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Factor out functions

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The topology update is now in a method. Also, the m_master-field
is only written inside a method so that the cycle info is always
updated.
This commit is contained in:
Esa Korhonen 2018-07-03 14:45:37 +03:00
parent 936bcde135
commit f2e0bf3caa
3 changed files with 92 additions and 73 deletions
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72
server/modules/monitor/mariadbmon/cluster_discovery.cc
View File

@ -842,4 +842,74 @@ bool MariaDBMonitor::cycle_has_master_server(ServerArray& cycle_servers)
}
return outside_replication;
}
}
void MariaDBMonitor::update_topology()
{
m_servers_by_id.clear();
for (auto server : m_servers)
{
m_servers_by_id[server->m_server_id] = server;
}
build_replication_graph();
find_graph_cycles();
/* Check if a failover/switchover was performed last loop and the master should change.
* In this case, update the master and its cycle info here. */
if (m_next_master)
{
assign_new_master(m_next_master);
m_next_master = NULL;
}
// Find the server that looks like it would be the best master. It does not yet overwrite the
// current master.
string topology_messages;
MariaDBServer* root_master = find_topology_master_server(&topology_messages);
// Check if current master is still valid.
string reason;
if (master_is_valid(&reason))
{
// Update master cycle info in case it has changed
update_master_cycle_info();
if (root_master && m_master != root_master)
{
// Master is still valid but it is no longer the best master. Print a warning.
MXS_WARNING("'%s' is a better master candidate than the current master '%s'. "
"Master will change if '%s' is no longer a valid master.",
root_master->name(), m_master->name(), m_master->name());
}
}
else
{
if (m_master && !reason.empty())
{
MXS_WARNING("The previous master server '%s' is no longer a valid master because %s. "
"Selecting new master.", m_master->name(), reason.c_str());
}
else
{
MXS_NOTICE("Selecting master server.");
}
// The current master is no longer ok (or it never was). Change the master, even though this may
// break replication. Master changes are logged by the log_master_changes()-method.
if (!topology_messages.empty())
{
MXS_WARNING("%s", topology_messages.c_str());
}
assign_new_master(root_master);
if (m_master)
{
MXS_NOTICE("'%s' is the best master candidate.", m_master->name());
}
else
{
MXS_WARNING("No valid master servers found.");
}
}
m_cluster_topology_changed = false;
}

90
server/modules/monitor/mariadbmon/mariadbmon.cc
View File

@ -102,7 +102,7 @@ void MariaDBMonitor::clear_server_info()
m_server_info.clear();
m_servers_by_id.clear();
m_excluded_servers.clear();
m_master = NULL;
assign_new_master(NULL);
m_next_master = NULL;
m_master_gtid_domain = GTID_DOMAIN_UNKNOWN;
m_external_master_host.clear();
@ -353,10 +353,16 @@ void MariaDBMonitor::update_server(MariaDBServer& server)
void MariaDBMonitor::pre_loop()
{
// MonitorInstance read the journal and has the last known master in its m_master member variable.
// MonitorInstance reads the journal and has the last known master in its m_master member variable.
// Write the corresponding MariaDBServer into the class-specific m_master variable.
m_master = MonitorInstance::m_master ? get_server_info(MonitorInstance::m_master) : NULL;
m_log_no_master = true;
auto journal_master = MonitorInstance::m_master;
if (journal_master)
{
// This is somewhat questionable, as the journal only contains status bits but no actual topology
// info. In a fringe case the actual queried topology may not match the journal data, freezing the
// master to a suboptimal choice.
assign_new_master(get_server_info(journal_master));
}
if (m_detect_replication_lag)
{
@ -401,74 +407,8 @@ void MariaDBMonitor::tick()
if (m_cluster_topology_changed)
{
// This means that a server id or a slave connection has changed, or read_only was set.
// Update the server id array and check various things.
m_servers_by_id.clear();
for (auto server : m_servers)
{
m_servers_by_id[server->m_server_id] = server;
}
build_replication_graph();
find_graph_cycles();
/* Check if a failover/switchover was performed last loop and the master should change.
* In this case, update the master and its cycle info here. */
if (m_next_master)
{
m_master = m_next_master;
update_master_cycle_info();
m_next_master = NULL;
}
// Find the server that looks like it would be the best master. It does not yet overwrite the
// current master.
string topology_messages;
MariaDBServer* root_master = find_topology_master_server(&topology_messages);
// Check if current master is still valid.
string reason;
if (master_is_valid(&reason))
{
// Update master cycle info in case it has changed
update_master_cycle_info();
if (root_master && m_master != root_master)
{
// Master is still valid but it is no longer the best master. Print a warning.
MXS_WARNING("'%s' is a better master candidate than the current master '%s'. "
"Master will change if '%s' is no longer a valid master.",
root_master->name(), m_master->name(), m_master->name());
}
}
else
{
if (m_master && !reason.empty())
{
MXS_WARNING("The previous master server '%s' is no longer a valid master because %s. "
"Selecting new master.", m_master->name(), reason.c_str());
}
else
{
MXS_NOTICE("Selecting master server.");
}
// The current master is no longer ok (or it never was). Change the master, even though this may
// break replication. Master changes are logged by the log_master_changes()-method.
if (!topology_messages.empty())
{
MXS_WARNING("%s", topology_messages.c_str());
}
m_master = root_master;
update_master_cycle_info();
if (m_master)
{
MXS_NOTICE("'%s' is the best master candidate.", m_master->name());
}
else
{
MXS_WARNING("No valid master servers found.");
}
}
m_cluster_topology_changed = false;
// Various things need to be checked and updated.
update_topology();
}
// Always re-assign master, slave etc bits as these depend on other factors outside topology
@ -715,6 +655,12 @@ void MariaDBMonitor::handle_auto_rejoin()
}
}
void MariaDBMonitor::assign_new_master(MariaDBServer* new_master)
{
m_master = new_master;
update_master_cycle_info();
}
/**
* Simple wrapper for mxs_mysql_query and mysql_num_rows
*

3
server/modules/monitor/mariadbmon/mariadbmon.hh
View File

@ -100,6 +100,7 @@ public:
protected:
void pre_loop();
void tick();
void process_state_changes();
private:
@ -192,6 +193,7 @@ private:
// Cluster discovery and status assignment methods
void update_server(MariaDBServer& server);
void find_graph_cycles();
void update_topology();
void log_master_changes();
void update_gtid_domain();
void update_external_master();
@ -211,6 +213,7 @@ private:
bool cycle_has_master_server(ServerArray& cycle_servers);
void update_master_cycle_info();
void set_low_disk_slaves_maintenance();
void assign_new_master(MariaDBServer* new_master);
// Switchover methods
bool manual_switchover(SERVER* new_master, SERVER* current_master, json_t** error_out);