For Galera cluster, try to find the most appropriate node if none seems healthy

include/MySQL_Monitor.hpp

@@ -188,6 +188,7 @@ class MySQL_Monitor {
 	void populate_monitor_mysql_server_group_replication_log();
 	void populate_monitor_mysql_server_galera_log();
 	char * galera_find_last_node(int);
+	std::vector<string> * galera_find_possible_last_nodes(int);
 	bool server_responds_to_ping(char *address, int port);
 };
 

lib/MySQL_HostGroups_Manager.cpp

@@ -3956,6 +3956,7 @@ void MySQL_HostGroups_Manager::converge_galera_config(int _writer_hostgroup) {
 						if (num_writers == 0 && num_backup_writers == 0) {
 							proxy_warning("Galera: we couldn't find any healthy node for writer HG %d\n", info->writer_hostgroup);
 							// ask Monitor to get the status of the whole cluster
+							/*
 							char * s0 = GloMyMon->galera_find_last_node(info->writer_hostgroup);
 							if (s0) {
 								std::string s = string(s0);
@@ -3980,6 +3981,63 @@ void MySQL_HostGroups_Manager::converge_galera_config(int _writer_hostgroup) {
 								}
 								free(s0);
 							}
+							*/
+							std::vector<string> * pn = GloMyMon->galera_find_possible_last_nodes(info->writer_hostgroup);
+							if (pn->size()) {
+								std::vector<string>::iterator it2;
+								for (it2=pn->begin(); it2!=pn->end(); ++it2) {
+									string s0 = *it2;
+									proxy_info("Galera: possible writer candidate for HG %d: %s\n", info->writer_hostgroup, s0.c_str());
+								}
+								char *error=NULL;
+								int cols;
+								int affected_rows;
+								SQLite3_result *resultset2=NULL;
+								q = (char *)"SELECT hostname, port FROM mysql_servers_incoming WHERE hostgroup_id IN (%d, %d, %d, %d) ORDER BY weight DESC, hostname DESC, port DESC";
+								query=(char *)malloc(strlen(q) + 256);
+								sprintf(query,q,info->writer_hostgroup, info->writer_hostgroup, info->backup_writer_hostgroup, info->reader_hostgroup, info->offline_hostgroup);
+								mydb->execute_statement(query, &error , &cols , &affected_rows , &resultset2);
+								free(query);
+								if (resultset2) {
+									bool stop = false;
+									for (std::vector<SQLite3_row *>::iterator it = resultset2->rows.begin() ; (it != resultset2->rows.end()) && !stop ; ++it) {
+										SQLite3_row *r=*it;
+										char *h = r->fields[0];
+										int p = atoi(r->fields[1]);
+										if (h) {
+											for (it2=pn->begin(); (it2!=pn->end()) && !stop; ++it2) {
+												std::string s = string(*it2);
+												std::size_t found=s.find_last_of(":");
+												std::string host=s.substr(0,found);
+												std::string port=s.substr(found+1);
+												int port_n = atoi(port.c_str());
+												if (strcmp(h,host.c_str())==0) {
+													if (p == port_n) {
+														stop = true; // we found a host to make a writer
+														proxy_info("Galera: trying to use server %s:%s as a writer for HG %d\n", host.c_str(), port.c_str(), info->writer_hostgroup);
+														q=(char *)"UPDATE OR REPLACE mysql_servers_incoming SET status=0, hostgroup_id=%d WHERE hostgroup_id IN (%d, %d, %d, %d)  AND hostname='%s' AND port=%d";
+														query=(char *)malloc(strlen(q) + s.length() + 512);
+														sprintf(query,q,info->writer_hostgroup, info->writer_hostgroup, info->backup_writer_hostgroup, info->reader_hostgroup, info->offline_hostgroup, host.c_str(), port_n);
+														mydb->execute(query);
+														free(query);
+														bool writer_is_also_reader = info->writer_is_also_reader;
+														if (writer_is_also_reader) {
+															int read_HG = info->reader_hostgroup;
+															q=(char *)"INSERT OR IGNORE INTO mysql_servers_incoming (hostgroup_id,hostname,port,gtid_port,status,weight,compression,max_connections,max_replication_lag,use_ssl,max_latency_ms,comment) SELECT %d,hostname,port,gtid_port,status,weight,compression,max_connections,max_replication_lag,use_ssl,max_latency_ms,comment FROM mysql_servers_incoming WHERE hostgroup_id=%d AND hostname='%s' AND port=%d";
+															query=(char *)malloc(strlen(q) + s.length() + 128);
+															sprintf(query,q,read_HG, info->writer_hostgroup, host.c_str(), port_n);
+															mydb->execute(query);
+															free(query);
+														}
+													}
+												}
+											}
+										}
+									}
+									delete resultset2;
+								}
+							}
+							delete pn;
 						}
 					}
 				}

lib/MySQL_Monitor.cpp

@@ -2768,3 +2768,38 @@ char * MySQL_Monitor::galera_find_last_node(int writer_hostgroup) {
 	pthread_mutex_unlock(&GloMyMon->galera_mutex);
 	return str;
 }
+
+std::vector<string> * MySQL_Monitor::galera_find_possible_last_nodes(int writer_hostgroup) {
+	std::vector<string> * result = new std::vector<string>();
+//	std::vector<Galera_monitor_node *> tmp_list;
+	char *str = NULL;
+	pthread_mutex_lock(&GloMyMon->galera_mutex);
+	std::map<std::string, Galera_monitor_node *>::iterator it2;
+	Galera_monitor_node *node=NULL;
+	unsigned int writer_nodes = 0;
+	unsigned long long curtime = monotonic_time();
+	unsigned long long ti = mysql_thread___monitor_galera_healthcheck_interval;
+	ti *= 2;
+	//std::string s = "";
+	for (it2=GloMyMon->Galera_Hosts_Map.begin(); it2!=GloMyMon->Galera_Hosts_Map.end(); ++it2) {
+		node=it2->second;
+		if (node->writer_hostgroup == writer_hostgroup) {
+			Galera_status_entry_t * st = node->last_entry();
+			if (st) {
+				if (st->start_time >= curtime - ti) { // only consider recent checks
+					if (st->error == NULL) { // no check error
+						if (st->read_only == false) { // the server is writable (this check is arguable)
+							if (st->wsrep_sst_donor_rejects_queries == false) {
+								//tmp_list.push_back(node);
+								string s = it2->first;
+								result->push_back(s);
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+	pthread_mutex_unlock(&GloMyMon->galera_mutex);
+	return result;
+}