Visual LANSA Forum

Hi all,

Does anyone run VLWeb application on AWS LANSA Scalabnle stack?
Or provide VLWeb application to the end user on on AWS LANSA Scalabnle stack?

I believe Web server instance and DB Web server instance are created when you deploy VLWeb application package(created with Deployment Tool) on AWS LANSA Scalable stak.
You can execute deployed VL web application on both instance and both instance refer the sam DB(e.g. SQL Server) via the same DBEndpoint.

1. Do you know why there are 2 instances(Web server instance and DB Web server instance)?

2. Do you know the role of each instances?

I cannot find any explanation in the document.

I appreciate your kind advice.

Best Regards,
Megumi Sawada

Hi Megumi,

The diagram below is from the LANSA Scalable Image page in the AWS Markteplace - under 'Usage Instructions' > 'View Cloud Formation Template':

The notes in this diagram are quite helpful.

Essentially, when a LANSA application is deployed using the LANSA Scalable stack in AWS, two instances are created (web server & DB web server).
They both act as web servers used by the load balancer.

The Database Web Server has the extra role of maintaining the database structure when tables are created (when the app is installed) or modified (when the app is upgraded).

There can be many instances of the Web Server running in an Auto-Scaling Group (for example if traffic increases and the app scales out), but there should only ever be one instance of a DB web server running, as this is the server that will make changes to the database structure.

I hope this helps,
Gerry.

Hi Gerry,

Thank you for the explanation and the image.
I think I have a better understanding now.

Thank you again!

Best Regards,
Megumi Sawada