lucene indexwriter锁机制
最近有个项目要用solr，solr是基于lucene的，今天在测试indexwriter时遇到了lock的问题：
测试代码：
import java.io.File;
import java.io.IOException;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import org.apache.lucene.util.Version;
public class TestLock {
private Directory dir;
public static TestLock ttt;
public static IndexWriter writer2;
private Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_48);
private IndexWriterConfig iwc = new IndexWriterConfig(Version.LUCENE_48, analyzer);
public void init() throws Exception {
String pathFile = "D://luceneindex";
try{
dir = FSDirectory. open(new File(pathFile));
} catch (IOException e) {
throw new RuntimeException(e);
}
IndexWriter writer = getWriter();
System. out.println("init ok,test IndexWriter lock" );
LockTest( writer);
//writer.close();
}
public IndexWriter getWriter() throws Exception {
//analyzer.close();
return new IndexWriter(dir, iwc);
}
public void LockTest(IndexWriter w1) {
try{
if(w1.isLocked (dir )){
System. out.println("write1 locked" );
IndexWriterConfig iwc1 = new IndexWriterConfig(Version.LUCENE_48 , analyzer );
writer2 = new IndexWriter(dir, iwc1);
} else{
System. out.println("write1 not locked" );
}
} catch(Exception e){
e.printStackTrace();
}
}
public static void main(String[] args){
ttt = new TestLock();
try{
ttt.init();
} catch(Exception e){
e. printStackTrace();
}
}
}
报错信息：
org.apache.lucene.store.LockObtainFailedException : Lock obtain timed out: NativeFSLock@D:\luceneindex\write.lock: java.nio.channels.OverlappingFileLockException at org.apache.lucene.store.Lock.obtain( Lock.java:89) at org.apache.lucene.index.IndexWriter.<init>( IndexWriter.java:710) at TestLock.LockTest( TestLock.java:38) at TestLock.init( TestLock.java:26) at TestLock.main( TestLock.java:51) Caused by: java.nio.channels.OverlappingFileLockException at sun.nio.ch.SharedFileLockTable.checkList(Unknown Source) at sun.nio.ch.SharedFileLockTable.add(Unknown Source) at sun.nio.ch.FileChannelImpl.tryLock(Unknown Source) at java.nio.channels.FileChannel.tryLock(Unknown Source) at org.apache.lucene.store.NativeFSLock.obtain(NativeFSLockFactory.java:148) at org.apache.lucene.store.Lock.obtain( Lock.java:100) ... 4 more
从错误信息可以看到是IndexWriter获取锁出错导致，从堆栈信息可以看到，是在运行IndexWriter的构造方法时，涉及到锁的操作。
查看IndexWriter的相关源码：
doc: Opening an IndexWriter creates a lock file for the directory in use. Trying to open another IndexWriter on the same directory will lead to a LockObtainFailedException. The LockObtainFailedException is also thrown if an IndexReader on the same directory is used to delete documents from the index.
两个和锁相关的属性：
public static final String WRITE_LOCK_NAME = "write.lock" ; private Lock writeLock;
在IndexWriter的构造函数中：
public IndexWriter(Directory d, IndexWriterConfig conf) throws IOException
....
directory = d;
.....
writeLock = directory.makeLock(WRITE_LOCK_NAME);
if (! writeLock.obtain(config .getWriteLockTimeout())) // obtain write lock（尝试获取锁）
throw new LockObtainFailedException("Index locked for write: " + writeLock );
其中Lock是一个抽象类（org.apache.lucene.store.Lock）：
锁的获取主要实现是在obtain方法：
public static long LOCK_POLL_INTERVAL = 1000;
public static final long LOCK_OBTAIN_WAIT_FOREVER = -1;
public final boolean obtain(long lockWaitTimeout) throws IOException {
failureReason = null;
boolean locked = obtain();
if (lockWaitTimeout < 0 && lockWaitTimeout != LOCK_OBTAIN_WAIT_FOREVER )
throw new IllegalArgumentException("lockWaitTimeout should be LOCK_OBTAIN_WAIT_FOREVER or a non-negative number (got " + lockWaitTimeout + ")");
long maxSleepCount = lockWaitTimeout / LOCK_POLL_INTERVAL;
long sleepCount = 0;
while (!locked) {
if (lockWaitTimeout != LOCK_OBTAIN_WAIT_FOREVER && sleepCount++ >= maxSleepCount) {
String reason = "Lock obtain timed out: " + this .toString();
if (failureReason != null) {
reason += ": " + failureReason ;
}
LockObtainFailedException e = new LockObtainFailedException(reason);
if (failureReason != null) {
e.initCause( failureReason);
}
throw e;
}
try {
Thread. sleep(LOCK_POLL_INTERVAL);
} catch (InterruptedException ie) {
throw new ThreadInterruptedException(ie);
}
locked = obtain();
}
return locked;
}
可以看到有由下面几个因素决定：
1.lockWaitTimeout 超时时间（总时间，超过这个时间即timeout）,默认1000ms
2.LOCK_OBTAIN_WAIT_FOREVER 是否无限获取(-1)，如果设置为-1，会永不超生
3.LOCK_POLL_INTERVAL 重试间隔时间，默认1000ms
在关闭IndexWriter时调用close方法（实现了Closeable接口的类都会有close方法）即可正常释放锁
更改代码为如下即可：
public void LockTest(IndexWriter w1) {
try{
if(w1.isLocked (dir )){
System. out.println("write1 locked" );
w1.close();
IndexWriterConfig iwc1 = new IndexWriterConfig(Version.LUCENE_48 , analyzer );
writer2 = new IndexWriter(dir, iwc1);
} else{
System. out.println("write1 not locked" );
}
} catch(Exception e){
e.printStackTrace();
}
}
另外关于lock的判断和unlock方法如下：
public static boolean isLocked(Directory directory) throws IOException { // 判断写目录是否被lock
return directory.makeLock( WRITE_LOCK_NAME).isLocked();
}
/**
* Forcibly unlocks the index in the named directory.
* <P>
* Caution: this should only be used by failure recovery code,
* when it is known that no other process nor thread is in fact
* currently accessing this index.
*/
public static void unlock(Directory directory) throws IOException { // 解锁
directory.makeLock(IndexWriter. WRITE_LOCK_NAME).close();
}