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MXS-2168 Add 'assume_unique_hostnames'-setting to MariaDBMonitor

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Adds the setting and takes it into use during replication graph creation
and the most important checks.
This commit is contained in:
Esa Korhonen
2018-11-16 10:19:49 +02:00
parent 64a9a5135e
commit 1a046bd453
5 changed files with 143 additions and 40 deletions
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72
server/modules/monitor/mariadbmon/cluster_discovery.cc
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@ -160,8 +160,13 @@ void MariaDBMonitor::tarjan_scc_visit_node(MariaDBServer* node,
}
}
/**
* Use slave status and server id information to build the replication graph. Needs to be called whenever
* topology has changed, or it's suspected.
*/
void MariaDBMonitor::build_replication_graph()
{
const bool use_hostnames = m_assume_unique_hostnames;
// First, reset all node data.
for (MariaDBServer* server : m_servers)
{
@ -169,39 +174,64 @@ void MariaDBMonitor::build_replication_graph()
server->m_node.reset_results();
}
/* Here, all slave connections are added to the graph, even if the IO thread cannot connect. Strictly
* speaking, building the parents-array is not required as the data already exists. This construction
* is more for convenience and faster access later on. */
for (MariaDBServer* slave : m_servers)
{
/* All servers are accepted in this loop, even if the server is [Down] or [Maintenance]. For these
* servers, we just use the latest available information. Not adding such servers could suddenly
* change the topology quite a bit and all it would take is a momentarily network failure. */
/* Check all slave connections of all servers. Connections are added even if one or both endpoints
* are down or in maintenance. */
for (SlaveStatus& slave_conn : slave->m_slave_status)
{
/* We always trust the "Master_Server_Id"-field of the SHOW SLAVE STATUS output, as long as
* the id is > 0 (server uses 0 for default). This means that the graph constructed is faulty if
* 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)
if (slave_conn.slave_io_running != SlaveStatus::SLAVE_IO_NO && slave_conn.slave_sql_running)
{
// Valid slave connection, find the MariaDBServer with this id.
auto master = get_server(master_id);
if (master != NULL)
// Looks promising, check hostname or server id.
MariaDBServer* found_master = NULL;
bool is_external = false;
if (use_hostnames)
{
slave->m_node.parents.push_back(master);
master->m_node.children.push_back(slave);
found_master = get_server(slave_conn.master_host, slave_conn.master_port);
if (!found_master)
{
// Must be an external server.
is_external = true;
}
}
else
{
/* Cannot trust hostname:port since network may be complicated. Instead,
* trust the "Master_Server_Id"-field of the SHOW SLAVE STATUS output if
* the slave connection has been seen connected before. This means that
* the graph will miss slave-master relations that have not connected
* while the monitor has been running. TODO: This data should be saved so
* that monitor restarts do not lose this information. */
if (slave_conn.seen_connected)
{
// Valid slave connection, find the MariaDBServer with the matching server id.
found_master = get_server(slave_conn.master_server_id);
if (!found_master)
{
/* Likely an external master. It's possible that the master is a monitored
* server which has not been queried yet and the monitor does not know its
* id. */
is_external = true;
}
}
}
// Valid slave connection, find the MariaDBServer with this id.
if (found_master)
{
/* Building the parents-array is not strictly required as the same data is in
* the children-array. This construction is more for convenience and faster
* access later on. */
slave->m_node.parents.push_back(found_master);
found_master->m_node.children.push_back(slave);
}
else if (is_external)
{
// This is an external master connection. Save just the master id for now.
slave->m_node.external_masters.push_back(master_id);
// TODO: Save host:port instead
slave->m_node.external_masters.push_back(slave_conn.master_server_id);
}
}
}