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On the other hand, there can be several disadvantages of this design such as thread creation overhead in case of frequent or recurring requests, significant processing overhead, resource exhaustion of threads (leading to {{OutOfMemoryError}}), thread scheduling and context switching overhead \[[Lea 00|AA. Java References#Lea 00]\]. |
An attacker can cause a denial of service by overwhelming the system with too many requests, all at once. Instead of degrading gracefully, the system goes down abruptly, resulting in an availability issue. Thread pools allow the system to service as many requests as it can comfortably sustain, instead of stopping all services when faced with a deluge of requests. From the safety point of view, it is possible for one component to exhaust all resources because of some intermittent error, starving all others from using them.
Thread Pools overcome these disadvantages issues as the maximum number of worker threads that can be initiated and executed simultaneously can be suitably controlled. Every worker accepts a Runnable object from a request and stores it in a temporary Channel like a buffer or a queue until resources become available. Because threads are reused and can be efficiently added to the Channel, most of the thread creation overhead is eliminated.
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