THsHaServer instantiates its ThreadPoolExecutor with a LinkedBlockingQueue. That behavior is documented in java as:
There are three general strategies for queuing:
2. Unbounded queues. Using an unbounded queue (for example a LinkedBlockingQueue without a predefined capacity) will cause new tasks to wait in the queue when all corePoolSize threads are busy. Thus, no more than corePoolSize threads will ever be created. (And the value of the maximumPoolSize therefore doesn't have any effect.) This may be appropriate when each task is completely independent of others, so tasks cannot affect each others execution; for example, in a web page server. While this style of queuing can be useful in smoothing out transient bursts of requests, it admits the possibility of unbounded work queue growth when commands continue to arrive on average faster than they can be processed.
therefore changing maxWorkerThreads (passed as maximumPoolSize) has no effect. The parameter should probably just be removed and minWorkerThreads renamed to numThreads, since setting minWorkerThreads does have an effect and is a workaround.