SQL Statements for Controlling Replica Servers Sources with Asynchronous Connection Failover” . SOURCE_DELAY Specifies how many seconds behind the source the replica must lag. An event received from the source is not executed until at least  interval seconds later than its execution on the source. The default is 0. An error occurs if  interval  is not a nonnegative integer in the range from 0 to 2 31 − 1. For more information, see Section 17.4.11, “Delayed Replication” . A  CHANGE REPLICATION SOURCE TO  statement using the  SOURCE_DELAY  option can be executed on a running replica when the replication SQL thread is stopped. SOURCE_HEARTBEAT_PERIOD Controls the heartbeat interval, which stops the connection timeout occurring in the absence of data if the connection is still good. A heartbeat signal is sent to the replica after that number of seconds, and the waiting period is reset whenever the source’s binary log is updated with an event. Heartbeats are therefore sent by the source only if there are no unsent events in the binary log file for a period longer than this. The heartbeat interval  interval  is a decimal value having the range 0 to 4294967 seconds and a resolution in milliseconds; the smallest nonzero value is 0.001. Setting  interval  to 0 disables heartbeats altogether. The heartbeat interval defaults to half the value of the  slave_net_timeout  system variable. It is recorded in the source metadata repository and shown in the replication_connection_configuration  Performance Schema table. Issuing  RESET REPLICA  resets the heartbeat interval to the default value. The  slave_net_timeout  system variable specifies the number of seconds that the replica waits for either more data or a heartbeat signal from the source, before the replica considers the connection broken, aborts the read, and tries to reconnect. The default value is 60 seconds (one minute). Note that a change to the value or default setting of  slave_net_timeout  does not automatically change the heartbeat interval, whether that has been set explicitly or is using a previously calculated default. A warning is issued if you set  @@GLOBAL.slave_net_timeout  to a value less than that of the current heartbeat interval. If  slave_net_timeout  is changed, you must also issue  CHANGE REPLICATION SOURCE TO  to adjust the heartbeat interval to an appropriate value so that the heartbeat signal occurs before the connection timeout. If you do not do this, the heartbeat signal has no effect, and if no data is received from the source, the replica can make repeated reconnection attempts, creating zombie dump threads. SOURCE_HOST The host name or IP address of the replication source server. The replica uses this to connect to the source. If you specify  SOURCE_HOST  or  SOURCE_PORT , the replica assumes that the source server is different from before (even if the option value is the same as its current value.) In this case, the old values for the source’s binary log file name and position are considered no longer applicable, so if you do not specify  SOURCE_LOG_FILE  and 2769