In April 2019, Microsoft announced the general availability of the Azure Front Door service.
The highlight of this service is layer 7 (HTTP/S) load balancing. In this post I want to briefly explore how Azure Front Door could sit in an example SAP landscape. But We Have Azure Application Gateway…
Yes, while the Azure Front Door service does provide similar capabilities with regards to load balancing an HTTP/s based back-end service, the similarities end when we start to consider multi-regional distribution of services. That is, multiple Azure regions actively servicing global clients.
Azure Application Gateway
The Azure Application Gateway service is the go-to service for HTTP/S load balancing for your Azure hosted HTTP/S IaaS or Container based services that are
contained within a region.
Event for some, limited, SAP uses, the Azure Application Gateway may be sufficient, but you really need an experienced SAP Solution Architect to help you plan your SAP landscape architecture at this point. The consequences of doing it wrong, could cause you to completely re-implement a new architecture pattern in your landscape and, of course, additional cost.
… and SAP Web Dispatcher
I have discussed the
features of the SAP Web Dispatcher before. The need for a SAP Web Dispatcher in a SAP landscape is clear and even more appropriate in a cloud deployment of SAP. Just like Azure Application Gateway, the SAP Web Dispatcher’s context should be limited to a single region. This is especially true because it is IaaS, which means the VMs on which the Web Dispatcher is deployed, are themselves bound to a specific region.
However, what is not clear is how disparate Web Dispatcher systems (i.e. different SAPGLOBALHOST values) can be used in different regions to correctly load balance. This is not the same as a single system with different instances in different regions!
How It All Hangs Together
If we go back to the purpose of this post, I wanted to show how Azure Front Door could be used within the context of a SAP system deployment in Azure.
To help convey the idea, I’ve put together a simple diagram:
In the above diagram, you can see that the Azure Front Door service is used to balance inbound requests from a customer booking system, across multiple Azure regions,
directly from the internet. This means that Azure Front Door is most definitely suited as a global customer facing load balancer. An example scenario is a 2 (or more) region architecture with primary region and disaster recovery region. If the primary region for our customer booking system is unavailable, a DR could be invoked and customers could be routed to the DR region, allowing customer bookings to be taken.
In the diagram, traffic routed from Azure Front Door, is then (for the sake of example) routed through Azure Application Gateway. This is just for example, but in reality it’s not really needed. It could be that you have a real mixture of SAP and non-SAP in some converged sub-domain, and it may be easier to load balance this mix of URLs at this level.
The main point at this point is, you are committed to returning data from a single region.
In our example diagram, the Azure Application Gateway then routes traffic to the SAP Web Dispatcher, which load balances the traffic over the back-end SAP ECC system available application servers using the ABAP stack message server (a feature that is
not easily replicated in any other load balancer). Where Does Azure Traffic Manager Sit?
The Azure Traffic Manager service is a DNS based routing and distribution service. If your company is a multinational conglomerate with a latency sensitive web based customer service, then the Azure Traffic Manager can be used to route customers to their nearest region, where you have your web service hosted and where they can potentially get the speedist and most appropriate content.
If you have only 2 or 3 regions, do not have latency issues and have no need to provide region specific content, then Azure Front Door is probably what you need. Summary:
I’ve tried to show how the Azure Front Door service can provide your internet sourced, customer entry point into your multi-region web service.
The diagram I’ve provided hopefully shows how Azure Front Door can be distinguished from other similar technologies in a SAP landscape including how Azure Application Gateway could also be in the mix (although rare). Finally I discuss how Azure Traffic Manager may not always be appropriate for load distribution. Useful Links
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