Having issue with Multi Threaded Java app in Cloud Foundry

Question

My Java app has a program which executes multiple threads on the same time to complete a task. It works really well on my local computer as it has 4 Cores and 8 Logical Processors but when I deploy my app on cloud foundry, it doesn't allow to create more than 1 thread. I debugged and found that Cloud Foundry JVM has only 1 CPU allocated therefore it cannot run multiple threads simultaneously.

How can I fix this problem?

Do I need to buy more CPUs or There is a way to change JVM configuration to set multiple CPUs for the java app.

Answer 1

In the SAP Cloud Platform Cloud Foundry, a number of CPUs depends on allocated memory. You can get a maximum vertical scaling of 8GB RAM and 2 CPUs. See the ration in the quote below.

In the Cloud Foundry environment, applications get guaranteed CPU share of ¼ core per GB instance memory. As the maximum instance memory per application is 8 GB, this allows for vertical scaling up to 2 CPUs.

Here you can find more on quotas and limitations of SAP Cloud Platform.

This blog provides interesting insights on performance testing on SCP

To update your quota go to overview section of your App and follow the steps on the screenshot:

Answer 2

I am giving an answer to my own question as I have figured out the issue. The thread deadlock was the root cause of the issue. Multiple threads were calling the same methods concurrently and the threads were getting trapped when waiting for each other to release the lock. Therefore the execution was becoming unresponsive. To fix it, I changed all the methods used in call method of Callable to have synchronisation using keyword "synchronized" in method declaration. It is now working fine locally and in the Cloud environment. The only thing, I still don't understand is why deadlock was only happening in cloud environment but not locally. I guess it might be the different JVM configuration in the cloud.

@Artyom Kovalyov, here is how I splited tasks for parallel processing.

final int numberOfWorkers = 4;
List<Callable<Void>> tasks = new ArrayList<Callable<Void>>();

//code here to create and add tasks to list

final List<List<Callable<Void>>> dividedTasks = Lists.partition(tasks, numberOfWorkers);
final ExecutorService executor = Executors.newFixedThreadPool(numberOfWorkers);
for (List<Callable<Void>> subsetOfTasks : dividedTasks) {
    try {

// you can invoke all tasks in one go but I prefer invoking number of taks same as thread pool max thread number

        executor.invokeAll(subsetOfTasks);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}
executor.shutdownNow();