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MDEV-225: Replace with dummy events an event that is not understood by a slave to which it should be sent

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Add function to replace arbitrary event with dummy event.

Add code which uses this to fix the bug that enabling row_annotate events
on the master breaks slaves which do not request such events.

Add that slaves set a variable @mariadb_slave_capability to inform the
master in a robust way about which events it can, and cannot, handle.

Add tests.
This commit is contained in:
unknown
2012-06-22 11:40:40 +02:00
parent c562c74478
commit 9fe317ffd6
8 changed files with 459 additions and 6 deletions
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69
sql/sql_repl.cc
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@ -491,6 +491,27 @@ static ulonglong get_heartbeat_period(THD * thd)
return entry? entry->val_int(&null_value) : 0;
}
/*
Lookup the capabilities of the slave, which it announces by setting a value
MARIA_SLAVE_CAPABILITY_XXX in @mariadb_slave_capability.
Older MariaDB slaves, and other MySQL slaves, do not set
@mariadb_slave_capability, corresponding to a capability of
MARIA_SLAVE_CAPABILITY_UNKNOWN (0).
*/
static int
get_mariadb_slave_capability(THD *thd)
{
bool null_value;
const LEX_STRING name= { C_STRING_WITH_LEN("mariadb_slave_capability") };
const user_var_entry *entry=
(user_var_entry*) my_hash_search(&thd->user_vars, (uchar*) name.str,
name.length);
return entry ?
(int)(entry->val_int(&null_value)) : MARIA_SLAVE_CAPABILITY_UNKNOWN;
}
/*
Function prepares and sends repliation heartbeat event.
@ -563,14 +584,44 @@ static int send_heartbeat_event(NET* net, String* packet,
static const char *
send_event_to_slave(THD *thd, NET *net, String* const packet, ushort flags,
Log_event_type event_type, char *log_file_name,
IO_CACHE *log)
IO_CACHE *log, int mariadb_slave_capability,
ulong ev_offset, uint8 current_checksum_alg)
{
my_off_t pos;
/* Do not send annotate_rows events unless slave requested it. */
if (event_type == ANNOTATE_ROWS_EVENT &&
!(flags & BINLOG_SEND_ANNOTATE_ROWS_EVENT))
return NULL;
if (event_type == ANNOTATE_ROWS_EVENT && !(flags & BINLOG_SEND_ANNOTATE_ROWS_EVENT))
{
if (mariadb_slave_capability >= MARIA_SLAVE_CAPABILITY_TOLERATE_HOLES)
{
/* This slave can tolerate events omitted from the binlog stream. */
return NULL;
}
else if (mariadb_slave_capability >= MARIA_SLAVE_CAPABILITY_ANNOTATE)
{
/*
The slave did not request ANNOTATE_ROWS_EVENT (it does not need them as
it will not log them in its own binary log). However, it understands the
event and will just ignore it, and it would break if we omitted it,
leaving a hole in the binlog stream. So just send the event as-is.
*/
}
else
{
/*
The slave does not understand ANNOTATE_ROWS_EVENT.
Older MariaDB slaves (and MySQL slaves) will break replication if there
are holes in the binlog stream (they will miscompute the binlog offset
and request the wrong position when reconnecting).
So replace the event with a dummy event of the same size that will be
a no-operation on the slave.
*/
if (Query_log_event::dummy_event(packet, ev_offset, current_checksum_alg))
return "Failed to replace row annotate event with dummy: too small event.";
}
}
/*
Skip events with the @@skip_replication flag set, if slave requested
@ -628,6 +679,7 @@ void mysql_binlog_send(THD* thd, char* log_ident, my_off_t pos,
NET* net = &thd->net;
mysql_mutex_t *log_lock;
mysql_cond_t *log_cond;
int mariadb_slave_capability;
uint8 current_checksum_alg= BINLOG_CHECKSUM_ALG_UNDEF;
int old_max_allowed_packet= thd->variables.max_allowed_packet;
@ -653,6 +705,7 @@ void mysql_binlog_send(THD* thd, char* log_ident, my_off_t pos,
heartbeat_ts= &heartbeat_buf;
set_timespec_nsec(*heartbeat_ts, 0);
}
mariadb_slave_capability= get_mariadb_slave_capability(thd);
if (global_system_variables.log_warnings > 1)
sql_print_information("Start binlog_dump to slave_server(%d), pos(%s, %lu)",
thd->server_id, log_ident, (ulong)pos);
@ -939,7 +992,9 @@ impossible position";
}
if ((tmp_msg= send_event_to_slave(thd, net, packet, flags, event_type,
log_file_name, &log)))
log_file_name, &log,
mariadb_slave_capability, ev_offset,
current_checksum_alg)))
{
errmsg= tmp_msg;
my_errno= ER_UNKNOWN_ERROR;
@ -1097,7 +1152,9 @@ impossible position";
if (read_packet &&
(tmp_msg= send_event_to_slave(thd, net, packet, flags, event_type,
log_file_name, &log)))
log_file_name, &log,
mariadb_slave_capability, ev_offset,
current_checksum_alg)))
{
errmsg= tmp_msg;
my_errno= ER_UNKNOWN_ERROR;