private void doEviction(BlockCacheKey key, CacheablePair evictedBlock) {
long evictedHeap = 0;
synchronized (evictedBlock) {
if (evictedBlock.serializedData == null) {
// someone else already freed
return;
}
evictedHeap = evictedBlock.heapSize();
ByteBuffer bb = evictedBlock.serializedData;
evictedBlock.serializedData = null;
backingStore.free(bb);
// We have to do this callback inside the synchronization here.
// Otherwise we can have the following interleaving:
// Thread A calls getBlock():
// SlabCache directs call to this SingleSizeCache
// It gets the CacheablePair object
// Thread B runs eviction
// doEviction() is called and sets serializedData = null, here.
// Thread A sees the null serializedData, and returns null
// Thread A calls cacheBlock on the same block, and gets
// "already cached" since the block is still in backingStore
if (actionWatcher != null) {
actionWatcher.onEviction(key, this);
}
}
stats.evicted();
size.addAndGet(-1 * evictedHeap);
}
@Override
public void cacheBlock(BlockCacheKey blockName, Cacheable toBeCached) {
ByteBuffer storedBlock;
try {
storedBlock = backingStore.alloc(toBeCached.getSerializedLength());
} catch (InterruptedException e) {
LOG.warn("SlabAllocator was interrupted while waiting for block to become available");
LOG.warn(e);
return;
}
CacheablePair newEntry = new CacheablePair(toBeCached.getDeserializer(), storedBlock);
toBeCached.serialize(storedBlock);
synchronized (this) {
CacheablePair alreadyCached = backingMap.putIfAbsent(blockName, newEntry);
if (alreadyCached != null) {
backingStore.free(storedBlock);
throw new RuntimeException("already cached " + blockName);
}
if (actionWatcher != null) {
actionWatcher.onInsertion(blockName, this);
}
}
newEntry.recentlyAccessed.set(System.nanoTime());
this.size.addAndGet(newEntry.heapSize());
}
