single thread executor

[Ron Pressler]

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