| /** |
| * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version |
| * 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions |
| * and limitations under the License. |
| */ |
| |
| package org.apache.storm.windowing; |
| |
| import static org.apache.storm.windowing.EvictionPolicy.Action.EXPIRE; |
| import static org.apache.storm.windowing.EvictionPolicy.Action.PROCESS; |
| import static org.apache.storm.windowing.EvictionPolicy.Action.STOP; |
| |
| import java.util.Collection; |
| import java.util.Iterator; |
| import java.util.NoSuchElementException; |
| import java.util.function.Supplier; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| /** |
| * Window manager that handles windows with state persistence. |
| */ |
| public class StatefulWindowManager<T> extends WindowManager<T> { |
| private static final Logger LOG = LoggerFactory.getLogger(StatefulWindowManager.class); |
| |
| public StatefulWindowManager(WindowLifecycleListener<T> lifecycleListener) { |
| super(lifecycleListener); |
| } |
| |
| /** |
| * Constructs a {@link StatefulWindowManager}. |
| * |
| * @param lifecycleListener the {@link WindowLifecycleListener} |
| * @param queue a collection where the events in the window can be enqueued. <br/> |
| * <b>Note:</b> This collection has to be thread safe. |
| */ |
| public StatefulWindowManager(WindowLifecycleListener<T> lifecycleListener, Collection<Event<T>> queue) { |
| super(lifecycleListener, queue); |
| } |
| |
| private static <T> Iterator<T> expiringIterator(Iterator<T> inner, IteratorStatus status) { |
| return new Iterator<T>() { |
| @Override |
| public boolean hasNext() { |
| if (status.isValid()) { |
| return inner.hasNext(); |
| } |
| throw new IllegalStateException("Stale iterator, the iterator is valid only within the corresponding execute"); |
| } |
| |
| @Override |
| public T next() { |
| if (status.isValid()) { |
| return inner.next(); |
| } |
| throw new IllegalStateException("Stale iterator, the iterator is valid only within the corresponding execute"); |
| } |
| }; |
| } |
| |
| @Override |
| protected void compactWindow() { |
| // NOOP |
| } |
| |
| @Override |
| public boolean onTrigger() { |
| Supplier<Iterator<T>> scanEventsStateful = this::scanEventsStateful; |
| Iterator<T> it = scanEventsStateful.get(); |
| boolean hasEvents = it.hasNext(); |
| if (hasEvents) { |
| final IteratorStatus status = new IteratorStatus(); |
| LOG.debug("invoking windowLifecycleListener onActivation with iterator"); |
| // reuse the retrieved iterator |
| Supplier<Iterator<T>> wrapper = new Supplier<Iterator<T>>() { |
| Iterator<T> initial = it; |
| |
| @Override |
| public Iterator<T> get() { |
| if (status.isValid()) { |
| Iterator<T> res; |
| if (initial != null) { |
| res = initial; |
| initial = null; |
| } else { |
| res = scanEventsStateful.get(); |
| } |
| return expiringIterator(res, status); |
| } |
| throw new IllegalStateException("Stale window, the window is valid only within the corresponding execute"); |
| } |
| }; |
| windowLifecycleListener.onActivation(wrapper, null, null, evictionPolicy.getContext().getReferenceTime()); |
| // invalidate the iterator |
| status.invalidate(); |
| } else { |
| LOG.debug("No events in the window, skipping onActivation"); |
| } |
| triggerPolicy.reset(); |
| return hasEvents; |
| } |
| |
| private Iterator<T> scanEventsStateful() { |
| LOG.debug("Scan events, eviction policy {}", evictionPolicy); |
| evictionPolicy.reset(); |
| Iterator<T> it = new Iterator<T>() { |
| private Iterator<Event<T>> inner = queue.iterator(); |
| private T windowEvent; |
| private boolean stopped; |
| |
| @Override |
| public boolean hasNext() { |
| while (!stopped && windowEvent == null && inner.hasNext()) { |
| Event<T> cur = inner.next(); |
| EvictionPolicy.Action action = evictionPolicy.evict(cur); |
| if (action == EXPIRE) { |
| inner.remove(); |
| } else if (action == STOP) { |
| stopped = true; |
| } else if (action == PROCESS) { |
| windowEvent = cur.get(); |
| } |
| } |
| return windowEvent != null; |
| } |
| |
| @Override |
| public T next() { |
| if (!hasNext()) { |
| throw new NoSuchElementException(); |
| } |
| T res = windowEvent; |
| windowEvent = null; |
| return res; |
| } |
| }; |
| |
| return it; |
| |
| } |
| |
| private static class IteratorStatus { |
| private boolean valid = true; |
| |
| void invalidate() { |
| valid = false; |
| } |
| |
| boolean isValid() { |
| return valid; |
| } |
| } |
| } |