package org.web3j.utils;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
/**
* Async task facilitation.
*/
public class Async {
private static final ExecutorService executor = Executors.newCachedThreadPool();
static {
Runtime.getRuntime().addShutdownHook(new Thread(() -> shutdown(executor)));
}
public static <T> CompletableFuture<T> run(Callable<T> callable) {
CompletableFuture<T> result = new CompletableFuture<>();
CompletableFuture.runAsync(() -> {
// we need to explicitly catch any exceptions,
// otherwise they will be silently discarded
try {
result.complete(callable.call());
} catch (Throwable e) {
result.completeExceptionally(e);
}
}, executor);
return result;
}
private static int getCpuCount() {
return Runtime.getRuntime().availableProcessors();
}
/**
* Provide a new ScheduledExecutorService instance.
*
* <p>A shutdown hook is created to terminate the thread pool on application termination.
*
* @return new ScheduledExecutorService
*/
public static ScheduledExecutorService defaultExecutorService() {
ScheduledExecutorService scheduledExecutorService =
Executors.newScheduledThreadPool(getCpuCount());
Runtime.getRuntime().addShutdownHook(new Thread(() -> shutdown(scheduledExecutorService)));
return scheduledExecutorService;
}
/**
* Shutdown as per {@link ExecutorService} Javadoc recommendation.
*
* @param executorService executor service we wish to shut down.
*/
private static void shutdown(ExecutorService executorService) {
executorService.shutdown();
try {
if (!executorService.awaitTermination(60, TimeUnit.SECONDS)) {
executorService.shutdownNow();
if (!executorService.awaitTermination(60, TimeUnit.SECONDS)) {
System.err.println("Thread pool did not terminate");
}
}
} catch (InterruptedException ie) {
executorService.shutdownNow();
Thread.currentThread().interrupt();
}
}
}
