package org.apache.lucene.index;
/*
* 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.
*/
import java.util.Random;
/**
*
* A <code>DocumentsWriterPerThreadPool<code> that selects thread states at random.
*
* @lucene.internal
* @lucene.experimental
*/
class RandomDocumentsWriterPerThreadPool extends DocumentsWriterPerThreadPool {
private final ThreadState[] states;
private final Random random;
private final int maxRetry;
public RandomDocumentsWriterPerThreadPool(int maxNumPerThreads, Random random) {
super(maxNumPerThreads);
assert getMaxThreadStates() >= 1;
states = new ThreadState[maxNumPerThreads];
this.random = new Random(random.nextLong());
this.maxRetry = 1 + random.nextInt(10);
}
@Override
ThreadState getAndLock(Thread requestingThread,
DocumentsWriter documentsWriter) {
ThreadState threadState = null;
if (getActiveThreadState() == 0) {
synchronized (this) {
if (getActiveThreadState() == 0) {
threadState = states[0] = newThreadState();
return threadState;
}
}
}
assert getActiveThreadState() > 0;
for (int i = 0; i < maxRetry; i++) {
int ord = random.nextInt(getActiveThreadState());
synchronized (this) {
threadState = states[ord];
assert threadState != null;
}
if (threadState.tryLock()) {
return threadState;
}
if (random.nextInt(20) == 0) {
break;
}
}
/*
* only try to create a new threadstate if we can not lock the randomly
* selected state. this is important since some tests rely on a single
* threadstate in the single threaded case. Eventually it would be nice if
* we would not have this limitation but for now we just make sure we only
* allocate one threadstate if indexing is single threaded
*/
synchronized (this) {
ThreadState newThreadState = newThreadState();
if (newThreadState != null) { // did we get a new state?
threadState = states[getActiveThreadState() - 1] = newThreadState;
assert threadState.isHeldByCurrentThread();
return threadState;
}
// if no new state is available lock the random one
}
assert threadState != null;
threadState.lock();
return threadState;
}
}