package org.infinispan.lucene.readlocks;
import java.util.HashMap;
import org.infinispan.Cache;
/**
* LocalLockMergingSegmentReadLocker decorates the {@link DistributedSegmentReadLocker} to minimize
* remote operations in case several IndexReaders are opened on the same Infinispan based {@link org.apache.lucene.store.Directory}.
* It keeps track of locks which where already acquired for a specific filename from another request on
* the same node and merges the request so that the different clients share the same remote lock.
*
* @author Sanne Grinovero
* @since 4.1
*/
@SuppressWarnings("unchecked")
public class LocalLockMergingSegmentReadLocker implements SegmentReadLocker {
//Concurrent access is guarded by synchronization on this: it's actually better to block
//the invoking thread than to trigger an additional RPC: since delete operations are never
//undone, a longer block window allows for better aggregation of operations.
private final HashMap<String, LocalReadLock> localLocks = new HashMap<String, LocalReadLock>();
private final DistributedSegmentReadLocker delegate;
/**
* Create a new LocalLockMergingSegmentReadLocker for specified cache and index name.
*
* @param cache
* @param indexName
*/
public LocalLockMergingSegmentReadLocker(Cache<?, ?> cache, String indexName, int affinitySegmentId) {
this.delegate = new DistributedSegmentReadLocker((Cache<Object, Integer>) cache, cache, cache, indexName, affinitySegmentId);
}
/**
* Create a new LocalLockMergingSegmentReadLocker with special purpose caches
* @param locksCache the cache to be used to store distributed locks
* @param chunksCache the cache containing the chunks, this is where the bulk of data is stored
* @param metadataCache smaller cache for the metadata of stored elements
* @param indexName
*/
public LocalLockMergingSegmentReadLocker(Cache<?, ?> locksCache, Cache<?, ?> chunksCache, Cache<?, ?> metadataCache, String indexName, int affinitySegmentId) {
this.delegate = new DistributedSegmentReadLocker((Cache<Object, Integer>) locksCache, chunksCache, metadataCache, indexName, affinitySegmentId);
}
public LocalLockMergingSegmentReadLocker(Cache<?, ?> locksCache, Cache<?, ?> chunksCache, Cache<?, ?> metadataCache, String indexName, boolean forceSynchronousDeletes, int affinitySegmentId) {
this.delegate = new DistributedSegmentReadLocker((Cache<Object, Integer>) locksCache, chunksCache, metadataCache, indexName, affinitySegmentId,forceSynchronousDeletes);
}
/**
* {@inheritDoc}
*/
@Override
public synchronized boolean acquireReadLock(String name) {
LocalReadLock localReadLock = getLocalLockByName(name);
boolean acquired = localReadLock.acquire();
if (acquired) {
return true;
}
else {
// cleanup
localLocks.remove(name);
return false;
}
}
private LocalReadLock getLocalLockByName(String name) {
LocalReadLock localReadLock = localLocks.get(name);
if (localReadLock == null) {
LocalReadLock newReadLock = new LocalReadLock(name);
localLocks.put(name, newReadLock);
return newReadLock;
}
return localReadLock;
}
/**
* {@inheritDoc}
*/
@Override
public synchronized void deleteOrReleaseReadLock(String name) {
getLocalLockByName(name).release();
}
private class LocalReadLock {
private final String name;
private int value = 0;
LocalReadLock(String name) {
this.name = name;
}
/**
* @return true if the lock was acquired, false if it's too late: the file
* was deleted and this LocalReadLock should be removed too.
*/
boolean acquire() {
if (value == 0) {
boolean haveIt = delegate.acquireReadLock(name);
if (haveIt) {
value = 1;
return true;
} else {
value = -1;
return false;
}
} else if (value == -1) {
// it was deleted just a two lines ago
return false;
} else {
value++;
return true;
}
}
void release() {
value--;
if (value <= 0) {
localLocks.remove(name);
delegate.deleteOrReleaseReadLock(name);
}
}
}
}