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STAGE4 - Migrate Database & Cutover.md

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Advanced Demo - Migrating a database with the Database MIgration Service

In this advanced demo you will be migrating a simple web application (wordpress) from an on-premises environment into AWS.
The on-premises environment is a virtual web server (simulated using EC2) and a self-managed mariaDB database server (also simulated via EC2)
You will be migrating this into AWS and running the architecture on an EC2 webserver and RDS managed SQL database.

Architecture Link : INSERT THE LINK HERE

This advanced demo consists of 5 stages :-

  • STAGE 1 : Provision the environment and review tasks
  • STAGE 2 : Establish Private Connectivity Between the environments (VPC Peer)
  • STAGE 3 : Create & Configure the AWS Side infrastructure (App and DB)
  • STAGE 4 : Migrate Database & Cutover <= THIS STAGE
  • STAGE 5 : Cleanup the account

StageArchitecture

STAGE 4A - CREATE THE DMS SUBNET GROUP

https://console.aws.amazon.com/dms/v2/home?region=us-east-1#subnetGroup
Click Create Subnet Group
For Name and Description use A4LDMSSNGROUP for VPC choose awsVPC
for Add Subnets choose aws-privateA and aws-privateB
Click Create subnet group

STAGE 4B - CREATE THE DMS REPLICATION INSTANCE

Move to the DMS Console https://console.aws.amazon.com/dms/v2/home?region=us-east-1#replicationInstances
Click create Replication Instance
for name enter A4LONPREMTOAWS use the same for Description
for Instance Class choose dms.t3.micro
for VPC choose awsVPC
For MultiAZ make sure it's set to dev or test workload (single AZ)
and for Pubicly Accessible uncheck the box
Expand Advanced security and network configuration
Ensure a4ldmssngroup is selected in Replication subnet group
For VPC security group(s) choose ***-awsSecurityGroupDB-***
Click Create

STAGE 4C - CREATE THE DMS SOURCE ENDPOINT

Move to https://console.aws.amazon.com/dms/v2/home?region=us-east-1#endpointList
Click Create Endpoint
For Endpoint type choose Source Endpoint and make sure that Select RDS DB Instance is UNCHECKED
Under Endpoint configuration set Endpoint identifier to be CatDBOnpremises
Under Source Engine set mariadb
Under Access to endpoint database choose Provide access information manually
Under Server name use the privateIPv4 address of CatDB (get it from EC2 console)
For port 3306
For username a4lwordpress
for password user the DBPassword you noted down in stage 1
click create endpoint

STAGE 4D - CREATE THE DMS DESTINATION ENDPOINT (RDS)

Move to https://console.aws.amazon.com/dms/v2/home?region=us-east-1#endpointList
Click Create Endpoint
For Endpoint type choose Target Endpoint
Check Select RDS DB Instance
Select a4lwordpress in the dropdown
It will prepopulate the boxes
Under Access to endpoint database choose Provide access information manually
For Password enter the DBPassword you noted down in stage1
Scroll down and click Create Endpoint

STAGE 4E - TEST THE ENDPOINTS

make sure the replication instance is ready Verify by going to Replication Instances and make sure the status is Available
Go back to Endspoints

Select the a4lwordpress endpoint, click Actions and then Test Connections
Click Run Test and make sure after a few minutes the status moves to successful
Go back to Endpoints
Select the catdbonpremises endpoint, click Actions and then Test Connections
Click Run Test and make sure after a few minutes the status moves to successful

If both of these are successful you can continue to the next step.

STAGE 4F - Migrate

Move to migration tasks https://console.aws.amazon.com/dms/v2/home?region=us-east-1#tasks
Click Create task
for Task identifier enter A4LONPREMTOAWSWORDPRESS for Replication instance pick the replication instance you just created
for Source database endpoint pick catdbonpremises
for Target database endpoint pick a4lwordpress
for Migration type pick migrate existing data you could pick and replicate changes here if this were a high volume production DB
for Table mappings pick Wizard
Click Add new selection rule
in Schema box select Enter a Schema
in Schema Name type a4lwordpress
Scroll down and click Create Task

This starts the replication task and does a full load from catdbonpremises to the RDS Instance.
It will create the task
then start the task
then it will be in the Running State until it moves into Load complete

At this point the data has been migrated into the RDS instance

STAGE 4G - Cutover the application instance

Move to the RDS Console https://console.aws.amazon.com/rds/home?region=us-east-1#
Click Databases
Click a4lwordpress
under Endpoint & Port copy the endpoint dns name into your clipboard

Move to the EC2 console https://console.aws.amazon.com/ec2/v2/home?region=us-east-1#Instances:
Select the awsCatWeb instance, right click, Connect
Select Session Manager and click Connect
When connected type sudo bash to run a privileged bash shell run cd /var/www/html run nano wp-config.php
locate the define DB_HOST line, and reolace the IP address with the RDS Host you just copied down into you clipboard
run ctrl+o to save and ctrl+x to exit.

Run the script below, to update the wordpress database with the new instance DNS name

#!/bin/bash
source <(php -r 'require("/var/www/html/wp-config.php"); echo("DB_NAME=".DB_NAME."; DB_USER=".DB_USER."; DB_PASSWORD=".DB_PASSWORD."; DB_HOST=".DB_HOST); ')
SQL_COMMAND="mysql -u $DB_USER -h $DB_HOST -p$DB_PASSWORD $DB_NAME -e"
OLD_URL=$(mysql -u $DB_USER -h $DB_HOST -p$DB_PASSWORD $DB_NAME -e 'select option_value from wp_options where option_id = 1;' | grep http)
TOKEN=$(curl -X PUT "http://169.254.169.254/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds: 21600")
HOST=$(curl -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/meta-data/public-ipv4)
$SQL_COMMAND "UPDATE wp_options SET option_value = replace(option_value, '$OLD_URL', 'http://$HOST') WHERE option_name = 'home' OR option_name = 'siteurl';"
$SQL_COMMAND "UPDATE wp_posts SET guid = replace(guid, '$OLD_URL','http://$HOST');"
$SQL_COMMAND "UPDATE wp_posts SET post_content = replace(post_content, '$OLD_URL', 'http://$HOST');"
$SQL_COMMAND "UPDATE wp_postmeta SET meta_value = replace(meta_value,'$OLD_URL','http://$HOST');"

Move to the EC2 console https://console.aws.amazon.com/ec2/v2/home?region=us-east-1#Instances:
Select CatDB, right click stop instance
Move to the EC2 console https://console.aws.amazon.com/ec2/v2/home?region=us-east-1#Instances:
Select CatWeb, right click stop instance

Move to the EC2 console https://console.aws.amazon.com/ec2/v2/home?region=us-east-1#Instances:
Select awsCatWeb and get its Public IPv4 DNS Open this in a new tab It should still show the application ... this is now pointed at the RDS instance after a full migration

STAGE 4 Finish

At this point you have created a VPC peer between the simulated On-premises environment and AWS You have fully migrated the wordpress application files from on-premises (simulated) into AWS
You have provisioned an RDS DB Instance
And you have used DMS to perform a simple migration of the database from on-premises (simulated) to AWS