[Architecture] Moving app logic to server side

Alessandro71

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Not quite a "Chit Chat" topic, but I've found no proper place for an architectural topic, on which I would like to hear views and experiences from other developers.

For various reasons I won't go into details here, I'm going to evaluate the option of moving my app core logic to server side, and making the app as lean as possible, just like a "thin client".
Since on the app side I have to deal with external devices connections, it can't be a fully web app, since I need some code and logic on the phone, to deal with connections management.
Since the app is obviously written in B4X, porting to B4J the server component should be easy.

I see an issue with the fact that, right now, the code works in a "single user/single instance" mode:
The app logic, running on the phone, works for a single user: porting it to server side, must deal with multiple users using it at once.

I see an "easy path" and a "right path":
  • "easy path": leave the code as-is (single user/single instance) and let something external deal with: when a user starts the app, a new server instance is created and bound to that app session.
  • "right path": rewrite the core code logic to deal with multiple sessions/multiple users at once, so the app will always connect to the same server instance.
the "easy path" resembles the way docker containers scales out for handling traffic increase behind a load balancer: is there anything similar for B4J server apps?
the "right path" has a deep impact on the code, with a massive rewrite involved.
 

hatzisn

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I always wanted to learn Kubernetes and I am not totally sure if it can create new instances of vps but If I remember correctly from some videos I have watched in the past, this might be the case.

According to this tutorial, this is not the case but you can use a Cloud Provider specific API to create/destroy nodes for the Kubernetes or just use Terraform which does this according to ChatGPT :


For containers though, it is a sure thing that Kubernetes does it and if you look at docker hub you can find an image with latest OpenJDK and use it to create a container with B4J utilizing an appropriate dockerfile. For an example creating a docker image with a B4J jar file and the corresponding www + logs check the B4J tutorials in my signature in my contributions. This is if you choose the server way.

To be honest I believe the transferring of an app to a server should be done only if there are issues of hiding something from the end user (f.e. an API Key or user validation/access granding or a specific procedure or something like this).

If you use the server way make sure you will avoid concurrent record manipulation.


And a free candy from ChatGPT (the question is: "Can Kubernetes and Terraform cooperate?") :

 
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b4x-de

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Architecture is a difficult topic. I used a Model-View-Presenter (MVP) pattern in conjunction with the Data-Access-Object (DAO) pattern for a clean layering. I separated each in their own b4xlib, i.e. a lib for models, a lib for views, a lib for presenters. For Android and iOS I created native projects that use these libraries in their Activities and Pages. That separates the platform specific logic. For the Web app I use the B4j server and call the presenters from the Handlers. Model and DAO is the same. I only needed a new View based on Thymeleaf. You might check the API Server that is available here in the forum instead. Hope this helps.
Thomas
 
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