CODEWITHSUNDEEP
javasocketsnetwork-programmingthreadpool
Martin Wickman
Martin Wickman

Reputation: 19925

Reliably closing client sockets in a thread pool on shutdown

I have a simple ServerSocket-based java program which accepts a client connection and puts it in a threadpool (ThreadPoolExecutor):

while() {
    socket = serverSocket.accept();
    pool.submit(new Client(socket)); // Client is a Runnable
}

Problem is when I try to shutdown the program and client threads stay around until the connection is closed on the other end (the jvm does not exit until then).

I could try to maintain all client objects and close all their sockets when server is about to shutdown. But I have no clue how maintain them? Especially removing them when done.

I tried beforeExecute etc, but that only gives me another object (a FutureTask), not the Client object I'm looking for.

Update:

The problem is not adding sockets to a list, the problem is removing them when they are done as there are no way (afaik) to use afterExecute for that.

Upvotes: 3

Views: 2200

Answers (3)

Martin Wickman
Martin Wickman

Reputation: 19925

One way is to to have the Client return itself (in the Future) when done. Just need a list and then use the afterExecute method.

Like this:

pool =new ThreadPoolExecutor(...) {
    @Override
    protected void afterExecute(Runnable r, Throwable t) {
        // The future returns the Client object!
        client = (Client)((FutureTask)r).get();
        // Remove it from list of known clients
        clients.remove(client);

    }
};

while() {
    socket = serverSocket.accept();
    Client client = new Client(socket)

    // Submit to pool, using client as the future return value          
    pool.submit(client, client);
    // Add to list of known clients
    clients.add(client);
}

// When app is closing
private shutdown() {
    for(Client client : clients){
        client.shutdown();
    }
}

Upvotes: 1

user207421
user207421

Reputation: 311039

Call shutdownInput() on all the client sockets. That will cause the associated threads to think that the peer has disconnected and so exit gracefully.

Upvotes: 0

Warren Dew
Warren Dew

Reputation: 8938

Store all the sockets in a List before submitting them to the pool. Then the shutdown thread can call close() on all the sockets, which should cause the blocked threads to throw SocketExceptions.

Upvotes: 1

Related Questions