/*
* 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.lucene.search;
import java.io.Closeable;
import java.io.IOException;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.util.ThreadInterruptedException;
/** Utility class that runs a thread to manage periodicc
* reopens of a {@link ReferenceManager}, with methods to wait for a specific
* index changes to become visible. When a given search request needs to see a specific
* index change, call the {#waitForGeneration} to wait for
* that change to be visible. Note that this will only
* scale well if most searches do not need to wait for a
* specific index generation.
*
* @lucene.experimental */
public class ControlledRealTimeReopenThread<T> extends Thread implements Closeable {
private final ReferenceManager<T> manager;
private final long targetMaxStaleNS;
private final long targetMinStaleNS;
private final IndexWriter writer;
private volatile boolean finish;
private volatile long waitingGen;
private volatile long searchingGen;
private long refreshStartGen;
private final ReentrantLock reopenLock = new ReentrantLock();
private final Condition reopenCond = reopenLock.newCondition();
/**
* Create ControlledRealTimeReopenThread, to periodically
* reopen the a {@link ReferenceManager}.
*
* @param targetMaxStaleSec Maximum time until a new
* reader must be opened; this sets the upper bound
* on how slowly reopens may occur, when no
* caller is waiting for a specific generation to
* become visible.
*
* @param targetMinStaleSec Mininum time until a new
* reader can be opened; this sets the lower bound
* on how quickly reopens may occur, when a caller
* is waiting for a specific generation to
* become visible.
*/
public ControlledRealTimeReopenThread(IndexWriter writer, ReferenceManager<T> manager, double targetMaxStaleSec, double targetMinStaleSec) {
if (targetMaxStaleSec < targetMinStaleSec) {
throw new IllegalArgumentException("targetMaxScaleSec (= " + targetMaxStaleSec + ") < targetMinStaleSec (=" + targetMinStaleSec + ")");
}
this.writer = writer;
this.manager = manager;
this.targetMaxStaleNS = (long) (1000000000*targetMaxStaleSec);
this.targetMinStaleNS = (long) (1000000000*targetMinStaleSec);
manager.addListener(new HandleRefresh());
}
private class HandleRefresh implements ReferenceManager.RefreshListener {
@Override
public void beforeRefresh() {
}
@Override
public void afterRefresh(boolean didRefresh) {
refreshDone();
}
}
private synchronized void refreshDone() {
searchingGen = refreshStartGen;
notifyAll();
}
@Override
public synchronized void close() {
//System.out.println("NRT: set finish");
finish = true;
// So thread wakes up and notices it should finish:
reopenLock.lock();
try {
reopenCond.signal();
} finally {
reopenLock.unlock();
}
try {
join();
} catch (InterruptedException ie) {
throw new ThreadInterruptedException(ie);
}
// Max it out so any waiting search threads will return:
searchingGen = Long.MAX_VALUE;
notifyAll();
}
/**
* Waits for the target generation to become visible in
* the searcher.
* If the current searcher is older than the
* target generation, this method will block
* until the searcher is reopened, by another via
* {@link ReferenceManager#maybeRefresh} or until the {@link ReferenceManager} is closed.
*
* @param targetGen the generation to wait for
*/
public void waitForGeneration(long targetGen) throws InterruptedException {
waitForGeneration(targetGen, -1);
}
/**
* Waits for the target generation to become visible in
* the searcher, up to a maximum specified milli-seconds.
* If the current searcher is older than the target
* generation, this method will block until the
* searcher has been reopened by another thread via
* {@link ReferenceManager#maybeRefresh}, the given waiting time has elapsed, or until
* the {@link ReferenceManager} is closed.
* <p>
* NOTE: if the waiting time elapses before the requested target generation is
* available the current {@link SearcherManager} is returned instead.
*
* @param targetGen
* the generation to wait for
* @param maxMS
* maximum milliseconds to wait, or -1 to wait indefinitely
* @return true if the targetGeneration is now available,
* or false if maxMS wait time was exceeded
*/
public synchronized boolean waitForGeneration(long targetGen, int maxMS) throws InterruptedException {
if (targetGen > searchingGen) {
// Notify the reopen thread that the waitingGen has
// changed, so it may wake up and realize it should
// not sleep for much or any longer before reopening:
reopenLock.lock();
// Need to find waitingGen inside lock as it's used to determine
// stale time
waitingGen = Math.max(waitingGen, targetGen);
try {
reopenCond.signal();
} finally {
reopenLock.unlock();
}
long startMS = System.nanoTime()/1000000;
while (targetGen > searchingGen) {
if (maxMS < 0) {
wait();
} else {
long msLeft = (startMS + maxMS) - System.nanoTime()/1000000;
if (msLeft <= 0) {
return false;
} else {
wait(msLeft);
}
}
}
}
return true;
}
@Override
public void run() {
// TODO: maybe use private thread ticktock timer, in
// case clock shift messes up nanoTime?
long lastReopenStartNS = System.nanoTime();
//System.out.println("reopen: start");
while (!finish) {
// TODO: try to guestimate how long reopen might
// take based on past data?
// Loop until we've waiting long enough before the
// next reopen:
while (!finish) {
// Need lock before finding out if has waiting
reopenLock.lock();
try {
// True if we have someone waiting for reopened searcher:
boolean hasWaiting = waitingGen > searchingGen;
final long nextReopenStartNS = lastReopenStartNS + (hasWaiting ? targetMinStaleNS : targetMaxStaleNS);
final long sleepNS = nextReopenStartNS - System.nanoTime();
if (sleepNS > 0) {
reopenCond.awaitNanos(sleepNS);
} else {
break;
}
} catch (InterruptedException ie) {
Thread.currentThread().interrupt();
return;
} finally {
reopenLock.unlock();
}
}
if (finish) {
break;
}
lastReopenStartNS = System.nanoTime();
// Save the gen as of when we started the reopen; the
// listener (HandleRefresh above) copies this to
// searchingGen once the reopen completes:
refreshStartGen = writer.getMaxCompletedSequenceNumber();
try {
manager.maybeRefreshBlocking();
} catch (IOException ioe) {
throw new RuntimeException(ioe);
}
}
}
/** Returns which {@code generation} the current searcher is guaranteed to include. */
public long getSearchingGen() {
return searchingGen;
}
}