Migrating legacy system to Azure Cloud
Some of the questions we need to answere is thatData Storage
3rd party libary
middleware
Things to considered each building block (technology stacks) at on premise app architecture has corresponding azure building blocks.
VM - Iaas vm service
db - azure db
storage - blob
distributed architecure -
cache
api
queue
bus
authenticstion
Phases the migration depend on the techinical challenges and business needs.
One catch all note: migration cannot be one stop shopping, inevitablly this can be done in phases, hybrid architecture will be helpful to organize the building block of a application in different env work together during transitinal period.
migration is Depend on the business initiative.
The end goal is for each migration stage, we need to keep the business running for customer without disruption.
Usually migrating db from sql server to azure sql is the easiest piece.
You always has the flexibility to consider hybrid architecture using relay service while keeping the front end at on prem and migrate the backend to azure or vice versa depend on your biz needs and the pace you want to plan the migration.
Then other options are migrate
Some limitation at azure sql compare to sql server.
[*]1msdtc (transaction) is not supported.
[*]2column level encrytion is not supported
[*]3.Cross db inquery
[*] 4.azure sql mandate primary key cluster index.
sql migration wizard and redgate is 2 recommended option.
click on db - task - export to azure. result of export will display detail error msg.
Nice about sql mw is it allows preview of the migrate compatibility issue before migrate happens.
change the setting to point to Azure db
Migrate services
ServiceBus.
Client app to communicate with backend app if they are in same net work which should be easy.
If they are in different env and communicating behind fire wall that will be cubersome.
ServiceBus Relay service can play a role of trusted party to help both side to communicate particularly useful in hybrid architecture.
MSMQ - > ServieBus Queue
SB queue is storage location for messages, msmq to servicebus queue is comparatively simple requires mimimum re-coding.
Relay service
The typical use scenario is point to point communiction, client to server service call or server to server service call
Access Control Service (ACS)
ACS help with moving AD authentioncation to Cloud
Setup at Azure AC service
Change application to use ServiceBus.
Having the service resides at on-prem to be called by client anywhere out of on-prem is a big challeges to be resloved with relay service
Client used to point to local msmq now to service bus queue with binding change to NetMessagingBinding
Client used to listen on local msmq now to service bus queue
Web applicaiton & Authentication migration
Our scenario - Moving the local website and authention to the azure using web role and authentication access control
Active Dirctory Federation Service will query Active Directory base on different standard, SAML claim returns comprehensive ifno for NAME, GROUP and EMAIL
ACS host at Azure offers endpoint for ADFS at local AD server to point to get meta data
Paste the ACS metadata URL to Relying Party at local AD
Map the rule
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