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/* * Copyright 2012 LinkedIn, Inc * * Licensed 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 com.linkedin.parseq; import com.linkedin.parseq.promise.Promise; import java.util.concurrent.TimeUnit; /** * A context provides an API to {@link Task}s for the purpose of scheduling * other tasks. Each task gets its own context, but contexts are hierarchical * such that any state changes made from this context are visible to other * contexts in the hierarchy. *

* If a task finished while it still has pending timers or tasks, those * timers and tasks will be cancelled - they are guaranteed not to execute. * * @author Chris Pettitt (cpettitt@linkedin.com) */ public interface Context { /** * Creates a timer that will invoke the given task if the calling task has * not yet finished. * * @param time the time for the timeout * @param unit the unit of the time * @param task the task to run if the timeout expires * @return a handle that can be used to explicitly cancel the timer */ Cancellable createTimer(long time, TimeUnit unit, Task task); /** * Runs one or more tasks in parallel. * * @param tasks the tasks to run */ void run(Task... tasks); /** * Provides a mechanism of ordering the execution of some child tasks after * the resolution of the given promises (which may also be tasks). * * @param promises the promises that must be resolved before executing * tasks from {@link After} * @return a handle that can be used to schedule tasks that will be executed * after the given promises are resolved. */ After after(Promise... promises); /** * Provides a mechanism for "plugins" to generate data which should be passed in via the context. * The intent is that the "plugin" registers engine specific data it needed via the engine builder. * Then the run method can access this data via the getEngineProperty() method. * * @param key The key to the engine related property which the Task will access. * @return The engine related property which has been stored with this key. */ Object getEngineProperty(String key); }

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