How to Successfully Migrate Legacy Applications to Azure WebApp Services
Consider a business scenario where the organization is running on old legacy applications and their technologies are already outdated, and there is no support from Microsoft. The need of the hour for the client is to upscale the existing systems and move the application to the cloud so that the business can accelerate its growth. At the same time, they want to strategize their risk assessment to avoid any impact on performance and security in the existing application during the transition.
Microsoft declared the end of support for legacy technologies like VB/ASP, ASP.NET 2.0.
Many customers’ legacy applications are still running on their on-premises with old OS like Window Servers 2000, Windows Server 2008, or Windows 7, which are end of support. Also, application agents have installed those servers related to the legacy application like COM+ VB library.
The same database may be used by other legacy applications or inter-communication between two or more applications on either DB or application sides.
Due to application code complexity or business revenue from any such application, it’s risky to deploy a new setup on the latest supported version of OS on new Azure VMs or Azure Web App (PaaS) without proper research.
There is also a risk of keeping these application setups running on unsupported versions of OS as its vulnerable to new threats and issues with performance due to less flexible scalability when loads increase.
As on Jan 2023, Microsoft doesn’t have any OOB tool to perform in-place upgrades for such unsupported OS running on the Azure cloud.
Deploy the Azure Migration tool on the On-Premises server where the legacy application is present for assessing & discovering legacy application dependencies.
Review application code to check how many portions of code can be replaced using Visual Studio IDE in the latest .NET framework in Azure WebApp with minimal effort.
Identify all the portion of code like COM+ VB which needs to remediate in the same latest .NET framework.
Identify security (Authentication & Authorization) related code that needs to change from .NET Window Authentication with Active Directory to token-based OAuth code with Azure AD.
If communication is needed between migrated applications and other existing applications, either DB end or application side, then set up a VPN tunnel between Azure Private VN and On-premises for smooth and secure communication.
Use the Azure SQL Migration tool to migrate SQL Database to either Azure SQL Database or Azure SQL Manage Instance (in case some other SQL services are required, like any SQL Job, SSIS, or SSRS present or the organization has its SQL Server license).
If the Database is huge, it will require configuring Azure data factory for delta data migration between legacy and new.
Update the SQL connection string for all the other applications present on-premises that use the same DB after complete migration.