com.github.dxee.dject.lifecycle.LifecycleManager Maven / Gradle / Ivy

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A collection of guice extensions, help to improve the developer experience of guice.
There is a newer version: 1.5.1
package com.github.dxee.dject.lifecycle;

import com.github.dxee.dject.annotations.SuppressLifecycleUninitialized;
import com.github.dxee.dject.lifecycle.impl.SafeLifecycleListener;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.inject.Singleton;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicReference;

/**
 * Manage state for lifecycle listeners
 *
 * @author elandau
 */
@Singleton
@SuppressLifecycleUninitialized
public final class LifecycleManager {
    private static final Logger LOGGER = LoggerFactory.getLogger(LifecycleManager.class);

    /**
     * Processes unreferenced LifecycleListeners from the referenceQueue, until
     * the 'running' flag is false or interrupted
     */
    private final class ListenerCleanupWorker implements Runnable {
        public void run() {
            try {
                while (running.get()) {
                    Reference ref = unreferencedListenersQueue.remove(1000);
                    if (ref != null && ref instanceof SafeLifecycleListener) {
                        removeListener((SafeLifecycleListener) ref);
                    }
                }
                LOGGER.info("LifecycleManager.ListenerCleanupWorker is exiting");
            } catch (InterruptedException e) {
                LOGGER.info("LifecycleManager.ListenerCleanupWorker is exiting due to thread interrupt");
            }
        }
    }


    private final Set listeners = new LinkedHashSet<>();
    private final AtomicReference state;
    private final ReferenceQueue unreferencedListenersQueue = new ReferenceQueue<>();
    private volatile Throwable failureReason;
    private final ExecutorService reqQueueExecutor = Executors.newSingleThreadExecutor(
            new ThreadFactoryBuilder()
                    .setDaemon(true)
                    .setNameFormat("lifecycle-listener-monitor-%d")
                    .build()
    );
    private final AtomicBoolean running = new AtomicBoolean(true);

    public enum State {
        Starting,
        Started,
        Stopped,
        Done
    }

    public LifecycleManager() {
        LOGGER.info("Starting '{}'", this);
        state = new AtomicReference<>(State.Starting);
        reqQueueExecutor.submit(new ListenerCleanupWorker());
    }

    private synchronized void removeListener(SafeLifecycleListener listenerRef) {
        listeners.remove(listenerRef);
    }

    public synchronized void addListener(LifecycleListener listener) {
        SafeLifecycleListener safeListener = SafeLifecycleListener.wrap(listener, unreferencedListenersQueue);

        if (!listeners.contains(safeListener) && listeners.add(safeListener)) {
            LOGGER.info("Adding listener '{}'", safeListener);
            switch (state.get()) {
              case Started:
                    safeListener.onStarted();
                    break;
                case Stopped:
                    safeListener.onStopped(failureReason);
                    break;
                default:
                    // ignore
                    break;
            }
        }
    }

    public synchronized void notifyStarted() {
        if (state.compareAndSet(State.Starting, State.Started)) {
            LOGGER.info("Started '{}'", this);

            listeners.forEach((listener) -> {
                listener.onStarted();
            });
        }
    }

    public synchronized void notifyStartFailed(final Throwable t) {
        // State.Started added here to allow for failure  when LifecycleListener.onStarted() is called
        if (state.compareAndSet(State.Starting, State.Stopped) || state.compareAndSet(State.Started, State.Stopped)) {
            LOGGER.info("Failed start of '{}'", this);
            if (running.compareAndSet(true, false)) {
                reqQueueExecutor.shutdown();
            }
            this.failureReason = t;
            Iterator shutdownIter = new LinkedList<>(listeners).descendingIterator();
            while (shutdownIter.hasNext()) {
                shutdownIter.next().onStopped(t);
            }
            listeners.clear();
        }
        state.set(State.Done);
    }

    public synchronized void notifyShutdown() {
        if (running.compareAndSet(true, false)) {
            reqQueueExecutor.shutdown();
        }
        if (state.compareAndSet(State.Started, State.Stopped)) {
            LOGGER.info("Stopping '{}'", this);
            Iterator shutdownIter = new LinkedList<>(listeners).descendingIterator();
            while (shutdownIter.hasNext()) {
                shutdownIter.next().onStopped(null);
            }
            listeners.clear();
        }
        state.set(State.Done);
    }

    public State getState() {
        return state.get();
    }

    public Throwable getFailureReason() {
        return failureReason;
    }

    @Override
    public String toString() {
        return "LifecycleManager@" + System.identityHashCode(this);
    }
}