Executor.java

/*
 * Copyright © 2018 Apple Inc. and the ServiceTalk project authors
 *
 * 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 io.servicetalk.concurrent.api;

import java.time.Duration;
import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;
import java.util.function.Supplier;

/**
 * A general abstraction to execute immediate and delayed tasks.
 *
 * <h2>Long running tasks</h2>
 * {@link Executor} implementations are expected to run long running (blocking) tasks which may depend on other tasks
 * submitted to the same {@link Executor} instance.
 * In order to avoid deadlocks, it is generally a good idea to not allow task queuing in the {@link Executor}.
 */
public interface Executor extends io.servicetalk.concurrent.Executor, ListenableAsyncCloseable {
    /**
     * Creates a new {@link Completable} that will complete after the time duration expires.
     *
     * @param delay The time duration which is allowed to elapse between subscribe and termination.
     * @param unit The units for {@code duration}.
     * @return a new {@link Completable} that will complete after the time duration expires.
     * @see <a href="http://reactivex.io/documentation/operators/timer.html">ReactiveX Timer.</a>
     */
    default Completable timer(long delay, TimeUnit unit) {
        return new TimerCompletable(delay, unit, this);
    }

    /**
     * Creates a new {@link Completable} that will complete after the time duration expires.
     * @param delay The time duration which is allowed to elapse between subscribe and termination.
     *
     * @return a new {@link Completable} that will complete after the time duration expires.
     * @see <a href="http://reactivex.io/documentation/operators/timer.html">ReactiveX Timer.</a>
     */
    default Completable timer(Duration delay) {
        return new TimerCompletable(delay, this);
    }

    /**
     * Create a new {@link Completable} that executes the passed {@link Runnable} on each subscribe.
     *
     * @param runnable The {@link Runnable} to execute on each subscribe.
     * @return a new {@link Completable} that executes a {@link Runnable} on each subscribe.
     */
    default Completable submit(Runnable runnable) {
        return new SubmitCompletable(runnable, this);
    }

    /**
     * Creates a new {@link Completable} that creates and executes a {@link Runnable} when subscribed to.
     *
     * @param runnableSupplier {@link Supplier} to create a new {@link Runnable} for every subscribe of the returned
     * {@link Completable}.
     * @return A new {@link Completable} that creates and executes a new {@link Runnable} using
     * {@code runnableSupplier} for every subscribe.
     */
    default Completable submitRunnable(Supplier<Runnable> runnableSupplier) {
        return new SubmitSupplierCompletable(runnableSupplier, this);
    }

    /**
     * Creates a new {@link Single} that creates and executes the passed {@link Callable} when subscribed to.
     *
     * @param callable The {@link Callable} to execute on each subscribe.
     * @param <T> Type of the {@link Single}.
     * @return a new {@link Single} that obtains a {@link Callable} from {@code callableSupplier} and executes it
     * on each subscribe.
     */
    default <T> Single<T> submit(Callable<? extends T> callable) {
        return new SubmitSingle<>(callable, this);
    }

    /**
     * Create a new {@link Single} that obtains a {@link Callable} from {@code callableSupplier} and executes on each
     * subscribe.
     *
     * @param callableSupplier {@link Supplier} to create a new {@link Callable} for every call to subscribe to the
     * returned {@link Single}.
     * @param <T> Type of the {@link Single}.
     * @return A new {@link Single} that creates and executes a new {@link Callable} using {@code callableSupplier}
     * for every subscribe.
     */
    default <T> Single<T> submitCallable(Supplier<? extends Callable<? extends T>> callableSupplier) {
        return new SubmitSupplierSingle<>(callableSupplier, this);
    }
}