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Azure Spring Cloud and DMZ

Starting from 2019, we can find a new service in Azure portfolio - Azure Spring Cloud. Microsoft together with Pivotal joined their forces by offering the capability of running Spring Boot applications inside Azure seamless.
Azure Spring Cloud is a SaaS, that is managed by Pivotal offering 100% compatibility with any type of Java application that was built for Spring Boot. It might not sound a big WOW, but having the ability to migrate the line of business applications that are running inside on-premises systems to a full managed Spring Boot environment is awesome. 
If you want to find about this service I invite you to check the service page.

A common discussion that arises when you need to take the on-premises application and put them inside Azure Spring Cloud is related to network security - more exactly DMZ. There are two different worlds that usually collide and it is important to understand both concerns and limitations. 

Azure Spring Cloud is running on top of Azure Kubernetes Services and use Service Registry and Spring Cloud Config Service to offer the high availability and the same experience that you have in Pivotal. The nice thing is that you have the same capability as you have in Pivotal to patch automatically your code inside containers and fully manage them using Pivotal Build Service.

From infrastructure and security point of view, at this step things can be a little confusing from a DMZ point of view. In general, when you are working with Azure and you want to build a DMZ landing node you can use with success the Azure network capabilities like VNETs, NVA (Network Virtual Appliances) and NSG (Network Security Groups).
Unfortunately, at this moment you cannot use the network features of Azure to build the DMZ inside Azure Spring Cloud. Things might change in the future, but for now, we cannot rely on network integration.

Even so, if you used Pivotal in the past, you know the capability to define a DMZ zone at the application layer. It's not as a DMZ at the network layer but can work with success if you don't want to put additional services in front of Azure Spring Cloud
A solution to limit the container-to-container communication is to configure Diego Brain in such a way that you limits what application can talk with what application (so-called Diego Cells). Using this approach you define and isolate the applications that are part of the DMZ and the channels that can be used to talk with the rest of the system. Unfortunately, Diego is not available inside Azure Spring Cloud, so you will not be able to use it.

The 3rd option available is to rely on Azure AD and add to each application the capability to allow requests from users with specific roles. In this way, you could virtual map and isolate a collection of applications that are part of DMZ.

This is a good trade-off until we will have the capability to use VNET features inside Azure Cloud Spring also. Nevertheless, I'm sure that we will see pretty soon the integration with VNET - it is just a matter of time.


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