Backport BUG#45848 Semisynchronous replication internals are visible in SHOW PROCESSLIST and logs

Semi-sync uses an extra connection from slave to master to send
replies, this is a normal client connection, and used a normal
SET query to set the reply information on master, which is visible
to user and may cause some confusion and complaining.

This problem is fixed by using the method of sending reply by
using the same connection that is used by master dump thread to
send binlog to slave. Since now the semi-sync plugins are integrated
with the server code, it is not a problem to use the internal net
interfaces to do this.

The master dump thread will mark the event requires a reply and
wait for the reply when the event just sent is the last event
of a transaction and semi-sync status is ON; And the slave will
send a reply to master when it received such an event that requires
a reply.

1 files changed, 2 insertions, 8 deletions

diff --git a/plugin/semisync/semisync_slave_plugin.cc b/plugin/semisync/semisync_slave_plugin.cc
index ffc663c9bdb..40c6ed9838c 100644
--- a/plugin/semisync/semisync_slave_plugin.cc
+++ b/plugin/semisync/semisync_slave_plugin.cc
@@ -45,13 +45,6 @@ int repl_semi_slave_request_dump(Binlog_relay_IO_param *param,
   if (!repl_semisync.getSlaveEnabled())
     return 0;
 
-  /*
-    Create the connection that is used to send slave ACK replies to
-    master
-  */
-  if (repl_semisync.slaveReplyConnect())
-    return 1;
-
   /* Check if master server has semi-sync plugin installed */
   query= "SHOW VARIABLES LIKE 'rpl_semi_sync_master_enabled'";
   if (mysql_real_query(mysql, query, strlen(query)) ||
@@ -106,7 +99,8 @@ int repl_semi_slave_queue_event(Binlog_relay_IO_param *param,
 				uint32 flags)
 {
   if (rpl_semi_sync_slave_status && semi_sync_need_reply)
-    return repl_semisync.slaveReply(param->master_log_name,
+    return repl_semisync.slaveReply(param->mysql,
+                                    param->master_log_name,
                                     param->master_log_pos);
   return 0;
 }