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Let proxysql makes sure that only one server in the writer group #2019

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Let proxysql makes sure that only one server in the writer group #2019

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26 changes: 26 additions & 0 deletions lib/MySQL_HostGroups_Manager.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1842,6 +1842,8 @@ void MySQL_HostGroups_Manager::read_only_action(char *hostname, int port, int re
const char *Q3B=(char *)"DELETE FROM mysql_servers WHERE hostname='%s' AND port=%d AND hostgroup_id IN (SELECT reader_hostgroup FROM mysql_replication_hostgroups WHERE reader_hostgroup=mysql_servers.hostgroup_id)";
const char *Q4=(char *)"UPDATE OR IGNORE mysql_servers SET hostgroup_id=(SELECT reader_hostgroup FROM mysql_replication_hostgroups WHERE writer_hostgroup=mysql_servers.hostgroup_id) WHERE hostname='%s' AND port=%d AND hostgroup_id IN (SELECT writer_hostgroup FROM mysql_replication_hostgroups WHERE writer_hostgroup=mysql_servers.hostgroup_id)";
const char *Q5=(char *)"DELETE FROM mysql_servers WHERE hostname='%s' AND port=%d AND hostgroup_id IN (SELECT writer_hostgroup FROM mysql_replication_hostgroups WHERE writer_hostgroup=mysql_servers.hostgroup_id)";
const char *Q6=(char *)"select hostname from (select writer_hostgroup from mysql_replication_hostgroups join mysql_servers on reader_hostgroup=hostgroup_id and hostname='%s' and port=%d) join mysql_servers on hostgroup_id=writer_hostgroup and status=0";

if (GloAdmin==NULL) {
return;
}
Expand Down Expand Up @@ -1879,6 +1881,30 @@ void MySQL_HostGroups_Manager::read_only_action(char *hostname, int port, int re
case 0:
if (num_rows==0) {
// the server has read_only=0 , but we can't find any writer, so we perform a swap

// before we perform a swap, check if there's already a server in writer group,if so, we stop swapping
// and print a warning message in the log
cols=0;
error=NULL;
affected_rows=0;
sprintf(query,Q6,hostname,port);

wrlock();
mydb->execute_statement(query,&error,&cols,&affected_rows,&resultset);
wrunlock();
if(resultset==NULL){
goto __exit_read_only_action;
}

int cc = 0;
cc=resultset->rows_count;
delete resultset;
resultset=NULL;
if(cc > 0){
// there's already one server with ONLINE status in the writer's group
proxy_warning("host:%s:%d with read_only=%d doesn't seem to be right. Please pay attention!!!\n",hostname,port,read_only);
break;
}
GloAdmin->mysql_servers_wrlock();
if (GloMTH->variables.hostgroup_manager_verbose) {
char *error2=NULL;
Expand Down