Clever Geek Handbook

Project Loom: Modern Scalable Multithreading for the Java Platform







— , . Java concurrency. concurrency-, , , .







— Project Loom. Java .







, OpenJDK Core Libraries Project, Loom , Java . Joker 2020. — .









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API



API.







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java.lang.Thread. API, JDK 1.0. , «». , , . API, , .







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API. Project Loom, , , API fiber.







API, , . , , — . Thread.currentThread() , , .







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25 . API java.lang.Thread. java.lang.Thread , .







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Thread — . , , . «», , , ThreadLocals .







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IDE .









IDE , .







import ...

public class Demo {
    public static void main(String[] args) throws Exception {...}

    void run() throws Exception {

    }
}


, , Thread.startVirtualThread(). 







import ...

public class Demo {
    public static void main(String[] args) throws Exception {...}

    void run() throws Exception {

        Thread thread = Thread.startVirtualThread(() -> System.out.println("hello"));
        thread.join();

    }
}


«hello», . start(), .







-, , , .







void run() throws Exception {

    Thread thread = Thread.startVirtualThread(Thread::dumpStack);
    thread.join();

}


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, , , , JDK. , . , .







API. startVirtualThread()



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virtual(). c startVirtualThread()



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void run() throws Exception {

    Thread thread = Thread.builder().virtual().task(() -> {
        System.out.println("hello");
    }).start();

    thread.join();

    }

}


, . , , setDaemon() setName(). .







API , Thread API . — , startVirtualThread().







ThreadFactory. 







void run() throws Exception {
    ThreadFactory factory = Thread.builder().name("worker-", 0).factory();
}


— , worker-0, worker-1, worker-2 . worker — , . .







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Thread API . JDK 5, ThreadExecutor API java.util.concurrent.







ThreadExecutor. , .







ExecutorService executor:







try (ExecutorService executor = Executors.newVirtualThreadExecutor()) {

}


Executors . , try-with-resources. , Loom, — ExecutorService AutoCloseable, try-with-resources.







, , , , , , , . , , . Executor' , , Executors.







.







import ...

  public class Demo {
      public static void main(String[] args) throws Exception {...}

      void run() throws Exception {
          try (ExecutorService executor = Executors.newVirtualThreadExecutor()) {
              IntStream.range(0, 1_000_000).forEach(i -> {
                  executor.submit(() -> { });
              });
          }
      }

      String fetch(String url) throws IOException {...}

      void sleep(Duration duration) {...}
  }


IntStream.range(), for. executor.submit() , , . , — «Process finished with exit code 0».







, .







import ...

public class Demo {
    public static void main(String[] args) throws Exception {...}

    void run() throws Exception {
        AtomicInteger counter = new AtomicInteger();
        try (ExecutorService executor = Executors.newVirtualThreadExecutor()) {
            IntStream.range(0, 1_000_000).forEach(i -> {
                executor.submit(counter::incrementAndGet);
            });
        }
        System.out.println(counter.get());
    }

    String fetch(String url) throws IOException {...}

    void sleep(Duration duration) {...}
  }


Executor, , , , . , , .







— , .







, Executor'. , URL-, . — , .







String fetch(String url) throws IOExpection {
    try (InputStream in = URI.create(url).toURL().openStream()) {
        byte[] bytes = in.readAllBytes();
        return new String(bytes, "ISO-8859-1");
    }
}


, HTTP- , .







:







void run() throws Exception {

       try (ExecutorService executor = Executors.newVirtualThreadExecutor()) {

           Callable<String> task1 = () -> fetch("https://jokerconf.com/");
           Callable<String> task1 = () -> fetch("https://jokerconf.com/en");

           String first = executor.invokeAny(List.of(task1, task2));
           System.out.println(first.length());
       }     
}


, HTML- jokerconf.com. , , . - , , .







executor.invokeAny()



.

ExecutorService , invokeAny()



, invokeAll()



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first , , .







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, : , URL-, — URL-, , . , : 178 , — 200 .







. , - , invokeAll()



.







void run() throws Exception {

       try (ExecutorService executor = Executors.newVirtualThreadExecutor()) {

           Callable<String> task1 = () -> fetch("https://jokerconf.com/");
           Callable<String> task1 = () -> fetch("https://jokerconf.com/en");

           executor.invokeAll(List.of(task1, task2))
                   .stream() 
                   .map(Future::join) 
                   .map(String::length) 
                   .forEach(System.out.println);
       }     
}


, — , , invokeAll()



. , . InvokeAll()



, , Future, . , , , . 200 178 . ExecutorService.







-. Loom CompletableFuture, . CompletableFuture, Future, :







void run() throws Exception {

       try (ExecutorService executor = Executors.newVirtualThreadExecutor()) {

           Callable<String> task1 = () -> fetch("https://jokerconf.com/");
           Callable<String> task1 = () -> fetch("https://jokerconf.com/en");

           CompletableFuture<String> future1 = executor.submitTask(task1);
           CompletableFuture<String> future2 = executor.submitTask(task2);

           CompletableFuture.completed(future1, future2)
                   .map(Future::join) 
                   .map(String::length) 
                   .forEach(System.out.println);
       }     
}


CompletableFuture- completed(). , Future . , invokeAll(), , , . . - CompletionService, - .







, , , . , , CompletableFuture, .







, , . . . , , IO-, . , IDE, , .







import ...

public class Demo {
    public static void main(String[] args) throws Exception {...}

    void run() throws Exception {

        Thread.startVirtualThread(() ->

            sleep(Duration.ofSeconds(2));

        }).join();
    }

    String fetch(String url) throws IOException {...}

    void sleep(Duration duration) {...}
  }


, , . . , , .







void run() throws Exception {

        Thread.startVirtualThread(() -> {

            Object lock = new Object();
            synchronized (lock) {
                sleep(Duration.ofSeconds(2));
            }
        }).join();

}


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package demo;

import ...

@Path("/")
public class SleepService {

    @GET
    @Path("sleep")
    @Producers(MediaType.APPLICATION_JSON)
    public String sleep(@QueryParam("millis") long millis) throws Exception {
        Thread.sleep(millis);
        return "{ \"millis\": \"" + millis + "\" };
    }
}


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Helidon MP. , MP MicroProfile. Helidon , , , . , . , , , .







, , — - «hello world» . , curl-.













Curl- JSON, .

, , , — . Thread.dumpStack():







public String sleep(@QueryParam("millis") long millis) throws Exception {
    Thread.dumpStack();
    Thread.sleep(millis);
    return "{ \"millis\": \"" + millis + "\" };
}


. curl, HTTP- , , — millis=100.







curl http://localhost:8081/sleep?millis=100









: , Thread.dumpStack()



.













, : Helidon, Weld, JAX-RS… . , , .







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invokeAny involeAll , ExecutorService.







import ...

@Path("/")
public class AggregatorServices {

    @GET
    @Path("anyOf")
    @Produces(MediaType.APPLICATION_JSON)
    public String anyOf(@QueryParam("left") String left,
                        @QueryParam("right") String right) throws Exception {
        if (left == null || right == null) {
            throw new WebApplicationException(Response.Status.BAD_REQUEST);
        }

        try (var executor = Executors.newVirtualThreadExecutor()) {
            Callable<String> task1 = () -> query(left);
            Callable<String> task2 = () -> query(right);

            // return the first to succeed, cancel the other
            return executor.invokeAny(List.of(task1, task2));
        }
    }

    @GET
    @Path("allOf")
    @Produces(MediaType.APPLICATION_JSON)
    public String allOf(@QueryParam("left") String left,
                        @QueryParam("right") String right) throws Exception {

        if (left == null || right == null) {
            throw new WebApplicationException(Response.Status.BAD_REQUEST)
        }

        try (var executor = Executors.newVirtualThreadExecutor()) {
            Callable<String> task1 = () -> query(left);
            Callable<String> task2 = () -> query(right);

            // if one falls, the other is cancelled
            return executor.invokeAll(List.of(task1, task2), true)
                    .stream() 
                    .map(Future::join) 
                    .collect(Collectors.joining(", ", "{", " }"));
        }
    }

    private String query(String endpoint) {...}
}


, AggregatorServices. , : anyOf allOf. anyOf , , .







anyOf. curl-:







curl http://localhost:8081/anyOf?left=/greeting\&right=/sleep?millis=200


localhost:8081 — , — anyOf, — left right. «hello world»:







{"message":"Hello World!"}









, «hello world», 200 . , «hello world» , 200 , «hello world».







1 , , , , .







allOf, :







curl http://localhost:8081/allOf?left=/greeting\&right=/sleep?millis=1


.







{ {"message":"Hello World!"}, { "millis": "1" } }









allOf, . 







private String query(String endpoint) {
        URI uri = URI.create("http://localhost:8081").resolve(endpoint);
        return ClientBuilder.newClient()
                    .target(uri)
                    .request(MediaType.APPLICATION_JSON)
                    .get(String.class);
    }


, . API JAX-RS . invokeAll(), .stream (), .map , Collectors.joining(), JSON.







. , invokeAll() — , cancelOnException. , , . , .







Loom. JDK 16, , — JDK 16, , Loom.









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Loom?







Loom , Loom, , .







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SimpleDateFormat.

SimpleDateFormat , , ThreadLocals.







JDK SimpleDateFormats java.date dateformatter. ,

static final , . ThreadLocals .







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JFR.













server.jfr, . Jetty, . , . . JFR , , 200 , , , .







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Flight Recorder, , , JVM TI, , JVM TI, .







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Serviceability



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Preview: ARM64 Aarch64, 64- Intel ; - .









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Project Loom . , , . , . , , ExecutorService, AutoCloseable, , , , , .







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, Project Loom, — ( ) . , , . .







: https://jdk.java.net/loom


: loom-dev@openjdk.java.net


-: https://wiki.openjdk.java.net/display/loom/Main







-, — -.







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«Safe harbor»: , .













, Java- : Java- , . JPoint, ( , , VMware). , .


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