camunda workflow engine cpu & ram specifications - spring-boot

Is there any official requirements on CPU & RAM specifications for running a Spring Boot application integrating Camunda in production server for thousands of users ?? to prevent OutOfMemoryError primarly. How about Camunda Workflow Engine too ?
Thanks

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From an Application Server to Spring Boot - How Tos for Performance Tuning

Currently we have Java applications deployed in an Application server (Websphere to be exact). To fix common performance and memory related problems we encounter, we do tweakings like:
Adjust the thread pool setting - to prevent waiting threads.
Adjust the application server's garbage collection behavior.
Now, there is a plan to move them to containers (via Docker and using Spring Boot). So essentially they would be converted to Spring boot apps running on Docker containers. Now my question is, what is the equivalent of doing #1 and #2 in this kind of setup? is there still a way to adjust thread pool and garbage collection? or is it a different way now? or this shouldn't be an issue because docker swarm can manage all this and scale?
Edit: for the meantime, docker swarm will be used for managing containers. Kubernetes is still not in the picture.

Websphere scheduler vs Liberty scheduler

I am working on a project where we are planning to use WLP (WebSphere liberty) instead of traditional WAS.
The code is using WAS scheduler for scheduling activities.
Does liberty also have the same level of support/features for scheduler as present in WAS .
How can I migrate the scheduler tasks from websphere to liberty?
Code using the Scheduler in traditional WebSphere Application Server should not be migrated to EE Concurrency Utilities unless you are certain that you do not need the transactional/persistent quality of service that the Scheduler provides (Scheduler tasks run in a transaction and can roll back and be retried, and they can also persist across server restart). To obtain a similar quality of service in Liberty, you should migrate your Scheduler tasks to Persistent EJB Timers. Note that while fail over support across multiple servers is not present in Persistent EJB Timers in Liberty at the time of writing this, it is currently being worked on.

How to achieve high TPS with Spring Boot

I am working on a application (Banking) which has a TPS requirement of 100 and multiple concurrent users.
Will Spring Boot 1.x.x allow me to achieve this?
Note: I would have used Spring Boot 2.x.x which supports Reactive paradigm but there is some legacy code which I have to use and it does not work on 2.x.x.
You can hit these numbers running a Java application on any reasonable hardware. LMAX claims that Disruptor can do over 100k TPS with 1ms latency. Spring Boot, or Java in general, won't be the limiting factor.
What will be the problem are the business requirements. If your application is to produce complex reports from over utilised database that's located in another data centre, well just the packet round-trip from CA to Netherlands is 150ms. If your SQL queries will take 30+ seconds, you are toast.
You can take a look at Tuning Tomcat For A High Throughput, Fail Fast System. It gives a good insight what can be tuned in a standard Tomcat deployment (assuming you will use Tomcat in Spring Boot). However it's unlikely that HTTP connections (assuming you will expose HTTP API) will be the initial bottleneck.

How to dynamic deploy for standalone Spring batch using Spring Cloud Task

We are planning to retire the existing legacy java batch applications and recreate it with the latest available batch framework.
Given that we have a large number of batch jobs to be modernised, we are looking for a framework or architecture that would allow us to
Develop a batch solution that would allow us to dynamically deploy a new batch as and when they are created, without disturbing the existing deployed applications. - Does Spring cloud Task provide any of this feature. Note: We are looking only to deploy the apps to our local server, and has nothing to do with cloud.
If Spring Batch/Boot can provide us the feature we typically expect from a batch application, what is the special value add to go for Spring Cloud Task? - I wasn't able to completely understand this from the Spring documentation available online.
From the documentation of the Spring Cloud Task, I was able to understand that it allows an application to have many tasks within it. What should I do if each of the tasks have their own library dependencies, which might contradict with the dependencies of other Tasks? So in that case, should each of these tasks moved to a new application or this there a work around for that?
To answer your questions:
Does Spring Cloud Task handle orchestration - No. Spring Cloud Task does not handle orchestration of tasks or jobs. The component in this ecosystem that handles the deployment/orchestration of tasks or jobs is really Spring Cloud Data Flow (which is why I asked if you use any type of cloud platform including YARN, Cloud Foundry, Kubernetes, or Mesos...the environments supported by Spring Cloud Data Flow).
What added value does Spring Cloud Task provide over Spring Boot/Spring Batch - Spring Cloud Task is designed to provide a few things:
Similar abilities to Spring Batch with regards to state management without needing to create a batch job. When running a Boot application on a cloud environment, there is no standard way of getting the results from environment to environment (YARN handles job results differently from tasks on Cloud Foundry which is different from jobs on Kubernetes, etc). Spring Batch provides this but now all short lived processes need the overhead of the Batch API so Spring Cloud Task provides a lighter touch to those use cases.
Automatically adds informational listeners. With Spring XD, when you ran a job in an XD container, the XD container automatically added a number of informational listeners that broadcast events that you could listen for. Spring Cloud Task brings the same functionality without the need for the XD container.
Integration with Spring Cloud Stream. Spring Cloud Task provides the ability to launch tasks from messages received from Spring Cloud Stream. Also, the informational messages previously mentioned (both Batch events as well as Task events) are sent via Spring Cloud Stream channels.
The DeployerPartitionHandler. When working in a cloud environment, this PartitionHandler implementation allows you to launch workers for a partitioned batch job as tasks. This allows for the dynamic scaling of partitioned batch jobs instead of the traditional option of pre-deploying workers that listen for work which wastes resources in a modern cloud environment.
How does the packaging of multiple tasks work with dependencies - In short, this is not recommended. The idea of a Spring Cloud Task is that the execution of the Spring Boot application is the Task. While you could package up multiple tasks and using different methods, have them execute based on different stimulus, that goes against the 12 factor application concepts which are essential for correct use of Spring Cloud Task.
My two cents
For the best option for a modern batch platform, you really need to look into some from of platform first and that begins at the Cloud Foundry/Kubernetes/Mesos/YARN layer. Without that, you end up building a large part of the infrastructure yourself. That is why Spring XD evolved into Spring Cloud Data Flow. The added complexity that lived in the containers of Spring XD is removed by requiring a modern platform to run on (since they all handle those guarantees themselves). Without that piece, you're going to spend a lot of time managing the deployment and orchestration of applications that most modern platforms handle for you.
From there, the choice becomes pretty easy IMHO with Spring Cloud Task for simple tasks, Spring Batch for batch jobs, and Spring Cloud Data Flow for orchestration.

RESTful Microservice failover & load balancing

At the moment we have some monolithic Web Applications and try to transfer the projects to an microservices infrastructure.
For the monolithic application is an HAProxy and Session Replication to have failover and load balancing.
Now we build some RESTful microservices with spring boot but it's not clear for me what is the best way to build the production environment.
Of course we can run all applications as unix services and still have a reverse proxy for load balancing and failover. This solution seems very heavy for me and have a lot of configuration and maintenance. Resource Management and scaling up or down servers will be always a manually process.
What are the best possibilities to setup production environment with 2-3 Servers and easy resource management?
Is there some solution the also support continuous deployment?
I'd recommend looking into service discovery. Netflix descibes this as:
A Service Discovery system provides a mechanism for:
Services to register their availability
Locating a single instance of a particular service
Notifying when the instances of a service change
Packages such as Netflix's Eureka could be of help. (EDIT - actually this looks like it might be AWS specific)
This should work well with continuous delivery as the services can make themselves unavailable, be updated and then register availability again.

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