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mariadb/sql/semisync_master.cc
Andrei Elkin e972125f11 MDEV-13073 This part merges the Ali semisync related changes 
and specifically the ack receiving functionality.
Semisync is turned to be static instead of plugin so its functions
are invoked at the same points as RUN_HOOKS.
The RUN_HOOKS and the observer interface remain to be removed by later
patch.

Todo:
  React on killed status by repl_semisync_master.wait_after_sync(). Currently
  Repl_semi_sync_master::commit_trx does not check the killed status.

  There were few bugfixes found that are present in mysql and its unclear
  whether/how they are covered. Those include:

  Bug#15985893: GTID SKIPPED EVENTS ON MASTER CAUSE SEMI SYNC TIME-OUTS
  Bug#17932935 CALLING IS_SEMI_SYNC_SLAVE() IN EACH FUNCTION CALL
                 HAS BAD PERFORMANCE
  Bug#20574628: SEMI-SYNC REPLICATION PERFORMANCE DEGRADES WITH A HIGH NUMBER OF THREADS
2017-12-18 13:43:37 +02:00

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/* Copyright (C) 2007 Google Inc.
Copyright (c) 2008, 2013, Oracle and/or its affiliates.
Copyright (c) 2011, 2016, MariaDB
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 St, Fifth Floor, Boston, MA 02110-1301 USA */
#include <my_global.h>
#include "semisync_master.h"
#define TIME_THOUSAND 1000
#define TIME_MILLION 1000000
#define TIME_BILLION 1000000000
/* This indicates whether semi-synchronous replication is enabled. */
my_bool rpl_semi_sync_master_enabled= 0;
unsigned long long rpl_semi_sync_master_request_ack = 0;
unsigned long long rpl_semi_sync_master_get_ack = 0;
my_bool rpl_semi_sync_master_wait_no_slave = 1;
my_bool rpl_semi_sync_master_status = 0;
ulong rpl_semi_sync_master_wait_point =
SEMI_SYNC_MASTER_WAIT_POINT_AFTER_STORAGE_COMMIT;
ulong rpl_semi_sync_master_timeout;
ulong rpl_semi_sync_master_trace_level;
ulong rpl_semi_sync_master_yes_transactions = 0;
ulong rpl_semi_sync_master_no_transactions = 0;
ulong rpl_semi_sync_master_off_times = 0;
ulong rpl_semi_sync_master_timefunc_fails = 0;
ulong rpl_semi_sync_master_wait_timeouts = 0;
ulong rpl_semi_sync_master_wait_sessions = 0;
ulong rpl_semi_sync_master_wait_pos_backtraverse = 0;
ulong rpl_semi_sync_master_avg_trx_wait_time = 0;
ulonglong rpl_semi_sync_master_trx_wait_num = 0;
ulong rpl_semi_sync_master_avg_net_wait_time = 0;
ulonglong rpl_semi_sync_master_net_wait_num = 0;
ulong rpl_semi_sync_master_clients = 0;
ulonglong rpl_semi_sync_master_net_wait_time = 0;
ulonglong rpl_semi_sync_master_trx_wait_time = 0;
ReplSemiSyncMaster repl_semisync_master;
Ack_receiver ack_receiver;
/*
structure to save transaction log filename and position
*/
typedef struct Trans_binlog_info {
my_off_t log_pos;
char log_file[FN_REFLEN];
} Trans_binlog_info;
static int getWaitTime(const struct timespec& start_ts);
static ulonglong timespec_to_usec(const struct timespec *ts)
{
return (ulonglong) ts->tv_sec * TIME_MILLION + ts->tv_nsec / TIME_THOUSAND;
}
/*******************************************************************************
*
* <ActiveTranx> class : manage all active transaction nodes
*
******************************************************************************/
ActiveTranx::ActiveTranx(mysql_mutex_t *lock,
ulong trace_level)
: Trace(trace_level), allocator_(max_connections),
num_entries_(max_connections << 1), /* Transaction hash table size
* is set to double the size
* of max_connections */
lock_(lock)
{
/* No transactions are in the list initially. */
trx_front_ = NULL;
trx_rear_ = NULL;
/* Create the hash table to find a transaction's ending event. */
trx_htb_ = new TranxNode *[num_entries_];
for (int idx = 0; idx < num_entries_; ++idx)
trx_htb_[idx] = NULL;
sql_print_information("Semi-sync replication initialized for transactions.");
}
ActiveTranx::~ActiveTranx()
{
delete [] trx_htb_;
trx_htb_ = NULL;
num_entries_ = 0;
}
unsigned int ActiveTranx::calc_hash(const unsigned char *key,
unsigned int length)
{
unsigned int nr = 1, nr2 = 4;
/* The hash implementation comes from calc_hashnr() in mysys/hash.c. */
while (length--)
{
nr ^= (((nr & 63)+nr2)*((unsigned int) (unsigned char) *key++))+ (nr << 8);
nr2 += 3;
}
return((unsigned int) nr);
}
unsigned int ActiveTranx::get_hash_value(const char *log_file_name,
my_off_t log_file_pos)
{
unsigned int hash1 = calc_hash((const unsigned char *)log_file_name,
strlen(log_file_name));
unsigned int hash2 = calc_hash((const unsigned char *)(&log_file_pos),
sizeof(log_file_pos));
return (hash1 + hash2) % num_entries_;
}
int ActiveTranx::compare(const char *log_file_name1, my_off_t log_file_pos1,
const char *log_file_name2, my_off_t log_file_pos2)
{
int cmp = strcmp(log_file_name1, log_file_name2);
if (cmp != 0)
return cmp;
if (log_file_pos1 > log_file_pos2)
return 1;
else if (log_file_pos1 < log_file_pos2)
return -1;
return 0;
}
int ActiveTranx::insert_tranx_node(const char *log_file_name,
my_off_t log_file_pos)
{
const char *kWho = "ActiveTranx:insert_tranx_node";
TranxNode *ins_node;
int result = 0;
unsigned int hash_val;
function_enter(kWho);
ins_node = allocator_.allocate_node();
if (!ins_node)
{
sql_print_error("%s: transaction node allocation failed for: (%s, %lu)",
kWho, log_file_name, (ulong)log_file_pos);
result = -1;
goto l_end;
}
/* insert the binlog position in the active transaction list. */
strncpy(ins_node->log_name_, log_file_name, FN_REFLEN-1);
ins_node->log_name_[FN_REFLEN-1] = 0; /* make sure it ends properly */
ins_node->log_pos_ = log_file_pos;
if (!trx_front_)
{
/* The list is empty. */
trx_front_ = trx_rear_ = ins_node;
}
else
{
int cmp = compare(ins_node, trx_rear_);
if (cmp > 0)
{
/* Compare with the tail first. If the transaction happens later in
* binlog, then make it the new tail.
*/
trx_rear_->next_ = ins_node;
trx_rear_ = ins_node;
}
else
{
/* Otherwise, it is an error because the transaction should hold the
* mysql_bin_log.LOCK_log when appending events.
*/
sql_print_error("%s: binlog write out-of-order, tail (%s, %lu), "
"new node (%s, %lu)", kWho,
trx_rear_->log_name_, (ulong)trx_rear_->log_pos_,
ins_node->log_name_, (ulong)ins_node->log_pos_);
result = -1;
goto l_end;
}
}
hash_val = get_hash_value(ins_node->log_name_, ins_node->log_pos_);
ins_node->hash_next_ = trx_htb_[hash_val];
trx_htb_[hash_val] = ins_node;
if (trace_level_ & kTraceDetail)
sql_print_information("%s: insert (%s, %lu) in entry(%u)", kWho,
ins_node->log_name_, (ulong)ins_node->log_pos_,
hash_val);
l_end:
return function_exit(kWho, result);
}
bool ActiveTranx::is_tranx_end_pos(const char *log_file_name,
my_off_t log_file_pos)
{
const char *kWho = "ActiveTranx::is_tranx_end_pos";
function_enter(kWho);
unsigned int hash_val = get_hash_value(log_file_name, log_file_pos);
TranxNode *entry = trx_htb_[hash_val];
while (entry != NULL)
{
if (compare(entry, log_file_name, log_file_pos) == 0)
break;
entry = entry->hash_next_;
}
if (trace_level_ & kTraceDetail)
sql_print_information("%s: probe (%s, %lu) in entry(%u)", kWho,
log_file_name, (ulong)log_file_pos, hash_val);
function_exit(kWho, (entry != NULL));
return (entry != NULL);
}
int ActiveTranx::clear_active_tranx_nodes(const char *log_file_name,
my_off_t log_file_pos)
{
const char *kWho = "ActiveTranx::::clear_active_tranx_nodes";
TranxNode *new_front;
function_enter(kWho);
if (log_file_name != NULL)
{
new_front = trx_front_;
while (new_front)
{
if (compare(new_front, log_file_name, log_file_pos) > 0)
break;
new_front = new_front->next_;
}
}
else
{
/* If log_file_name is NULL, clear everything. */
new_front = NULL;
}
if (new_front == NULL)
{
/* No active transaction nodes after the call. */
/* Clear the hash table. */
memset(trx_htb_, 0, num_entries_ * sizeof(TranxNode *));
allocator_.free_all_nodes();
/* Clear the active transaction list. */
if (trx_front_ != NULL)
{
trx_front_ = NULL;
trx_rear_ = NULL;
}
if (trace_level_ & kTraceDetail)
sql_print_information("%s: cleared all nodes", kWho);
}
else if (new_front != trx_front_)
{
TranxNode *curr_node, *next_node;
/* Delete all transaction nodes before the confirmation point. */
int n_frees = 0;
curr_node = trx_front_;
while (curr_node != new_front)
{
next_node = curr_node->next_;
n_frees++;
/* Remove the node from the hash table. */
unsigned int hash_val = get_hash_value(curr_node->log_name_, curr_node->log_pos_);
TranxNode **hash_ptr = &(trx_htb_[hash_val]);
while ((*hash_ptr) != NULL)
{
if ((*hash_ptr) == curr_node)
{
(*hash_ptr) = curr_node->hash_next_;
break;
}
hash_ptr = &((*hash_ptr)->hash_next_);
}
curr_node = next_node;
}
trx_front_ = new_front;
allocator_.free_nodes_before(trx_front_);
if (trace_level_ & kTraceDetail)
sql_print_information("%s: cleared %d nodes back until pos (%s, %lu)",
kWho, n_frees,
trx_front_->log_name_, (ulong)trx_front_->log_pos_);
}
return function_exit(kWho, 0);
}
/*******************************************************************************
*
* <ReplSemiSyncMaster> class: the basic code layer for sync-replication master.
* <ReplSemiSyncSlave> class: the basic code layer for sync-replication slave.
*
* The most important functions during semi-syn replication listed:
*
* Master:
* . reportReplyBinlog(): called by the binlog dump thread when it receives
* the slave's status information.
* . updateSyncHeader(): based on transaction waiting information, decide
* whether to request the slave to reply.
* . writeTranxInBinlog(): called by the transaction thread when it finishes
* writing all transaction events in binlog.
* . commitTrx(): transaction thread wait for the slave reply.
*
* Slave:
* . slaveReadSyncHeader(): read the semi-sync header from the master, get the
* sync status and get the payload for events.
* . slaveReply(): reply to the master about the replication progress.
*
******************************************************************************/
ReplSemiSyncMaster::ReplSemiSyncMaster()
: active_tranxs_(NULL),
init_done_(false),
reply_file_name_inited_(false),
reply_file_pos_(0L),
wait_file_name_inited_(false),
wait_file_pos_(0),
master_enabled_(false),
wait_timeout_(0L),
state_(0),
wait_point_(0)
{
strcpy(reply_file_name_, "");
strcpy(wait_file_name_, "");
}
int ReplSemiSyncMaster::initObject()
{
int result;
init_done_ = true;
/* References to the parameter works after set_options(). */
setWaitTimeout(rpl_semi_sync_master_timeout);
setTraceLevel(rpl_semi_sync_master_trace_level);
setWaitPoint(rpl_semi_sync_master_wait_point);
/* Mutex initialization can only be done after MY_INIT(). */
mysql_mutex_init(key_LOCK_binlog,
&LOCK_binlog, MY_MUTEX_INIT_FAST);
mysql_cond_init(key_COND_binlog_send,
&COND_binlog_send, NULL);
if (rpl_semi_sync_master_enabled)
{
result = enableMaster();
if (!result)
result= ack_receiver.start(); /* Start the ACK thread. */
}
else
{
result = disableMaster();
}
/*
If rpl_semi_sync_master_wait_no_slave is disabled, let's temporarily
switch off semisync to avoid hang if there's none active slave.
*/
if (!rpl_semi_sync_master_wait_no_slave)
switch_off();
return result;
}
int ReplSemiSyncMaster::enableMaster()
{
int result = 0;
/* Must have the lock when we do enable of disable. */
lock();
if (!getMasterEnabled())
{
active_tranxs_ = new ActiveTranx(&LOCK_binlog, trace_level_);
if (active_tranxs_ != NULL)
{
commit_file_name_inited_ = false;
reply_file_name_inited_ = false;
wait_file_name_inited_ = false;
set_master_enabled(true);
state_ = true;
sql_print_information("Semi-sync replication enabled on the master.");
}
else
{
sql_print_error("Cannot allocate memory to enable semi-sync on the master.");
result = -1;
}
}
unlock();
return result;
}
int ReplSemiSyncMaster::disableMaster()
{
/* Must have the lock when we do enable of disable. */
lock();
if (getMasterEnabled())
{
/* Switch off the semi-sync first so that waiting transaction will be
* waken up.
*/
switch_off();
assert(active_tranxs_ != NULL);
delete active_tranxs_;
active_tranxs_ = NULL;
reply_file_name_inited_ = false;
wait_file_name_inited_ = false;
commit_file_name_inited_ = false;
set_master_enabled(false);
sql_print_information("Semi-sync replication disabled on the master.");
}
unlock();
return 0;
}
void ReplSemiSyncMaster::cleanup()
{
if (init_done_)
{
mysql_mutex_destroy(&LOCK_binlog);
mysql_cond_destroy(&COND_binlog_send);
init_done_= 0;
}
delete active_tranxs_;
}
void ReplSemiSyncMaster::lock()
{
mysql_mutex_lock(&LOCK_binlog);
}
void ReplSemiSyncMaster::unlock()
{
mysql_mutex_unlock(&LOCK_binlog);
}
void ReplSemiSyncMaster::cond_broadcast()
{
mysql_cond_broadcast(&COND_binlog_send);
}
int ReplSemiSyncMaster::cond_timewait(struct timespec *wait_time)
{
const char *kWho = "ReplSemiSyncMaster::cond_timewait()";
int wait_res;
function_enter(kWho);
wait_res= mysql_cond_timedwait(&COND_binlog_send,
&LOCK_binlog, wait_time);
return function_exit(kWho, wait_res);
}
void ReplSemiSyncMaster::add_slave()
{
lock();
rpl_semi_sync_master_clients++;
unlock();
}
void ReplSemiSyncMaster::remove_slave()
{
lock();
rpl_semi_sync_master_clients--;
/* Only switch off if semi-sync is enabled and is on */
if (getMasterEnabled() && is_on())
{
/* If user has chosen not to wait if no semi-sync slave available
and the last semi-sync slave exits, turn off semi-sync on master
immediately.
*/
if (!rpl_semi_sync_master_wait_no_slave &&
rpl_semi_sync_master_clients == 0)
switch_off();
}
unlock();
}
int ReplSemiSyncMaster::reportReplyPacket(uint32 server_id, const uchar *packet,
ulong packet_len)
{
const char *kWho = "ReplSemiSyncMaster::reportReplyPacket";
int result= -1;
char log_file_name[FN_REFLEN+1];
my_off_t log_file_pos;
ulong log_file_len = 0;
function_enter(kWho);
if (unlikely(packet[REPLY_MAGIC_NUM_OFFSET] != ReplSemiSyncMaster::kPacketMagicNum))
{
sql_print_error("Read semi-sync reply magic number error");
goto l_end;
}
if (unlikely(packet_len < REPLY_BINLOG_NAME_OFFSET))
{
sql_print_error("Read semi-sync reply length error: packet is too small");
goto l_end;
}
log_file_pos = uint8korr(packet + REPLY_BINLOG_POS_OFFSET);
log_file_len = packet_len - REPLY_BINLOG_NAME_OFFSET;
if (unlikely(log_file_len >= FN_REFLEN))
{
sql_print_error("Read semi-sync reply binlog file length too large");
goto l_end;
}
strncpy(log_file_name, (const char*)packet + REPLY_BINLOG_NAME_OFFSET, log_file_len);
log_file_name[log_file_len] = 0;
DBUG_ASSERT(dirname_length(log_file_name) == 0);
if (trace_level_ & kTraceDetail)
sql_print_information("%s: Got reply(%s, %lu) from server %u",
kWho, log_file_name, (ulong)log_file_pos, server_id);
rpl_semi_sync_master_get_ack++;
reportReplyBinlog(server_id, log_file_name, log_file_pos);
l_end:
return function_exit(kWho, result);
}
int ReplSemiSyncMaster::reportReplyBinlog(uint32 server_id,
const char *log_file_name,
my_off_t log_file_pos)
{
const char *kWho = "ReplSemiSyncMaster::reportReplyBinlog";
int cmp;
bool can_release_threads = false;
bool need_copy_send_pos = true;
if (!(getMasterEnabled()))
return 0;
function_enter(kWho);
lock();
/* This is the real check inside the mutex. */
if (!getMasterEnabled())
goto l_end;
if (!is_on())
/* We check to see whether we can switch semi-sync ON. */
try_switch_on(server_id, log_file_name, log_file_pos);
/* The position should increase monotonically, if there is only one
* thread sending the binlog to the slave.
* In reality, to improve the transaction availability, we allow multiple
* sync replication slaves. So, if any one of them get the transaction,
* the transaction session in the primary can move forward.
*/
if (reply_file_name_inited_)
{
cmp = ActiveTranx::compare(log_file_name, log_file_pos,
reply_file_name_, reply_file_pos_);
/* If the requested position is behind the sending binlog position,
* would not adjust sending binlog position.
* We based on the assumption that there are multiple semi-sync slave,
* and at least one of them shou/ld be up to date.
* If all semi-sync slaves are behind, at least initially, the primary
* can find the situation after the waiting timeout. After that, some
* slaves should catch up quickly.
*/
if (cmp < 0)
{
/* If the position is behind, do not copy it. */
need_copy_send_pos = false;
}
}
if (need_copy_send_pos)
{
strmake_buf(reply_file_name_, log_file_name);
reply_file_pos_ = log_file_pos;
reply_file_name_inited_ = true;
/* Remove all active transaction nodes before this point. */
assert(active_tranxs_ != NULL);
active_tranxs_->clear_active_tranx_nodes(log_file_name, log_file_pos);
if (trace_level_ & kTraceDetail)
sql_print_information("%s: Got reply at (%s, %lu)", kWho,
log_file_name, (ulong)log_file_pos);
}
if (rpl_semi_sync_master_wait_sessions > 0)
{
/* Let us check if some of the waiting threads doing a trx
* commit can now proceed.
*/
cmp = ActiveTranx::compare(reply_file_name_, reply_file_pos_,
wait_file_name_, wait_file_pos_);
if (cmp >= 0)
{
/* Yes, at least one waiting thread can now proceed:
* let us release all waiting threads with a broadcast
*/
can_release_threads = true;
wait_file_name_inited_ = false;
}
}
l_end:
unlock();
if (can_release_threads)
{
if (trace_level_ & kTraceDetail)
sql_print_information("%s: signal all waiting threads.", kWho);
cond_broadcast();
}
return function_exit(kWho, 0);
}
int ReplSemiSyncMaster::waitAfterSync(const char *log_file, my_off_t log_pos)
{
if (!getMasterEnabled())
return 0;
int ret= 0;
if(log_pos &&
waitPoint() == SEMI_SYNC_MASTER_WAIT_POINT_AFTER_BINLOG_SYNC)
ret= commitTrx(log_file + dirname_length(log_file), log_pos);
return ret;
}
int ReplSemiSyncMaster::waitAfterCommit(THD* thd, bool all)
{
if (!getMasterEnabled())
return 0;
int ret= 0;
const char *log_file;
my_off_t log_pos;
bool is_real_trans=
(all || thd->transaction.all.ha_list == 0);
/*
The coordinates are propagated to this point having been computed
in reportBinlogUpdate
*/
Trans_binlog_info *log_info= thd->semisync_info;
log_file= log_info && log_info->log_file[0] ? log_info->log_file : 0;
log_pos= log_info ? log_info->log_pos : 0;
DBUG_ASSERT(!log_file || dirname_length(log_file) == 0);
if (is_real_trans &&
log_pos &&
waitPoint() == SEMI_SYNC_MASTER_WAIT_POINT_AFTER_STORAGE_COMMIT)
ret= commitTrx(log_file, log_pos);
if (is_real_trans && log_info)
{
log_info->log_file[0]= 0;
log_info->log_pos= 0;
}
return ret;
}
int ReplSemiSyncMaster::waitAfterRollback(THD *thd, bool all)
{
return waitAfterCommit(thd, all);
}
/**
The method runs after flush to binary log is done.
*/
int ReplSemiSyncMaster::reportBinlogUpdate(THD* thd, const char *log_file,
my_off_t log_pos)
{
if (getMasterEnabled())
{
Trans_binlog_info *log_info;
if (!(log_info= thd->semisync_info))
{
if(!(log_info=
(Trans_binlog_info*) my_malloc(sizeof(Trans_binlog_info), MYF(0))))
return 1;
thd->semisync_info= log_info;
}
strcpy(log_info->log_file, log_file + dirname_length(log_file));
log_info->log_pos = log_pos;
return writeTranxInBinlog(log_info->log_file, log_pos);
}
return 0;
}
void ReplSemiSyncMaster::dump_start(THD* thd,
const char *log_file,
my_off_t log_pos)
{
if (!thd->semi_sync_slave)
return;
if (ack_receiver.add_slave(thd))
{
sql_print_error("Failed to register slave to semi-sync ACK receiver "
"thread. Turning off semisync");
thd->semi_sync_slave= 0;
return;
}
add_slave();
reportReplyBinlog(thd->variables.server_id, log_file + dirname_length(log_file), log_pos);
sql_print_information("Start semi-sync binlog_dump to slave (server_id: %d), pos(%s, %lu",
thd->variables.server_id, log_file, (unsigned long)log_pos);
return;
}
void ReplSemiSyncMaster::dump_end(THD* thd)
{
if (!thd->semi_sync_slave)
return;
sql_print_information("Stop semi-sync binlog_dump to slave (server_id: %d)", thd->variables.server_id);
remove_slave();
ack_receiver.remove_slave(thd);
return;
}
int ReplSemiSyncMaster::commitTrx(const char* trx_wait_binlog_name,
my_off_t trx_wait_binlog_pos)
{
const char *kWho = "ReplSemiSyncMaster::commitTrx";
function_enter(kWho);
if (getMasterEnabled() && trx_wait_binlog_name)
{
struct timespec start_ts;
struct timespec abstime;
int wait_result;
PSI_stage_info old_stage;
set_timespec(start_ts, 0);
DEBUG_SYNC(current_thd, "rpl_semisync_master_commit_trx_before_lock");
/* Acquire the mutex. */
lock();
/* This must be called after acquired the lock */
THD_ENTER_COND(NULL, &COND_binlog_send, &LOCK_binlog,
& stage_waiting_for_semi_sync_ack_from_slave,
& old_stage);
/* This is the real check inside the mutex. */
if (!getMasterEnabled() || !is_on())
goto l_end;
if (trace_level_ & kTraceDetail)
{
sql_print_information("%s: wait pos (%s, %lu), repl(%d)\n", kWho,
trx_wait_binlog_name, (ulong)trx_wait_binlog_pos,
(int)is_on());
}
while (is_on() && !thd_killed(current_thd))
{
if (reply_file_name_inited_)
{
int cmp = ActiveTranx::compare(reply_file_name_, reply_file_pos_,
trx_wait_binlog_name, trx_wait_binlog_pos);
if (cmp >= 0)
{
/* We have already sent the relevant binlog to the slave: no need to
* wait here.
*/
if (trace_level_ & kTraceDetail)
sql_print_information("%s: Binlog reply is ahead (%s, %lu),",
kWho, reply_file_name_, (ulong)reply_file_pos_);
break;
}
}
/* Let us update the info about the minimum binlog position of waiting
* threads.
*/
if (wait_file_name_inited_)
{
int cmp = ActiveTranx::compare(trx_wait_binlog_name, trx_wait_binlog_pos,
wait_file_name_, wait_file_pos_);
if (cmp <= 0)
{
/* This thd has a lower position, let's update the minimum info. */
strmake_buf(wait_file_name_, trx_wait_binlog_name);
wait_file_pos_ = trx_wait_binlog_pos;
rpl_semi_sync_master_wait_pos_backtraverse++;
if (trace_level_ & kTraceDetail)
sql_print_information("%s: move back wait position (%s, %lu),",
kWho, wait_file_name_, (ulong)wait_file_pos_);
}
}
else
{
strmake_buf(wait_file_name_, trx_wait_binlog_name);
wait_file_pos_ = trx_wait_binlog_pos;
wait_file_name_inited_ = true;
if (trace_level_ & kTraceDetail)
sql_print_information("%s: init wait position (%s, %lu),",
kWho, wait_file_name_, (ulong)wait_file_pos_);
}
/* Calcuate the waiting period. */
long diff_secs = (long) (wait_timeout_ / TIME_THOUSAND);
long diff_nsecs = (long) ((wait_timeout_ % TIME_THOUSAND) * TIME_MILLION);
long nsecs = start_ts.tv_nsec + diff_nsecs;
abstime.tv_sec = start_ts.tv_sec + diff_secs + nsecs/TIME_BILLION;
abstime.tv_nsec = nsecs % TIME_BILLION;
/* In semi-synchronous replication, we wait until the binlog-dump
* thread has received the reply on the relevant binlog segment from the
* replication slave.
*
* Let us suspend this thread to wait on the condition;
* when replication has progressed far enough, we will release
* these waiting threads.
*/
rpl_semi_sync_master_wait_sessions++;
if (trace_level_ & kTraceDetail)
sql_print_information("%s: wait %lu ms for binlog sent (%s, %lu)",
kWho, wait_timeout_,
wait_file_name_, (ulong)wait_file_pos_);
wait_result = cond_timewait(&abstime);
rpl_semi_sync_master_wait_sessions--;
if (wait_result != 0)
{
/* This is a real wait timeout. */
sql_print_warning("Timeout waiting for reply of binlog (file: %s, pos: %lu), "
"semi-sync up to file %s, position %lu.",
trx_wait_binlog_name, (ulong)trx_wait_binlog_pos,
reply_file_name_, (ulong)reply_file_pos_);
rpl_semi_sync_master_wait_timeouts++;
/* switch semi-sync off */
switch_off();
}
else
{
int wait_time;
wait_time = getWaitTime(start_ts);
if (wait_time < 0)
{
if (trace_level_ & kTraceGeneral)
{
sql_print_error("Replication semi-sync getWaitTime fail at "
"wait position (%s, %lu)",
trx_wait_binlog_name, (ulong)trx_wait_binlog_pos);
}
rpl_semi_sync_master_timefunc_fails++;
}
else
{
rpl_semi_sync_master_trx_wait_num++;
rpl_semi_sync_master_trx_wait_time += wait_time;
}
}
}
/*
At this point, the binlog file and position of this transaction
must have been removed from ActiveTranx.
active_tranxs_ may be NULL if someone disabled semi sync during
cond_timewait()
*/
assert(thd_killed(current_thd) || !active_tranxs_ ||
!active_tranxs_->is_tranx_end_pos(trx_wait_binlog_name,
trx_wait_binlog_pos));
l_end:
/* Update the status counter. */
if (is_on())
rpl_semi_sync_master_yes_transactions++;
else
rpl_semi_sync_master_no_transactions++;
/* The lock held will be released by thd_exit_cond, so no need to
call unlock() here */
THD_EXIT_COND(NULL, & old_stage);
}
return function_exit(kWho, 0);
}
/* Indicate that semi-sync replication is OFF now.
*
* What should we do when it is disabled? The problem is that we want
* the semi-sync replication enabled again when the slave catches up
* later. But, it is not that easy to detect that the slave has caught
* up. This is caused by the fact that MySQL's replication protocol is
* asynchronous, meaning that if the master does not use the semi-sync
* protocol, the slave would not send anything to the master.
* Still, if the master is sending (N+1)-th event, we assume that it is
* an indicator that the slave has received N-th event and earlier ones.
*
* If semi-sync is disabled, all transactions still update the wait
* position with the last position in binlog. But no transactions will
* wait for confirmations and the active transaction list would not be
* maintained. In binlog dump thread, updateSyncHeader() checks whether
* the current sending event catches up with last wait position. If it
* does match, semi-sync will be switched on again.
*/
int ReplSemiSyncMaster::switch_off()
{
const char *kWho = "ReplSemiSyncMaster::switch_off";
int result;
function_enter(kWho);
state_ = false;
/* Clear the active transaction list. */
assert(active_tranxs_ != NULL);
result = active_tranxs_->clear_active_tranx_nodes(NULL, 0);
rpl_semi_sync_master_off_times++;
wait_file_name_inited_ = false;
reply_file_name_inited_ = false;
sql_print_information("Semi-sync replication switched OFF.");
cond_broadcast(); /* wake up all waiting threads */
return function_exit(kWho, result);
}
int ReplSemiSyncMaster::try_switch_on(int server_id,
const char *log_file_name,
my_off_t log_file_pos)
{
const char *kWho = "ReplSemiSyncMaster::try_switch_on";
bool semi_sync_on = false;
function_enter(kWho);
/* If the current sending event's position is larger than or equal to the
* 'largest' commit transaction binlog position, the slave is already
* catching up now and we can switch semi-sync on here.
* If commit_file_name_inited_ indicates there are no recent transactions,
* we can enable semi-sync immediately.
*/
if (commit_file_name_inited_)
{
int cmp = ActiveTranx::compare(log_file_name, log_file_pos,
commit_file_name_, commit_file_pos_);
semi_sync_on = (cmp >= 0);
}
else
{
semi_sync_on = true;
}
if (semi_sync_on)
{
/* Switch semi-sync replication on. */
state_ = true;
sql_print_information("Semi-sync replication switched ON with slave (server_id: %d) "
"at (%s, %lu)",
server_id, log_file_name,
(ulong)log_file_pos);
}
return function_exit(kWho, 0);
}
int ReplSemiSyncMaster::reserveSyncHeader(String* packet)
{
const char *kWho = "ReplSemiSyncMaster::reserveSyncHeader";
function_enter(kWho);
/* Set the magic number and the sync status. By default, no sync
* is required.
*/
packet->append(reinterpret_cast<const char*>(kSyncHeader),
sizeof(kSyncHeader));
return function_exit(kWho, 0);
}
int ReplSemiSyncMaster::updateSyncHeader(THD* thd, unsigned char *packet,
const char *log_file_name,
my_off_t log_file_pos,
bool* need_sync)
{
const char *kWho = "ReplSemiSyncMaster::updateSyncHeader";
int cmp = 0;
bool sync = false;
/* If the semi-sync master is not enabled, or the slave is not a semi-sync
* target, do not request replies from the slave.
*/
if (!getMasterEnabled() || !thd->semi_sync_slave)
{
*need_sync = false;
return 0;
}
function_enter(kWho);
lock();
/* This is the real check inside the mutex. */
if (!getMasterEnabled())
{
assert(sync == false);
goto l_end;
}
if (is_on())
{
/* semi-sync is ON */
sync = false; /* No sync unless a transaction is involved. */
if (reply_file_name_inited_)
{
cmp = ActiveTranx::compare(log_file_name, log_file_pos,
reply_file_name_, reply_file_pos_);
if (cmp <= 0)
{
/* If we have already got the reply for the event, then we do
* not need to sync the transaction again.
*/
goto l_end;
}
}
if (wait_file_name_inited_)
{
cmp = ActiveTranx::compare(log_file_name, log_file_pos,
wait_file_name_, wait_file_pos_);
}
else
{
cmp = 1;
}
/* If we are already waiting for some transaction replies which
* are later in binlog, do not wait for this one event.
*/
if (cmp >= 0)
{
/*
* We only wait if the event is a transaction's ending event.
*/
assert(active_tranxs_ != NULL);
sync = active_tranxs_->is_tranx_end_pos(log_file_name,
log_file_pos);
}
}
else
{
if (commit_file_name_inited_)
{
int cmp = ActiveTranx::compare(log_file_name, log_file_pos,
commit_file_name_, commit_file_pos_);
sync = (cmp >= 0);
}
else
{
sync = true;
}
}
if (trace_level_ & kTraceDetail)
sql_print_information("%s: server(%d), (%s, %lu) sync(%d), repl(%d)",
kWho, thd->variables.server_id, log_file_name,
(ulong)log_file_pos, sync, (int)is_on());
*need_sync= sync;
l_end:
unlock();
/* We do not need to clear sync flag because we set it to 0 when we
* reserve the packet header.
*/
if (sync)
{
(packet)[2] = kPacketFlagSync;
}
return function_exit(kWho, 0);
}
int ReplSemiSyncMaster::writeTranxInBinlog(const char* log_file_name,
my_off_t log_file_pos)
{
const char *kWho = "ReplSemiSyncMaster::writeTranxInBinlog";
int result = 0;
function_enter(kWho);
lock();
/* This is the real check inside the mutex. */
if (!getMasterEnabled())
goto l_end;
/* Update the 'largest' transaction commit position seen so far even
* though semi-sync is switched off.
* It is much better that we update commit_file_* here, instead of
* inside commitTrx(). This is mostly because updateSyncHeader()
* will watch for commit_file_* to decide whether to switch semi-sync
* on. The detailed reason is explained in function updateSyncHeader().
*/
if (commit_file_name_inited_)
{
int cmp = ActiveTranx::compare(log_file_name, log_file_pos,
commit_file_name_, commit_file_pos_);
if (cmp > 0)
{
/* This is a larger position, let's update the maximum info. */
strncpy(commit_file_name_, log_file_name, FN_REFLEN-1);
commit_file_name_[FN_REFLEN-1] = 0; /* make sure it ends properly */
commit_file_pos_ = log_file_pos;
}
}
else
{
strncpy(commit_file_name_, log_file_name, FN_REFLEN-1);
commit_file_name_[FN_REFLEN-1] = 0; /* make sure it ends properly */
commit_file_pos_ = log_file_pos;
commit_file_name_inited_ = true;
}
if (is_on())
{
assert(active_tranxs_ != NULL);
if(active_tranxs_->insert_tranx_node(log_file_name, log_file_pos))
{
/*
if insert tranx_node failed, print a warning message
and turn off semi-sync
*/
sql_print_warning("Semi-sync failed to insert tranx_node for binlog file: %s, position: %lu",
log_file_name, (ulong)log_file_pos);
switch_off();
}
else
{
rpl_semi_sync_master_request_ack++;
}
}
l_end:
unlock();
return function_exit(kWho, result);
}
int ReplSemiSyncMaster::flushNet(THD *thd,
const char *event_buf)
{
const char *kWho = "ReplSemiSyncMaster::flushNet";
int result = -1;
NET* net= &thd->net;
function_enter(kWho);
assert((unsigned char)event_buf[1] == kPacketMagicNum);
if ((unsigned char)event_buf[2] != kPacketFlagSync)
{
/* current event does not require reply */
result = 0;
goto l_end;
}
/* We flush to make sure that the current event is sent to the network,
* instead of being buffered in the TCP/IP stack.
*/
if (net_flush(net))
{
sql_print_error("Semi-sync master failed on net_flush() "
"before waiting for slave reply");
goto l_end;
}
net_clear(net, 0);
net->pkt_nr++;
result = 0;
rpl_semi_sync_master_net_wait_num++;
l_end:
thd->clear_error();
return function_exit(kWho, result);
}
int ReplSemiSyncMaster::afterResetMaster()
{
const char *kWho = "ReplSemiSyncMaster::afterResetMaster";
int result = 0;
function_enter(kWho);
if (rpl_semi_sync_master_enabled)
{
sql_print_information("Enable Semi-sync Master after reset master");
enableMaster();
}
lock();
if (rpl_semi_sync_master_clients == 0 &&
!rpl_semi_sync_master_wait_no_slave)
state_ = 0;
else
state_ = getMasterEnabled()? 1 : 0;
wait_file_name_inited_ = false;
reply_file_name_inited_ = false;
commit_file_name_inited_ = false;
rpl_semi_sync_master_yes_transactions = 0;
rpl_semi_sync_master_no_transactions = 0;
rpl_semi_sync_master_off_times = 0;
rpl_semi_sync_master_timefunc_fails = 0;
rpl_semi_sync_master_wait_sessions = 0;
rpl_semi_sync_master_wait_pos_backtraverse = 0;
rpl_semi_sync_master_trx_wait_num = 0;
rpl_semi_sync_master_trx_wait_time = 0;
rpl_semi_sync_master_net_wait_num = 0;
rpl_semi_sync_master_net_wait_time = 0;
unlock();
return function_exit(kWho, result);
}
int ReplSemiSyncMaster::beforeResetMaster()
{
const char *kWho = "ReplSemiSyncMaster::beforeResetMaster";
int result = 0;
function_enter(kWho);
if (rpl_semi_sync_master_enabled)
disableMaster();
return function_exit(kWho, result);
}
void ReplSemiSyncMaster::checkAndSwitch()
{
lock();
if (getMasterEnabled() && is_on())
{
if (!rpl_semi_sync_master_wait_no_slave
&& rpl_semi_sync_master_clients == 0)
switch_off();
}
unlock();
}
void ReplSemiSyncMaster::setExportStats()
{
lock();
rpl_semi_sync_master_status = state_;
rpl_semi_sync_master_avg_trx_wait_time=
((rpl_semi_sync_master_trx_wait_num) ?
(ulong)((double)rpl_semi_sync_master_trx_wait_time /
((double)rpl_semi_sync_master_trx_wait_num)) : 0);
rpl_semi_sync_master_avg_net_wait_time=
((rpl_semi_sync_master_net_wait_num) ?
(ulong)((double)rpl_semi_sync_master_net_wait_time /
((double)rpl_semi_sync_master_net_wait_num)) : 0);
unlock();
}
/* Get the waiting time given the wait's staring time.
*
* Return:
* >= 0: the waiting time in microsecons(us)
* < 0: error in get time or time back traverse
*/
static int getWaitTime(const struct timespec& start_ts)
{
ulonglong start_usecs, end_usecs;
struct timespec end_ts;
/* Starting time in microseconds(us). */
start_usecs = timespec_to_usec(&start_ts);
/* Get the wait time interval. */
set_timespec(end_ts, 0);
/* Ending time in microseconds(us). */
end_usecs = timespec_to_usec(&end_ts);
if (end_usecs < start_usecs)
return -1;
return (int)(end_usecs - start_usecs);
}
void semi_sync_master_deinit()
{
repl_semisync_master.cleanup();
ack_receiver.cleanup();
}
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