reuse */
DBUG_PRINT("info", ("Blocking pthread for reuse"));
/*
mysys_var is bound to the physical thread,
so make sure mysys_var->dbug is reset to a clean state
before picking another session in the thread cache.
*/
DBUG_POP();
DBUG_ASSERT(!_db_is_pushed_());
// Block pthread
blocked_pthread_count++;
while (!connection_events_loop_aborted() && !wake_pthread && !shrink_cache)
mysql_cond_wait(&COND_thread_cache, &LOCK_thread_cache);
blocked_pthread_count--;
if (shrink_cache && blocked_pthread_count <= max_blocked_pthreads) {
mysql_cond_signal(&COND_flush_thread_cache);
}
if (wake_pthread) {
wake_pthread--;
if (!waiting_channel_info_list->empty()) {
new_conn = waiting_channel_info_list->front();
waiting_channel_info_list->pop_front();
DBUG_PRINT("info", ("waiting_channel_info_list->pop %p", new_conn));
} else {
DBUG_ASSERT(0); // We should not get here.
}
}
}
mysql_mutex_unlock(&LOCK_thread_cache);
return new_conn;
}
/**
Construct and initialize a THD object for a new connection.
@param channel_info Channel_info object representing the new connection.
Will be destroyed by this function.
@retval NULL Initialization failed.
@retval !NULL Pointer to new THD object for the new connection.
*/
static THD *init_new_thd(Channel_info *channel_info) {
THD *thd = channel_info->create_thd();
if (thd == NULL) {
channel_info->send_error_and_close_channel(ER_OUT_OF_RESOURCES, 0, false);
delete channel_info;
return NULL;
}
thd->set_new_thread_id();
if (channel_info->get_prior_thr_create_utime() != 0) {
/*
A pthread was created to handle this connection:
increment slow_launch_threads counter if it took more than
slow_launch_time seconds to create the pthread.
*/
ulonglong launch_time =
thd->start_utime - channel_info->get_prior_thr_create_utime();
if (launch_time >= slow_launch_time * 1000000ULL)
Per_thread_connection_handler::slow_launch_threads++;
}
delete channel_info;
/*
handle_one_connection() is normally the only way a thread would
start and would always be on the very high end of the stack ,
therefore, the thread stack always starts at the address of the
first local variable of handle_one_connection, which is thd. We
need to know the start of the stack so that we could check for
stack overruns.
*/
thd_set_thread_stack(thd, (char *)&thd);
thd->store_globals();
return thd;
}
/**
Thread handler for a connection
@param arg Connection object (Channel_info)
This function (normally) does the following:
- Initialize thread
- Initialize THD to be used with this thread
- Authenticate user
- Execute all queries sent on the connection
- Take connection down
- End thread / Handle next connection using thread from thread cache
*/
extern "C" {
static void *handle_connection(void *arg) {
Global_THD_manager *thd_manager = Global_THD_manager::get_instance();
Connection_handler_manager *handler_manager =
Connection_handler_manager::get_instance();
Channel_info *channel_info = static_cast<Channel_info *>(arg);
bool pthread_reused MY_ATTRIBUTE((unused)) = false;
if (my_thread_init()) {
connection_errors_internal++;
channel_info->send_error_and_close_channel(ER_OUT_OF_RESOURCES, 0, false);
handler_manager->inc_aborted_connects();
Connection_handler_manager::dec_connection_count();
delete channel_info;
my_thread_exit(0);
return NULL;
}
for (;;) {
THD *thd = init_new_thd(channel_info);
if (thd == NULL) {
connection_errors_internal++;
handler_manager->inc_aborted_connects();
Connection_handler_manager::dec_connection_count();
break; // We are out of resources, no sense in continuing.
}
#ifdef HAVE_PSI_THREAD_INTERFACE
if (pthread_reused) {
/*
Reusing existing pthread:
Create new instrumentation for the new THD job,
and attach it to this running pthread.
*/
PSI_thread *psi = PSI_THREAD_CALL(new_thread)(key_thread_one_connection,
thd, thd->thread_id());
PSI_THREAD_CALL(set_thread_os_id)(psi);
PSI_THREAD_CALL(set_thread)(psi);
}
#endif
thd->ppi_thread = PPI_THREAD_CALL(create_thread)();
#ifdef HAVE_PSI_THREAD_INTERFACE
/* Find the instrumented thread */
PSI_thread *psi = PSI_THREAD_CALL(get_thread)();
/* Save it within THD, so it can be inspected */
thd->set_psi(psi);
#endif /* HAVE_PSI_THREAD_INTERFACE */
mysql_thread_set_psi_id(thd->thread_id());
mysql_thread_set_psi_THD(thd);
mysql_socket_set_thread_owner(
thd->get_protocol_classic()->get_vio()->mysql_socket);
thd_manager->add_thd(thd);
if (thd_prepare_connection(thd))
handler_manager->inc_aborted_connects();
else {
while (thd_connection_alive(thd)) {
if (do_command(thd)) break;
}
end_connection(thd);
}
close_connection(thd, 0, false, false);
thd->get_stmt_da()->reset_diagnostics_area();
thd->release_resources();
// Clean up errors now, before possibly waiting for a new connection.
#if OPENSSL_VERSION_NUMBER < 0x10100000L
ERR_remove_thread_state(0);
#endif /* OPENSSL_VERSION_NUMBER < 0x10100000L */
thd_manager->remove_thd(thd);
Connection_handler_manager::dec_connection_count();
#ifdef HAVE_PSI_THREAD_INTERFACE
/*
Delete the instrumentation for the job that just completed.
*/
thd->set_psi(NULL);
PSI_THREAD_CALL(delete_current_thread)();
#endif /* HAVE_PSI_THREAD_INTERFACE */
PPI_THREAD_CALL(destroy_thread)(thd->ppi_thread);
thd->ppi_thread = nullptr;
delete thd;
// Server is shutting down so end the pthread.
if (connection_events_loop_aborted()) break;
channel_info = Per_thread_connection_handler::block_until_new_connection();
if (channel_info == NULL) break;
pthread_reused = true;
if (connection_events_loop_aborted()) {
// Close the channel and exit as server is undergoing shutdown.
channel_info->send_error_and_close_channel(ER_SERVER_SHUTDOWN, 0, false);
delete channel_info;
channel_info = nullptr;
Connection_handler_manager::dec_connection_count();
break;
}
}
my_thread_end();
my_thread_exit(0);
return NULL;
}
} // extern "C"
void Per_thread_connection_handler::modify_thread_cache_size(
const ulong thread_cache_size) {
mysql_mutex_lock(&LOCK_thread_cache);
if (thread_cache_size >= blocked_pthread_count) {
mysql_mutex_unlock(&LOCK_thread_cache);
return;
}
shrink_cache = true;
if (thread_cache_size == 0) {
mysql_cond_broadcast(&COND_thread_cache);
} else {
ulong num_threads = blocked_pthread_count - thread_cache_size;
for (ulong i = 0; i < num_threads; i++)
mysql_cond_signal(&COND_thread_cache);
}
// Wait until threads have been unblocked from thread cache.
while (blocked_pthread_count > thread_cache_size)
mysql_cond_wait(&COND_flush_thread_cache, &LOCK_thread_cache);
shrink_cache = false;
mysql_mutex_unlock(&LOCK_thread_cache);
}
void Per_thread_connection_handler::kill_blocked_pthreads() {
modify_thread_cache_size(0);
}
bool Per_thread_connection_handler::check_idle_thread_and_enqueue_connection(
Channel_info *channel_info) {
bool res = true;
mysql_mutex_lock(&LOCK_thread_cache);
if (Per_thread_connection_handler::blocked_pthread_count > wake_pthread) {
DBUG_PRINT("info", ("waiting_channel_info_list->push %p", channel_info));
waiting_channel_info_list->push_back(channel_info);
wake_pthread++;
mysql_cond_signal(&COND_thread_cache);
res = false;
}
mysql_mutex_unlock(&LOCK_thread_cache);
return res;
}
bool Per_thread_connection_handler::add_connection(Channel_info *channel_info) {
int error = 0;
my_thread_handle id;
DBUG_TRACE;
// Simulate thread creation for test case before we check thread cache
DBUG_EXECUTE_IF("fail_thread_create", error = 1; goto handle_error;);
if (!check_idle_thread_and_enqueue_connection(channel_info)) return false;
/*
There are no idle threads avaliable to take up the new
connection. Create a new thread to handle the connection
*/
channel_info->set_prior_thr_create_utime();
error =
mysql_thread_create(key_thread_one_connection, &id, &connection_attrib,
handle_connection, (void *)channel_info);
#ifndef DBUG_OFF
handle_error:
#endif // !DBUG_OFF
if (error) {
connection_errors_internal++;
if (!create_thd_err_log_throttle.log())
LogErr(ERROR_LEVEL, ER_CONN_PER_THREAD_NO_THREAD, error);
channel_info->send_error_and_close_channel(ER_CANT_CREATE_THREAD, error,
true);
Connection_handler_manager::dec_connection_count();
return true;
}
Global_THD_manager::get_instance()->inc_thread_created();
DBUG_PRINT("info", ("Thread created"));
return false;
}
uint Per_thread_connection_handler::get_max_threads() const {
return max_connections;
}
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