update comment

mysql-replication/README.md

@@ -11,7 +11,7 @@ This template deploys a MySQL replication environment with one master and one sl
 - Deploys 2 VMs in an Azure VNet, each has 2 data disks striped into Raid0
 - Deploys a load balancer in front of the 2 VMs, so that the VMs are not directly exposed to the internet.  MySQL and SSH ports are exposed through the load balancer using Network Security Group rules
 - Configures a http based health probe for each MySQL instance that can be used to monitor MySQL health
-- Installs LIS4 driver and reboots each VM 3 minutes after the installation script on each VM completes
+- Installs LIS4 driver on each VM. Note that the VM is not automatically rebooted, so LIS4 will take effect the next time the VM reboots
 
 ### How to Deploy
 You can deploy the template with Azure Portal, or PowerShell, or Azure cross platform command line tools.  The example here uses PowerShell to deploy.
@@ -63,7 +63,7 @@ High availability and failover are no different from other GTID based MySQL repl
 > $nic0=Get-AzureNetworkInterface -Name mysqldns-nic0 -ResourceGroupName mysqlrg
 > $nic1=Get-AzureNetworkInterface -Name mysqldns-nic1 -ResourceGroupName mysqlrg
 ...
-# $i is the index of the target nat rule, for full powershell script, see switchMySQLNatRule.sql
+# $i is the index of the target nat rule, for full powershell script, please see [switchMySQLNatRule.ps1](/mysql-replication/switchMySQLNatRule.ps1)
 ...
 > $rule0=$nic0.IpConfigurations[0].LoadBalancerInboundNatRules[$i]
 > $nic0.IpConfigurations[0].LoadBalancerInboundNatRules.removeRange($i,1)
@@ -77,7 +77,7 @@ mysql> change master to master_host='10.0.1.5', master_user='admin', master_pass
 * Switch the old master's NAT rule with the new master
 ```sh
 ...
-# $j is the index of the target nat rule, for full powershell script, see switchMySQLNatRule.sql
+# $j is the index of the target nat rule, for full powershell script, see please see [switchMySQLNatRule.ps1](/mysql-replication/switchMySQLNatRule.ps1)
 ...
 > $rule1=$nic1.IpConfigurations[0].LoadBalancerInboundNatRules[$j]
 > $nic1.IpConfigurations[0].LoadBalancerInboundNatRules.removeRange($j,1)

mysql-replication/switchMySQLNatRule.ps1

@@ -1,3 +1,4 @@
+#this script switches the NAT rule on the Azure Load Balancer from the old MySQL master to the new one
 $rg="mySQLResourceGroupName"
 $dns="mySQLDNSName"
 $from="0" #current mysql master VM postfix, disable its mysql public port 
@@ -12,13 +13,15 @@ $nic1Rules=$nic1.IpConfigurations[0].LoadBalancerInboundNatRules
 $nic0RuleCnt=$nic0.IpConfigurations[0].LoadBalancerInboundNatRules.Count
 $nic1RuleCnt=$nic1.IpConfigurations[0].LoadBalancerInboundNatRules.Count
 
+#find the mysql NAT rule on the old master and remove it
 for ($i=0; $i -lt $nic0RuleCnt; ++$i) {if ($nic0Rules[$i].Id -like "*MySQLNatRule*") {break;}}; 
 if ($i -ge $nic0RuleCnt) {exit 1}
 
 $rule0=$nic0.IpConfigurations[0].LoadBalancerInboundNatRules[$i]
 $nic0.IpConfigurations[0].LoadBalancerInboundNatRules.removeRange($i,1)
 Set-AzureNetworkInterface -NetworkInterface $nic0
 
+#find the mysql NAT rule on the new master, replace it with the old master's NAT rule
 for ($j=0; $j -lt $nic1RuleCnt; ++$j) {if ($nic1Rules[$j].Id -like "*MySQLNatRule*") {break;}}; 
 if ($j -ge $nic1RuleCnt) {exit 1}
 
@@ -27,6 +30,7 @@ $nic1.IpConfigurations[0].LoadBalancerInboundNatRules.removeRange($j,1)
 $nic1.IpConfigurations[0].LoadBalancerInboundNatRules.add($rule0)
 Set-AzureNetworkInterface -NetworkInterface $nic1
 
+#the old master resumes the new master's previous NAT rule
 $nic0.IpConfigurations[0].LoadBalancerInboundNatRules.add($rule1)
 Set-AzureNetworkInterface -NetworkInterface $nic0
 exit 0