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MXS-1751: Fix crash with available_when_donor=true

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The `MYSQL_ROW row` variable was being overwritten by the extra query done
by the SST method detection code. Moving it into its own function prevents
this and makes the code significantly easier to comprehend.

Added a test case that reproduced the problem (MaxScale crashed) and
verifies that the patch fixes the problem.
This commit is contained in:
Markus Mäkelä
2018-03-29 18:00:12 +03:00
parent b11fb53b95
commit 4167e88719
4 changed files with 128 additions and 28 deletions
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69
server/modules/monitor/galeramon/galeramon.c
View File

@ -260,6 +260,41 @@ static json_t* diagnostics_json(const MXS_MONITOR *mon)
return rval;
}
static bool using_xtrabackup(MXS_MONITORED_SERVER *database, const char* server_string)
{
bool rval = false;
MYSQL_RES* result;
if (mxs_mysql_query(database->con, "SHOW VARIABLES LIKE 'wsrep_sst_method'") == 0
&& (result = mysql_store_result(database->con)) != NULL)
{
if (mysql_field_count(database->con) < 2)
{
mysql_free_result(result);
MXS_ERROR("Unexpected result for \"SHOW VARIABLES LIKE "
"'wsrep_sst_method'\". Expected 2 columns."
" MySQL Version: %s", server_string);
}
MYSQL_ROW row;
while ((row = mysql_fetch_row(result)))
{
if (row[1] && strncmp(row[1], "xtrabackup", 10) == 0)
{
rval = true;
}
}
mysql_free_result(result);
}
else
{
mon_report_query_error(database);
}
return rval;
}
/**
* Monitor an individual server. Does not deal with the setting of master or
* slave bits, except for clearing them when a server is not joined to the
@ -273,8 +308,7 @@ monitorDatabase(MXS_MONITOR *mon, MXS_MONITORED_SERVER *database)
{
GALERA_MONITOR* handle = (GALERA_MONITOR*) mon->handle;
MYSQL_ROW row;
MYSQL_RES *result, *result2;
int isjoined = 0;
MYSQL_RES *result;
char *server_string;
/* Don't even probe server flagged as in maintenance */
@ -364,6 +398,8 @@ monitorDatabase(MXS_MONITOR *mon, MXS_MONITORED_SERVER *database)
info.local_index = local_index;
}
ss_dassert(row[0] && row[1]);
if (strcmp(row[0], "wsrep_local_state") == 0)
{
if (strcmp(row[1], "4") == 0)
@ -371,33 +407,10 @@ monitorDatabase(MXS_MONITOR *mon, MXS_MONITORED_SERVER *database)
info.joined = 1;
}
/* Check if the node is a donor and is using xtrabackup, in this case it can stay alive */
else if (strcmp(row[1], "2") == 0 && handle->availableWhenDonor == 1)
else if (strcmp(row[1], "2") == 0 && handle->availableWhenDonor == 1 &&
using_xtrabackup(database, server_string))
{
if (mxs_mysql_query(database->con, "SHOW VARIABLES LIKE 'wsrep_sst_method'") == 0
&& (result2 = mysql_store_result(database->con)) != NULL)
{
if (mysql_field_count(database->con) < 2)
{
mysql_free_result(result);
mysql_free_result(result2);
MXS_ERROR("Unexpected result for \"SHOW VARIABLES LIKE "
"'wsrep_sst_method'\". Expected 2 columns."
" MySQL Version: %s", server_string);
return;
}
while ((row = mysql_fetch_row(result2)))
{
if (strncmp(row[1], "xtrabackup", 10) == 0)
{
info.joined = 1;
}
}
mysql_free_result(result2);
}
else
{
mon_report_query_error(database);
}
info.joined = 1;
}
else
{