DeferredUtils.java

package io.cattle.platform.deferred.util;

import io.cattle.platform.eventing.EventService;
import io.cattle.platform.eventing.model.Event;
import io.cattle.platform.util.exception.ExceptionUtils;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;

import org.apache.cloudstack.managed.threadlocal.ManagedThreadLocal;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class DeferredUtils {

    private static final Logger log = LoggerFactory.getLogger(DeferredUtils.class);

    private static final ManagedThreadLocal<List<Runnable>> TL = new ManagedThreadLocal<List<Runnable>>() {
        @Override
        protected List<Runnable> initialValue() {
            return new ArrayList<Runnable>();
        }
    };

    public static void deferPublish(final EventService service, final Event event) {
        defer(new Runnable() {
            @Override
            public void run() {
                service.publish(event);
            }
        });
    }

    public static void defer(Runnable runnable) {
        TL.get().add(runnable);
    }

    public static void nest(final Runnable runnable) {
        nest(new Callable<Object>() {
            @Override
            public Object call() throws Exception {
                runnable.run();
                return null;
            }
        });
    }

    public static <T> T nest(Callable<T> callable) {
        List<Runnable> old = TL.get();
        TL.set(new ArrayList<Runnable>());
        try {
            T result = callable.call();
            runDeferred();
            return result;
        } catch (Exception e) {
            ExceptionUtils.rethrowExpectedRuntime(e);
        } finally {
            TL.set(old);
        }

        /*
         * This really isn't possible to get to due to rethrowExpectedRuntime()
         * above
         */
        return null;
    }

    public static void resetDeferred() {
        TL.get().clear();
    }

    public static void runDeferred() {
        while (TL.get().size() > 0) {
            List<Runnable> toRun = TL.get();
            TL.remove();

            for (Runnable runnable : toRun) {
                try {
                    runnable.run();
                } catch (Throwable t) {
                    log.error("Failed to run deferred action", t);
                }
            }
        }
    }
}