single thread executor

[Miguel Ping]

Yeah I was about to reply exactly this.

I always thought I knew basic executors, but now I find the api confusing:
I create a ThreadExecutor that runs off a ThreadFactory (so far so good)
that is built using virtual threads using a singleThreadExecutor.
It's a bit confusing to see two executors here, but I guess the
newThreadExecutor is just wrapping the threadFactory.

Anyway, thanks alot for replying, especially on a saturday.
I'm anxiously looking forward to continuing experimenting with Loom.

Have a nice weekend.

On Sat, Sep 5, 2020 at 6:02 PM Ron Pressler <ron.pressler at oracle.com> wrote:

> Correction:
>
> It should be Executors.newThreadExecutor(tf) rather than
> Executors.newUnboundedExecutor(tf).
> The latter was the old API method, which has been renamed to the former.
>
> — Ron
>
>
> On 4 September 2020 at 18:50:27, Ron Pressler (ron.pressler at oracle.com)
> wrote:
>
> Remember, you want multiple virtual threads, but use only on platform
> thread to schedule them. So you need to pass the single-thread executor
> as the virtual thread scheduler:
>
>     ThreadFactory tf =
> Thread.builder().virtual(Executors.newSingleThreadExecutor()).factory();
>
> And then you can use the thread factory directly to create virtual
> threads,
> or use it like so:
>
>     ExecutorService e = Executors.newUnboundedExecutor(tf);
>
> - Ron
>
>
> On 4 September 2020 at 18:21:45, Miguel Ping (miguel.ping at gmail.com)
> wrote:
>
> Hi all,
>
> I was experimenting with single thread executor and loom, and I was
> expecting that if I have two tasks where the first call goes through
> Socket.read, loom would schedule the second one. I'm pretty sure I'm doing
> something wrong.
>
> Here's the output I got (I was expecting "Hello world" to appear before
> "Connected!"; the program only concludes after I Ctrl+C the netcat
> process):
>
>
> $ nc -p 5555 -kl
>
> -- output --
> sleeping 1s
> Connected!
> Hello world
>
> -- java --
>
> import java.net.InetSocketAddress;
> import java.nio.ByteBuffer;
> import java.nio.channels.SocketChannel;
> import java.util.Arrays;
> import java.util.concurrent.Callable;
> import java.util.concurrent.Executors;
>
> public class Test {
>
> public static String block() {
> // nc -p 5555 -kl
> try {
> System.out.println("sleeping 1s");
> Thread.sleep(1000);
> var socket = SocketChannel.open();
> socket.connect(new InetSocketAddress("localhost", 5555));
> System.out.println("Connected!");
> socket.read(ByteBuffer.allocate(10)); // I was hoping this would allow the
> other task to be scheduled
> return "End";
> } catch (Exception e) {
> e.printStackTrace();
> return "Failed";
> }
> }
>
> public static String print() {
> System.out.println("Hello world");
> return "Printed";
> }
>
> public static void main(String[] args) throws Throwable {
> var e = Executors.newFixedThreadPool(1,
> Thread.builder().virtual().factory());
> Callable<String> t1 = Test::block;
> Callable<String> t2 = Test::print;
>
> var tasks = Arrays.asList(t1, t2);
> var fut = e.invokeAll(tasks);
> }
> }
>
> --
> Thanks
>
>