add mysql84 support

Author: shanth96

config/embed.go

@@ -16,3 +16,6 @@ var MycnfMySQL57 string
 
 //go:embed mycnf/mysql80.cnf
 var MycnfMySQL80 string
+
+//go:embed mycnf/mysql84.cnf
+var MycnfMySQL84 string

config/mycnf/mysql84.cnf

@@ -0,0 +1,43 @@
+# This file is auto-included when MySQL 8.4.0 or later is detected.
+
+# all db instances should skip starting replication threads - that way we can do any
+# additional configuration (like enabling semi-sync) before we connect to
+# the source.
+skip_replica_start
+
+# MySQL 8.0 enables binlog by default with sync_binlog and TABLE info repositories
+# It does not enable GTIDs or enforced GTID consistency
+
+gtid_mode = ON
+enforce_gtid_consistency
+relay_log_recovery = 1
+binlog_expire_logs_seconds = 259200
+
+# disable mysqlx
+mysqlx = 0
+
+# 8.4 changes the default auth-plugin to caching_sha2_password and
+# disables mysql_native_password by default.
+mysql_native_password = ON
+authentication_policy = 'mysql_native_password'
+
+# Semi-sync replication is required for automated unplanned failover
+# (when the primary goes away). Here we just load the plugin so it's
+# available if desired, but it's disabled at startup.
+#
+# VTTablet will enable semi-sync at the proper time when replication is set up,
+# or when a primary is promoted or demoted based on the durability policy configured.
+plugin-load = rpl_semi_sync_source=semisync_source.so;rpl_semi_sync_replica=semisync_replica.so
+
+# MySQL 8.0.26 and later will not load plugins during --initialize
+# which makes these options unknown. Prefixing with --loose
+# tells the server it's fine if they are not understood.
+loose_rpl_semi_sync_source_timeout = 1000000000000000000
+loose_rpl_semi_sync_source_wait_no_replica = 1
+
+# In order to protect against any errand GTIDs we will start the mysql instance
+# in super-read-only mode.
+super-read-only
+
+# Replication parameters to ensure reparents are fast.
+replica_net_timeout = 8

go/vt/mysqlctl/mysqld.go

@@ -820,7 +820,11 @@ func (mysqld *Mysqld) getMycnfTemplate() string {
 				log.Infof("this version of Vitess does not include built-in support for %v %v", mysqld.capabilities.flavor, mysqld.capabilities.version)
 			}
 		case 8:
-			versionConfig = config.MycnfMySQL80
+			if mysqld.capabilities.version.Minor < 4 {
+				versionConfig = config.MycnfMySQL80
+			} else {
+				versionConfig = config.MycnfMySQL84
+			}
 		default:
 			log.Infof("this version of Vitess does not include built-in support for %v %v", mysqld.capabilities.flavor, mysqld.capabilities.version)
 		}