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/*
* 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.tinkerpop.gremlin.driver;
import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
import org.javatuples.Pair;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.atomic.AtomicReference;
/**
* A queue of incoming {@link Result} objects. The queue is updated by the {@link Handler.GremlinResponseHandler}
* until a response terminator is identified.
*
* @author Stephen Mallette (http://stephen.genoprime.com)
*/
@SuppressWarnings("ThrowableResultOfMethodCallIgnored")
final class ResultQueue {
private final LinkedBlockingQueue<Result> resultLinkedBlockingQueue;
private Object aggregatedResult = null;
private final AtomicReference<Throwable> error = new AtomicReference<>();
private final CompletableFuture<Void> readComplete;
private final Queue<Pair<CompletableFuture<List<Result>>,Integer>> waiting = new ConcurrentLinkedQueue<>();
private Map<String,Object> statusAttributes = null;
public ResultQueue(final LinkedBlockingQueue<Result> resultLinkedBlockingQueue, final CompletableFuture<Void> readComplete) {
this.resultLinkedBlockingQueue = resultLinkedBlockingQueue;
this.readComplete = readComplete;
}
/**
* Adds a {@link Result} to the queue which will be later read by the {@link ResultSet}.
*
* @param result a return value from the {@link Traversal} or script submitted for execution
*/
public void add(final Result result) {
this.resultLinkedBlockingQueue.offer(result);
tryDrainNextWaiting(false);
}
private <V> V validate(final String aggregateTo, final Class<?> expected) {
if (!(expected.isAssignableFrom(aggregatedResult.getClass())))
throw new IllegalStateException(String.format("Side-effect \"%s\" contains the type %s that is not acceptable for %s",
aggregatedResult.getClass().getSimpleName(), aggregateTo));
return (V) aggregatedResult;
}
public CompletableFuture<List<Result>> await(final int items) {
final CompletableFuture<List<Result>> result = new CompletableFuture<>();
waiting.add(Pair.with(result, items));
tryDrainNextWaiting(false);
return result;
}
public int size() {
if (error.get() != null) throw new RuntimeException(error.get());
return this.resultLinkedBlockingQueue.size();
}
public boolean isEmpty() {
if (error.get() != null) throw new RuntimeException(error.get());
return this.size() == 0;
}
public boolean isComplete() {
return readComplete.isDone();
}
void drainTo(final Collection<Result> collection) {
if (error.get() != null) throw new RuntimeException(error.get());
resultLinkedBlockingQueue.drainTo(collection);
}
void markComplete(final Map<String,Object> statusAttributes) {
// if there was some aggregation performed in the queue then the full object is hanging out waiting to be
// added to the ResultSet
if (aggregatedResult != null)
add(new Result(aggregatedResult));
this.statusAttributes = null == statusAttributes ? Collections.emptyMap() : statusAttributes;
this.readComplete.complete(null);
this.drainAllWaiting();
}
void markError(final Throwable throwable) {
error.set(throwable);
this.readComplete.completeExceptionally(throwable);
this.drainAllWaiting();
}
Map<String,Object> getStatusAttributes() {
return statusAttributes;
}
/**
* Completes the next waiting future if there is one.
*/
private synchronized void tryDrainNextWaiting(final boolean force) {
// need to peek because the number of available items needs to be >= the expected size for that future. if not
// it needs to keep waiting
final Pair<CompletableFuture<List<Result>>, Integer> nextWaiting = waiting.peek();
if (nextWaiting != null && (force || (resultLinkedBlockingQueue.size() >= nextWaiting.getValue1() || readComplete.isDone()))) {
final int items = nextWaiting.getValue1();
final CompletableFuture<List<Result>> future = nextWaiting.getValue0();
final List<Result> results = new ArrayList<>(items);
resultLinkedBlockingQueue.drainTo(results, items);
// it's important to check for error here because a future may have already been queued in "waiting" prior
// to the first response back from the server. if that happens, any "waiting" futures should be completed
// exceptionally otherwise it will look like success.
if (null == error.get())
future.complete(results);
else
future.completeExceptionally(error.get());
waiting.remove(nextWaiting);
}
}
/**
* Completes all remaining futures.
*/
private void drainAllWaiting() {
while (!waiting.isEmpty()) {
tryDrainNextWaiting(true);
}
}
}