hcq/MaxScale
hcq/MaxScale
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

MXS-1490: Query binlog & gtid settings, read @@gtid_slave_pos

Browse Source 
The Gtid_Slave_Pos returned by SHOW ALL SLAVES STATUS is not quite
reliable (MDEV-14182) so the variable version is used instead. Added
a convenience function for querying a single row of values.

Also,  gtid_strict_mode, log_bin and log_slave_updates are now
queried during failover. The first only causes a warning message
if disabled, the last two affect new master selection.
This commit is contained in:
Esa Korhonen 2017-11-02 11:43:43 +02:00
parent 8cac26a14d
commit 0bb54511b7
1 changed files with 157 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

175
server/modules/monitor/mysqlmon/mysql_mon.cc
View File

@ -57,8 +57,11 @@
#define SLAVE_HOSTS_PORT 2
using std::string;
static void monitorMain(void *);
typedef std::vector<MXS_MONITORED_SERVER*> ServerVector;
typedef std::vector<string> StringVector;
class MySqlServerInfo;
static void monitorMain(void *);
static void *startMonitor(MXS_MONITOR *, const MXS_CONFIG_PARAMETER*);
static void stopMonitor(MXS_MONITOR *);
static bool stop_monitor(MXS_MONITOR *);
@ -76,6 +79,9 @@ static bool mon_process_failover(MYSQL_MONITOR* monitor,
const char* failover_script,
uint32_t failover_timeout);
static bool do_failover(MYSQL_MONITOR* mon);
static void update_gtid_slave_pos(MXS_MONITORED_SERVER *database, int64_t domain, MySqlServerInfo* info);
static bool update_replication_settings(MXS_MONITORED_SERVER *database, MySqlServerInfo* info);
static bool report_version_err = true;
static const char* hb_table_name = "maxscale_schema.replication_heartbeat";
@ -103,8 +109,6 @@ static const char CN_REPLICATION_PASSWORD[] = "replication_password";
/** Default master failure verification timeout */
#define DEFAULT_MASTER_FAILURE_TIMEOUT "10"
typedef std::vector<MXS_MONITORED_SERVER*> ServerVector;
// TODO: Specify the real default failover script.
static const char DEFAULT_FAILOVER_SCRIPT[] =
"/usr/bin/echo INITIATOR=$INITIATOR "
@ -646,6 +650,20 @@ public:
{}
};
// This class groups some miscellaneous replication related settings together.
class ReplicationSettings
{
public:
bool gtid_strict_mode; /**< Enable additional checks for replication */
bool log_bin; /**< Is binary logging enabled */
bool log_slave_updates;/**< Does the slave log replicated events to binlog */
ReplicationSettings()
: gtid_strict_mode(false)
, log_bin(false)
, log_slave_updates(false)
{}
};
/**
* Monitor specific information about a server
*
@ -664,9 +682,10 @@ public:
int slave_heartbeats; /**< Number of received heartbeats */
double heartbeat_period; /**< The time interval between heartbeats */
time_t latest_event; /**< Time when latest event was received from the master */
Gtid gtid_slave_pos; /**< Gtid of latest replicated event. Only shows the triplet with the same
* domain as Gtid_IO_Pos. */
Gtid gtid_slave_pos; /**< Gtid of latest replicated event. Only shows the triplet with the
* same domain as Gtid_IO_Pos. */
SlaveStatusInfo slave_status; /**< Data returned from SHOW SLAVE STATUS */
ReplicationSettings rpl_settings; /**< Miscellaneous replication related settings */
MySqlServerInfo()
: server_id(0),
@ -1162,7 +1181,6 @@ static bool do_show_slave_status(MySqlServerInfo* serv_info, MXS_MONITORED_SERVE
{
const char* beats = mxs_mysql_get_value(result, row, "Slave_received_heartbeats");
const char* period = mxs_mysql_get_value(result, row, "Slave_heartbeat_period");
const char* gtid_slave_pos = mxs_mysql_get_value(result, row, "Gtid_Slave_Pos");
const char* gtid_io_pos = mxs_mysql_get_value(result, row, "Gtid_IO_Pos");
ss_dassert(beats && period);
@ -1174,10 +1192,11 @@ static bool do_show_slave_status(MySqlServerInfo* serv_info, MXS_MONITORED_SERVE
serv_info->heartbeat_period = atof(period);
}
if (serv_info->slave_status.slave_sql_running && gtid_io_pos && gtid_slave_pos)
if (serv_info->slave_status.slave_sql_running && gtid_io_pos)
{
serv_info->slave_status.gtid_io_pos = Gtid(gtid_io_pos);
serv_info->gtid_slave_pos = Gtid(gtid_slave_pos, serv_info->slave_status.gtid_io_pos.domain);
Gtid io_pos = Gtid(gtid_io_pos);
serv_info->slave_status.gtid_io_pos = io_pos;
update_gtid_slave_pos(database, io_pos.domain, serv_info);
}
else
{
@ -3046,21 +3065,57 @@ MXS_MONITORED_SERVER* failover_select_new_master(MYSQL_MONITOR* mon, ServerVecto
mon_server = mon_server->next)
{
MySqlServerInfo* cand_info = get_server_info(mon, mon_server);
if (cand_info->slave_status.slave_sql_running) // Assumed to be a valid slave.
if (cand_info->slave_status.slave_sql_running && update_replication_settings(mon_server, cand_info))
{
if (out_slaves)
{
out_slaves->push_back(mon_server);
}
if (cand_info->rpl_settings.log_bin == false)
{
MXS_WARNING("Failover: Slave '%s' has binary log disabled and is not a valid promotion "
"candidate.", mon_server->server->unique_name);
continue;
}
if (cand_info->rpl_settings.gtid_strict_mode == false)
{
MXS_WARNING("Failover: Slave '%s' has gtid_strict_mode disabled. Enabling this setting is "
"recommended. For more information, see "
"https://mariadb.com/kb/en/library/gtid/#gtid_strict_mode",
mon_server->server->unique_name);
}
if (cand_info->rpl_settings.log_slave_updates == false)
{
MXS_WARNING("Failover: Slave '%s' has log_slave_updates disabled. It is a valid candidate "
"but replication will break for lagging slaves if '%s' is promoted.",
mon_server->server->unique_name, mon_server->server->unique_name);
}
bool select_this = false;
// If no candidate yet, accept any.
if (new_master == NULL ||
if (new_master == NULL)
{
select_this = true;
}
else
{
uint64_t cand_io = cand_info->slave_status.gtid_io_pos.sequence;
uint64_t cand_processed = cand_info->gtid_slave_pos.sequence;
uint64_t master_io = new_master_info->slave_status.gtid_io_pos.sequence;
uint64_t master_processed = new_master_info->gtid_slave_pos.sequence;
bool cand_updates = cand_info->rpl_settings.log_slave_updates;
bool master_updates = new_master_info->rpl_settings.log_slave_updates;
// Otherwise accept a slave with a later event in relay log.
cand_info->slave_status.gtid_io_pos.sequence >
new_master_info->slave_status.gtid_io_pos.sequence ||
// If io sequences are identical, the slave with more events processed wins.
(cand_info->slave_status.gtid_io_pos.sequence ==
new_master_info->slave_status.gtid_io_pos.sequence &&
cand_info->gtid_slave_pos.sequence > new_master_info->gtid_slave_pos.sequence))
if (cand_io > master_io ||
// If io sequences are identical, the slave with more events processed wins.
(cand_io == master_io && (cand_processed > master_processed ||
// Finally, if binlog positions are identical, prefer a slave with log_slave_updates.
(cand_processed == master_processed && cand_updates && !master_updates))))
{
select_this = true;
}
}
if (select_this)
{
new_master = mon_server;
new_master_info = cand_info;
@ -3197,7 +3252,7 @@ bool failover_redirect_slaves(MYSQL_MONITOR* mon, ServerVector& slaves, MXS_MONI
* @param mon Server cluster monitor
* @return True if successful
*/
bool do_failover(MYSQL_MONITOR* mon)
static bool do_failover(MYSQL_MONITOR* mon)
{
// Topology has already been tested to be simple.
// Step 1: Select new master. Also populate a vector with all slaves not the selected master.
@ -3219,3 +3274,87 @@ bool do_failover(MYSQL_MONITOR* mon)
}
return false;
}
/**
* Query one row of results, save strings to array. Any additional rows are ignored.
*
* @param database The database to query.
* @param query The query to execute.
* @param expected_cols How many columns the result should have.
* @param output The output array to populate.
* @return True on success.
*/
static bool query_one_row(MXS_MONITORED_SERVER *database, const char* query, unsigned int expected_cols,
StringVector* output)
{
bool rval = false;
MYSQL_RES *result;
if (mxs_mysql_query(database->con, query) == 0 && (result = mysql_store_result(database->con)) != NULL)
{
unsigned int columns = mysql_field_count(database->con);
if (columns != expected_cols)
{
mysql_free_result(result);
MXS_ERROR("Unexpected result for '%s'. Expected %d columns, got %d. MySQL Version: %s",
query, expected_cols, columns, database->server->version_string);
}
else
{
MYSQL_ROW row = mysql_fetch_row(result);
if (row)
{
for (unsigned int i = 0; i < columns; i++)
{
output->push_back((row[i] != NULL) ? row[i] : "");
}
rval = true;
}
else
{
MXS_ERROR("Query '%s' returned no rows.", query);
}
mysql_free_result(result);
}
}
else
{
mon_report_query_error(database);
}
return rval;
}
/**
* Query a few miscellaneous replication settings.
*
* @param database The slave server to query
* @param info Where to save results
* @return True on success
*/
static bool update_replication_settings(MXS_MONITORED_SERVER *database, MySqlServerInfo* info)
{
StringVector row;
bool ok = query_one_row(database, "SELECT @@gtid_strict_mode, @@log_bin, @@log_slave_updates;", 3, &row);
if (ok)
{
info->rpl_settings.gtid_strict_mode = (row[0] == "1");
info->rpl_settings.log_bin = (row[1] == "1");
info->rpl_settings.log_slave_updates = (row[2] == "1");
}
return ok;
}
/**
* Query gtid_slave_pos and save it to the server info object.
*
* @param database The server to query.
* @param domain Which gtid domain should be saved.
* @param info Server info structure for saving result.
*/
static void update_gtid_slave_pos(MXS_MONITORED_SERVER *database, int64_t domain, MySqlServerInfo* info)
{
StringVector row;
if (query_one_row(database, "SELECT @@gtid_slave_pos;", 1, &row))
{
info->gtid_slave_pos = Gtid(row.front().c_str(), domain);
}
}