You are designing a web server that has one server thread reading requests from
ID: 2247520 • Letter: Y
Question
You are designing a web server that has one server thread reading requests from n-number of users that stream in at a given rate. The requests are put in a buffer of constant size that are services by a thread pool of m-threads.
a) Break this problem into 1 or more producer-consumer problems, describing the producer and the consumer at each sub-problem.
Additionally, you decide to forgo the use of lock primitives such as pthread_lock and pthread_unlock to reduce latency on running threads.
b) Describe how compare-and-swap operations can be used to ensure mutual exclusion during produce and consume operations on the buffer.
Explanation / Answer
For the server that is handling thread ,we create a specified number of threads at start and then assign task to them. So we dont need to implement threads every now and then
Use these threads as a buffer for queueing processes
Threads are constantly looking for queue and when a request come one of the thread dispatch the request and perform action
Here are some queue methods
add(); //add a socket at the end
removeFront();//remove socket from front
isEmpty();//True if queue is empty
size(); //return size of queue
getMaxSize();//get maximum size for queue
Your Request processing runnable
public class Processor implements Runnable {
private Queue<Socket> requests;
private boolean stops;
Processor(Queue<Socket> req) {
this.requests = req;
stops = false;
}
@Override
public void run() {
while(!stops) {
if(requests.isEmpty()) {
try{
Thread.sleep(#rendomeTimemill);
} catch(InterruptedException e){}
}else {
Socket st = Queue.removeFront();
try {
//System.out.println("processing request from " + socket.getInetAddress().getHostName());
//do you want
} catch (Exception e) {
} finally {
if(st != null) {
try{ st.close(); st = null; } catch(IOException ex){}
}
}
}
}
}
public void stopNow() {
stops = true;
Thread.interrupt();
}
}
in your main thread create a queue to put requests
//start your server socket
Queue<Socket> requests = new Queue<Socket>();
Start worker thread pool
Precessor []workers = new Processor[NUM_WORKER];
for(int i=0;i<NUM_WORKER; i++) {
worker[i] = new Processor(requests);
Thread th = new Thread(worker[i]);
th.strat();
}
in request listening
//while loope that run forever
// accept socket
if(requests.size() == requests.getMaxSize()) {
socket.getOutputStream().write("HTTP/1.0 505 Error ".getBytes());
socket.getOutputStream().write("<html><body>Try again</body></html> ".getBytes());
socket.close();
} else {
requests.add(socket);
}
when you want to shout down server
for(int i=0;i<NUM_WORKER; i++) {
worker[i].stopNow();
}
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