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

MXS-1845 Only rebuild topology when required

Browse Source 
The monitor now detects when a server has changed such that a replication
graph rebuild is needed and only then rebuilds the graph and detects
cycles and master.

Also, some old code is no longer called in the monitor cycle. It will be
removed in later commits. Refactored some of the related functions.
This commit is contained in:
Esa Korhonen
2018-06-20 15:26:27 +03:00
parent dc4a555c70
commit 6bf10904d7
5 changed files with 224 additions and 162 deletions
Download Patch File Download Diff File Expand all files Collapse all files

54
server/modules/monitor/mariadbmon/cluster_discovery.cc
View File

@ -27,8 +27,6 @@ static bool check_replicate_wild_do_table(MXS_MONITORED_SERVER* database);
static bool check_replicate_wild_ignore_table(MXS_MONITORED_SERVER* database);
static const char HB_TABLE_NAME[] = "maxscale_schema.replication_heartbeat";
static const char SERVER_DISQUALIFIED[] = "Server '%s' was disqualified from new master selection because "
"it is %s.";
static const int64_t MASTER_BITS = SERVER_MASTER | SERVER_WAS_MASTER;
static const int64_t SLAVE_BITS = SERVER_SLAVE | SERVER_WAS_SLAVE;
@ -383,6 +381,9 @@ void MariaDBMonitor::build_replication_graph()
* an old "Master_Server_Id"- value is read from a slave which is still trying to connect to
* a new master. However, a server is only designated [Slave] if both IO- and SQL-threads are
* running fine, so the faulty graph does not cause wrong status settings. */
/* IF THIS PART IS CHANGED, CHANGE THE COMPARISON IN 'sstatus_arrays_topology_equal'
* (in MariaDBServer) accordingly so that any possible topology changes are detected. */
auto master_id = slave_conn.master_server_id;
if (slave_conn.slave_io_running != SlaveStatus::SLAVE_IO_NO && master_id > 0)
{
@ -977,15 +978,20 @@ static string disqualify_reasons_to_string(MariaDBServer* disqualified)
* the current master making it unsuitable. Because of this, the method can be quite vocal and not
* consider the previous master.
*
* @param msg_out Message output. Includes explanations on why potential candidates were not selected.
* @return The master with most slaves
*/
MariaDBServer* MariaDBMonitor::find_topology_master_server()
MariaDBServer* MariaDBMonitor::find_topology_master_server(string* msg_out)
{
/* Finding the best master server may get somewhat tricky if the graph is complicated. The general
* criteria for the best master is that it reaches the most slaves (possibly in multiple layers and
* cycles). To avoid having to calculate this reachability (doable by a recursive search) to all nodes,
* let's use the knowledge that the best master is either a server with no masters (external ones don't
* count) or is part of a cycle. The server must be running and writable to be eligible. */
* count) or is part of a cycle with no out-cycle masters. The server must be running and writable
* to be eligible. */
string messages;
string separator;
const char disq[] = "is not a valid master candidate because it is ";
ServerArray master_candidates;
for (auto iter = m_servers.begin(); iter != m_servers.end(); iter++)
{
@ -999,7 +1005,8 @@ MariaDBServer* MariaDBMonitor::find_topology_master_server()
else
{
string reasons = disqualify_reasons_to_string(server);
MXS_WARNING(SERVER_DISQUALIFIED, server->name(), reasons.c_str());
messages += separator + "'" + server->name() + "' " + disq + reasons + ".";
separator = "\n";
}
}
}
@ -1021,31 +1028,25 @@ MariaDBServer* MariaDBMonitor::find_topology_master_server()
else
{
// No single server in the cycle was viable.
const char WARN_MSG[] = "No valid master server could be found in the cycle with "
"servers '%s'.";
const char no_valid_servers[] = "No valid master server could be found in the cycle with "
"servers";
string server_names = monitored_servers_to_string(cycle_members);
MXS_WARNING(WARN_MSG, server_names.c_str());
messages += separator + no_valid_servers + " '" + server_names + "'.";
separator = "\n";
for (auto iter2 = cycle_members.begin(); iter2 != cycle_members.end(); iter2++)
{
MariaDBServer* disqualified_server = *iter2;
string reasons = disqualify_reasons_to_string(disqualified_server);
MXS_WARNING(SERVER_DISQUALIFIED, disqualified_server->name(), reasons.c_str());
messages += separator + "'" + disqualified_server->name() + "' " + disq + reasons + ".";
separator = "\n";
}
}
}
}
MariaDBServer* found_master = NULL;
if (!master_candidates.empty())
{
found_master = find_best_reach_server(master_candidates);
}
else
{
MXS_WARNING("No valid master servers in the cluster.");
}
return found_master;
*msg_out = messages;
return master_candidates.empty() ? NULL : find_best_reach_server(master_candidates);
}
static void node_reach_visit(MariaDBServer* node, int* reach)
@ -1176,7 +1177,7 @@ void MariaDBMonitor::assign_slave_and_relay_master(MariaDBServer* node)
{
MariaDBServer* slave = *iter;
// If the node has an index, it has already been labeled master/slave and visited. Even when this
// is the case, the slave has to be checked to get correct [Relay Master] labels.
// is the case, the node has to be checked to get correct [Relay Master] labels.
if (slave->m_node.index == NodeData::INDEX_NOT_VISITED)
{
slave->clear_status(MASTER_BITS);
@ -1214,10 +1215,15 @@ void MariaDBMonitor::assign_slave_and_relay_master(MariaDBServer* node)
}
// Finally, if the node itself is a slave and has slaves of its own, label it as relay slave.
if ((node->m_server_base->pending_status & SERVER_SLAVE) && slaves > 0)
if (node->has_status(SERVER_SLAVE) && slaves > 0)
{
node->set_status(SERVER_RELAY_MASTER);
}
// If the node is a binlog relay, remove any slave bits that may have been set. Relay master bit can stay.
if (node->m_version == MariaDBServer::version::BINLOG_ROUTER)
{
node->clear_status(SERVER_SLAVE);
}
}
/**
@ -1248,7 +1254,7 @@ bool MariaDBMonitor::master_no_longer_valid(std::string* reason_out)
if (!m_master->m_node.parents.empty())
{
rval = true;
*reason_out = "it has started replicating from another server in the cluster.";
*reason_out = "it has started replicating from another server in the cluster";
}
}
// 4) The master was part of a cycle but is no longer, or one of the servers in the cycle is
@ -1265,7 +1271,7 @@ bool MariaDBMonitor::master_no_longer_valid(std::string* reason_out)
rval = true;
ServerArray& old_members = m_master_cycle_status.cycle_members;
string server_names_old = monitored_servers_to_string(old_members);
*reason_out = "it is no longer in the multimaster group (" + server_names_old + ").";
*reason_out = "it is no longer in the multimaster group (" + server_names_old + ")";
}
// 4b) The master is still in a cycle but the cycle has gained a master outside of the cycle.
else
@ -1276,7 +1282,7 @@ bool MariaDBMonitor::master_no_longer_valid(std::string* reason_out)
rval = true;
string server_names_current = monitored_servers_to_string(current_members);
*reason_out = "a server in the master's multimaster group (" + server_names_current +
") is replicating from a server not in the group.";
") is replicating from a server not in the group";
}
}
}