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| 1 | +/** |
| 2 | + * Copyright 2014 Netflix, Inc. |
| 3 | + * |
| 4 | + * Licensed under the Apache License, Version 2.0 (the "License"); you may not |
| 5 | + * use this file except in compliance with the License. You may obtain a copy of |
| 6 | + * the License at |
| 7 | + * |
| 8 | + * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | + * |
| 10 | + * Unless required by applicable law or agreed to in writing, software |
| 11 | + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT |
| 12 | + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the |
| 13 | + * License for the specific language governing permissions and limitations under |
| 14 | + * the License. |
| 15 | + */ |
| 16 | +package rx.schedulers; |
| 17 | + |
| 18 | +import java.util.concurrent.ConcurrentLinkedQueue; |
| 19 | +import java.util.concurrent.Executor; |
| 20 | +import java.util.concurrent.Future; |
| 21 | +import java.util.concurrent.RejectedExecutionException; |
| 22 | +import java.util.concurrent.ScheduledExecutorService; |
| 23 | +import java.util.concurrent.TimeUnit; |
| 24 | +import java.util.concurrent.atomic.AtomicInteger; |
| 25 | +import java.util.concurrent.atomic.AtomicIntegerFieldUpdater; |
| 26 | +import rx.Scheduler; |
| 27 | +import rx.Subscription; |
| 28 | +import rx.functions.Action0; |
| 29 | +import rx.plugins.RxJavaPlugins; |
| 30 | +import rx.subscriptions.CompositeSubscription; |
| 31 | +import rx.subscriptions.MultipleAssignmentSubscription; |
| 32 | +import rx.subscriptions.Subscriptions; |
| 33 | + |
| 34 | +/** |
| 35 | + * Scheduler that wraps an Executor instance and establishes the Scheduler contract upon it. |
| 36 | + * <p> |
| 37 | + * Note that thread-hopping is unavoidable with this kind of Scheduler as we don't know about the underlying |
| 38 | + * threading behavior of the executor. |
| 39 | + */ |
| 40 | +/* public */final class ExecutorScheduler extends Scheduler { |
| 41 | + final Executor executor; |
| 42 | + public ExecutorScheduler(Executor executor) { |
| 43 | + this.executor = executor; |
| 44 | + } |
| 45 | + |
| 46 | + /** |
| 47 | + * @warn javadoc missing |
| 48 | + * @return |
| 49 | + */ |
| 50 | + @Override |
| 51 | + public Worker createWorker() { |
| 52 | + return new ExecutorSchedulerWorker(executor); |
| 53 | + } |
| 54 | + |
| 55 | + /** Worker that schedules tasks on the executor indirectly through a trampoline mechanism. */ |
| 56 | + static final class ExecutorSchedulerWorker extends Scheduler.Worker implements Runnable { |
| 57 | + final Executor executor; |
| 58 | + // TODO: use a better performing structure for task tracking |
| 59 | + final CompositeSubscription tasks; |
| 60 | + // TODO: use MpscLinkedQueue once available |
| 61 | + final ConcurrentLinkedQueue<ExecutorAction> queue; |
| 62 | + final AtomicInteger wip; |
| 63 | + |
| 64 | + public ExecutorSchedulerWorker(Executor executor) { |
| 65 | + this.executor = executor; |
| 66 | + this.queue = new ConcurrentLinkedQueue<ExecutorAction>(); |
| 67 | + this.wip = new AtomicInteger(); |
| 68 | + this.tasks = new CompositeSubscription(); |
| 69 | + } |
| 70 | + |
| 71 | + @Override |
| 72 | + public Subscription schedule(Action0 action) { |
| 73 | + if (isUnsubscribed()) { |
| 74 | + return Subscriptions.empty(); |
| 75 | + } |
| 76 | + ExecutorAction ea = new ExecutorAction(action, tasks); |
| 77 | + tasks.add(ea); |
| 78 | + queue.offer(ea); |
| 79 | + if (wip.getAndIncrement() == 0) { |
| 80 | + try { |
| 81 | + executor.execute(this); |
| 82 | + } catch (RejectedExecutionException t) { |
| 83 | + // cleanup if rejected |
| 84 | + tasks.remove(ea); |
| 85 | + wip.decrementAndGet(); |
| 86 | + // report the error to the plugin |
| 87 | + RxJavaPlugins.getInstance().getErrorHandler().handleError(t); |
| 88 | + // throw it to the caller |
| 89 | + throw t; |
| 90 | + } |
| 91 | + } |
| 92 | + |
| 93 | + return ea; |
| 94 | + } |
| 95 | + |
| 96 | + @Override |
| 97 | + public void run() { |
| 98 | + do { |
| 99 | + queue.poll().run(); |
| 100 | + } while (wip.decrementAndGet() > 0); |
| 101 | + } |
| 102 | + |
| 103 | + @Override |
| 104 | + public Subscription schedule(final Action0 action, long delayTime, TimeUnit unit) { |
| 105 | + if (delayTime <= 0) { |
| 106 | + return schedule(action); |
| 107 | + } |
| 108 | + if (isUnsubscribed()) { |
| 109 | + return Subscriptions.empty(); |
| 110 | + } |
| 111 | + ScheduledExecutorService service; |
| 112 | + if (executor instanceof ScheduledExecutorService) { |
| 113 | + service = (ScheduledExecutorService)executor; |
| 114 | + } else { |
| 115 | + service = GenericScheduledExecutorService.getInstance(); |
| 116 | + } |
| 117 | + |
| 118 | + final MultipleAssignmentSubscription mas = new MultipleAssignmentSubscription(); |
| 119 | + // tasks.add(mas); // Needs a removal without unsubscription |
| 120 | + |
| 121 | + try { |
| 122 | + Future<?> f = service.schedule(new Runnable() { |
| 123 | + @Override |
| 124 | + public void run() { |
| 125 | + if (mas.isUnsubscribed()) { |
| 126 | + return; |
| 127 | + } |
| 128 | + mas.set(schedule(action)); |
| 129 | + // tasks.delete(mas); // Needs a removal without unsubscription |
| 130 | + } |
| 131 | + }, delayTime, unit); |
| 132 | + mas.set(Subscriptions.from(f)); |
| 133 | + } catch (RejectedExecutionException t) { |
| 134 | + // report the rejection to plugins |
| 135 | + RxJavaPlugins.getInstance().getErrorHandler().handleError(t); |
| 136 | + throw t; |
| 137 | + } |
| 138 | + |
| 139 | + return mas; |
| 140 | + } |
| 141 | + |
| 142 | + @Override |
| 143 | + public boolean isUnsubscribed() { |
| 144 | + return tasks.isUnsubscribed(); |
| 145 | + } |
| 146 | + |
| 147 | + @Override |
| 148 | + public void unsubscribe() { |
| 149 | + tasks.unsubscribe(); |
| 150 | + } |
| 151 | + |
| 152 | + } |
| 153 | + |
| 154 | + /** Runs the actual action and maintains an unsubscription state. */ |
| 155 | + static final class ExecutorAction implements Runnable, Subscription { |
| 156 | + final Action0 actual; |
| 157 | + final CompositeSubscription parent; |
| 158 | + volatile int unsubscribed; |
| 159 | + static final AtomicIntegerFieldUpdater<ExecutorAction> UNSUBSCRIBED_UPDATER |
| 160 | + = AtomicIntegerFieldUpdater.newUpdater(ExecutorAction.class, "unsubscribed"); |
| 161 | + |
| 162 | + public ExecutorAction(Action0 actual, CompositeSubscription parent) { |
| 163 | + this.actual = actual; |
| 164 | + this.parent = parent; |
| 165 | + } |
| 166 | + |
| 167 | + @Override |
| 168 | + public void run() { |
| 169 | + if (isUnsubscribed()) { |
| 170 | + return; |
| 171 | + } |
| 172 | + try { |
| 173 | + actual.call(); |
| 174 | + } catch (Throwable t) { |
| 175 | + RxJavaPlugins.getInstance().getErrorHandler().handleError(t); |
| 176 | + } finally { |
| 177 | + unsubscribe(); |
| 178 | + } |
| 179 | + } |
| 180 | + @Override |
| 181 | + public boolean isUnsubscribed() { |
| 182 | + return unsubscribed != 0; |
| 183 | + } |
| 184 | + |
| 185 | + @Override |
| 186 | + public void unsubscribe() { |
| 187 | + if (UNSUBSCRIBED_UPDATER.compareAndSet(this, 0, 1)) { |
| 188 | + parent.remove(this); |
| 189 | + } |
| 190 | + } |
| 191 | + |
| 192 | + } |
| 193 | +} |
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