CODEWITHSUNDEEP
javanio
Сашка724ая
Сашка724ая

Reputation: 682

Multithreaded Non-Blocking-IO Selector

Has Non-blocking server, now it looks like:

ServerSocketChannel server = ServerSocketChannel.open();
// ... Many stuff like initialise selector, load world, etc
while(server.isOpen())
{
    selector.select();
    Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
    while(iterator.hasNext())
    {
        SelectionKey key = iterator.next();
        switch(key.interestOps())
        {
            case SelectionKey.OP_ACCEPT:
                // .... Accepting, register selector, packet handler etc
                break;
            case SelectionKey.OP_READ:
                // .... Read-write stuff
                break;
        }
        iterator.remove();
    }
}

I need to e.g. 1 thread handles 100 connections. Other 100 connections handles another thread. I tried do it with this code:

public class ConnectionsHandler implements Runnable
{
    private Selector selector;// For each thread gets its own selector

    @Override public void run()
    {
        while(Server.server.isOpen())
        {
            selector.select();
            Iterator<SelectionKey> iterator = selector.selectedKeys().iterator();
            while(iterator.hasNext())
            {
                SelectionKey key = iterator.next();
                // .... Read-write stuff
                iterator.remove()
            }
        }
    }
}

But both threads after first accepted connection freezes... No any exception thrown, it's simply freezes.

Upvotes: 1

Views: 696

Answers (1)

user207421
user207421

Reputation: 310860

register() is a blocking operation and so is select(). If getMostFreeSelector() returns the other selector and it is in select() at the time, the register() will block until the selector wakes up. You could call selector.wakeup() to fix this, or always register to the current selector, but I would question the whole architecture. Unless you have many thousands of connections there is little point in the second selector and thread.

Note also my comment above about the switch statement.

Upvotes: 1

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