/*
* 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.driver.message.ResponseMessage;
import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
import org.apache.tinkerpop.gremlin.process.traversal.Traverser;
import org.apache.tinkerpop.gremlin.process.traversal.step.util.BulkSet;
import org.javatuples.Pair;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
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<>();
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);
}
/**
* Adds a side-effect to the queue which may later be read by the {@link ResultSet}. Note that the side-effect
* is only returned when a {@link Traversal} is submitted and refers to the side-effects defined in that traversal.
* A "script" will not return side-effects.
*
* @param aggregateTo the value of the {@link ResponseMessage} metadata for {@link Tokens#ARGS_AGGREGATE_TO}.
* @param sideEffectValue the value of the side-effect itself
*/
public void addSideEffect(final String aggregateTo, final Object sideEffectValue) {
switch (aggregateTo) {
case Tokens.VAL_AGGREGATE_TO_BULKSET:
if (!(sideEffectValue instanceof Traverser.Admin))
throw new IllegalStateException(String.format("Side-effect value %s is a %s which does not aggregate to %s",
sideEffectValue, sideEffectValue.getClass().getSimpleName(), aggregateTo));
if (null == aggregatedResult) aggregatedResult = new BulkSet();
final BulkSet<Object> bs = validate(aggregateTo, BulkSet.class);
final Traverser.Admin traverser = (Traverser.Admin) sideEffectValue;
bs.add(traverser.get(), traverser.bulk());
break;
case Tokens.VAL_AGGREGATE_TO_LIST:
if (null == aggregatedResult) aggregatedResult = new ArrayList();
final List<Object> list = validate(aggregateTo, List.class);
list.add(sideEffectValue);
break;
case Tokens.VAL_AGGREGATE_TO_SET:
if (null == aggregatedResult) aggregatedResult = new HashSet();
final Set<Object> set = validate(aggregateTo, Set.class);
set.add(sideEffectValue);
break;
case Tokens.VAL_AGGREGATE_TO_MAP:
if (!(sideEffectValue instanceof Map.Entry) && !(sideEffectValue instanceof Map))
throw new IllegalStateException(String.format("Side-effect value %s is a %s which does not aggregate to %s",
sideEffectValue, sideEffectValue.getClass().getSimpleName(), aggregateTo));
// some serialization formats (e.g. graphson) may deserialize a Map.Entry to a Map with a single entry
if (sideEffectValue instanceof Map && ((Map) sideEffectValue).size() != 1)
throw new IllegalStateException(String.format("Side-effect value %s is a %s which does not aggregate to %s as it is a Map that does not have one entry",
sideEffectValue, sideEffectValue.getClass().getSimpleName(), aggregateTo));
if (null == aggregatedResult) aggregatedResult = new HashMap();
final Map<Object,Object > m = validate(aggregateTo, Map.class);
final Map.Entry entry = sideEffectValue instanceof Map.Entry ?
(Map.Entry) sideEffectValue : (Map.Entry) ((Map) sideEffectValue).entrySet().iterator().next();
m.put(entry.getKey(), entry.getValue());
break;
case Tokens.VAL_AGGREGATE_TO_NONE:
if (null == aggregatedResult) aggregatedResult = sideEffectValue;
break;
default:
throw new IllegalStateException(String.format("%s is an invalid value for %s", aggregateTo, Tokens.ARGS_AGGREGATE_TO));
}
}
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() {
// 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.readComplete.complete(null);
this.drainAllWaiting();
}
void markError(final Throwable throwable) {
error.set(throwable);
this.readComplete.completeExceptionally(throwable);
this.drainAllWaiting();
}
/**
* 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);
}
}
}