ratpack.sep.exec.Parallel.java Source code

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Here is the source code for ratpack.sep.exec.Parallel.java

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/*
 * Copyright 2015 the original author or 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 ratpack.sep.exec;

import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;
import ratpack.sep.Action;
import ratpack.sep.ActionResult;
import ratpack.sep.ActionResults;
import ratpack.exec.ExecControl;
import ratpack.exec.Promise;
import ratpack.registry.Registry;

import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Lets actions to execute in parallel.
 *
 * Actions execute independently as {@code promises}. They are not notified about each other.
 *
 * [source, java]
 * --
 * include::{test-dir}/ratpack/sep/exec/ParallelTest.java[tags=all]
 * --
 *
 * @see ratpack.sep.Action
 * @see ratpack.sep.ActionResult
 * @see ratpack.sep.ActionResults
 */
public class Parallel<T, O> {

    /**
     * The name of the pattern that indicates pattern to execute in handler.
     *
     * Value: {@value}
     */
    public static final String PATTERN_NAME = "parallel";

    /**
     * The name of the pattern
     *
     * @return the name of the pattern
     */
    public String getName() {
        return PATTERN_NAME;
    }

    /**
     * Executes {@code Params.actions} in parallel.
     * <p>
     * The result of each {@code action} execution is added to {@link ActionResults}.
     * <p>
     * if {@code action} throws an exception it is equivalent to error result.
     *
     * @param execControl an execution control
     * @param registry the server registry
     * @param actions the collections of actions to execute in parallel
     * @return a promise for the results
     * @throws Exception any
     */
    public Promise<ActionResults<O>> apply(ExecControl execControl, Registry registry,
            Iterable<Action<T, O>> actions) throws Exception {
        Iterator<Action<T, O>> iterator = actions.iterator();
        if (!iterator.hasNext()) {
            return execControl.promiseOf(new ActionResults<>(ImmutableMap.of()));
        }

        return execControl.<Map<String, ActionResult<O>>>promise(fulfiller -> {
            AtomicInteger counter = new AtomicInteger();
            Map<String, ActionResult<O>> results = Maps.newConcurrentMap();
            while (iterator.hasNext()) {
                counter.incrementAndGet();
                Action<T, O> action = iterator.next();
                if (action == null || action.getName() == null) {
                    int i = counter.decrementAndGet();
                    results.put("ACTION_NULL_IDX_" + i, ActionResult.error(new NullPointerException()));
                    if (i == 0 && !iterator.hasNext()) {
                        fulfiller.success(results);
                        return;
                    }
                    continue;
                }
                execControl.exec()
                        .start(execution -> apply(execution, action).defer(Runnable::run).wiretap(result -> {

                        }).then(result -> {
                            results.put(action.getName(), result);
                            if (counter.decrementAndGet() == 0 && !iterator.hasNext()) {
                                fulfiller.success(results);
                            }
                        }));
            }
        }).map(ImmutableMap::copyOf).map(map -> new ActionResults<O>(map));
    }

    private Promise<ActionResult<O>> apply(ExecControl execControl, Action<T, O> action) {
        try {
            return action.exec(execControl).mapError(ActionResult::error);
        } catch (Exception ex) {
            return execControl.promiseOf(ActionResult.error(ex));
        }
    }
}